Table 1.
List of candidate variables with a summary of the units of measurement, methods and reliability of measurement, and data type
| Candidate variable type | Name of candidate variable | Candidate variable identification no. | Measurement unit | Measurement method | Reliability (if applicable/available) | Validity (if applicable/available) | Data type | |
| Anthropometric | Age | 1 | Years | Medical records | – | – | Cont. | |
| Height | 2 | Centimetres (cm) | Standing height measure | – | – | Cont. | ||
| Weight | 3 | Kilograms (kg) | Digital scales | – | – | Cont. | ||
| Medical history | Within 3 years prior to PHE, the frequency of: | Foot/ankle injuries | 4 | Count | Medical records | – | – | Dis./cont. |
| Hip/groin injuries | 5 | Count | Medical records | – | – | Dis./cont. | ||
| Knee injuries | 6 | Count | Medical records | – | – | Dis./cont. | ||
| Shoulder injuries | 7 | Count | Medical records | – | – | Dis./cont. | ||
| Lumbar spine injuries | 8 | Count | Medical records | – | – | Dis./cont. | ||
| Iliopsoas injuries | 9 | Count | Medical records | – | – | Dis./cont. | ||
| Hip adductor IMIs | 10 | Count | Medical records | – | – | Dis./cont. | ||
| Hamstring IMIs | 11 | Count | Medical records | – | – | Dis./cont. | ||
| Quadriceps IMIs | 12 | Count | Medical records | – | – | Dis./cont. | ||
| Calf IMIs | 13 | Count | Medical records | – | – | Dis./cont. | ||
| Within 3 years prior to PHE, the most recent | Foot/ankle injury | 14 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | |
| Hip/groin injury | 15 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Knee injury | 16 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Shoulder injury | 17 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Lumbar spine injury | 18 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Iliopsoas injury | 19 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Hip adductor IMI | 20 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Hamstring IMI | 21 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Quadriceps IMI | 22 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Calf IMI | 23 | Never, <6 months, 6–12 months, >12 months. | Medical records | – | – | Cat. | ||
| Musculoskeletal | Mean PROM hip internal rotation | 24 | Degrees | Digital inclinometer+ROM | Intrarater ICC=0.9042 | – | Cont. | |
| Mean PROM hip external rotation | 25 | Degrees | Digital inclinometer+ROM | Intrarater ICC=0.9042 | – | Cont. | ||
| Mean hip flexor length | 26 | Degrees | Digital inclinometer+Thomas Test | Inter-rater ICC=0.8943 | Concurrent validity with handheld goniometer (r=0.86–0.92)43 and IMC (r=0.49–0.53)44 | Cont. | ||
| Mean hamstring length/neural mobility | 27 | Degrees | Digital inclinometer+SLR | Intrarater ICC=0.95–0.9845 Inter-rater ICC=0.80–0.9745 |
Construct validity with handheld inclinometer (r=0.98–0.99)46 | Cont. | ||
| Mean calf muscle length | 28 | Degrees | Digital inclinometer+WBL | Inter-rater ICC=0.80–0.9547 48 Intrarater ICC=0.8848 |
Concurrent validity of inclinometer with 2D motion analysis (r range=0.71–0.76)49 | Cont. | ||
| Strength/power | Max. leg extension power difference | 29 | Normalised watts per kilo (W/kg−0.67) | Double leg press using Keiser Air 300 machine | Test–retest ICC=0.88650 | Concurrent validity with mounted force plate (r=0.952)51 | Cont. | |
| Mean of max. leg extension power | 30 | Normalised watts per kilo (W/kg−0.67) | Double leg press using Keiser Air 300 machine | Test–retest ICC=0.88650 | Concurrent validity with mounted force plate (r=0.977)51 | Cont. | ||
| Max. leg extension velocity difference | 31 | Peak velocity (m.s-1) | Double leg press using Keiser Air 300 machine | Test–retest ICC=0.79250 | Concurrent validity with mounted force plate (r=0.999)51 | Cont. | ||
| Mean of max. leg extension velocity | 32 | Peak velocity (m.s-1) | Double leg press using Keiser Air 300 machine | Test–retest ICC=0.79250 | Concurrent validity with mounted force plate (r=0.999)51 | Cont. | ||
| Max leg extension force difference | 33 | Normalised peak force (N/kg−0.67) | Double leg press using Keiser Air 300 machine | Test–retest ICC=0.91450 | Concurrent validity with mounted force plate (r=0.994)51 | Cont. | ||
| Mean of max. leg extension force | 34 | Normalised peak force (N/kg−0.67) | Double leg press using Keiser Air 300 machine | Test–retest ICC=0.91450 | Concurrent validity with mounted force plate (r=0.994)51 | Cont. | ||
| CMJ Force per kg of body mass | 35 | Force per kg (N/kg) | CMJ+force plate | Test–retest ICC=0.80–0.8852 | Concurrent validity with other force plate (r≥0.99)53 | Cont. | ||
| CMJ height | 36 | Centimetres (cm) | CMJ+force plate | Test–retest ICC=0.80–0.8852 | Concurrent validity with other force plate (r≥0.99)53 | Cont. | ||
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
Cat., categorical; CMJ, countermovement jump; Cont., Continuous; dis./cont., discrete treated as continuous; ICC, intraclass correlation coefficient; I-IMI, index indirect muscle injury; IMC, inertial motion capture; IMI, indirect muscle injury; m.s-1, metres per second; PHE, periodic health examination; PROM, passive range of movement; ROM, range of movement; SLR, straight leg raise; WBL, weight-bearing lunge.