Perfis de aceleração e o exercício de agachamento isoinercial: há efeito direto na força concêntrica-excêntrica, potência e eficiência neuromuscular?

Abstract

BACKGRGOUND: Resistance training has become increasingly popular, used with groups of different levels of training, age and gender and it’s also recommended to achieve different physical goals. Exercises with an emphasis on the eccentric phase have often been used in resistance training, rehabilitation and injury prevention actions in the most diverse categories, including athletes. Isoinertial training has shown potential as an effective tool for the rehabilitation of muscle injuries due to its positive training effects. Improvements in strength, hypertrophy, muscle activation and muscle length lead to positive adaptations and muscle recovery. Functional and effective strength training associated with performance increases using an isoinertial device should include a measurement of power during the concentric and eccentric phases. This power control output becomes more important during rehab due to the risk of overloading musculoskeletal structures increase the risk of further injury. However, there are some technical difficulties in acquiring power and strength data from isointerial devices. As the system overload is based on inertia, acceleration is closely linked to the production of force and power during isoinertial tasks. An alternative to characterize this overload is to evaluate the differences between the upper and lower acceleration profiles. Given the scarcity of associating the aforementioned parameters, the biomechanical demands of each phase must be examined to integrate isoinertial resistance training as an overload mechanism. Objective: To examine the selective influences of distinct acceleration profiles on the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. Design: Cross-sectional study. Participants: A total of 38 active adults were divided according to their acceleration profiles: higher (n = 17; >2.5 m/s2 ) (H-ACC) and lower acceleration group (L-ACC) (n = 21; <2.5 m/s2 ). Intervention: All subjects performed squats until failure attached to an isoinertial conic pulley device monitored by surface electromyography of rectus femoris, vastus medialis, vastus lateralis, biceps femoris, and semitendinosus. Methods: An incremental optical encoder was used to assess maximal and mean power and force during concentric and eccentric phases. The neuromuscular efficiency was calculated using the mean force and the electromyographic linear envelope. Results: Between-group differences were observed for the maximal and mean force (Prange = .001–.005), power (P = .001), and neuromuscular efficiency (Prange = .001–.03) with higher significant values for the higher acceleration group in both concentric and eccentric phases. Conclusion: Distinct acceleration profiles affect the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. To ensure immediate higher levels of power and force output without depriving the neuromuscular system, acceleration profiles higher than 2.5 m/s2 are preferable. The acceleration profiles could be an alternative to evolve the isoinertial exercise.