Changes in Strength, Endurance, and Fatigue During a Resistance-Training Program for the Triceps Brachii Muscle

Abstract

Context: As a result of the adaptation process, some functional properties show different functions over time during strength training. Muscle strength and fatigue may show different adaptation patterns in reaching the improvement plateau after several weeks of training. Objective: To follow muscle endurance and fatigue values during resistance training of the elbow extensors in young nonathletes. Design: Descriptive laboratory study. Setting: Controlled laboratory. Patients or Other Participants: Nineteen healthy young nonathletes (age = 21.0 ± 1.1 years; body mass index = 25.2 ± 2.9 kg/m2). Intervention(s): Triceps brachii resistance training was performed on the isoacceleration dynamometer for 10 weeks (frequency = 5 times a week, 5 sets of 10 maximal elbow extensions, 1-minute resting period between sets). Main Outcome Measure(s): Measurements of endurance strength and fatigability were conducted using the same equipment, and endurance strength (ES), fatigue rate (FR), and decrease in strength (DS) were defined. Results: All measured values for triceps brachii strength changed after training (ES increased by 57%, FR decreased by 68%, and DS improved by 59%; P < .001). No correlation was found between ES and the fatigability values—FR and DS (r2 = 0.37 for FR and r2 = 0.04 for DS; P > .05). The FR and DS trends showed specific functions, which reached a plateau after 4 weeks of training, and we found no further weekly changes in these values as the training continued. As an adaptation to exercise, ES showed a continuous, yet not linear, increase. Conclusions: Fatigability in the triceps brachii decreased in the first 4 weeks of training. After that period, muscle functional properties improved as a result of increased endurance.