| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
2 Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
* To whom correspondence should be addressed. E-mail: mmourtza{at}uoguelph.ca.
To elucidate the potential limitations on maximal human quadriceps O2 capacity, 6 subjects trained (T) one quadriceps on the single-legged knee-extensor ergometer (1h/day at 70%Wmax for 5 days/wk) while their contralateral quadriceps remained untrained (UT). Following 5 weeks of training, subjects underwent incremental knee-extensor tests under normoxic (FIO2=21%) and hyperoxic (FIO2=60%) conditions with the T and UT quadriceps. Training increased quadriceps muscle mass (2.9±0.2 to 3.1±0.2 kg), but did not change fiber type composition or capillary density. The T quadriceps performed at a greater peak power output than UT both under normoxia (101±10 vs 80±7 W, respectively; p<0.05) and hyperoxia (97±11 vs 81±7 W, respectively; p<0.05) without further increases with hyperoxia. Similarly, thigh peak VO2, blood flow, vascular conductance and O2 delivery were greater in the T versus the UT thigh (1.4±0.2 vs 1.1±0.1 L/min, 8.4±0.8 vs 7.2±0.8 L/min, 42±6 vs. 35±4 mL/min/mmHg, 1.71±0.18 vs 1.51±0.15 L/min, respectively) but were not enhanced with hyperoxia. Oxygen extraction was elevated in the T versus the UT thigh while (a-v)O2 difference tended to be higher (78±2 vs 72±4 %, p<0.05; 160±8 vs 154±11 mL/L, respectively; p=0.098) but again were unaltered with hyperoxia. In conclusion, the present results demonstrate that the increase in quadriceps muscle O2 uptake with training is largely associated with increases in blood flow and O2 delivery with smaller contribution from increases in O2 extraction. Furthermore, the elevation in peak muscle blood flow and vascular conductance with endurance training seem to be related to an enhanced capillary density of the vasculature perfusing the quadriceps muscle that is unaltered by moderate hyperoxia.
This article has been cited by other articles:
|
|
 |
|
  M. Mourtzakis, T. E. Graham, J. Gonzalez-Alonso, and B. Saltin Glutamate availability is important in intramuscular amino acid metabolism and TCA cycle intermediates but does not affect peak oxidative metabolism J Appl Physiol, August 1, 2008; 105(2): 547 - 554. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Liguzinski and B. Korzeniewski Oxygen delivery by blood determines the maximal VO2 and work rate during whole body exercise in humans: in silico studies Am J Physiol Heart Circ Physiol, July 1, 2007; 293(1): H343 - H353. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Barden, L. Lawrenson, J. G. Poole, J. Kim, D. W. Wray, D. M. Bailey, and R. S. Richardson Limitations to vasodilatory capacity and VO2 max in trained human skeletal muscle Am J Physiol Heart Circ Physiol, May 1, 2007; 292(5): H2491 - H2497. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Hahn, L. F. Ferreira, J. B. Williams, K. P. Jansson, B. J. Behnke, T. I. Musch, and D. C. Poole Downhill treadmill running trains the rat spinotrapezius muscle J Appl Physiol, January 1, 2007; 102(1): 412 - 416. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Stellingwerff, P. J. LeBlanc, M. G. Hollidge, G. J. F. Heigenhauser, and L. L. Spriet Hyperoxia decreases muscle glycogenolysis, lactate production, and lactate efflux during steady-state exercise Am J Physiol Endocrinol Metab, June 1, 2006; 290(6): E1180 - E1190. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
