Investigating the Impact of Inter-Set Stretching on Vastus Lateralis Fascicle Dynamics and Knee Extensor Torque during Resistance Training

Abstract

Abstract Purpose Although stretching applied between sets can affect performance, it is unknown whether the muscle architecture is associated with the fatigue of subsequent sets. Here we compare the effect of inter-set stretching on maximal concentric and eccentric knee extension torque and vastus lateralis fascicle behavior in physically active men. Methods Fifteen men performed 4 × 10 maximal knee extensions. Passive static stretching in the inter-set resting periods was applied to one limb's knee extensors (inter-set stretching protocol), while the other limb recovered passively (passive rest protocol). The vastus lateralis fascicle architecture (pennation angle and fascicle length; proximal and distal regions) and knee extensor torque (peak torque and peak torque angle; concentric and eccentric contractions; set one–four) were compared between the inter-set stretching and passive rest protocols. Results Concentric and eccentric peak torques significantly decreased across sets for both protocols (p ≤ 0.001); however, there were no differences between them. There were no significant differences between the inter-set stretching and passive rest protocols for variations in peak torque angle. The fascicle length and pennation angle also did not change significantly between the protocols (p > 0.06 for all cases), regardless of the vastus lateralis region. Conclusion Incorporating 30-s intra-set quadriceps stretching during maximal leg extension exercise does not affect the ability to produce maximum force and did not change the fascicle behavior. Coaches and practitioners can benefit from this time-efficient approach for the targeted muscle group without compromising exercise performance across four sets.