Adaptações musculares após diferentes protocolos de treinamento de força com cargas baixas: efeito da oclusão vascular, cargas e volume

Abstract

Introduction: Resistance training (RT) is an excellent intervention to improve strength and the muscle mass. Traditionally it is accepted that muscle hypertrophy occurs primarily due to extreme overload above 70% of one maximum repetition (1RM) imposed to muscle. However, this concept cannot be applicable for many conditions in which the traditional training with high loads cannot be used (e.g. compromised muscle tendon integrity). Growing evidences have suggested that RT with low loads when performed under low blood flow (vascular occlusion) promotes muscle hypertrophy similar to RT with high loads, being an alternative to conditions where the traditionally RT cannot be applicable. On the other hand, recent studies have suggested that RT with low loads and performed until muscle failure (in other words, task failure), but without vascular occlusion, is efficient to induce protein synthesis and promote hypertrophy similar to RT with high loads. However, the dose of exercise required, combined or not with the vascular occlusion, to maximize the muscular hypertrophy has not been totally elucidated. Objective: Analyze the effects of different RT programs with and without vascular occlusion on muscular strength and hypertrophy. Methodology: Thirty eight young eutrophic men were submitted to quadriceps muscle crosssection area assessment by means of magnetic resonance image (MRI) and maximum strength by test of 1RM before and after eight weeks of RT with or without vascular occlusion, except to strength that was also evaluated after four weeks. The individuals were randomly allocated in one of four RT conditions: (1) low-load low volume resistance exercise (one set performed to voluntary failure with 20% of 1RM), (2) low-load high volume resistance exercise (three sets performed to voluntary failure with 20% of 1RM), (3) high-load low volume resistance exercise (one set performed to voluntary failure with 50% of 1RM) or (4) high load high volume resistance exercise (three sets performed to voluntary failure with 50% of 1RM) and performed dynamic knee extension exercise in a leg extension machine during eight weeks. One leg of each individual was randomly occluded. Ten individuals were selected to electromyographic activity comparison (RMS) between conditions and groups. Results: After eight weeks of training, the strength and the muscle mass increased in all groups, without interaction with occlusion. However, the group which performed the RT with 20% was superior in gain of muscle mass. For the muscular strength, there was a greater increase in the group that performed three sets with 20% compared to the other training groups after four weeks, but there was no difference between groups after eight weeks. The RMS at the beginning of the set was lower in the group 1x20 compared to the other groups. However, at the end of the set, there was no difference between the groups. There was not occlusion interaction with the groups to RMS. Conclusion: The vascular occlusion has not shown additive effect to low-load RT to strength gains and muscle mass. The low-load RT (20% and 50%) increases strength and muscle mass after eight weeks of RT. However, muscle mass gain is superior in the group of 20% of 1RM and strength adaptations are anticipated when the RT with 20% of 1RM is performed with more repetitions (three sets vs. one set).