Key result
Low-intensity steady-state cycling decreased end-expiratory lung volume compared with rest (P<0.001 at 60-W), while total lung capacity did not differ significantly.
Why the study?
Does low-intensity steady-state cycling alter total lung capacity and end-expiratory lung volume in healthy men compared to rest?
Does low-intensity steady-state cycling alter total lung capacity and end-expiratory lung volume in healthy men compared to rest?
p-value: p=<0.001
Total lung capacity remains constant during low-intensity steady-state cycling, validating the use of inspiratory capacity to estimate changes in end-expiratory lung volume.
Supports inspiratory capacity use to estimate end-expiratory lung volume shifts during low-intensity exercise; extends resting validations to dynamic conditions but requires larger confirmation.
The use of inspiratory capacity (IC) to estimate end-expiratory lung volume (EELV) during exercise has been questioned because of the assumption of constant total lung capacity (TLC). To investigate lung volumes during low-intensity steady-state cycling, we measured EELV by the open-circuit N2 washout method (MR-1, currently Sensormedics 2100) in eight healthy men while at rest and during unloaded and 60-W cycling. TLC was calculated by adding EELV and IC. Measurement variation of TLC was 142 ml at rest, 121 ml during unloaded cycling, and 158 ml during 60-W cycling. TLC did not differ significantly among the three conditions studied. EELV decreased during unloaded (P less than 0.002) and 60-W cycling (P less than 0.001) compared with rest. End-inspiratory lung volume increased only during 60-W cycling (P = 0.03). The decrease in EELV accounted for 100% of the increase in tidal volume during unloaded cycling. Although minute ventilation was similar in the subjects during unloaded cycling, we noted that breathing patterns varied among the subjects. The increase in respiratory frequency was negatively correlated to the change in tidal volume (R2 = 0.54, P = 0.038) and to the change in end-inspiratory lung volume (R2 = 0.68, P = 0.012). We conclude that TLC does not differ significantly during low-intensity steady-state cycling and that use of IC to estimate changes in EELV is appropriate.
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Babb et al. (1991) studied Healthy (n=8). Low-intensity steady-state cycling vs. Rest was evaluated on Total lung capacity (TLC) and end-expiratory lung volume (EELV) (p=<0.001). Low-intensity steady-state cycling decreased end-expiratory lung volume compared with rest (P<0.001 at 60-W), while total lung capacity did not differ significantly.
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