(1) THE EFFECT OF DIFFERENT TRAINING VOLUMES ON ISOMETRIC AND DYNAMIC STRENGTH IN RESISTANCE-TRAINED INDIVIDUALS

Purpose: The purpose of this study was to examine the impact of resistance training (RT) volume on strength parameters of the quadriceps over 8 weeks of supervised RT. Methods: 25 resistance-trained individuals (12 F/13 M) participated in this 8-week progressive RT intervention. Participants were randomized into two RT groups: high volume (HV; F/M: 7/6) or low volume (LV; F/M: 6/6). Subjects completed 2 lower body training sessions each week for 8 weeks performing the leg press (LP) exercise during each session with different training volumes based on their group allocation. Subjects in the HV completed 4 sets per session, while the LV group completed 2 sets of LP per session. The initial training session consisted of 65% of the participants’ LP e1RM. To progress the load each session, the final set on the LP exercise was taken to concentric muscular failure, whereby subsequent sessions were progressed in load based on autoregulatory progressive resistance exercise (APRE). Before (PRE) and following (POST) the RT intervention, estimated LP 1RM (LP e1RM), which was estimated using a 3-5RM testing protocol, and maximal voluntary isometric contraction (MVIC) strength of the subject’s dominant knee extensors at 90 degrees of knee flexion were measured. Separate group (HV/LV) × sex (M/F) × time (PRE/POST) repeated measures ANOVAs were used to examine each dependent variable. Post-hoc tests were conducted to examine significant effects and the alpha level was set a-priori at 0.05. Results: There were no 3-way (p= 0.100-0.916) or 2-way (p= 0.092-0.575) interaction effects for MVIC strength or LP e1RM. For MVIC strength, there was a main effect for sex (p< 0.001), by which males exhibited significantly greater MVIC strength than females when collapsed across time and group (M: 315.8 ± 100.4 Nm vs. F: 163.2 ± 31.5 Nm; p< 0.001). For LP e1RM, there were significant main effects for both sex and time (p< 0.001 for both). Post-hoc analyses indicated that when collapsed across time and group, males exhibited greater LP e1RM than females (M: 395.5 ± 82.6 kg; F: 223.8 ± 53.8 kg). When collapsed across sex and group, LP e1RM significantly increased from PRE (270.5 ± 98.3 kg) to POST (355.6 ± 127.5 kg). Conclusions: Based on the present data, LP e1RM may be more sensitive to changes in maximal strength than knee extension MVIC. Importantly, this increase in LP e1RM was independent of training volume, suggesting that there may be more important factors than training volume contributing to maximal strength adaptations. Moreover, maximal isometric strength did not increase significantly over time showcasing the principle of specificity and sensitivity of strength as an adaptive skill. Practical Applications: Coaches and practitioners should choose a task-specific modality when assessing changes in maximal strength following a RT program. Further, the interplay of training volume and biological sex on maximal strength adaptations remains unclear, warranting further investigation. Acknowledgements: None.