Abstract
The purpose of this investigation was to determine if p70s6k phosphorylation is dependent on the mode of resistance exercise (e.g. isometric vs. lengthening). Two groups (n = 5 each) of Female Sprague Dawley rats, ∼12 weeks old, were tested. Rats were anesthetized and indwelling electrodes used to stimulate the right hind limb muscles via the sciatic nerve. The tibialis anterior (TA) muscle of Group 1 rats were exposed to three sets of ten isometric resistance contractions while the TA of Group 2 rats were exposed to three sets of ten resistance contractions that involved lengthening. Contralateral TA muscles served as non-exercised controls. The TA muscle was harvested 6 h post exercise and then the rat was euthanized. Muscle samples were processed to compare p70s6k phosphorylation between groups. A single bout of TA contractions that involved muscle lengthening resulted in significantly (p < 0.05) higher levels of phospho-p70s6k six hours post exercise compared to controls and isometric contractions. The differences in total p70s6k six hours post exercise were not significantly different between groups. Results suggest that signal transduction pathways activated by isometric exercise may differ (i.e., a non-p70s6k activation pathway) from that activated by lengthening exercise.
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Acknowledgments
The authors wish to thank Emily Pettycrew for outstanding technical support. Also partial support to Dr E. E. Spangenburg was received from NIH (AR051396). Dr. E. E. Spangenburg current address is University of Maryland, Department of Kinesiology, College Park, MD 20742.
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The authors have no relationships that present a conflict of interest regarding the worked presented in this article.
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Burry, M., Hawkins, D. & Spangenburg, E.E. Lengthening contractions differentially affect p70s6k phosphorylation compared to isometric contractions in rat skeletal muscle. Eur J Appl Physiol 100, 409–415 (2007). https://doi.org/10.1007/s00421-007-0444-5
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DOI: https://doi.org/10.1007/s00421-007-0444-5