The evidence base

The research
underneath the game.

Every publication this Institute's positions rest on — readiness, recovery, injury, return to play, head injury, heat, youth and the women's game. Named authors, named departments, resolvable DOIs, and what each study does not say.

75Publications
8Domains
100%DOI resolvable
4Open disputes
Evidence Systematic reviews, meta-analyses, randomised trials, prospective cohorts, validations. Consensus Expert agreement. Valuable, and not the same as pooled data. Contested A live dispute, or a finding routinely misquoted.

Load & readiness

What load does to a player, and what monitoring can and cannot tell you.

Consensus2016

How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury

Soligard T, Schwellnus M, Alonso J-M, et al.
British Journal of Sports Medicine 50(17):1030–1041

Medical and Scientific Department, International Olympic Committee, LausanneDOI 10.1136/bjsports-2016-096581

Injury risk is driven not by how much load a player carries but by how rapidly and how badly timed the changes in that load are — and load means training, matches, travel, psychological and life stress, not minutes on the pitch.

What it does not say

Expert consensus rather than pooled evidence, and its endorsement of the acute:chronic workload ratio has since been substantially challenged.

Consensus2016

How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness

Schwellnus M, Soligard T, Alonso J-M, et al.
British Journal of Sports Medicine 50(17):1043–1052

Sport, Exercise Medicine and Lifestyle Institute, University of PretoriaDOI 10.1136/bjsports-2016-096572

Illness is a load-related outcome too — a squad repeatedly losing availability to infection is usually showing a load-management failure, not bad luck.

What it does not say

Illness surveillance in club football is far less standardised than injury surveillance, so the underlying evidence base is thinner than for Part 1.

Consensus2017

Monitoring Athlete Training Loads: Consensus Statement

Bourdon PC, Cardinale M, Murray A, et al.
International Journal of Sports Physiology and Performance 12(s2):S2-161–S2-170

Sport Science Department, Aspire Academy, DohaDOI 10.1123/IJSPP.2017-0208

The reference definition of what a credible monitoring system contains — internal and external, objective and subjective — and a plain statement that no single metric captures readiness.

What it does not say

Describes what can be measured more confidently than what should be acted upon; it stops short of decision thresholds.

ConsensusNarrative review2014

Monitoring training load to understand fatigue in athletes

Halson SL
Sports Medicine 44(S2):S139–S147

Department of Physiology, Australian Institute of Sport, CanberraDOI 10.1007/s40279-014-0253-z

The cheap, simple, athlete-reported tools generally outperform the expensive physiological ones — compliance and consistency matter more than sophistication.

What it does not say

A narrative review with no formal search protocol, so selection of evidence is at the author's discretion.

EvidenceValidation study2001

A new approach to monitoring exercise training

Foster C, Florhaug JA, Franklin J, et al.
Journal of Strength and Conditioning Research 15(1):109–115

Department of Exercise and Sport Science, University of Wisconsin–La CrossePubMed record

The origin of session-RPE: session duration multiplied by the player's 0–10 rating of how hard it felt tracks heart-rate-based load closely, at zero cost.

What it does not say

Validated in small non-football cohorts; the rating is easily distorted by collection timing and by players who suspect it affects selection. Predates DOI registration — cited by PMID 11708692.

ConsensusConceptual review2019

Internal and External Training Load: 15 Years On

Impellizzeri FM, Marcora SM, Coutts AJ
International Journal of Sports Physiology and Performance 14(2):270–273

Human Performance Research Centre, University of Technology SydneyDOI 10.1123/ijspp.2018-0935

External load is what you prescribe — distance, sprints, accelerations. Internal load is what the player's body actually experiences. Only the second one causes adaptation or breakdown.

What it does not say

Clarifies definitions but does not resolve how the two should be combined in practice.

ContestedNarrative review2016

The training-injury prevention paradox: should athletes be training smarter and harder?

Gabbett TJ
British Journal of Sports Medicine 50(5):273–280

School of Exercise Science, Australian Catholic University, BrisbaneDOI 10.1136/bjsports-2015-095788

The most influential idea in modern load management: under-training is itself a risk factor, and progressively loaded players tolerate hard weeks better than undertrained ones.

What it does not say

The paper at the centre of the dispute — critics argue the central claim rests on a statistically flawed ratio and on cross-sectional associations presented as prediction.

ContestedProspective cohort2016

The acute:chronic workload ratio predicts injury: high chronic workload may decrease injury risk in elite rugby league players

Hulin BT, Gabbett TJ, Lawson DW, Caputi P, Sampson JA
British Journal of Sports Medicine 50(4):231–236

Centre for Human and Applied Physiology, University of WollongongDOI 10.1136/bjsports-2015-094817

The primary study behind the ACWR: across 53 players over two seasons, weeks where load spiked far above the four-week average carried elevated injury risk.

What it does not say

Rugby league, single cohort, 53 players — the title claims prediction but the design supports association only, a point the authors later conceded in print.

EvidenceMethodological critique2020

Acute:Chronic Workload Ratio: Conceptual Issues and Fundamental Pitfalls

Impellizzeri FM, Tenan MS, Kempton T, Novak A, Coutts AJ
International Journal of Sports Physiology and Performance 15(6):907–913

Human Performance Research Centre, University of Technology SydneyDOI 10.1123/ijspp.2019-0864

The clearest statement of why the ratio is broken: the acute week sits inside the chronic average, so the two are mathematically coupled and will appear correlated even with random data.

What it does not say

Dismantles the metric without offering an equally simple validated replacement.

ContestedSimulation and re-analysis2021

What Role Do Chronic Workloads Play in the Acute to Chronic Workload Ratio? Time to Dismiss ACWR and Its Underlying Theory

Impellizzeri FM, Woodcock S, Coutts AJ, Fanchini M, McCall A, Vigotsky AD
Sports Medicine 51(3):581–592

Human Performance Research Centre, University of Technology SydneyDOI 10.1007/s40279-020-01378-6

The strongest formal argument to abandon the ACWR: the apparent protective effect of high chronic load is an artefact of how the ratio is constructed, not a training effect.

What it does not say

A live and unresolved dispute — the original authors reject the conclusion, and many clubs still run ACWR dashboards.

EvidenceMethodological critique2019

The acute-to-chronic workload ratio: an inaccurate scaling index for an unnecessary normalisation process?

Lolli L, Batterham AM, Hawkins R, et al.
British Journal of Sports Medicine 53(24):1510–1512

Health and Social Care Institute, Teesside UniversityDOI 10.1136/bjsports-2017-098884

The ratio fails on its own terms as a scaling index — dividing acute by chronic load does not remove the influence of chronic load, so the number does not mean what practitioners assume.

What it does not say

A short editorial; the full statistical argument is spread across the authors' companion letters.

EvidenceMethodological critique2017

Are rolling averages a good way to assess training load for injury prevention?

Menaspà P
British Journal of Sports Medicine 51(7):618–619

School of Medical and Health Sciences, Edith Cowan University, PerthDOI 10.1136/bjsports-2016-096131

A flat rolling average treats a session four weeks ago as equally important as yesterday's, which is not how fitness and fatigue decay — the argument that produced exponentially weighted models.

What it does not say

The exponentially weighted alternative it inspired inherits the same coupling problem and is therefore not a fix.

ConsensusConceptual critique2018

Training load and structure-specific load: applications for sport injury causality and data analyses

Nielsen RØ, Bertelsen ML, Møller M, et al.
British Journal of Sports Medicine 52(16):1016–1017

Section for Sports Science, Department of Public Health, Aarhus UniversityDOI 10.1136/bjsports-2017-097838

The field measures the wrong thing: total session load says little about the load reaching the specific tissue that fails, which is why squad-level numbers predict individual injuries so poorly.

What it does not say

Structure-specific load is not currently measurable in a live football environment, so the critique is easier to accept than to act on.

EvidenceSystematic review2020

The Association Between the Acute:Chronic Workload Ratio and Injury and its Application in Team Sports: A Systematic Review

Griffin A, Kenny IC, Comyns TM, Lyons M
Sports Medicine 50(3):561–580

Department of Physical Education and Sport Sciences, University of LimerickDOI 10.1007/s40279-019-01218-2

The formal evidence audit: findings are inconsistent between studies, methods differ too widely to pool, and no defensible universal danger threshold exists.

What it does not say

Its own quality-appraisal method was publicly challenged in a subsequent Sports Medicine letter.

EvidenceReview2016

The Validity and Reliability of Global Positioning Systems in Team Sport: A Brief Review

Scott MTU, Scott TJ, Kelly VG
Journal of Strength and Conditioning Research 30(5):1470–1490

School of Human Movement and Nutrition Sciences, University of QueenslandDOI 10.1519/JSC.0000000000001221

How far GPS can be trusted: acceptable for total distance and low-speed running, progressively less reliable as speed rises and movements become short, sharp and multidirectional — exactly the actions that matter most in football.

What it does not say

Predates current 10 Hz/18 Hz and hybrid GPS-LPS units, so the specific error figures are dated even though the principle holds.

EvidenceValidation study2018

Validation of electronic performance and tracking systems EPTS under field conditions

Linke D, Link D, Lames M
PLOS ONE 13(7):e0199519

Chair of Performance Analysis and Sports Informatics, Technical University of MunichDOI 10.1371/journal.pone.0199519

A head-to-head field validation of GPS, local positioning and optical tracking against a gold standard: the same match produces materially different numbers depending on which system generated them.

What it does not say

System- and firmware-specific — which also means historical load data cannot be compared across a change of supplier.

EvidenceSystematic review2016

Monitoring the athlete training response: subjective self-reported measures trump commonly used objective measures: a systematic review

Saw AE, Main LC, Gastin PB
British Journal of Sports Medicine 50(5):281–291

Centre for Exercise and Sport Science, Deakin University, MelbourneDOI 10.1136/bjsports-2015-094758

A short daily wellness questionnaire responds to changes in training load more sensitively and more consistently than blood markers, heart rate or hormonal measures.

What it does not say

Sensitivity to load is not prediction of injury — these measures reflect what has already happened, not reliably what will.

ConsensusNarrative review2014

Monitoring training status with HR measures: do all roads lead to Rome?

Buchheit M
Frontiers in Physiology 5:73

Sport Science Department, Myorobie Association, MontvalezanDOI 10.3389/fphys.2014.00073

Heart-rate variability and submaximal heart rate carry real signal — but only as individual trends over weeks against that player's own baseline and measurement error, never as a single-day green or red light.

What it does not say

Day-to-day biological noise is large enough that isolated readings should not drive selection; evidence for predicting injury specifically is weak.

EvidenceProspective cohort, 11 seasons2013

Muscle injury rates in professional football increase with fixture congestion: an 11-year follow-up of the UEFA Champions League injury study

Bengtsson H, Ekstrand J, Hägglund M
British Journal of Sports Medicine 47(12):743–747

Football Research Group, Linköping UniversityDOI 10.1136/bjsports-2013-092383

Matches played on four recovery days or fewer carried a 32% higher muscle injury rate than those on six or more, driven by hamstring and quadriceps injuries — while team results were essentially unaffected.

What it does not say

Observational, so squad rotation and selection confound the comparison; it cannot prove congestion itself causes the injuries.

EvidenceProspective cohort2010

Effect of 2 soccer matches in a week on physical performance and injury rate

Dupont G, Nedelec M, McCall A, McCormack D, Berthoin S, Wisløff U
The American Journal of Sports Medicine 38(9):1752–1758

Laboratory of Human Movement Studies, Université Lille 2DOI 10.1177/0363546510361236

With two matches a week, running output held up completely — but the injury rate was roughly six times higher (25.6 vs 4.1 per 1000 hours). A player can look fine on the GPS report and be badly under-recovered.

What it does not say

Single club, 32 players, physical output measured only in home matches — the effect size is almost certainly imprecise even if the direction is robust.

Recovery, sleep & fuel

How long recovery actually takes, and which interventions survive scrutiny.

ConsensusExpert consensus2021

Sleep and the athlete: narrative review and 2021 expert consensus recommendations

Walsh NP, Halson SL, Sargent C, et al.
British Journal of Sports Medicine 55(7):356–368

Research Institute for Sport and Exercise Sciences, Liverpool John Moores UniversityDOI 10.1136/bjsports-2020-102025

Elite athletes sleep less and worse than the general population — and the panel argues against a blanket 'seven to nine hours' rule in favour of individualised sleep targets built on each athlete's own perceived need.

What it does not say

The panel is explicit that the performance effect of realistic one-to-three-night partial sleep restriction remains unclear, that most athlete sleep studies lack female participants, and that common sleep-tracking tools are of questionable validity.

ConsensusNarrative review2014

Sleep in elite athletes and nutritional interventions to enhance sleep

Halson SL
Sports Medicine 44(S1):S13–S23

AIS Performance Recovery, Australian Institute of Sport, CanberraDOI 10.1007/s40279-014-0147-0

The review that established sleep as a performance variable rather than a lifestyle one, cataloguing why athletes sleep badly — travel, late kick-offs, schedules, anxiety — and which nutritional levers may help.

What it does not say

The nutritional interventions rest largely on small non-athlete laboratory studies, so dose and real-world effect in football are extrapolated.

EvidenceSleep extension intervention2011

The effects of sleep extension on the athletic performance of collegiate basketball players

Mah CD, Mah KE, Kezirian EJ, Dement WC
Sleep 34(7):943–950

Stanford Sleep Disorders Clinic and Research Laboratory, Stanford University School of MedicineDOI 10.5665/SLEEP.1132

The landmark demonstration that sleep is an intervention, not just a state: roughly 111 extra minutes a night for 5–7 weeks improved sprint time, free-throw accuracy by 9% and three-point accuracy by 9.2%.

What it does not say

Eleven male basketball players, no control group, and a season-long practice effect that cannot be separated from the sleep effect — the magnitude is almost certainly inflated.

EvidenceCross-sectional with injury records2014

Chronic lack of sleep is associated with increased sports injuries in adolescent athletes

Milewski MD, Skaggs DL, Bishop GA, et al.
Journal of Pediatric Orthopaedics 34(2):129–133

Children's Orthopaedic Center, Children's Hospital Los AngelesDOI 10.1097/BPO.0000000000000151

The first study to link sleep directly to injury: athletes averaging under eight hours a night were 1.7 times more likely to have been injured.

What it does not say

Adolescent, non-football, self-reported sleep and retrospective records — and the lower confidence bound touches 1.0, so this is association, not a proven risk ratio for senior professionals.

EvidenceSystematic review and meta-analysis, 77 studies2018

Acute and Residual Soccer Match-Related Fatigue: A Systematic Review and Meta-analysis

Silva JR, Rumpf MC, Hertzog M, et al.
Sports Medicine 48(3):539–583

National Sports Medicine Programme, Aspetar Orthopaedic and Sports Medicine Hospital, DohaDOI 10.1007/s40279-017-0798-8

The definitive quantification of the post-match recovery curve: hamstring force, physical performance, creatine kinase, wellbeing and soreness are all still meaningfully impaired at 72 hours after a real match.

What it does not say

Match simulation protocols produce substantially smaller muscle-damage responses than real 11-a-side competition, so much of the underlying literature understates true match load.

Consensus2018

Recovery and Performance in Sport: Consensus Statement

Kellmann M, Bertollo M, Bosquet L, et al.
International Journal of Sports Physiology and Performance 13(2):240–245

Faculty of Sport Science, Ruhr University BochumDOI 10.1123/ijspp.2017-0759

No single marker captures recovery status, so monitoring must be multivariate, individualised and periodised — and results come from a few well-matched interventions, not from stacking many recovery activities.

What it does not say

A principles document reached by expert agreement, and it deliberately declines to specify which markers or thresholds a club should use.

EvidenceSystematic review and meta-analysis, 99 studies2018

An Evidence-Based Approach for Choosing Post-exercise Recovery Techniques to Reduce Markers of Muscle Damage, Soreness, Fatigue, and Inflammation: A Systematic Review With Meta-Analysis

Dupuy O, Douzi W, Theurot D, Bosquet L, Dugué B
Frontiers in Physiology 9:403

Laboratoire MOVE, Faculty of Sport Sciences, University of PoitiersDOI 10.3389/fphys.2018.00403

The head-to-head comparison: massage came out strongest for soreness and perceived fatigue, with active recovery, compression, immersion and contrast therapy producing smaller reductions — while stretching and electrostimulation produced no meaningful change.

What it does not say

The outcomes are soreness, perceived fatigue and blood markers — not restored performance — and it says nothing about interference with training adaptation across a season.

EvidenceRandomised controlled trial2015

Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training

Roberts LA, Raastad T, Markworth JF, et al.
The Journal of Physiology 593(18):4285–4301

School of Human Movement Studies and Nutrition Sciences, University of QueenslandDOI 10.1113/JP270570

The study that changed practice on ice baths: over twelve weeks, athletes using active recovery gained significantly more strength and muscle than those using cold water immersion, which blunted the anabolic signal.

What it does not say

Resistance training in recreationally active men, not in-season football — the practical resolution is periodising cold exposure, not abandoning it.

EvidenceMeta-analysis, 23 studies2017

Compression Garments and Recovery from Exercise: A Meta-Analysis

Brown F, Gissane C, Howatson G, van Someren K, Pedlar C, Hill J
Sports Medicine 47(11):2245–2267

School of Sport, Health and Applied Science, St Mary's University, TwickenhamDOI 10.1007/s40279-017-0728-9

Compression garments produce a small but reliable recovery benefit, largest for strength recovery at 2–8 hours and beyond 24 hours — and the benefit does not depend on garment pressure or training status.

What it does not say

Dominated by resistance and running protocols rather than football, and a substantial part of the effect may be placebo — blinding a compression garment is effectively impossible.

Consensus2021

Managing Travel Fatigue and Jet Lag in Athletes: A Review and Consensus Statement

Janse van Rensburg DCC, Jansen van Rensburg A, Fowler PM, et al.
Sports Medicine 51(10):2029–2050

Section Sports Medicine, University of PretoriaDOI 10.1007/s40279-021-01502-0

The reference separation of travel fatigue — which any journey causes and rest resolves — from jet lag, which follows crossing time zones at roughly a day of adjustment per zone, with distinct interventions for each.

What it does not say

The companion systematic review by the same group found the underlying intervention evidence in athletes to be limited and largely low quality.

ConsensusExpert group statement, 31 authors2021

UEFA expert group statement on nutrition in elite football

Collins J, Maughan RJ, Gleeson M, et al.
British Journal of Sports Medicine 55(8):416

Performance and Research Team, Arsenal Football Club, LondonDOI 10.1136/bjsports-2019-101961

The most authoritative football-specific nutrition document there is — match-day and training-day fuelling, body composition, hydration, travel, supplements, rehabilitation, referees and junior players — anchored on food first.

What it does not say

The authors describe it as a narrative synthesis of the group's knowledge and practice rather than a systematic review, so recommendation strength is not formally graded.

ConsensusTheoretical framework review2018

Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis

Impey SG, Hearris MA, Hammond KM, et al.
Sports Medicine 48(5):1031–1048

Research Institute for Sport and Exercise Sciences, Liverpool John Moores UniversityDOI 10.1007/s40279-018-0867-7

The model behind modern carbohydrate periodisation: intake should be matched to the session about to be performed rather than kept uniformly high, because training with reduced glycogen amplifies the signal for oxidative adaptation.

What it does not say

The authors are candid that amplified signalling does not reliably become improved performance — only around 37% of relevant studies showed a performance benefit — and the framework comes from endurance rather than football.

EvidenceSystematic review and meta-analysis, 49 studies2018

A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults

Morton RW, Murphy KT, McKellar SR, et al.
British Journal of Sports Medicine 52(6):376–384

Department of Kinesiology, McMaster University, HamiltonDOI 10.1136/bjsports-2017-097608

The reference point for protein prescription: supplementation meaningfully augments strength and lean mass gains, but the benefit plateaus at about 1.6 g per kg body mass per day. Above that, more protein adds nothing.

What it does not say

Resistance-training contexts rather than in-season football, and the plateau carries wide confidence intervals; a published correction should be cited alongside the original.

EvidenceSystematic review and meta-analysis2017

The countermovement jump to monitor neuromuscular status: A meta-analysis

Claudino JG, Cronin J, Mezêncio B, et al.
Journal of Science and Medicine in Sport 20(4):397–402

Laboratory of Biomechanics, School of Physical Education and Sport, University of São PauloDOI 10.1016/j.jsams.2016.08.011

A correction to how most clubs use the countermovement jump: the average of a player's jumps detects fatigue and supercompensation more sensitively than the single best jump — which is what 85% of studies report.

What it does not say

The sensitivity of other variables such as peak power remains unresolved, and it does not establish what size of change should trigger a decision for an individual.

EvidenceControlled experimental study2016

Blood-Borne Markers of Fatigue in Competitive Athletes — Results from Simulated Training Camps

Hecksteden A, Skorski S, Schwindling S, et al.
PLOS ONE 11(2):e0148810

Institute of Sports and Preventive Medicine, Saarland UniversityDOI 10.1371/journal.pone.0148810

A reality check on blood panels: creatine kinase tracked fatigue consistently in strength and high-intensity work, urea and IGF-1 in endurance work — the useful marker differs by training mode, so no single panel monitors a squad.

What it does not say

Simulated camps rather than competitive football, and even for CK the between-athlete variability means values are only interpretable against an individual's own baseline.

ConsensusNarrative review2012

Recovery in Soccer: Part I — Post-Match Fatigue and Time Course of Recovery

Nédélec M, McCall A, Carling C, Legall F, Berthoin S, Dupont G
Sports Medicine 42(12):997–1015

Laboratory of Human Movement Studies, Université Lille 2DOI 10.2165/11635270-000000000-00000

The football-specific reference on what a match actually does to a player — mechanical, metabolic, neural and psychological fatigue with different recovery timescales, which is why one recovery protocol cannot address all of it.

What it does not say

A narrative review; its companion Part II covers interventions and is now partly superseded by later meta-analyses.

Injury & prevention

How football counts its injuries, and what has been shown to reduce them.

Consensus2006

Consensus statement on injury definitions and data collection procedures in studies of football (soccer) injuries

Fuller CW, Ekstrand J, Junge A, et al.
British Journal of Sports Medicine 40(3):193–201

Centre for Sports Medicine, University of NottinghamDOI 10.1136/bjsm.2005.025270

The document that made football injury data comparable at all — fixing what counts as an injury, a recurrence, a severity band and an exposure hour, so numbers from different clubs and leagues mean the same thing.

What it does not say

Built on a time-loss definition, so it systematically under-counts overuse and non-time-loss complaints that still degrade performance.

Consensus2020

International Olympic Committee consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension, STROBE-SIIS)

Bahr R, Clarsen B, Derman W, et al.
British Journal of Sports Medicine 54(7):372–389

Oslo Sports Trauma Research Center, Norwegian School of Sport SciencesDOI 10.1136/bjsports-2019-101969

The current cross-sport standard — including the shift from counting injuries to reporting injury burden, days lost per 1000 hours — and a checklist for judging whether any injury report you are shown is credible.

What it does not say

Deliberately sport-generic, so football-specific classification detail still has to come from the 2006 football consensus.

EvidenceCritical review2016

Why screening tests to predict injury do not work — and probably never will: a critical review

Bahr R
British Journal of Sports Medicine 50(13):776–780

Oslo Sports Trauma Research Center, Norwegian School of Sport SciencesDOI 10.1136/bjsports-2016-096256

No screening test yet exists that can tell you which individual player will be injured: a statistically significant association with risk is not predictive accuracy, and no study has shown that treating only high-risk players beats giving everyone the same programme.

What it does not say

An argument rather than new data — testing may still be defensible for individualising load and rehabilitation, just not for prediction.

EvidenceProspective cohort, 18 seasons2021

Injury rates decreased in men's professional football: an 18-year prospective cohort study of almost 12 000 injuries sustained during 1.8 million hours of play

Ekstrand J, Spreco A, Bengtsson H, Bahr R
British Journal of Sports Medicine 55(19):1084–1092

Football Research Group, Linköping UniversityDOI 10.1136/bjsports-2020-103159

Across eighteen seasons of Europe's biggest clubs, injury incidence fell roughly 3% per season in both training and matches, re-injury rates fell and availability rose — the headline evidence that elite medical practice has been working.

What it does not say

Participating clubs are self-selected elite European teams with well-resourced medical departments, and all data are staff-reported, so this may not generalise to the wider game.

EvidenceProspective cohort, 21 seasons2023

Hamstring injury rates have increased during recent seasons and now constitute 24% of all injuries in men's professional football: the UEFA Elite Club Injury Study from 2001/02 to 2021/22

Ekstrand J, Bengtsson H, Waldén M, Davison M, Khan KM, Hägglund M
British Journal of Sports Medicine 57(5):292–298

Football Research Group, Linköping UniversityDOI 10.1136/bjsports-2021-105407

Hamstring injury has doubled its share of the elite men's game in twenty years — from 12% to 24% of all injuries and from 10% to 20% of all days lost. Overall progress has not reached football's most common injury.

What it does not say

Descriptive time-trend data: it documents the rise but cannot attribute it to congestion, sprint volume or changed training practice.

EvidenceCluster-randomised controlled trial2011

Preventive Effect of Eccentric Training on Acute Hamstring Injuries in Men's Soccer: A Cluster-Randomized Controlled Trial

Petersen J, Thorborg K, Nielsen MB, Budtz-Jørgensen E, Hölmich P
The American Journal of Sports Medicine 39(11):2296–2303

Department of Orthopaedic Surgery, Amager Hospital, CopenhagenDOI 10.1177/0363546511419277

Adding the Nordic hamstring exercise to normal training cut acute hamstring injuries by roughly 70% across 942 players and 50 teams, for both new and recurrent injuries.

What it does not say

Unblinded, mixed professional and amateur squads, and the effect is larger than later pooled estimates — elite clubs should expect a smaller real-world benefit.

EvidenceSystematic review and meta-analysis2019

Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes

van Dyk N, Behan FP, Whiteley R
British Journal of Sports Medicine 53(21):1362–1370

Aspetar Injury and Illness Prevention Program, Aspetar, DohaDOI 10.1136/bjsports-2018-100045

Pooled across sports and sexes, prevention programmes containing the Nordic hamstring exercise roughly halve hamstring injury rates.

What it does not say

Eight of fifteen studies were at high risk of bias, and the estimate assumes the exercise is actually done — which in elite football it usually is not.

EvidenceImplementation survey, 150 club-seasons2015

Evidence-based hamstring injury prevention is not adopted by the majority of Champions League or Norwegian Premier League football teams: the Nordic Hamstring survey

Bahr R, Thorborg K, Ekstrand J
British Journal of Sports Medicine 49(22):1466–1471

Oslo Sports Trauma Research Center, Norwegian School of Sport SciencesDOI 10.1136/bjsports-2015-094826

The implementation problem, in numbers: of 150 elite club-seasons, the programme was completed in full in 10.7% and partially in a further 6%. Proven efficacy has not become fewer injuries because the work is not being done.

What it does not say

Self-reported and covering 2012–2014 only; it measures completion of one programme rather than total eccentric loading by any means.

EvidenceCluster-randomised controlled trial2008

Comprehensive warm-up programme to prevent injuries in young female footballers: cluster randomised controlled trial

Soligard T, Myklebust G, Steffen K, et al.
BMJ 337:a2469

Oslo Sports Trauma Research Center, Norwegian School of Sport SciencesDOI 10.1136/bmj.a2469

The foundational trial behind the FIFA 11+: a structured twenty-minute warm-up reduced overall injuries by 32%, overuse injuries by 53% and severe injuries by 45% across 125 clubs.

What it does not say

The pre-specified primary outcome — lower-extremity injury — did not reach statistical significance. The widely quoted reductions are secondary outcomes.

EvidenceSystematic review and meta-analysis of 6 RCTs2017

Effect of specific exercise-based football injury prevention programmes on the overall injury rate in football: a systematic review and meta-analysis of the FIFA 11 and 11+ programmes

Thorborg K, Krommes KK, Esteve E, Clausen MB, Bartels EM, Rathleff MS
British Journal of Sports Medicine 51(7):562–571

Sports Orthopedic Research Center–Copenhagen, Amager-Hvidovre Hospital, University of CopenhagenDOI 10.1136/bjsports-2016-097066

The FIFA 11+ reduces overall football injuries by about 39%, while its predecessor showed no demonstrable effect — the specific programme, not just 'a warm-up', is what matters.

What it does not say

All included trials were in recreational or sub-elite football; the 39% figure has never been demonstrated in elite professional squads.

ConsensusClassification system2014

British athletics muscle injury classification: a new grading system

Pollock N, James SLJ, Lee JC, Chakraverty R
British Journal of Sports Medicine 48(18):1347–1351

British Athletics Medical Team, LondonDOI 10.1136/bjsports-2013-093302

Replaces the crude grade 1–2–3 strain with an MRI-based grade plus a site suffix, because where the tear sits — myofascial, musculotendinous or intratendinous — drives time out and re-injury risk more than how big it is.

What it does not say

Developed in elite track and field rather than football, and it competes with the Munich consensus system, so clubs using different classifications still cannot compare timelines.

Consensus2013

Terminology and classification of muscle injuries in sport: The Munich consensus statement

Mueller-Wohlfahrt H-W, Haensel L, Mithoefer K, et al.
British Journal of Sports Medicine 47(6):342–350

MW Center of Orthopedics and Sports Medicine, MunichDOI 10.1136/bjsports-2012-091448

The competing muscle injury taxonomy, separating functional muscle disorders from structural injury — a distinction that changes both the rehabilitation plan and the expected return date.

What it does not say

Expert consensus, and its coexistence with the British Athletics system is precisely why cross-club comparison of muscle injury data remains unreliable.

EvidenceSystematic review2023

The Effects of Fixture Congestion on Injury in Professional Male Soccer: A Systematic Review

Page RM, Field A, Langley B, Harper LD, Julian R
Sports Medicine 53(3):667–685

Department of Sport and Physical Activity, Edge Hill UniversityDOI 10.1007/s40279-022-01799-5

Playing on four or fewer recovery days raises injury risk — five of eight studies found higher match injury incidence in congested blocks — though injuries sustained then tend to cost fewer days.

What it does not say

Only eight eligible studies with inconsistent definitions of congestion and no meta-analysis, so the size of the effect, and how much is squad rotation, remains unresolved.

EvidenceProspective cohort, 11 seasons2013

Injuries affect team performance negatively in professional football: an 11-year follow-up of the UEFA Champions League injury study

Hägglund M, Waldén M, Magnusson H, Kristenson K, Bengtsson H, Ekstrand J
British Journal of Sports Medicine 47(12):738–742

Football Research Group, Linköping UniversityDOI 10.1136/bjsports-2013-092215

The study that made availability a boardroom metric: lower injury burden and higher player availability were associated with better league position and better European performance.

What it does not say

Association, not causation — better-run clubs may simply be better at both — but the relationship has held across a decade of the largest dataset in the game.

EvidenceProspective cohort, 7 seasons2011

Injury incidence and injury patterns in professional football: the UEFA injury study

Ekstrand J, Hägglund M, Waldén M
British Journal of Sports Medicine 45(7):553–558

Football Research Group, Linköping UniversityDOI 10.1136/bjsm.2009.060582

The baseline description of elite football's injury profile — roughly 50 injuries per squad per season, match incidence far above training, thigh strains the single largest category.

What it does not say

Predates a decade of change in calendar density, pitch surfaces and medical practice; the current benchmark is the 18-season update.

Return to play

Getting a player back — the decision, the criteria and the real rates.

Consensus2016

2016 Consensus statement on return to sport from the First World Congress in Sports Physical Therapy, Bern

Ardern CL, Glasgow P, Schneiders A, et al.
British Journal of Sports Medicine 50(14):853–864

Aspetar, Doha; Linköping University; La Trobe UniversityDOI 10.1136/bjsports-2016-096278

Return to play is a continuum — return to participation, return to sport, return to performance — and the decision is a shared, multi-factor risk judgement, not a single test a player passes or fails.

What it does not say

Expert opinion rather than graded evidence; it gives a decision architecture but no validated sport-specific discharge criteria, and nothing football-specific has superseded it.

EvidenceSystematic review and meta-analysis, 7556 patients2014

Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors

Ardern CL, Taylor NF, Feller JA, Webster KE
British Journal of Sports Medicine 48(21):1543–1552

School of Allied Health, La Trobe University, MelbourneDOI 10.1136/bjsports-2013-093398

Surgery does not equal return: 81% go back to some sport, 65% to their pre-injury level, and only 55% to competitive sport — and psychological response predicts who makes it back as strongly as physical function.

What it does not say

Pooled across many sports and surgical techniques rather than football, with variable follow-up and largely self-reported return status.

ConsensusClinical practice guideline2023

Aspetar clinical practice guideline on rehabilitation after anterior cruciate ligament reconstruction

Kotsifaki R, Korakakis V, King E, et al.
British Journal of Sports Medicine 57(9):500–514

Aspetar Orthopaedic and Sports Medicine Hospital, DohaDOI 10.1136/bjsports-2022-106158

The most current structured rehabilitation pathway after ACL reconstruction, built around criterion-based progression rather than elapsed time since surgery.

What it does not say

A guideline synthesising evidence of mixed quality; several of its criteria thresholds are pragmatic rather than validated against re-injury outcomes.

EvidenceProspective cohort2025

Return-to-play times in women's elite football

Ekstrand J, Bengtsson H, et al.
BMJ Open Sport & Exercise Medicine 11:e002724

Football Research Group, Linköping UniversityDOI 10.1136/bmjsem-2025-002724

Return-to-play benchmarks drawn from the women's elite club cohort — the first systematically collected timelines for a game that has been managed on men's data by default.

What it does not say

A young dataset with fewer clubs and seasons than the men's study, so estimates for less common injuries remain imprecise.

Head injury

Concussion protocol, heading exposure and long-term neurodegenerative risk.

Consensus2023

Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport, Amsterdam, October 2022

Patricios JS, Schneider KJ, Dvorak J, et al.
British Journal of Sports Medicine 57(11):695–711

Wits Sport and Health, University of the Witwatersrand, JohannesburgDOI 10.1136/bjsports-2023-106898

The current international reference for recognising, assessing and managing sport-related concussion, introducing the SCAT6 and SCOAT6 tools and a more graduated return-to-learn and return-to-sport pathway.

What it does not say

Consensus rather than primary evidence; the process has been repeatedly criticised for conflicts of interest arising from governing-body funding, and it explicitly declines to affirm a causal link between head impacts and CTE — a position several independent groups contest.

ContestedConsensus statement2017

Consensus statement on concussion in sport — the 5th international conference on concussion in sport held in Berlin, October 2016

McCrory P, Meeuwisse W, Dvořák J, et al.
British Journal of Sports Medicine 51(11):838–847

Florey Institute of Neuroscience and Mental Health, University of Melbourne (first author's affiliation at time of publication)DOI 10.1136/bjsports-2017-097699

It defined sport-related concussion for a generation of clinicians and codified the SCAT5 and the six-stage graduated return-to-play protocol that most football federations still base their rules on.

What it does not say

Integrity note, verified: the first author, a former BJSM Editor-in-Chief, has since accrued seventeen retractions and expressions of concern on roughly seventy-eight further articles, for plagiarism and duplicate publication. Those retractions concern his single-authored editorials, reviews and letters — this consensus statement has not been retracted. We publish the distinction rather than bury it or overstate it.

EvidenceMatched cohort, 7676 players2019

Neurodegenerative Disease Mortality among Former Professional Soccer Players

Mackay DF, Russell ER, Stewart K, MacLean JA, Pell JP, Stewart W
New England Journal of Medicine 381(19):1801–1808

Institute of Health and Wellbeing, University of GlasgowDOI 10.1056/NEJMoa1908483

The FIELD study: former professional footballers died from neurodegenerative disease about 3.5 times more often than matched members of the general population, with roughly a fivefold excess for Alzheimer's disease — while dying less often from common cancers and heart disease.

What it does not say

It measured no heading exposure at all, so it establishes an association with a football career rather than with heading; all-male, all-Scottish, dominated by eras with heavier balls. Funded by The FA and the PFA.

EvidenceCohort secondary analysis2021

Association of Field Position and Career Length With Risk of Neurodegenerative Disease in Male Former Professional Soccer Players

Russell ER, Mackay DF, Stewart K, MacLean JA, Pell JP, Stewart W
JAMA Neurology 78(9):1057–1063

Institute of Neuroscience and Psychology, University of GlasgowDOI 10.1001/jamaneurol.2021.2403

Risk rose with longer careers and was markedly higher for outfield players than goalkeepers — the closest thing football has to dose-response evidence implicating repetitive head impacts rather than the sport itself.

What it does not say

Field position is only a proxy for heading exposure; goalkeepers differ from outfield players in collisions, training load and body composition too, and no head-impact data were recorded.

EvidenceNationwide register cohort, 6007 players2023

Neurodegenerative disease among male elite football (soccer) players in Sweden: a cohort study

Ueda P, Pasternak B, Lim C-E, et al.
The Lancet Public Health 8(4):e256–e265

Clinical Epidemiology Division, Karolinska Institutet, StockholmDOI 10.1016/S2468-2667(23)00027-0

An independent Swedish cohort replicated the elevated dementia risk and the outfield-versus-goalkeeper gradient, with no elevated risk in goalkeepers.

What it does not say

The effect is considerably smaller than the Scottish estimate, Parkinson's disease was actually less common among players, and all-cause mortality was slightly lower — the picture is more nuanced than 'football causes neurodegeneration'.

ContestedConsensus statement2013

Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012

McCrory P, Meeuwisse WH, Aubry M, et al.
British Journal of Sports Medicine 47(5):250–258

Florey Institute of Neuroscience and Mental Health, University of Melbourne (first author's affiliation at time of publication)DOI 10.1136/bjsports-2013-092313

It replaced concussion grading scales with individualised, symptom-led assessment and introduced the SCAT3, moving the sport away from same-day return to play.

What it does not say

Same authorship-integrity caveat as the Berlin statement; its claim that effects typically resolve within 7–10 days has since been substantially revised in light of persisting post-concussive symptom evidence.

Heat & environment

Competing in conditions the body was not built to compete in.

Consensus2023

IOC consensus statement on recommendations and regulations for sport events in the heat

Racinais S, Hosokawa Y, Akama T, et al.
British Journal of Sports Medicine 57(1):8–25

Research and Scientific Support Department, Aspetar, DohaDOI 10.1136/bjsports-2022-105942

The current international template for competing safely in heat: environmental monitoring before and during events, ice, shade and cooling provision, acclimatisation and hydration protocols, and a field-to-hospital pathway for exertional heat stroke.

What it does not say

Consensus rather than trial evidence, and it deliberately stops short of a single universal cancellation threshold — which is precisely where football's policy inconsistency lives.

EvidenceObservational analysis of 64 matches2015

The association of environmental heat stress with performance: analysis of the 2014 FIFA World Cup Brazil

Nassis GP, Brito J, Dvorak J, Chalabi H, Racinais S
British Journal of Sports Medicine 49(9):609–613

National Sports Medicine Programme, Aspetar, DohaDOI 10.1136/bjsports-2014-094449

In hot, humid conditions elite teams did not cover less total distance or score fewer goals — they sprinted about 10% less and passed more accurately, self-regulating intensity to protect the shape of the match.

What it does not say

A single tournament with few matches in the high heat-stress category, no individual physiological data, and tactics confound any environmental reading — it describes behaviour, not health risk.

Youth & maturation

Growth, selection bias, specialisation and the academy years.

Consensus2015

International Olympic Committee consensus statement on youth athletic development

Bergeron MF, Mountjoy M, Armstrong N, et al.
British Journal of Sports Medicine 49(13):843–851

Youth Sports of the Americas, Birmingham, AlabamaDOI 10.1136/bjsports-2015-094962

The foundational international position that youth development should be built around health, psychosocial wellbeing and long-term participation rather than early selection and early specialisation.

What it does not say

Consensus opinion, generic across sports, and now a decade old — it predates most of the bio-banding and academy-workload literature that operationalises its principles.

EvidenceObservational analysis, 2175 players2005

The relative age effect in youth soccer across Europe

Helsen WF, van Winckel J, Williams AM
Journal of Sports Sciences 23(6):629–636

Department of Kinesiology, KU LeuvenDOI 10.1080/02640410400021310

Players born in the first quarter of the selection year are systematically over-represented in national youth teams and elite club squads across Europe. Talent identification is measurably confounded by birth date.

What it does not say

It demonstrates the bias but cannot isolate the mechanism — physical maturity, coach expectancy or accumulated practice — and predates most modern academy structures.

EvidenceCase-control study, 1190 athletes2015

Sports-specialized intensive training and the risk of injury in young athletes: a clinical case-control study

Jayanthi NA, LaBella CR, Fischer D, Pasulka J, Dugas LR
The American Journal of Sports Medicine 43(4):794–801

Stritch School of Medicine, Loyola University ChicagoDOI 10.1177/0363546514567298

Young athletes who specialise in a single sport carry an independent higher risk of injury and of serious overuse injury, over and above total training hours.

What it does not say

A US sports-medicine clinic sample rather than a football academy, with self-reported training exposure; its null finding on growth rate sits in tension with the football-specific maturation literature.

ConsensusApplied framework review2017

Bio-banding in Sport: Applications to Competition, Talent Identification, and Strength and Conditioning of Youth Athletes

Cumming SP, Lloyd RS, Oliver JL, Eisenmann JC, Malina RM
Strength and Conditioning Journal 39(2):34–47

Department for Health, University of BathDOI 10.1519/SSC.0000000000000281

The rationale and method for grouping young players by biological maturity rather than chronological age — the paper most academy bio-banding programmes cite as their origin.

What it does not say

A conceptual review, not a trial: benefits for talent identification and injury reduction remain largely inferred, and the non-invasive maturity equations carry real prediction error at the individual level — which matters when the output is a selection decision.

EvidenceSix-year prospective cohort, 292 players2009

Investigation of growth, development, and factors associated with injury in elite schoolboy footballers: prospective study

Johnson A, Doherty PJ, Freemont A
BMJ 338:b490

Manchester United Football Club academy, with the University of ManchesterDOI 10.1136/bmj.b490

Maturity status, training hours and playing hours together explained about 48% of the variance in injury incidence in an elite academy, with match play carrying roughly seven times the exposure rate of training.

What it does not say

Often over-claimed: once adjusted for training time, playing time, height and position, maturity status alone did not significantly predict injury incidence. Single club, boys only.

Women's football

The specific evidence — and the size of the gap where it should be.

EvidenceProspective cohort, 15 clubs2024

UEFA Women's Elite Club Injury Study: a prospective study on 1527 injuries over four consecutive seasons 2018/2019 to 2021/2022

Hallén A, Tomás R, Ekstrand J, et al.
British Journal of Sports Medicine 58(3):128–136

Football Research Group, Linköping UniversityDOI 10.1136/bjsports-2023-107133

The first multinational injury benchmark for elite women's football: about 35 time-loss injuries per team per season, match injury rate nearly four times training, thigh muscle injuries most frequent — and ACL injury by far the most costly at a median 292 days lost.

What it does not say

Fifteen clubs over four seasons, so ACL burden estimates rest on relatively few cases and precision is limited.

ContestedSystematic literature review2011

The epidemiology of anterior cruciate ligament injury in football (soccer): a review of the literature from a gender-related perspective

Waldén M, Hägglund M, Werner J, Ekstrand J
Knee Surgery, Sports Traumatology, Arthroscopy 19(1):3–10

Department of Medical and Health Sciences, Linköping UniversityDOI 10.1007/s00167-010-1172-7

The reference synthesis establishing that female footballers sustain ACL injuries at a higher rate than male footballers, with the difference concentrated in match play rather than training.

What it does not say

The authors themselves flag genuine controversy over the magnitude: the frequently repeated 'two to three times' figure is not stable across studies and several studies found no difference at all. Treat any single multiplier quoted publicly as contested.

ContestedSystematic review and meta-analysis, 28 studies2019

'What's my risk of sustaining an ACL injury while playing football (soccer)?' A systematic review with meta-analysis

Montalvo AM, Schneider DK, Silva PL, et al.
British Journal of Sports Medicine 53(21):1333–1340

Department of Athletic Training, Florida International University, MiamiDOI 10.1136/bjsports-2016-097261

Per hour of football played, women tear their ACL 2.2 times more often than men, and the gap holds across every level of the game.

What it does not say

Routinely mis-cited: because men played far more exposure hours in the included studies, the raw incidence proportion was actually higher in men, and matched-cohort comparisons showed no difference in relative risk. Heterogeneity was very high.

ContestedSystematic review and Bayesian meta-analysis, 78 studies2020

The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis

McNulty KL, Elliott-Sale KJ, Dolan E, et al.
Sports Medicine 50(10):1813–1827

Department of Sport, Exercise and Rehabilitation, Northumbria UniversityDOI 10.1007/s40279-020-01319-3

Across the available literature, menstrual cycle phase has only a trivial average effect on exercise performance — far smaller than popular claims imply.

What it does not say

The authors rate the overall quality of evidence as low, individual variation may be large even where the group mean is trivial, and almost no included study used hormonal verification of cycle phase. There is essentially no adequately powered evidence on cycle phase and injury risk in football.

ConsensusMethodological guidance2021

Methodological Considerations for Studies in Sport and Exercise Science with Women as Participants: A Working Guide for Standards of Practice for Research on Women

Elliott-Sale KJ, Minahan CL, de Jonge XAKJ, et al.
Sports Medicine 51(5):843–861

SHAPE Research Centre, Nottingham Trent UniversityDOI 10.1007/s40279-021-01435-8

The best single explanation of why the female evidence base is weak methodologically and not merely thin — and the standards any new study on female athletes should be held to.

What it does not say

Guidance rather than evidence; adoption across the field remains partial, so most newly published female-athlete research still falls short of it.

EvidenceBibliometric review, 5261 publications2021

'Invisible Sportswomen': The Sex Data Gap in Sport and Exercise Science Research

Cowley ES, Olenick AA, McNulty KL, Ross EZ
Women in Sport and Physical Activity Journal 29(2):146–151

Liverpool John Moores UniversityDOI 10.1123/wspaj.2021-0028

Only 34% of participants in leading sport and exercise science research were female; 6% of publications studied females exclusively and 31% studied males exclusively. This quantifies the gap women's football inherits.

What it does not say

Participant counts are skewed by a few very large epidemiological datasets, and it counts representation without assessing whether female data were analysed separately — so it likely understates the practical gap.

EvidenceProspective cohort, 5 seasons2018

A comparison of injuries in elite male and female football players: A five-season prospective study

Larruskain J, Lekue JA, Diaz N, Odriozola A, Gil SM
Scandinavian Journal of Medicine and Science in Sports 28(1):237–245

University of the Basque Country (UPV/EHU), BilbaoDOI 10.1111/sms.12860

A rare same-club male and female comparison — and a useful corrective: overall injury incidence was 30–40% higher in the men, driven by contusions, even though the women's ACL burden was higher.

What it does not say

One club, one country, five seasons — the sample cannot settle the question, only complicate the assumption that women's football is uniformly higher-risk.

Open disputes

Four things football repeats with confidence that the evidence does not support. Published because the entries we do not flag then mean something.

01

The workload ratio is mathematically broken — and still on the dashboard

The acute:chronic workload ratio became the default load metric in professional sport after 2016. It has since been shown that the acute period sits inside the chronic average, so the two are coupled by construction and will correlate even with random data. The critique is a mathematical argument, not an interpretation, and it has not been rebutted on its own terms.

What survives is the underlying idea: rapid change in load matters more than absolute load, and undertrained players are fragile. What does not survive is the specific number. If your club is still red-flagging players on a ratio threshold, you are acting on an artefact.

Read: Gabbett 2016 · Hulin 2016 · Impellizzeri 2020, 2021 · Lolli 2019 · Griffin 2020
02

The concussion consensus lineage has an authorship problem

Paul McCrory, first author of the 2012 Zurich and 2016 Berlin concussion consensus statements and former Editor-in-Chief of the British Journal of Sports Medicine, has since accrued seventeen retractions and expressions of concern on roughly seventy-eight further articles, for plagiarism and duplicate publication.

The retractions concern his single-authored editorials, reviews and letters. Neither consensus statement has itself been retracted, and the 2023 Amsterdam statement supersedes both. We state the distinction precisely because both the temptation to bury it and the temptation to overstate it are real — and because most football protocols in force today descend from that lineage.

Read: McCrory 2013, 2017 · Patricios 2023 · BMJ Group retraction notices
03

The most-quoted number in women's football is contested

The claim that female footballers tear their ACL two to three times more often than men is repeated constantly. The best meta-analysis reports 2.2 times per exposure hour — but in that same dataset the raw incidence proportion was higher in men, matched-cohort comparisons showed no difference in relative risk, and heterogeneity was very high.

The ACL burden in women's elite football is real and severe — a median 292 days lost per injury in the UEFA women's study. That is the finding worth acting on. The multiplier is the finding worth quoting carefully.

Read: Montalvo 2019 · Waldén 2011 · Hallén 2024 · Larruskain 2018
04

Prevention that works is not being done

The Nordic hamstring exercise roughly halves hamstring injury rates. Across 150 elite club-seasons, the programme was completed in full in 10.7% of them. Meanwhile hamstring injury has risen from 12% to 24% of all injuries in men's professional football over two decades.

This is not an evidence problem. It is an implementation problem — which means it is a leadership problem. The most valuable research question in football medicine is no longer what works, but what makes a club actually do it.

Read: Petersen 2011 · van Dyk 2019 · Bahr 2015 · Ekstrand 2023
The Constitution of Football Intelligence

Seven articles.
How we are obliged to behave.

A manifesto states what we believe. A constitution states what we are bound to do — particularly when it is commercially inconvenient.

These articles govern what the Institute publishes, who it accepts money from, and how it labels the difference between evidence and opinion.

The Institute exists to advance football through better understanding and better decisions. It does not exist to sell technology, to represent a vendor, to promote a methodology for commercial gain, or to flatter any club, federation or company.

Understanding before informationDecisions before dashboardsPeople before systems

The Institute accepts no funding, sponsorship, equity, or commercial relationship that could reasonably be understood to influence its published conclusions. Where any relationship exists, it is disclosed at the top of the work, not in a footnote.

No paid conclusionsFull disclosure at point of publicationThe right to publish unwelcome findings

Every claim published by the Institute is labelled by its epistemic status. Readers are entitled to know the difference between what is demonstrated, what is observed, what is inferred and what is believed — and to disagree with the last three.

Evidence: demonstrated by researchObservation: seen directly and repeatedlyInterpretation: our reading of the evidenceOpinion: our position, offered as such

Football exists for people. The players are not assets, the staff are not resources, and the supporters are not an audience segment. Any recommendation that improves a number while degrading a person is rejected by this Institute regardless of its efficiency.

Player welfare is not a constraint on performance. It is a component of it.

No intelligence is analysed in isolation. Findings in performance must be tested against medicine, findings in medicine against psychology, findings in technology against leadership. Connected problems require connected inquiry.

One system, seven intelligencesCross-disciplinary review before publication

Complexity is not a sign of rigour. If the work cannot be explained to an intelligent person inside football in plain language, the work is not finished.

No jargon without definitionNo conclusion without a 'so what'Every publication readable by a coach and a chief executive

The Institute optimises for relevance in ten years, not attention in ten days. It does not chase news cycles, does not publish for volume, and does not measure its success in impressions.

Publish less, mean moreBuild intellectual property, not content
Positioning

What this is.
What it is not.

What this is

  • +The single open source for football technology advancement
  • +A published, dated record of what is actually landing
  • +A cross-disciplinary community of football decision-makers
  • +A neutral place to evaluate technology honestly
  • +A movement for a more intelligent, more human game

What it is not

  • A technology company or a software vendor
  • A consultancy selling a proprietary methodology
  • A media outlet chasing the news cycle
  • An agency, an intermediary, or a recruitment business
  • Aligned to any club, federation, league or supplier
The standard of evidence

Every claim we publish is labelled by what kind of claim it is.

Evidence Demonstrated by research we can cite
Observation Seen directly, repeatedly, inside the game
Interpretation Our reading of what the evidence means
Opinion Our position, offered as a position

Where the science is made

The departments behind the papers. Individuals are named only where the role is verified on the organisation's own current page.

Football Research Group

Linköping University · Sweden

Runs the UEFA Elite Club Injury Study and its women's counterpart — the largest homogeneous injury database in professional football, with roughly 22,000 injuries across more than two million exposure hours since 2001.

Prof. Martin Hägglund leads the group; Prof. Jan Ekstrand founded it and remains its long-standing principal investigator.

Visit →

Oslo Sports Trauma Research Center

Norwegian School of Sport Sciences · Norway

Founded 2000. Research on risk factors, injury mechanisms and prevention, with football among its three priority sports. Origin of the OSTRC Questionnaire on Health Problems, now the standard method for capturing overuse injury burden worldwide.

Chaired by Prof. Roald Bahr and Prof. Lars Engebretsen. A FIFA Medical Centre of Excellence and one of the original IOC research centres.

Visit →

Aspetar Orthopaedic and Sports Medicine Hospital

Aspire Zone Foundation, Doha · Qatar

Clinical sports medicine, orthopaedic surgery and scientific support for elite athletes, alongside a substantial research programme in hamstring and groin injury, return to play, and heat.

Prof. Marco Cardinale is Executive Director of Research and Scientific Support. Publishes the Aspetar Clinical Practice Guidelines free to practitioners.

Visit →

Academic Center for Evidence-based Sports medicine (ACES)

Amsterdam UMC · Netherlands

Integrated diagnostics, treatment and rehabilitation for injured athletes across orthopaedics, sports cardiology, neurology and psychiatry, with clinical partners in professional football.

Led by Hans Tol, Gino Kerkhoffs and Vincent Gouttebarge. One of the eleven IOC research centres.

Visit →

Amsterdam Collaboration on Health & Safety in Sports

Amsterdam UMC and VU Amsterdam · Netherlands

Established 2013. Implementation research — the discipline of why proven prevention programmes are not actually used, which is football's central prevention problem.

Coordinated by Prof. Evert Verhagen.

Visit →

FIFA Medical

Fédération Internationale de Football Association, Zurich · Switzerland

The successor to F-MARC, which ran from 1994 and produced the FIFA 11+. Operates a published medical strategy across 211 member associations, an accredited network of Medical Centres of Excellence, and the FIFA Medical Network education platform.

Dr Andrew Massey is Director of the Medical Department.

Visit →

UEFA Medical Committee

Union of European Football Associations, Nyon · Switzerland

Sets medical policy for European competition and commissions the Elite Club Injury Study. UEFA separately funds independent research through its Research Grant Programme and its Medical and Anti-Doping Research Grant Programme.

Chaired by Prof. Tim Meyer, with Dr Charlotte Cowie as Deputy Chair.

Visit →

Research Institute for Sport and Exercise Sciences

Liverpool John Moores University · United Kingdom

One of the world's leading applied football physiology groups — nutrition, muscle metabolism, carbohydrate periodisation and training load.

Visit →

Centre for Health and Injury and Illness Prevention in Sport

University of Bath · United Kingdom

Holds the Premier League academy injury, illness and growth surveillance programme. Strength in growth, maturation and bio-banding.

Prof. Sean Cumming is a leading authority on maturation and bio-banding in academy football.

Visit →

The FA Performance Medicine and Research

The Football Association, St George's Park · United Kingdom

Runs national-team medical provision and commissions large-scale football research, including the FIELD study into neurodegenerative disease in former professionals, co-funded with the PFA.

Dr Charlotte Cowie is Head of Performance Medicine.

Visit →

Research cited from

Institutions whose published work appears in this library. Names only — no logos, by policy.

FIFAUEFAThe Football AssociationPremier LeagueInternational Olympic CommitteeAspetarOslo Sports Trauma Research CenterLinköping UniversityAmsterdam UMCNorwegian School of Sport SciencesLiverpool John Moores UniversityUniversity of BathKU LeuvenLa Trobe UniversityUniversity of QueenslandKarolinska InstitutetUniversity of GlasgowMcMaster UniversityNorthumbria UniversityUniversity of CopenhagenStanford UniversityAustralian Institute of Sport
Independence and non-affiliation

FootballIntelligence.IO is an independent research and education body. It is not affiliated with, endorsed by, sponsored by or connected to FIFA, UEFA, the International Olympic Committee, any national association, league, club or commercial supplier. All organisation names and trade marks referred to on this site are the property of their respective owners and are used solely to identify the source of cited published research. We display no third-party logos, by deliberate policy: an institution that borrows another's letterhead has not earned the claim it is making.

Use it

Football is not short of data. It is short of intelligence.

This library is free, and it will keep growing. If your organisation is making a decision that one of these papers speaks to, that is what it is here for.