| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Departments of 1 Biomechanics and Movement Science and 4 Physical Therapy, University of Delaware, Newark, Delaware 19716; and Departments of 2 Radiology and 3 Physiology, University of Pennsylvania, Philadelphia, Pennsylvania 19014
During isometric contractions, no true work is performed, so the force-time integral (FTI) is often used to approximate isometric work. However, the relationship between FTI and metabolic cost is not as linear. We tested the hypothesis that this nonlinearity was due to the cost of attaining a given force being greater than that of maintaining it. The ATP consumed per contraction in the human medial gastrocnemius muscle (n = 6) was determined by use of 31P-NMR spectroscopy during eight different electrical stimulation protocols. Each protocol consisted of 8 trains of a single frequency (20 or 80 Hz) and duration (300, 600, 1,200, or 1,800 ms) performed under ischemic conditions. The cost of force generation was determined from the ATP turnover during the short-duration trains that did not attain a steady force level. Estimates of the cost of force maintenance at each frequency were determined by subtracting the ATP turnover during the shorter-duration trains from the turnover during the long-duration trains. The force generation phase of an isometric contraction was indeed more metabolically costly than the force maintenance phase during both 20- and 80-Hz stimulation. Thus the mean rate of ATP hydrolysis appeared to decline as contraction duration increased. Interestingly, the metabolic costs of maintaining force during 20-Hz and 80-Hz stimulation were comparable, although different levels of force were produced.
skeletal muscle; metabolism; contractile cost; 31P-nuclear magnetic resonance
This article has been cited by other articles:
|
|
 |
|
  R. C. I. Wust, C. I. Morse, A. de Haan, D. A. Jones, and H. Degens Sex differences in contractile properties and fatigue resistance of human skeletal muscle Exp Physiol, July 1, 2008; 93(7): 843 - 850. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. A. Jubrias, N. K. Vollestad, R. K. Gronka, and M. J. Kushmerick Contraction coupling efficiency of human first dorsal interosseous muscle J. Physiol., April 1, 2008; 586(7): 1993 - 2002. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Armstrong, A. K. Dua, and C. L. Murrant Time course of vasodilation at the onset of repetitive skeletal muscle contractions Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R505 - R515. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. W. Russ and R. M. Lovering Influence of activation frequency on cellular signalling pathways during fatiguing contractions in rat skeletal muscle Exp Physiol, November 1, 2006; 91(6): 957 - 966. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Kesar and S. Binder-Macleod Effect of frequency and pulse duration on human muscle fatigue during repetitive electrical stimulation Exp Physiol, November 1, 2006; 91(6): 967 - 976. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Kemp Lactate accumulation, proton buffering, and pH change in ischemically exercising muscle Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2005; 289(3): R895 - R901. [Full Text] [PDF]
|
|
|
|
 |
|
 T. F. Towse, J. M. Slade, and R. A. Meyer Effect of physical activity on MRI-measured blood oxygen level-dependent transients in skeletal muscle after brief contractions J Appl Physiol, August 1, 2005; 99(2): 715 - 722. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. L. Murrant Stimulation characteristics that determine arteriolar dilation in skeletal muscle Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2005; 289(2): R505 - R513. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. J. Hamann, H. A. Kluess, J. B. Buckwalter, and P. S. Clifford Blood flow response to muscle contractions is more closely related to metabolic rate than contractile work J Appl Physiol, June 1, 2005; 98(6): 2096 - 2100. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Pathare, G. A. Walter, J. E. Stevens, Z. Yang, E. Okerke, J. D. Gibbs, J. L. Esterhai, M. T. Scarborough, C. P. Gibbs, H. L. Sweeney, et al. Changes in inorganic phosphate and force production in human skeletal muscle after cast immobilization J Appl Physiol, January 1, 2005; 98(1): 307 - 314. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kristensen and T. Hansen Statistical analyses of repeated measures in physiological research: a tutorial Advan Physiol Educ, March 1, 2004; 28(1): 2 - 14. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. W. Russ and J. A. Kent-Braun Sex differences in human skeletal muscle fatigue are eliminated under ischemic conditions J Appl Physiol, June 1, 2003; 94(6): 2414 - 2422. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. W. Russ, K. Vandenborne, and S. A. Binder-Macleod Factors in fatigue during intermittent electrical stimulation of human skeletal muscle J Appl Physiol, August 1, 2002; 93(2): 469 - 478. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
