| Autor: |
Skelly LE; Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada., Gillen JB; Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.; Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada., Frankish BP; Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, Melbourne, Victoria, Australia., MacInnis MJ; Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.; Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada., Godkin FE; Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada., Tarnopolsky MA; Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.; Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada., Murphy RM; Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, Melbourne, Victoria, Australia.; Department of Physiology, Anatomy and Microbiology, School of Life Sciences, La Trobe University, Melbourne, Victoria, Australia., Gibala MJ; Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada. |
| Abstrakt: |
There are limited and equivocal data regarding potential fiber type-specific differences in the human skeletal muscle response to sprint interval training (SIT), including how this compares with moderate-intensity continuous training (MICT). We examined mixed-muscle and fiber type-specific responses to a single session ( study 1 ) and to 12 wk ( study 2 ) of MICT and SIT using Western blot analysis. MICT consisted of 45 min of cycling at ∼70% of maximal heart rate, and SIT involved 3 × 20-s "all-out" sprints interspersed with 2 min of recovery. Changes in signaling proteins involved in mitochondrial biogenesis in mixed-muscle and pooled fiber samples were similar after acute MICT and SIT. This included increases in the ratios of phosphorylated to total acetyl-CoA carboxylase and p38 mitogen-activated protein kinase protein content (main effects, P < 0.05). Following training, mitochondrial content markers including the protein content of cytochrome c oxidase subunit IV and NADH:ubiquinone oxidoreductase subunit A9 were increased similarly in mixed-muscle and type IIa fibers (main effects, P < 0.05). In contrast, only MICT increased these markers of mitochondrial content in type I fibers (interactions, P < 0.05). MICT and SIT also similarly increased the content of mitochondrial fusion proteins optic atrophy 1 (OPA1) and mitofusin 2 in mixed-muscle, and OPA1 in pooled fiber samples (main effects, P < 0.02). In summary, acute MICT and SIT elicited similar fiber type-specific responses of signaling proteins involved in mitochondrial biogenesis, whereas 12 wk of training revealed differential responses of mitochondrial content markers in type I but not type IIa fibers. NEW & NOTEWORTHY We examined mixed-muscle and fiber type-specific responses to a single session and to 12 wk of moderate-intensity continuous training (MICT) and sprint interval training (SIT) in humans. Both interventions elicited generally similar responses, although the training-induced increases in type I fiber-specific markers of mitochondrial content were greater in MICT than in SIT. These findings advance our understanding of the potential role of fiber type-specific changes in determining the human skeletal muscle response to intermittent and continuous exercise. |
