DISCUSSION
hypertrophic, hypertrophy, muscle hypertrophy
HYPERTROPHIC, RECRUITMENT, HYPERTROPHY
This study investigated the effects of low‐RIR versus high‐RIR training on strength, hypertrophy, and motor unit adaptations in previously trained males and females. Strength outcomes and changes in proximal and mid VL mCSA occurred between groups. Surprisingly, a decrease in distal VL mCSA was observed (i.e., a significant main effect of time), but no significant interaction was observed between training groups. Regarding neural adaptations, differences between conditions were observed for slope and Given that the high‐RIR group performed training further from failure, volume‐load (i.e., sets × repetitions × load per repetition; Figure Back squat, deadlift, and bench press strength metrics similarly increased in both groups, and these results are in line with a meta‐analysis by Grgic and colleagues suggesting that training to failure in previously trained individuals (shown in their subgroup analysis) is not necessary to maximize strength gains (Grgic et al., There were no significant main effects of time in either group for proximal or middle VL mCSA changes. These data can potentially be explained by the high average training age (6 ± 4 years) for the cohort, as less muscle hypertrophy in well‐trained individuals would be expected given the short duration of the intervention. However, there was a large degree of inter‐individual variability in these outcomes. No significant associations were found to exist between training age and these hypertrophic outcomes as reported in the Results section, and we have published prior data in trained individuals showing that training age does not significantly correlate with hypertrophic outcomes in trained men following 6 weeks of high volume training (Haun et al., Perhaps the most interesting observation herein was the changes in motor unit characteristics in the low‐RIR group. Closer inspection of the regressed recruitment threshold and firing rate relationship in the low‐RIR group after the intervention show a significant decrease in slope values and significant increases in There are limitations to consider with the current study. Our study had a total of 19 participants, which limited our statistical power. Another significant limitation is that our study was unsupervised. While we did employ a training log and weekly check‐ins, it is within the realm of possibility that participants were not truthful when logging their training sessions. Furthermore, there may have been unintended effects due to changes in nutrition between groups, as nutrition was not tracked or directly prescribed beyond encouraging participants to continue to practice normal dietary habits. However, there were very few changes in weight (or body composition) suggesting that there were not large differences between caloric consumption above or below maintenance between groups. Our study was also only 6 weeks in duration (5 weeks of progressive overload and a 1‐week deload), thus perhaps not allowing enough time for hypertrophy adaptations to occur in a well‐trained population. We also decided a priori that implementing a deload week for both groups prior to post‐intervention testing was practical given that advanced resistance training programs implement a deload week between training blocks (Ogasawara et al., 