Chronic effects of different loads in the leg press exercise on muscle strength in young women

Introduction: Resistance training is an excellent strategy to promote increases in strength muscular. The use of different loads can cause distinct stimuli in various physiological systems and, consequently, promote specific long-term changes. Objectives: The aim of the present study was to verify the chronic effects of different loads (90% and 100% of 10-12 RM) in the leg press exercise on muscle strength in young women. Methods: Seventeen students from the local university completed the study. An 5-week randomized design was used to compare the effects of different loads on dynamic muscle strength of lower limbs. The 10-12 RM loads were determined pre- and post-training using the same procedures. After 10-12 RM pre-training test, the participants were stratified according to their leg-press loads and randomly assigned to either 90% of the 10-12 RM (G-90% of 10-12 RM; n = 10; 24.4  2.8 years; 58.5  5.6 kg; 164.5  6.0 cm) or 100% of the 10-12 RM (G-100% of 10-12 RM; n = 7; 23.4  4.6 years; 57.4  5.1 kg; 160.7  8.0 cm). The G-90% of 10-12 RM training program consisted of two sets of 12 repetitions and one final set until concentric muscle failure. The G-100% of 10-12 RM performed of three sets to concentric muscle failure. In both training program, the rest interval between sets was of 2-min. The frequency adopted was two weekly sessions. Total volume of each experimental session was registered (∑ repetitions x load). The duration of each set was recorded from the beginning of the first repetition to the end of the last repetition using a handheld stopwatch. The time under tension was defined as the sum of the duration of the three sets in seconds. The internal load was calculed (ratings of perceived exertion measured 30-min post-session by total duration of the session). Results: A significant increase in the 10-12 RM was observed in G-90% and G-100% de 10-12 RM (p < 0.05; 9,6% e 10,6%; respectively). However, post-training results showed no significant diferences between G-90% of 10-12 RM and G-100% of 10-12 RM for the 10-12 RM loads, total volume of training, time under tension, and internal load (p > 0.05). Conclusions: The findings of the present study suggest that different loads in the leg press exercise not influence muscle strength adaptations in young women.