Functional assessment of respiratory muscles and lung capacity of CrossFit athletes

CrossFit is a high-intensity training related to physical fitness and respiratory capacity that can promote changes in lung function. This cross-sectional study was aimed at evaluating respiratory muscle strength, electromyographic (EMG) activity, and lung capacity in CrossFit athletes. Thirty subjects aged between 25 and 35 years were divided into groups: CrossFit athletes (n=15) and sedentary individuals without comorbidities (n=15). Respiratory muscle strength was evaluated using maximal inspiratory and expiratory pressures, lung capacity, and EMG of the sternocleidomastoid, serratus anterior, external intercostal, and diaphragm muscles at respiratory rest, maximal inspiration and expiration, and respiratory cycle. Data were tabulated and subjected to statistical analyses (t-test and Spearman test, P<0.05). Respiratory muscle strength on EMG of the sternocleidomastoid, serratus, external intercostal, and diaphragm muscles at the respiratory cycle and maximal forced inspiration and expiration were higher in the CrossFit athletes group than in the sedentary group without comorbidities. CrossFit athlete group showed significantly strong positive correlation between maximal inspiratory and expiratory muscle strengths (Spearman rho= 0.903, P=0.000), with increasing muscle strength during inspiration favoring an increase in strength during expiration. The forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV₁) also showed a significantly high positive correlation (Spearman rho=0.912, P=0.000) in the CrossFit athletes group, showing that higher FVC favors higher FEV₁. The results of this study suggest that improved fitness is based on increased respiratory muscle strength on EMG in CrossFit athletes.