Purpose: To investigate the kinetics of O2 uptake (VO2) and m. vastus lateralis [deoxyhemoglobin] ([Hb]) (near-infrared spectroscopy) for supramaximal intermittent cycling.
Methods: Six males performed a ramp test for determination of VO2peak and lactate threshold. On different days, they completed four intermittent "work:recovery" tests (10 s:20 s, 30 s:60 s, 60 s:120 s, 90 s:180 s) for 30 min or to the tolerable limit; "work" = 120% peak work rate (WRpeak) attained on the ramp, "recovery" = 20 W.
Results: Arterialized capillary [lactate] ([L−]c) profiles were dependent on duty-cycle length and resembled those for constant-load exercise classically used to assign exercise intensity: 10 s:20 s-no increase (i.e., "moderate", with first-order VO2 kinetics); 30 s:60 s-increased but stable (i.e., "heavy," with first-order VO2 kinetics supplemented by a slow component (VO2 sc) that stabilizes); 60s:120s-progressive increase that was more marked for 90 s:180 s (i.e., "very heavy" or "severe," with first-order VO2 kinetics supplemented by a VO2 sc projecting to VO2peak). VO2 and Δ[Hb] oscillated with WR, the ensemble-averaged single-cycle oscillation amplitudes (peak-to-nadir) for each individual subject increasing with WR duty-cycle duration. In the 30-s:60-s test, with [L−]c being elevated, there was also a tendency towards a modest VO2 sc, with an increase in individual VO2 peak values early in the test and VO2 not fully recovering back to baseline in recovery. This was more marked for the 60-s:120-s duty cycle: VO2 failed to recover completely back to baseline, and the peaks of the VO2 oscillations increased significantly with time (F = 30.7, P < 0.001); in some cases, VO2peak was attained and exhaustion rapidly ensued.
Conclusion: VO2 kinetics in intermittent exercise over a range of duty-cycle durations tended to associate with blood [lactate] profiles, similarly to previous demonstrations for sustained constant-load exercise.
1Centre for Exercise Science and Medicine, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, UNITED KINGDOM; 2Department of Physical Education, Sport and Leisure Studies, Moray House School of Education, University of Edinburgh, Edinburgh, UNITED KINGDOM; 3School of Sport and Exercise Sciences, University of Leeds, Leeds, UNITED KINGDOM; and 4English Institute of Sport, Sportcity, Manchester, UNITED KINGDOM
Submitted for publication December 2004.
Accepted for publication September 2005.
Address for correspondence: Dr. Tony Turner, Dept. of Physical Education, Sport & Leisure Studies, Moray House School of Education, University of Edinburgh, Edinburgh EH8 8AQ, United Kingdom; E-mail: firstname.lastname@example.org.