This study compared the effects of various training methods while keeping the training volume equated on the enhancement of muscle strength, endurance, and hypertrophy. The main findings revealed that traditional, pre-exhaustion and drop sets groups exhibited similar muscle strength, endurance, and hypertrophy after six-week resistance training program. Furthermore, our results revealed that delayed onset of muscle soreness and perceived rated exertion were higher for Pre-ex and DS compared to TRT.
Our results corroborate previous studies showing that when the training volume is equated, the improvements on muscle strength and hypertrophy are similar despite of different resistance training methods (16, 25, 26). When comparing TRT with DS, comparable enhancements in the cross-sectional area of the VL muscle were observed previously (25, 27). Angleri et al. (25) assessed hypertrophy at the midpoint of the VL, while we and Varović et al. (27) evaluated muscle thickness of the VL and RF muscles at multiple sites along their length. Similarly to those studies, we found no significant differences between different methods of resistance training once we revealed, without significant difference, that the DS group increased 43% the VL, while TRT group increased 35% the VL. Even though DS and TRT differ in terms of structure, with the equivalence of total training volume between them, the overall stimulus to the muscle may be similar.
Evidence suggest that metabolic stress may have a role in facilitating muscle growth (5). It has also been hypothesized that metabolic accumulation and local fatigue may increase of recruitment of type II fibers, resulting in higher hypertrophic adaptations (5). Thus, inducing the activation of type II muscle fibers can serve as a beneficial approach for increasing both muscle strength and hypertrophy in RT programs. Therefore, researchers attempted to trigger metabolic accumulation and local muscle fatigue, especially for type I fibers with low load RT before a high load RT (14–16), likewise during Pre-ex method. Our results do not provide support for the proposed hypothesis. Aguiar et al. (14) pre-exhaustive set until failure with a knee extension exercise performed at 20%1RM, before initiating high load resistance training. They showed improvements in maximal strength, muscle cross-sectional area, and muscle endurance. However, repetition numbers for failure sets were 45–55, much lower than our Pre-Ex group (81.76 ± 15.30). In contrast to our Pre-Ex group, the comparison group employed just an additional set at 20%1RM. The possible explanation for the differences between the studies is unequal training volume (28). The findings by Trindade et al. (16) and Fisher et al. (15) similar to our results, supported the idea that Pre-Ex training cannot offer more significant benefits for neuromuscular adaptations when compared to traditional RT.
Despite the absence of difference for strength, endurance and hypertrophy outcomes, the DOMS and RPE were different comparing groups. The TRT presented lower rates of DOMS and RPE when compared to Pre-ex and DS groups. Despite the equated volume, probably this happened due to the repetitions to failure achieved in both Pre-ex and DS groups. In both groups, the time under tension was longer, and previous study reported that RPE gradually increases in longer time under tension (29). Furthermore, our results corroborates Enes et al. (17), indicating that even with equated volume, the DS showed higher rates of RPE compared to TRT.
The present study has come limitations that should be considered. While the Jones pre-exhaustion method (7) was not strictly adhered with respect to rest intervals between single-joint and multi-joint exercises, a rest period of three-minute was deemed necessary based on previous findings (8, 10), which indicated that a Pre-ex set reduces the number of subsequent exercise repetitions significantly. As it could be considered as a limitation of the study, we chosen this approach aiming to achieve metabolic stress while also avoiding a decrease in volume load. Future investigations examining the effects of Pre-ex training should consider incorporating assessments of metabolic markers, muscle biopsies, and intracellular hypertrophy pathways to enable a more accurate and comprehensive conclusion to be drawn.