Energy expenditure of submaximal running does not increase after cycle-run transition.
OBJECTIVE
This study was performed to determine the relationship between increased fat oxidation and decreased running efficiency following intense cycling exercise.


METHODS
Twenty-two middle-level triathletes were studied during submaximal running before and after submaximal cycling exercise. All subjects completed a 13-min run on a track at a velocity corresponding to 75% of their maximal aerobic speed (MAS) before (T1) and after (T2) submaximal cycling exercise at 75 % of maximal aerobic power (MAP). The energy cost of running (Cr) was quantified using the O(2) uptake (.VO(2)) and energy expenditure (EE) using the respiratory exchange ratio (RER). Gas exchange was measured over 30 s during the 3(rd) min and last 30 s of each run.


RESULTS
The results show that after cardiorespiratory equilibration (12 min 30 s), Cr (calculated in mL(O(2))*kg(-1)*m(-1)) during T2 was higher than during T1 (+ 8.2+/-4.3%; P = 0.03). Similar observations were made for .VO(2) (+ 8.2+/-4.3%; P = 0.03) and pulmonary ventilation (+ 7.0+/-12.3%; P = 0.04). RER decreased between T1 and T2 (- 8.6+/-9.2 %; p = 0.01). EE and Cr expressed in kJ.kg(-1).m(-1) did not vary significantly between T1 and T2.


CONCLUSIONS
We suggest that the decrease in RER drop may be a result of greater lipid oxidation as metabolic substrate after cycling exercise.
Pialoux
V
V
Laboratory of Biology and Physical Fitness, University of Auvergne, Clermont-Ferrand, France. pialouxvincent@yahoo.fr
Proust
O
O
Mounier
R
R
D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology; D012420:Running / Q000502:physiology*