Functional assessment of respiratory muscles and lung capacity of CrossFit athletes

CrossFit is a high-intensity training related to physical fitness and respi- ratory 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 ath- letes. Thirty subjects aged between 25 and 35 years were divided into groups: CrossFit athletes (n=15) and sedentary individuals without co - morbidities (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 expira- tion, and respiratory cycle. Data were tabulated and subjected to statis- tical analyses (t-test and Spearman test, P< 0.05). Respiratory muscle strength on EMG of the sternocleidomastoid, serratus, external inter- costal, 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 ath- lete 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 fa- voring an increase in strength during expiration. The forced vital capac- ity (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 in- creased respiratory muscle strength on EMG in CrossFit athletes.