Document Type : Original Article
Authors
1
Department of Sports Biomechanics, Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran
2
Department of Orthopaedic surgery, Ardebil University of Medical Sciences, Ardebil, Iran
10.30491/tm.2026.595648.1977
Abstract
Introduction: Chronic non-specific low back pain (LBP) combined with hamstring tightness may disrupt lumbopelvic mechanics and alter lower-limb neuromuscular control during gait. Although ACSM-based exercise programs are widely recommended for chronic LBP, their effects on phase-specific lower-limb muscle activation during walking remain unclear. This study investigated the effect of an 8-week ACSM-based exercise program on lower-limb electrical activity during walking in young men with hamstring tightness and chronic LBP.
Method: In this semi-experimental laboratory study, 30 young men with chronic non-specific LBP and hamstring tightness were assigned to either an exercise group (n=15) or a control group (n=15). The exercise group completed an 8-week supervised ACSM-based program, three sessions per week, consisting of hamstring stretching, core stabilization, and lower-limb strengthening exercises. Surface electromyography (EMG) was used to record the electrical activity of the tibialis anterior (TA), medial gastrocnemius(MG), gluteus medius (GM), biceps femoris (BF), semitendinosus (ST), rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL) muscles of the dominant lower limb during walking at 1.3 m/s (±5%). EMG amplitudes were normalized to maximum voluntary isometric contraction (MVIC) and expressed as %MVIC across the loading response, midstance, and push-off phases. Data were analyzed using a 2×2 mixed repeated-measures ANOVA with Bonferroni-adjusted post hoc tests, and effect sizes were reported as partial eta squared (η2p).
Result: Significant time×group interactions were observed in loading response for TA (p=0.030, η2p=0.157) and GM (p=0.030, η2p=0.158); in midstance for VM (p=0.005, η2p=0.250) and GM (p=0.012, η2p=0.210); and in push-off for MG (p=0.010, η2p=0.218) and BF (p=0.024, η2p=0.174). The exercise group showed reduced activation from pre- to post-intervention in TA, GM during loading response, VM and GM during midstance, and MG and BF during push-off, whereas the control group remained relatively stable.
Conclusion: An 8-week ACSM-based exercise program induced selective, phase-dependent reductions in lower-limb EMG activity during walking in young men with chronic LBP and hamstring tightness. These findings indicate selective, phase-dependent reductions in lower-limb EMG activity after an 8-week ACSM-based exercise program. Although consistent with a shift away from compensatory overactivation, reduced EMG amplitude could also reflect decreased effort or motivation, reduced muscle capacity, or altered gait mechanics; concurrent kinematic, kinetic, or metabolic measures would be needed to confirm improved movement efficiency.
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