Effects of Short Isokinetic Eccentric Resistance Training on Neuromuscular Induced Adaptations Among Obese, Untrained Women

1.1 Introduction

Exercise-induced neuromuscular and functional changes are mode-specific. Exercise-induced muscular adaptations may be influenced by mechanical tension, subcellular damage, and metabolic stress. Eccentric (ECC) contraction happens when the external force exerted on the muscle exceeds the momentary force generated by the muscle. As a result, the muscle's strength is sufficient to overcome the load or resistance that causes the muscle to lengthen. Compared with concentric (CON) or isometric (ISO) contractions, ECC training elicits greater mechanical strain and microlesions in the muscles, which may lead to more pronounced muscular adaptations. ECC exercise is traditionally performed against a constant external load or at a constant velocity (isokinetic). Depending on the type of training, this produces varying mechanical demands, resulting in distinct neuromuscular and muscle-tendon adaptation mechanisms. In contrast to ISO or CON muscular contractions, the central nervous system employs a distinct neural strategy to govern skeletal muscle contraction. Different activation levels among synergistic muscles during ECC contractions compared with CON contractions, and the preferential recruitment of rapid-twitch motor units, are two examples of how this is demonstrated.

1.2 Problem statement & study rationale

Emerging data suggest that adiposity is associated with muscular weakness and reduced muscle quality. Regular resistance training (RT) has been shown to enhance a muscle's maximal regenerative capacity. It is believed that neural mechanisms primarily contribute to the initial (<2-4 weeks) gains in muscle force production during resistance training, followed by adaptations in muscle morphology (>5-8 weeks). However, this evidence is based on combining both ECC and CON contraction exercises. Studies have shown that ECC contraction elicits greater neuromuscular adaptation than CON contraction. Therefore, ECC RT is a promising approach for individuals with muscular weakness, such as the obese. Hence, it is postulated that short progressive eccentric isokinetic resistance training (ECCISO RT) will increase neuromuscular adaptations in obese untrained women compared to concentric isokinetic resistance training (CONISO RT)

2.0 Literature Review