DLCO response to experimental cycle-run succession in triathletes.

BACKGROUND

We still know relatively little about the factors that define the ability to perform a good run after cycling in triathlon, however, and the perception of discomfort during the first minutes of this post-cycling running has yet to be satisfactorily explained. The pulmonary diffusion capacity for carbon monoxide (DLCO) has been demonstrated to be impaired after the cycle-run succession. Numerous causes have been suggested to explain this phenomenon, but the exact mechanism has not yet been determined.

METHODS

Thirteen young male triathletes participated in four different exercise trials: 30 min of cycling followed by 20 min of running (C-R, 1 min rest between C and R), 30 min of running followed by 20 min of running (R-R, 1 min rest between R and R), 30 min of cycling (C), and 30 min of running (R). DLCO and alveolar volume were simultaneously measured during 9 sec of breath-holding before and 10 min after exercise. The transfer coefficient (KCO=DLCO/VA) was then calculated. During all trials, ventilatory data were collected every minute using an automated breath-by-breath system.

RESULTS

The results showed that 1) C-R and C induced significant and identical decreases in DLCO and KCO in post-trial compared with pre-trial measurement (40.41+/-2.24 vs 43.49+/-2.36 ml x min(-1) x mm Hg(-1), p<0.01, and 39.37+/-2.16 vs 42.99+/-2.38 ml x min(-1) x mm Hg(-1), p<0.02, for C-R and C, respectively) and 2) there were no DLCO decreases in post-trial compared with pre-trial measurement in R-R and R.

CONCLUSIONS

We concluded that cycling exercise in itself seems to increase the immediate post-exercise DLCO impairment.