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 ¼ 21.0 6 1.1 years; body mass index ¼ 25.2 6 2.9 kg/m 2 ). Intervention(s): Triceps brachii resistance training was performed on the isoacceleration dynamometer for 10 weeks (frequency ¼ 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 (r 2 ¼ 0.37 for FR and r 2 ¼ 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.Key Words: conditioning, upper extremity, athletes Key PointsFatigue of the triceps brachii muscle decreased during the first 4 weeks of strength training. Decreased strength of the triceps brachii muscle during multiple contractions plateaued after 4 training weeks. Further improvement in muscle functional properties was a result of increased endurance.S trength training leads to functional and morphologic adaptations of skeletal muscles. 1-5 Different effects are expected from different intensities, frequencies, and durations of a training protocol. A greater increase in strength is accomplished with maximal loads, a smaller number of repetitions, and shorter rest periods between sessions. More repetitions in a series with smaller loads and longer interseries intervals increase endurance.6-8 Surely, the adaptation effects are also closely related to age, genetic predisposition, muscle or fiber types, previous training history, and hormonal or other influences. 8,9 In any case, the objective of a training program is to increase the function of skeletal muscles, which relates not only to maximal muscle strength and power but also to endurance and fatigue. Endurance is the ability of a muscle to maintain its function throughout time and multiple contractions. Muscle endurance can be expre...

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