Background: An increased sympathetic activity during muscular effort is a well established physiological response, whose intensity is known to increase with the muscular load. Spirometry was described to improve as an effect of swimming training in healthy and asthmatic subjects, suggesting a decrease in airway resistance The aim was to investigate the possible effect of muscular exercise (swimming) on spirometry, in particular searching for possible differences because of different swimming times.
Methods: The measurements were performed on 9 highly trained male competitive swimmers (age: 41±12.79 years, height: 1.69±0.06 meters, weight: 66.14±14.28 kg, BMI: 22.8±3.61 kg/m2) during an official competition. The data were collected at the border of the swimming-pool before (control, C) and few minutes after the swimming sessions (exercise, E), which consisted either of 800 meter (7 subjects) or 1500 meter (5 subjects) free style.
Results: A general trend indicating a postexercise increase in spirometry was observed. We found post-exercise significant increments in FEV1 and in MEF75 for both the 800 and 1500 meter swimming sessions, and in FEF25-75 and in MEF25 for the shorter distance.
Conclusions: We conclude that, as it may be expected, muscular exercise induces an improvement of spirometry both because of a smooth muscle relaxation-induced modulation of airway diameter and resistance to airflow, and because of an enhanced expiratory muscle contraction strength. Both of these mechanisms are related to an increased sympathetic activity which is well known to accompany muscular exercise.