Post by John A. Casler on Sept 15, 2009 7:58:39 GMT -8
This is from Jamie Carruthers as posted to SuperTraining
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THE SATELLITE CELL RESPONSE TO AN ACUTE BOUT OF OCCLUSION EXERCISE.
NILSEN, T., WERNBOM, M., PAULSEN, G., KOSKINEN, S., RAASTAD, T.
NORWEGIAN SCHOOL OF SPORT SCIENCES
Introduction: Low load exercise with vascular occlusion has attained increased interest the last years due to the observed effects on muscle hypertrophy (Wernbom et al 2008). Although the potential to induce muscle growth over a training period has been well documented, the effects of occlusion exercise on the cellular level remains to be investigated. Because satellite cells (SC) are important for skeletal muscle hypertrophy and the satellite cell expresses myogenic regulation factors (MRFs) upon activation, the aim of this study was to investigate the effect of one bout of occlusion exercise on the number of SC and the number of SC expressing either MyoD or myogenin.
Methods: Nine subjects completed one bout of unilateral knee extension with five sets till failure with a load representing 30 % of 1 RM.
One leg completed the bout with partial vascular occlusion provided by an inflatable pressure cuff. The other leg preformed a repetitionmatched bout, and thus served as a non occluded control. Maximal isometric voluntary contraction force (MVC) was measured before exercise and repeatedly for one week after the bout. Biopsies were obtained pre-exercise, control leg only, 1 h-, 24 h- and 48 h post exercise from both legs. Cross sections from the biopsies were stained with antibody against NCAM, which recognises SC, and counterstained with antibodies against MyoD or myogenin, on neighbour sections. SC was counted as NCAM positive ring like staining in close relation to the muscle fibre. MyoD- og myogenin positive SC were identified as MRF positive staining inside the SC.
Results: Immediately after exercise there was a larger reduction in MVC force in the occluded leg than in the non occluded leg. Four hrs after exercise this difference was reduced, but the occluded leg generated less force throughout the recorded period compared to the control leg. Our data indicates a tendency towards an increased number of SC expressing one of the two MRF's. There were no differences in the increase of SC between the two legs. However, when combining the two legs an increased number of SC per fibre was observed one hour after exercise, and the number remained increased throughout the 48 h period.
Discussion: An increased number of SC expressing MRF indicates a SC response to the exercise. The immediate increase in number of SCper fibre is an interesting observation, and to our knowledge this has not been described earlier. However, it's rather unlikely that this is due to a real increase in the number of SC per whole muscle fibre; it's more likely that it's a methodical issue. One explanation could be an increased SC volume in activated SC, leading to in an increased number of counted SC per cross section. In further analysis we will elucidate the possible mechanisms for the early increase in the number of SC and further describe the time course of activated satellite cells after low load occlusion exercise.
Wernbom et al. Scand J Med Sci Sports 18: 401-416. 2008.
To visit SUPERTRAINING FORUM
health.groups.yahoo.com/group/Supertraining/?yguid=44276758
THE SATELLITE CELL RESPONSE TO AN ACUTE BOUT OF OCCLUSION EXERCISE.
NILSEN, T., WERNBOM, M., PAULSEN, G., KOSKINEN, S., RAASTAD, T.
NORWEGIAN SCHOOL OF SPORT SCIENCES
Introduction: Low load exercise with vascular occlusion has attained increased interest the last years due to the observed effects on muscle hypertrophy (Wernbom et al 2008). Although the potential to induce muscle growth over a training period has been well documented, the effects of occlusion exercise on the cellular level remains to be investigated. Because satellite cells (SC) are important for skeletal muscle hypertrophy and the satellite cell expresses myogenic regulation factors (MRFs) upon activation, the aim of this study was to investigate the effect of one bout of occlusion exercise on the number of SC and the number of SC expressing either MyoD or myogenin.
Methods: Nine subjects completed one bout of unilateral knee extension with five sets till failure with a load representing 30 % of 1 RM.
One leg completed the bout with partial vascular occlusion provided by an inflatable pressure cuff. The other leg preformed a repetitionmatched bout, and thus served as a non occluded control. Maximal isometric voluntary contraction force (MVC) was measured before exercise and repeatedly for one week after the bout. Biopsies were obtained pre-exercise, control leg only, 1 h-, 24 h- and 48 h post exercise from both legs. Cross sections from the biopsies were stained with antibody against NCAM, which recognises SC, and counterstained with antibodies against MyoD or myogenin, on neighbour sections. SC was counted as NCAM positive ring like staining in close relation to the muscle fibre. MyoD- og myogenin positive SC were identified as MRF positive staining inside the SC.
Results: Immediately after exercise there was a larger reduction in MVC force in the occluded leg than in the non occluded leg. Four hrs after exercise this difference was reduced, but the occluded leg generated less force throughout the recorded period compared to the control leg. Our data indicates a tendency towards an increased number of SC expressing one of the two MRF's. There were no differences in the increase of SC between the two legs. However, when combining the two legs an increased number of SC per fibre was observed one hour after exercise, and the number remained increased throughout the 48 h period.
Discussion: An increased number of SC expressing MRF indicates a SC response to the exercise. The immediate increase in number of SCper fibre is an interesting observation, and to our knowledge this has not been described earlier. However, it's rather unlikely that this is due to a real increase in the number of SC per whole muscle fibre; it's more likely that it's a methodical issue. One explanation could be an increased SC volume in activated SC, leading to in an increased number of counted SC per cross section. In further analysis we will elucidate the possible mechanisms for the early increase in the number of SC and further describe the time course of activated satellite cells after low load occlusion exercise.
Wernbom et al. Scand J Med Sci Sports 18: 401-416. 2008.