Abstract
Eight well-trained male cyclists participated in two testing sessions each
including two sets of 10 cycle exercise bouts at 150% of maximal
aerobic power. In the first session, subjects performed the exercise bouts
with end-expiratory breath holding (EEBH) of maximal duration. Each exercise
bout started at the onset of EEBH and ended at its release (mean duration:
9.6±0.9 s; range: 8.6–11.1 s). At the second testing
session, subjects performed the exercise bouts (same duration as in the
first session) with normal breathing. Heart rate, left ventricular stroke
volume (LVSV), and cardiac output were continuously measured through
bio-impedancemetry. Data were analysed for the 4 s preceding and following
the end of each exercise bout. LVSV (peak values: 163±33 vs.
124±17 mL, p<0.01) was higher and heart rate lower both in
the end phase and in the early recovery of the exercise bouts with EEBH as
compared with exercise with normal breathing. Cardiac output was generally
not different between exercise conditions. This study showed that performing
maximal EEBH during high-intensity exercise led to a large increase in LVSV.
This phenomenon is likely explained by greater left ventricular filling as a
result of an augmented filling time and decreased right ventricular volume
at peak EEBH.
Key words
hypoxia - hypoventilation - hypoxaemia - cycling
