Exercise tolerance in intermittent cycling:  application of the critical power concept.
OBJECTIVE
This study tested the relevance of the critical power (CP) model for explaining exercise tolerance during intermittent high-intensity exercise with different recovery intensities.


METHODS
After estimation of CP and W' from a 3-min all-out test, seven male subjects completed, in randomized order, a cycle test to exhaustion at a severe-intensity constant-work-rate (S-CWR) and four cycle tests to exhaustion using different intermittent ("work-recovery") protocols (i.e., severe-severe (S-S), severe-heavy (S-H), severe-moderate (S-M), and severe-light (S-L)).


RESULTS
The tolerable duration of exercise in S-CWR was 384 ± 48 s, and this was increased by 47%, 100%, and 219% for S-H, S-M, and S-L, respectively (all P < 0.05). Consistent with this, compared with S-CWR (22.9 ± 7.4 kJ), the work done above the CP was significantly greater by 46%, 98%, and 220% for S-H, S-M, and S-L, respectively (all P < 0.05). The slope of the relationship between V˙O₂ and time was significantly reduced for S-H, S-M, and S-L (0.09 ± 0.02, 0.09 ± 0.01, and 0.07 ± 0.02 L·min⁻², respectively) compared with S-CWR (0.16 ± 0.03 L·min⁻², P < 0.05). In addition, the slope of the relationship between integrated EMG and time showed a systematic decline for S-H, S-M, and S-L compared with S-CWR (P < 0.05).


CONCLUSIONS
These results indicate that, when recovery intervals during intermittent exercise are performed below the CP, exercise tolerance is improved in proportion to the reconstitution of the finite W'. The enhanced exercise tolerance with the lower-intensity recovery intervals was associated with a blunted increase in both V˙O₂ and integrated EMG with time.
Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, Devon, England, United Kingdom.
Weerapong
W
Chidnok
Fred J
FJ
Dimenna
Stephen J
SJ
Bailey
Anni
A
Vanhatalo
R Hugh
RH
Morton
Daryl P
DP
Wilkerson
Andrew M
AM
Jones
D000328:Adult; D000704:Analysis of Variance; D001642:Bicycling / Q000502:physiology*; D004576:Electromyography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange; D020127:Recovery of Function / Q000502:physiology*