Cardiorespiratory Function on Swimmers With Relaxed Versus Contracted Abdominal Muscles

Purpose: Pulmonary function does not limit exercise capacity because postures and segmental movements produced during activity do not impede the ventilatory muscles and there is time between segmental movements to ventilate the lungs adequately. In the competitive swimming Crawl Stroke (CS) the position of the head in the water and movement sequence permits adequate pulmonary ventilation and ventilation has not been shown to limit CS performance. Some sport theorists have suggested that posture should be altered during CS to decrease the hydrodynamic resistance to increase speed. However, postural alteration has never been documented to improve performance and it may impose limits on the cardiorespiratory system. The proposal changes in posture involve contracting the abdominal muscles, obliques and muscles controlling the lumbar spine to keep the body streamlined. We hypothesized that this posture interferes with the coordination of movement between the abdominal muscles and the diaphragm while simultaneously working in direct opposition to the accessory respiratory muscles limiting the swimmer's ability to ventilate air and consume oxygen. Prior to initiating a logistically complex study of swimmers in the water we developed this pilot study to determine if contracted muscles negatively affected pulmonary ventilation and oxygen consumption measured in a controlled laboratory setting. Methods: Thirteen subjects involved in swimming activities (8 Males, 5 Females) ages 22-60±6.9 y volunteered to participate. We measured Vital Capacity (VC), Maximal Ventilatory Volume (MVV), Forced Vital Capacity (FVC) and Resting VO2 (RVO2) under Controlled (CON), normal seated posture, and Experimental (EXP), abdominal muscles contracted in a seated posture, using a Flowmate III Spirometer for pulmonary function and a metabolic cart for RVO2 with 3 minute rest periods between counter-balanced trials. Pulmonary functions and RVO2 were expressed relative to age, weight and height. Analysis/Results: A repeated measures t-test was used to compare EXP and CON conditions. Significant differences between EXP and CON on all pulmonary functions and RVO2 were found. [VC (4.1±1.05, 5.2±.97, p < .01), MVV (87.6±34.4, 127.1±44.3), p < .01), FVC (4.1±.92, 5.1±.98, p <.01), and RVO2 (6.7±1.1, 5.13±.97), p < .01)]. Conclusions: There was a negative affect on pulmonary functions and an increase in energy cost to maintain a hardened abdominal posture, resulting in less oxygen being available to the propulsive muscles and offsetting proposed benefits of a flatter body. Significant findings in this investigation demonstrate that contraction of musculature to alter posture has a negative affect on pulmonary ventilation and oxygen consumption.