Effects of Adding Inter-Set Static Stretching to Flywheel Resistance Training on Flexibility, Muscular Strength, and Regional Hypertrophy in Young Men.

Masatoshi Nakamura,Kaoru Yahata,João Pedro Nunes,Shigeru Sato,Riku Yoshida,Kosuke Takeuchi,Ryosuke Kiyono,Hirotaka Ikezu

doi:10.3390/ijerph18073770

Abstract

Performing static stretching (SS) during resistance training (RT) rest periods is posited to potentiate muscular adaptations, but the literature is scarce on the topic. Thus, the purpose of this study was to investigate the effects of adding inter-set SS to a lower-limb flywheel RT program on joint flexibility, muscular strength, and regional hypertrophy. Sixteen untrained male adults (21 ± 1 y) completed the study, where they performed progressive flywheel bilateral squatting twice a week for 5 weeks. One leg of each participant was randomly allocated to perform SS during the inter-set rest period (RT+SS), while the other leg served as control (RT only). Before and after the intervention, knee flexion range of motion; knee extension isometric, concentric, and eccentric peak torque; 1-repetition maximum; and muscle thickness of the lower-limb muscles were assessed. Following the training period, additional effects were observed for the inter-set SS side on increasing joint flexibility (p < 0.05), whereas the average increase in strength measures was 5.3% for the control side, and 10.1% for the inter-set SS side, however, SS intervention induced significantly greater gains only for knee extension isometric strength, but not for dynamic 1-RM, concentric, and eccentric tests. Hamstrings and gluteus maximus did not hypertrophy with training; increases quadriceps muscle thickness depended on the site/portion analyzed, but no significant difference was observed between legs (average: RT = 7.3%, RT+SS = 8.0%). The results indicate that adding inter-set SS to RT may provide large gains in flexibility, slightly benefits for muscular strength (especially for isometric action), but do not impact muscle hypertrophy in untrained young men.

Highlights

Paired t-tests showed no significant differences between the intervention and control sides for all variables in the PRE value
The analysis of variance (ANOVA) showed a significant interaction effect for knee flexion ROM (F = 4.85, p = 0.044, ηp 2 = 0.244), and the post hoc test showed a significant difference between the PRE and POST values on the inter-set static stretching (SS) side (p < 0.01, d = 1.63), but not on the control side (p = 0.81, d = 0.10)
Previous studies indicated that inter-set SS could achieve additional results [15,16], this is the first paper to investigate the effect of inter-set SS intervention on muscle strength in different contraction modes and muscle hypertrophy in different regions

Summary

Introduction

Resistance training (RT) is prescribed to increase muscular strength and hypertrophy in both sports and clinical settings. In addition to traditional RT, several strategies have been investigated in an attempt to potentiate muscular adaptations in shorter time frames [1]. Flywheel RT is a relatively new training method that accentuates the eccentric phase of movement through the inertial force generated by rotation [2,3], and it tends to be more effective for muscle strengthening and hypertrophy [4,5,6], with better results being shown even in the first phases (e.g., 5 weeks) of the training programs [7]. In the same way, adding static stretching (SS) to RT interventions has been used to enhance muscular adaptations [8,9]

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