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Table 3 Study characteristics—asymmetry examined during a loading protocol/task

From: The Influence of Exercise-Induced Fatigue on Inter-Limb Asymmetries: a Systematic Review

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
  1. 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