Table 4.
Study characteristics—asymmetries examined pre and post a loading protocol/task
| Study | Subjects (Sex, age, sport) | Physical load/fatigue loading protocol | Measure of fatigue | Task/procedure | Outcome measures | Asymmetry equation |
|---|---|---|---|---|---|---|
| Bell et al. [7] |
n = 40 20 M (20.9 ± 1.2)/ 20 F (21.2 ± 1.4) Recreationally active |
Exercise loading protocol based on literature: warm-up–running course––30 s wall sit–10 fast-paced two-legged vertical jumps––30 s prone plank | Loading protocol was repeated until a RPE of 17 on the scale by Borg was reached | Jump landings | Peak vGRF, loading rate, LESS score | % asymmetry: ([dominant limb – non-dominant limb]/ 1/2 [dominant limb + non-dominant limb]) × 100% |
| Bishop et al. [38] |
n = 18 18 M (16.89 ± 0.32) Elite academy soccer players |
Five Soccer matches (played for a minimum of 60 min in each match) | Not measured | SLCMJ, SLDJ |
SLCMJ: jump height, peak force, concentric impulse SLDJ: jump height, ground contact time, RSI Global positioning system data |
Percentage difference: 100/ (maximum value) × (minimum value) × -1 + 100 |
| Bromley et al. [16] |
n = 14 14 M (17.6 ± 0.5) Elite soccer players |
Single 90-min soccer match | Not measured | SLCMJ | Jump height, peak force, eccentric impulse, concentric impulse, peak landing force, peak landing impulse | Percentage difference: 100/ (maximum value) × (minimum value) × − 1 + 100 |
| Delextrat et al. [37] |
n = 14 14 F (26.1 ± 4.6) Amateur soccer players |
Modified Loughborough Intermittent Shuttle Test | RPE | Isokinetic strength assessment | Peak torque of the quadriceps, peak torque of the hamstrings, Hecc:Qcon | Calculated afterwards by the authors with percentage difference: 100/ (maximum value) × (minimum value) × − 1 + 100 |
| Radzak et al. [35] |
n = 20 14 M / 6 F (20.8 ± 2.48) No sporting background mentioned |
Speed blinded exhaustive loading protocol |
RPE Until volitional exhaustion |
Gait analysis | Kinematic data (joint angles - ankle, knee, hip), kinetic data (external joint moment - ankle, knee, hip), GRF, stiffness, spatio-temporal parameters |
Symmetry angle: [(45° - arctan (Xleft/Xright)/90°)] × 100% X = the mean value for a variable on each leg |
| Webster et al. [36] |
n = 20 20 M 10 ACLR (23 ± 3) 10 CG (23 ± 2) Engaged in sports activities weekly |
Generalized loading protocol: squats 10 ×, two vertical jumps, 10 drop landings (5 right/ 5 left) (repeated several times) | Fatigue was operationally defined: jump height reduced by 20% OR when the subject could no longer complete the fatigue loading protocol | Squats | Kinetic data (external joint moments), ground reaction force (peak vGRF) − weight-bearing symmetry, kinematic data (joint angles) |
Symmetry Index = [vaffected – vunaffected / ½ (vaffected + vunaffacted)] × 100 vaffected = value of the the former injured leg vunaffected = value of the “healthy” leg |
ACLR anterior cruciate ligament rupture, CG control group, F female, GRF ground reaction force, Hecc:Qcon functional ratio of the peak eccentric torque of the hamstrings to the peak concentric torque of the quadriceps, LESS landing error scoring system, M male, N/A not available, RPE rate of perceived exertion, RSI reactive strength index, SLCMJ single-leg countermovement jump, SLDJ single-leg drop jumps, vGRF vertical ground reaction force