Respiratory Muscle Analysis

Exercise demands on the respiratory muscles
During moderate exercise, respiratory control system maintains the alveolar ventilation in regards to metabolic demand placed on it. So that, arterial blood-gas tension and acid-base balance remains in equilibrium. While exercising, metabolic acidosis can be compensated by hyperventilation that reduces fall of arterial pH and prevent arterial hypoxemia. Breathing pattern and ventilation should be regulated accurately so respiratory muscle work is reduced. Structure of respiratory muscle is such that can coup with the increased ventilatory demands of exercise. For instance, diaphragm has a high oxidative capacity, distance for O2 diffusion between capillary and mitochondria is short, and velocity of …show more content…
Eight male subjects performed high-intensity cycling at 90% of peak power output and they were divided into induced expiratory muscle fatigue (EMF- EX) group and without induction of expiratory muscle fatigue group (CON-EX). EMF-EX group did breathing against expiratory flow resistor until they could tolerate. Gastric twitch pressure (Pgatw) and quadriceps twitch pressure (Qtw) was recorded to measure abdominal and quadriceps muscle fatigue, respectively. The exercise time was reduced by 33 ± 10% in EMF-EX vs. CON-EX (6.85 ± 2.88 vs. 9.90 ± 2.94 min). Muscle fatigue was greater after EMF-EX and at 1 and 3 min dyspnea and leg discomfort was higher at the end of exercise during EMF-EX (Taylor & Romer, 2008). Therefore, it concluded that exercise tolerance and limb fatigue can be affected by exercise in hypoxia. Acute moderate hypoxia produces one-third of the total limb locomotor muscle fatigue and reduces exercise tolerance (Amann, Pegelow, Jacques, & Dempsey, 2007). During heavy endurance exercise, prolonged expiratory time and expiratory flow limitation result in positive intrathoracic pressure that causes compression of airways (Romer et al., 2008). This in turn will reduce ventricular pressure, ventricular filling rate during …show more content…
Subjects were divided into placebo control and sham training control group, and their responses were recorded 20 and 40-km time trials immediately before and after 6-wks of inspiratory muscle training (IMT). Subjects’ peak inspiratory mouth pressure (P0) was reduced by 18% and 13% within 2 min of completing the 20 and 40-km time trial sessions accordingly and at 30 min P0 remained lower than the pre-exercise level. After post-exercise inspiratory muscle relaxation rate was slow. This concluded that inspiratory muscle fatigue occurs after sustained heavy endurance exercise, but the extent of fatigue can be reduced by IMT (Romer et al., 2001). In untrained individual, respiratory system can limit endurance exercise performance (Boutellier, Buchel, Kundert & Spengler, 1992). After respiratory muscle training, minute ventilation was reduced for endurance cycling test at anaerobic threshold and time for the test performance was increased by 38% in eight subjects (one woman and seven men) (Boutellier et al., 1992).
Another study depicts that, respiratory muscle training (RMT) does not alter cardiovascular responses but though improves cycling endurance at 70% maximal aerobic power. The fifteen weeks of RMT did not affect blood gas concentration i.e. partial pressure of oxygen in arterial blood and or oxygen saturation, cardiac stroke volume, VO2 or substrate utilization

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