Table 3.
Characteristics of included participants
| Characteristics/candidate variables | Min | Lower quartile | Median | Upper quartile | Max. | Freq. (%)—if categorical | Missing values n (%) | |
| Anthropometrics | ||||||||
| 1. Age at PHE (years) | 16.01 | 17.80 | 19.69 | 23.56 | 39.59 | – | 0 (0) | |
| 2. Height (cm) | 164.3 | 176.0 | 180.0 | 185.5 | 195.0 | – | 18 (5.68) | |
| 3. Weight (kg) | 56.8 | 69.2 | 73.6 | 80.0 | 94.0 | – | 18 (5.68) | |
| Past medical history | ||||||||
| Within 3 years prior to PHE, freq. of: | ||||||||
| 4. Foot/ankle injuries | 0 | 0 | 1 | 2 | 7 | – | 0 (0) | |
| 5. Hip/groin injuries | 0 | 0 | 0 | 1 | 5 | – | 0 (0) | |
| 6. Knee injuries | 0 | 0 | 0 | 1 | 3 | – | 0 (0) | |
| 7. Shoulder injuries | 0 | 0 | 0 | 0 | 2 | – | 0 (0) | |
| 8. Lumbar spine injuries | 0 | 0 | 0 | 0 | 3 | – | 0 (0) | |
| 9. Iliopsoas IMIs | 0 | 0 | 0 | 0 | 2 | – | 0 (0) | |
| 10. Hip adductor IMIs | 0 | 0 | 0 | 0 | 3 | – | 0 (0) | |
| 11. Hamstring IMIs | 0 | 0 | 0 | 1 | 6 | – | 0 (0) | |
| 12. Quadriceps IMIs | 0 | 0 | 0 | 0 | 3 | – | 0 (0) | |
| 13. Calf IMIs | 0 | 0 | 0 | 0 | 4 | – | 0 (0) | |
| Within 3 years prior to PHE, most recent: | ||||||||
| 14. Foot/ankle injury | Never | – | – | – | – | – | 143 (45.11) | 0 (0) |
| <6 months | – | – | – | – | – | 43 (13.56) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 34 (10.73) | 0 (0) | |
| >12 months | – | – | – | – | – | 97 (30.60) | 0 (0) | |
| 15. Hip/groin injury | Never | – | – | – | – | – | 217 (68.45) | 0 (0) |
| <6 months | – | – | – | – | – | 23 (7.26) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 23 (7.26) | 0 (0) | |
| >12 months | – | – | – | – | – | 54 (17.03) | 0 (0) | |
| 16. Knee injury | Never | – | – | – | – | – | 201 (63.41) | 0 (0) |
| <6 months | – | – | – | – | – | 15 (4.73) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 31 (9.78) | 0 (0) | |
| >12 months | – | – | – | – | – | 70 (22.08) | 0 (0) | |
| 17. Shoulder injury | Never | – | – | – | – | – | 297 (93.69) | 0 (0) |
| <6 months | – | – | – | – | – | 6 (1.89) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 4 (1.26) | 0 (0) | |
| >12 months | – | – | – | – | – | 10 (3.15) | 0 (0) | |
| 18. Lumbar spine injury | Never | – | – | – | – | – | 264 (83.28) | 0 (0) |
| <6 months | – | – | – | – | – | 8 (2.52) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 9 (2.84) | 0 (0) | |
| >12 months | – | – | – | – | – | 36 (11.36) | 0 (0) | |
| 19. Iliopsoas IMI | Never | – | – | – | – | – | 287 (90.54) | 0 (0) |
| <6 months | – | – | – | – | – | 2 (0.63) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 9 (2.84) | 0 (0) | |
| >12 months | – | – | – | – | – | 19 (5.99) | 0 (0) | |
| 20. Hip adductor IMI | Never | – | – | – | – | – | 263 (82.92) | 0 (0) |
| <6 months | – | – | – | – | – | 18 (5.68) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 12 (3.79) | 0 (0) | |
| >12 months | – | – | – | – | – | 24 (7.57) | 0 (0) | |
| 21. Hamstring IMI | Never | – | – | – | – | – | 231 (72.87) | 0 (0) |
| <6 months | – | – | – | – | – | 11 (3.47) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 30 (9.46) | 0 (0) | |
| >12 months | – | – | – | – | – | 45 (14.20) | 0 (0) | |
| 22. Quadriceps IMI | Never | – | – | – | – | – | 267 (84.23) | 0 (0) |
| <6 months | – | – | – | – | – | 7 (2.21) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 13 (4.10) | 0 (0) | |
| >12 months | – | – | – | – | – | 30 (9.46) | 0 (0) | |
| 23. Calf IMI | Never | – | – | – | – | – | 283 (89.27) | 0 (0) |
| <6 months | – | – | – | – | – | 11 (3.47) | 0 (0) | |
| 6–12 months | – | – | – | – | – | 6 (1.89) | 0 (0) | |
| >12 months | – | – | – | – | – | 17 (5.36) | 0 (0) | |
| Musculoskeletal examination | ||||||||
| 24. Mean PROM hip IR (deg.) | 9.5 | 22.5 | 33.0 | 40.0 | 55.0 | – | 20 (6.31) | |
| 25. Mean PROM hip ER (deg.) | 17.5 | 33.5 | 38.5 | 43.0 | 62.0 | – | 20 (6.31) | |
| 26. Mean hip flexor length (deg.) | −7.0 | 3.5 | 9.0 | 15.0 | 55.0 | – | 23 (7.26) | |
| 27. Mean hamstring/neural mobility length (deg.) | 45.0 | 84.0 | 90.0 | 90.0 | 102.0 | – | 20 (6.31) | |
| 28. Mean calf muscle length (deg.) | 9.5 | 25.0 | 30.0 | 36.0 | 57.5 | – | 20 (6.31) | |
| Strength/power tests | ||||||||
| 29: Max. leg extension power difference (W/kg−0.67) | −11.94 | −1.55 | 0.29 | 1.77 | 15.26 | – | 45 (14.20) | |
| 30: Mean of max. leg extension power (W/kg−0.67) | 23.01 | 42.12 | 46.52 | 51.95 | 78.69 | – | 45 (14.20) | |
| 31: Max. leg extension velocity difference (m.s −1) | −0.34 | −0.05 | 0.02 | 0.11 | 0.40 | – | 41 (12.93) | |
| 32: Mean of max. leg extension velocity (m.s −1) | 1.02 | 1.68 | 1.84 | 1.98 | 2.35 | – | 41 (12.93) | |
| 33: Max leg extension force difference (N/kg−0.67) | −83.59 | −6.18 | 1.17 | 4.40 | 55.41 | – | 45 (14.20) | |
| 34: Mean of max. leg extension force (N/kg−0.67) | 50.19 | 98.59 | 101.44 | 113.44 | 217.95 | – | 45 (14.20) | |
| 35: CMJ force per kg of body mass | 20.20 | 23.40 | 25.40 | 28.04 | 39.20 | – | 42 (13.25) | |
| 36: CMJ height (cm) | 28.7 | 37.3 | 40.2 | 43.0 | 58.0 | – | 42 (13.25) |
Note that for variables that state between limb differences (ie, variables 29, 31 and 33), positive values indicate greater left limb values compared with right limb values; negative values indicate greater right limb values compared to left limb values.
N (note: N/kg–0.67 has a scaling factor to normalise force to body mass).54 W (note: W/kg–0.67 has a scaling factor to normalise force to body mass).54
CMJ, countermovement jump; deg., degrees; ER, external rotation; IMI, indirect muscle injury; IR, internal rotation; m.s-1, metres per second; PHE, periodic health examination; PROM, passive range of movement.