The effects of prior cycling and a successive run on respiratory muscle performance in triathletes

The aim of the present study was to compare the effects of prior cycling and a successive run on respiratory muscle performance during a cycle-run succession as performed in the triathlon. We hypothesized that despite the moderate intensity of exercise and the absence of exhaustion, the crouched cycling position would induce a decrease in respiratory muscle performance that would be reversed by the successive vertical run position. Ten male triathletes (22.6 +/- 1.1 yr) performed a four-trial protocol: 1) an incremental cycle test to assess maximal oxygen uptake ((V) over dot O(2)max), 2) 20 min of cycling (C), 3) 20 min of running (R), and 4) 20 min of cycling followed by 20 min of running (C-R). Trials 2, 3 and 4 were performed at the same metabolic intensity, i.e., 75% Of (V) over dot O(2)max. Respiratory muscle force was assessed by measuring maximal expiratory (P-Emax) and inspiratory (P-lmax) pressures from the functional residual capacity (FRC) before and 10 min after C, R, and C-R. Respiratory muscle endurance was assessed one day before and 30 min after C, R, and C-R, by measuring the time limit (T-lim), which corresponds to the length of time a respiratory load can be sustained before the process of fatigue develops sufficiently to cause task failure. The results showed a similar significant decrease in P-lmax (132.4 +/- 4.9 versus 125.7 +/- 5.6cmH(2)O, p<0.05) and T-lim (5.22 +/- 0.28 versus 3.68 +/- 0.32 min, p < 0.05) post-C and post-C-R (133.7 +/- 4.0 versus 126.9 +/- 5.2 cmH(2)O, and 5.29 +/- 0.18 versus 3.49 +/- 0.41 min, respectively, p < 0.05) compared with the pre-trial values. In contrast, P-lmax and T-lim were not significantly decreased post-R (131.8 +/- 6.1 cm H2O versus 129.6 +/- 6.4 cmH(2)O, and 4.90 +/- 0.69 versus 4.40 +/- 0.56 min, respectively, p>0.05). We concluded that moderate intensity exercise not performed to exhaustion induced a decrease in respiratory muscle performance. Moreover, the respiratory muscle fatigue induced by prior cycling was maintained, and neither reversed nor worsened, by the successive run.