Table 3.
Study characteristics—asymmetry examined during a loading protocol/task
| Study | Subjects (Sex, age, sport) | Physical load/fatigue loading protocol | Measure of fatigue | Task/procedure | Outcome measures | Asymmetry equation |
|---|---|---|---|---|---|---|
| Bishop et al. [30] |
n = 18 18 M (28.9 ± 5. 1) Recreationally active |
4 rounds of 6 × 40 m sprints on running track (interspersed with a SLCMJ) | Fatigue index = (100 × (total sprint time/ideal sprint time)) - 100) | SLCMJ | Jump height | Percentage difference: 100 / (maximum value) × (minimum value) × − 1 + 100 |
| Girard et al. [20] |
n = 13 13 M (31.2 ± 4.8) Recreational team- and/or racket-sport |
RSA test | Sprint decrement score | Running on a treadmill | Running kinetics, running kinematics and spring-mass characteristics | Bilateral leg asymmetry (BLA%): [(high value − low value)/ low value] × 100 |
| Hanley and Tucker [31] |
n = 14 14 M (31 ± 7) Competitive runners (best time 10 km 31:00–35:20) |
10,000 m run (103% of season's best) | RPE scale by Borg | Running on a treadmill | vGRF, spatio-temporal data (step length, step frequency, contact time, flight time, impact force, maximum force, impulse), gait variability |
Symmetry angle: [(45° - arctan (Xleft/Xright)/90°)] × 100% X = the mean value for a variable on each leg |
| Hodges et al. [32] |
n = 17 9 M / 8 F (22.3 ± 2.5) Recreationally trained |
5 sets with 8 repetitions of free-weight barbell back squats, 3 min rest between each set, 90% of 8 repetitions maximum | Not measured | Free-weight barbell back squats | vGRF | GRF asymmetry: left vGRF% - right vGRF% |
| Jordan et al. [21] |
n = 22 12 M, 10 F 11 ACLR (age N/A) 6 M (26.5 ± 5.8) / 5 F (23.6 ± 1.8) 11 CG (age N/A) 6 M (23.3 ± 3.3 / 5 F (21.8 ± 3.2) Elite skiers |
Jump test loading protocol (20 squat jumps in 80 s) | Operational definition of fatigue: exercise-induced decrease in lower limb muscle power | Jump test (Squat jumps) | Vertical ground reaction force (Fz), EMG data, vertical jump HBCM |
Asymmetry Index control: [(left limb impulse – right limb impulse) / (maximum of left and right impulse)] × 100 Asymmetry Index ACLR: [(contralateral limb impulse – affected limb impulse) / (maximum of contralateral and affected limb impulse)] × 100 |
| Mattes and Wolf [33] |
n = 32 16 M, 16 F (age N/A) High-performance junior rowers (German National Team U19) |
2000-meter race test | Not measured | On-water rowing test | Leg stretcher force |
Symmetry Index: [(x1 - x2) / 0.5 (x1 + x2)] × 100% x1 = outside leg x2 = inside leg |
| Tucker and Hanley [34] |
n = 10 5 M / 5 F (age N/A for the subgroup) Elite race walkers |
10 km race-walk on treadmill − 103% of their most recent 20 km speed | Not measured | Race walking on a treadmill | vGRF data (impact peak force, loading peak force, mid-stance force, push off peak force, impulse) |
Symmetry angle: [(45° - arctan (Xleft/Xright)/90°)] × 100% X = the mean value for a variable on each leg |
ACLR anterior cruciate ligament rupture, BLA bilateral leg asymmetry, CG control group, EMG electromyography F female, GRF ground reaction forces, HBCM height of body center of mass, M male, N/A not available, RPE rate of perceive exertion, RSA repeated sprint ability, SLCMJ single-leg countermovement jump, vGRF vertical ground reaction force