Blood gas changes during incremental and sprint exercise

Authors


Department of Veterinary Clinical Science, University of Sydney, NSW 2006, Australia.

Summary

We investigated and compared arterial blood gas and ventilatory changes during rapid acceleration sprint and during incremental treadmill exercise. Seven clinically normal racehorses completed standardised incremental exercise tests and rapid acceleration tests at speeds calculated to elicit 115% V̇o2max. Arterial oxygen tension decreased (P<.001) between 15 s (mean ± s.d. 103.8 ± 14.3 mmHg) and 30 s (85.0 ± 7.7 mmHg) after the onset of rapid acceleration exercise, but did not change significantly during the remainder of the sprint. This was accompanied by an increase in Paco2 of 5.9 mmHg (P<.05). Despite reductions in Sao2 during exercise, Cao2 did not change due to increases in haemoglobin concentration. Heart rate increased rapidly (P<.001) during the first 15 s of exercise and thereafter remained constant. The mean maximum speed during the incremental test (11.4 ± 0.5m/s) was not significantly different to the speed calculated to elicit 115% V̇o2max during the sprint test (12.2 ± 0.8 m/s). The mean peak HR and Hb during the sprint test were significantly less than during the incremental test. However, there were no significant differences in the maximum or minimum values achieved for other variables.

We conclude that rapid acceleration exercise is accompanied by rapid changes in blood gas variables, reaching steady state within 45 s. Blood gas responses during the simpler incremental test describe maximal changes during high-intensity sprint exercise.

Abbreviations
Pao2

Arterial oxygen tension

Paco2

Arterial carbon dioxide tension

Sao2

Arterial saturation of haemoglobin with oxygen

Cao2

Arterial oxygen content

PAo2

Alveolar oxygen tension

P(A-a)o2

Alveolar-arterial oxygen tension difference

o2

Oxygen consumption

V̇A

Alveolar ventilation

HR

Heart rate

Ancillary