Effect of 5-Week Combined Upper-Body and Hamstring Resistance Training on Muscle Reaction Time

Objective: This study investigated whether incorporating upper-body isometric resistance exercises targeting the posterior oblique sling (POS) in a standard ham-string training programme would enhance hamstring reaction times, strength, and flexibility in moderately active adults. Methods: Thirty participants (18 males, 12 females; aged 18–40 years) were randomly assigned to intervention (ULC) or control (CON) groups. Both groups completed a five-week, home-based ham-string strengthening and stretching programme. The ULC group performed additional upper-body isometric resistance exercises involving shoulder flexion, abduction, and diagonal patterns. Reaction time of the biceps femoris was measured using surface electromyography (sEMG) in response to visual cues. Secondary outcomes included isometric hamstring strength using a hand-held dynamometer, while flexibility was measured using the Active Knee Extension test. A two-way mixed-design ANOVA was used to assess time × group effects. Results: A significant group × time interaction was found for reaction time (p = 0.003), with greater improvements in the ULC (−5.73 ms) compared to the CON (−2.89 ms). Strength also improved more in the ULC (+1.06 kg vs. +0.56 kg; p < 0.001). Flexibility gains were negligible between groups (p = 0.411). Conclusion: Upper-body isometric priming enhanced hamstring reaction time and strength be-yond traditional training, suggesting practical value for improving lower-limb neuromotor performance in sport settings. These findings point to the potential of integrating POS activation into preparatory routines to optimise intersegmental coordination and force transfer before lower-limb tasks.