Effects of deload periods in resistance training on muscle hypertrophy and strength endurance in untrained young men using a randomized within subject design

This study aimed to investigate the effects of deload periods implemented through reductions in weekly set volume and training frequency at the midpoint and endpoint of an 8-week resistance training (RT) program on muscle hypertrophy and strength-endurance in untrained individuals. 19 untrained young men participated in the study using a within-subject design. Each participant's legs and arms were randomly assigned to the continuous and deload training conditions. In the continuous condition, unilateral leg extension and biceps curl exercises were performed twice per week for 8 weeks (6-8 sets per exercise, 8-12RM). In the deload condition, a similar training program was followed; however, during weeks 4 and 8, the exercises were performed only once per week with 2 sets per exercise. Muscle thickness was measured with ultrasound, while strength-endurance was assessed with 10-repetition maximum (10RM) testing, pre- and post-intervention. Both conditions produced similar, statistically significant increases in quadriceps/biceps muscle thickness and 10RM (single exception: lateral 30%-deload, p = 0.073). No time × condition interactions were detected for muscle thickness or strength-endurance (p = 0.239-0.955); between-condition effects were small (ηp² = 0.001-0.076), and all Δ 95% confidence intervals included zero. In conclusion, reducing training volume and frequency at the midpoint and endpoint of an 8-week resistance training program does not appear to hinder adaptations in muscle hypertrophy and strength-endurance in untrained young men.