Author(s): TROVATO, B., ROGGIO, F., SORTINO, M., MUSUMECI, G., Institution: UNIVERSITY OF CATANIA, Country: ITALY, Abstract-ID: 1891

INTRODUCTION:
Rests interval between resistance training sets is fundamental for performance and recovery. This area of research was already explored for traditional resistance training methods, however its impact on muscle mechanical properties, like tone, stiffness, and relaxation time, still needs more investigation in isoinertial training. The aim of this preliminary study is to investigate how different inter-set rest durations, 60 seconds and 120 seconds, influence these mechanical parameters, e.g. muscle tone, stiffness and relaxation, in an isoinertial biceps curl exercise.
METHODS:
A total of 24 physically active males, aged between 18 and 30, were enrolled in this study and randomly assigned to two groups, each performing three sets of ten maximal effort repetitions of isoinertial biceps curls. One group rested for 60 second between set, while the other rested for 120 seconds between sets. Muscle mechanical properties, tone, stiffness, and relaxation time, were assessed with the MyotonPro device (Myoton AS, Tallinn, Estonia) at four time points: baseline (T0), after the first set (T1), after the second set (T2), and after the third set (T3). The statistical analysis was performed using Python (v. 3.11) and a two-way repeated measures ANOVA with the Tukey HSD post-hoc test was used to analyze the differences between groups.
RESULTS:
The two-way ANOVA revealed that the group factor had a significant effect on stiffness (p = 0.004) ,and relaxation (p = 0.005), while muscle tone was not significant (p = 0.179). The Tukey HSD post-hoc tests revealed that stiffness was significantly higher in the 60 sec group compared to the 120 sec group (p = 0.003), and relaxation time was significantly lower in the 60 sec group compared to the 120 sec group (p = 0.004).
CONCLUSION:
This preliminary study indicate that 60 seconds inter-set rest durations may lead to increased muscle stiffness and reduced relaxation time compared to 120 seconds rest periods during isoinertial biceps curl training. These findings suggest potential differences in the response of the mechanical properties of the muscle regarding the rest time between sets; however, they should be interpreted with caution considering the small sample size. Further researches with larger cohorts and additional physiological assessments are needed to confirm these effects and better understand the implications for isoinertial training optimization.