| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Research Institute MOVE, VU University, Amsterdam, Netherlands
2 Institute for Biophysical and Clinical Reserach into Human Movement, Manchester Metropolitan University, Alsager, United Kingdom
3 EMGO Institute and Department of Social Medicine, VU Medical Centre, Amsterdam, Netherlands
4 IRM Research Institute, Manchester Metropolitan Hospital, Hassall Road, Alsager, st72hl, United Kingdom; Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan Hospital, Alsager, United Kingdom
* To whom correspondence should be addressed. E-mail: t.altenburg{at}fbw.vu.nl.
In literature, an inconsistency exists in the submaximal exercise intensity at which type II fibers are activated. In the present study, the recruitment of type I and II fibers was investigated from the very beginning and throughout a 45-min cycle exercise at 75% VO2max, which corresponded to 38% of the maximal dynamic muscle force. Biopsies of the vastus lateralis muscle were taken from six subjects at rest and during the exercise, two at each time point. From the first biopsy single fibers were isolated, characterized as type I and II, and PCr/Cr ratios and periodic acid Schiff (PAS) stain intensities were measured. Cross-sections were cut from the second biopsy, individual fibers were characterized as type I and II and PAS stain intensities were measured. A decline in PCr/Cr ratio and in PAS stain intensity was used as indication of fiber recruitment. Within 1 min of exercise both type I and, though to a lesser extent, type II fibers were recruited. Furthermore, the PCr/Cr ratio revealed that the same proportion of fibers was recruited during the whole 45 min of exercise, indicating a rather constant recruitment. The PAS staining, however, proved inadequate to fully demonstrate fiber recruitment even after 45 min of exercise. We conclude that during cycling exercise a greater proportion of type II fibers are recruited than previously reported for isometric contractions, probably due to the dynamic character of the exercise. Furthermore, the PCr/Cr ratio method is more sensitive in determining fiber activation than the PAS stain intensity method.
This article has been cited by other articles:
|
|
 |
|
  S. Perrey, M. Burnley, G. P. Millet, F. Borrani, A. M. Jones, D. C. Poole, S. W. Copp, D. M. Hirai, P. Gimenez, T. Busso, et al. Comments on point: counterpoint: the kinetics of oxygen uptake during muscular exercise do/do not manifest time-delayed phase. Modeling concerns. J Appl Physiol, November 1, 2009; 107(5): 1669 - 1670. [Full Text] [PDF]
|
|
|
|
|
|
M. P. Bell and R. A. Ferguson Interaction between muscle temperature and contraction velocity affects mechanical efficiency during moderate-intensity cycling exercise in young and older women J Appl Physiol, September 1, 2009; 107(3): 763 - 769. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Marcora Is peripheral locomotor muscle fatigue during endurance exercise a variable carefully regulated by a negative feedback system? J. Physiol., April 1, 2008; 586(7): 2027 - 2028. [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
