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Isotonic fatigue effects on neuromuscular coordination control mechanisms underlying ballistic limb movement in males and females
Abstract
The purpose of this study was to investigate the effects of selective isotonic muscle fatigue upon the neuromuscular coordination control mechanisms underlying ballistic limb movement in males and females. Eight males and eight females served as subjects and were tested across eight days which involved the monitoring of three inertial load conditions (L0 = no load, L1 = 1.5, L2 = 3.0 $\times$ moment of inertia) of a Class B, ballistic forearm flexion movement. Following the first three practice days, selective isotonic muscle fatigue was imposed at one of two intensities, high (6RM) or low (20RM) resistance, in either the agonist (biceps brachii) or antagonist (triceps brachii) muscle group. Exercise days involved pre and post testing of the movement task interspersed by fatiguing isotonic resistance exercise. Kinematic, temporal and quantitative integrated electromyographic pattern and strength measures were analyzed. All measures were reliable (R = 0.14-0.98). Eight days of practice generated significant decreases (p $<$ 0.05) in movement time (MVT). Males exhibited a larger decrease across days (L0 = 14.9%) as compared to females (L0 = 4.7%). Although, males generated a 25% faster MVT than females, both sexes demonstrated a similar reduction in MVT improvements as inertial loading increased. Practice effects manifested in agonist and antagonist temporal pattern measures were pronounced. Several substantial sex differences persisted following the eight days of practice. Antagonist delay (T2D) was significantly (p $<$ 0.05) shorter (32.9%) in males. Across days, males reduced this delay (13.5%) while females exhibited a large (43.2%) increase. The increase in T2D exhibited by females represents an uncoupled temporal association between the decelerating action of the antagonist and the point of maximum acceleration. This modification contributed to the comparatively small improvements in MVT displayed by females across days; explaining the MVT differential observed between the sexes. Low resistance (20RM) selective isotonic muscle fatigue generated the largest decrease in maximum isometric strength (13.6%-21.1%) with low resistance (20RM) flexion fatigue increasing MVT to the greatest extent (15.6%). Males responded more dramatically to isotonic muscle fatigue. However, comparisons of fatigue modifications in neuromuscular coordination control mechanisms between the sexes warrants caution due to the persistent sex differences observed in stabilized performance.
Subject Area
Anatomy & physiology|Animals
Recommended Citation
Bultman, Linda Lucille, "Isotonic fatigue effects on neuromuscular coordination control mechanisms underlying ballistic limb movement in males and females" (1987). Doctoral Dissertations Available from Proquest. AAI8805899.
https://scholarworks.umass.edu/dissertations/AAI8805899