Characteristics of included studies
| Study | Study design | Sample and/or sport | Number/rate of CMSI or ‘lower leg’ | Risk factors | Specific outcome | Length of tracking |
| Bengtsson et al (2013)7 | Prospective cohort | 27 European professional football (soccer) teams from 10 countries—621 individual players | CMSI RR=1.13/1000 hours match exposure | Match load, between match recovery, match characteristics | Acute calf muscle injury diagnosed and recorded on electronic injury registry by club medical staff | 11 seasons |
| Brooks and Kemp (2011)10 | Prospective cohort | 899 players from 14 English Premiership rugby union clubs | NA | Playing position, match-related injury | Acute calf muscle strain injury diagnosed and reported by club medical staff | 4 seasons |
| Hägglund et al (2013)8 | Prospective cohort | 1401 players from 26 soccer clubs across 10 countries | CMSI (n=306) | Previous calf muscle injury, previous other muscle injuries, age, stature, body mass, playing position | Acute calf muscle injury as diagnosed by club medical staff | 2001–2010 seasons |
| Orchard et al (2014)11 | Prospective cohort | 1607 elite Australian Rules football players | CMSI (n=140) | Age, height, weight, BMI, month, environmental conditions, calf injury within 8 weeks, previous calf injury beyond 8 weeks, older players (age>23), past quadriceps injury beyond 8 weeks | Calf strain injury assessment and diagnosis by club medical staff, with or without imaging investigations | 1992–1999 competition seasons |
| Carling et al (2015)14 | Prospective observational | 25 professional soccer players from one club | Calf IRR=4.1/1000 hours match exposure | Fixture congestion and match characteristics | Calf muscle injury as diagnosed and recorded by club | 6 seasons (2009–2015) |
| Nilstad et al (2014)23 | Prospective cohort | 173 elite female Norwegian soccer players from 12 teams | ‘Leg/foot’ injuries (n=28) | Previous knee injury, age, BMI, lower extremity strength, dynamic balance, knee biomechanics and laxity, foot posture (pronation) | Calf injuries (as captured leg/foot injury data) | 1 season |
| McKay et al (2001)25 | Prospective cohort | Elite and recreational Australian basketball players—190 players | ‘Calf/anterior leg’ injuries (n=12) | Gender, level of competition | Calf muscle injury (as captured in ‘Calf/Anterior Leg' injuries data) | 2 seasons |
| Faude et al (2006)22 | Prospective cohort | 143 German national league soccer players over 12 teams | ‘Lower leg’ injuries (n=19) | Anthropometric measurements, playing position, injury history, training and match exposure time | Calf muscle injury (as captured in ‘lower leg’ data pool) | 1 season |
| Korkia et al (1994)13 | Prospective study | 155 British triathletes | ‘Lower leg’ injuries (n=13) | Training history, injury history | Calf muscle injuries (as reported in ‘lower leg’ injury) as self-reported questionnaire | 1 season |
| Gabbett and Domrow (2007)24 | Prospective cohort | 183 subelite rugby league players | ‘Thigh and calf’ injuries 41.3/1000 hours | Training load and injury data according to competition phases | Calf muscle injury (as described in combined ‘Thigh and Calf’ data) | 2 seasons |
BMI, body mass index; CMSI, calf muscle strain injury; IRR, injury rate ratio; NA, not applicable; RR, rate ratio.