Muscular adaptations and insulin-like growth factor-1 responses to resistance training are stretch-mediated

Authors

  • Gerard McMahon MSc,

    1. Institute for Performance Research, Department of Exercise & Sport Science, Manchester Metropolitan University, Valentine Building, Crewe Green Road, Crewe, UK
    2. Sports Institute Northern Ireland, University of Ulster, Newtownabbey, Belfast, UK
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  • Christopher I. Morse PhD,

    1. Institute for Performance Research, Department of Exercise & Sport Science, Manchester Metropolitan University, Valentine Building, Crewe Green Road, Crewe, UK
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  • Adrian Burden PhD,

    1. Institute for Performance Research, Department of Exercise & Sport Science, Manchester Metropolitan University, Valentine Building, Crewe Green Road, Crewe, UK
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  • Keith Winwood PhD,

    1. Institute for Performance Research, Department of Exercise & Sport Science, Manchester Metropolitan University, Valentine Building, Crewe Green Road, Crewe, UK
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  • Gladys Leopoldine Onambélé PhD

    Corresponding author
    1. Institute for Performance Research, Department of Exercise & Sport Science, Manchester Metropolitan University, Valentine Building, Crewe Green Road, Crewe, UK
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  • This study was supported by the Institute for Performance Research, Manchester Metropolitan University.

ABSTRACT

Introduction: Modulation of muscle characteristics was attempted through altering muscle stretch during resistance training. We hypothesized that stretch would enhance muscle responses. Methods: Participants trained for 8 weeks, loading the quadriceps in a shortened (SL, 0–50° knee flexion; n = 10) or lengthened (LL, 40–90°; n = 11) position, followed by 4 weeks of detraining. Controls (CON; n = 10) were untrained. Quadriceps strength, vastus lateralis architecture, anatomical cross-sectional area (aCSA), and serum insulin-like growth factor-1 (IGF-1) were measured at weeks 0, 8, 10, and 12. Results: Increases in fascicle length (29 ± 4% vs. 14 ± 4%), distal aCSA (53 ± 12% vs. 18 ± 8%), strength (26 ± 6% vs. 7 ± 3%), and IGF-1 (31 ± 6% vs. 7 ± 6%) were greater in LL compared with SL muscles (P < 0.05). No changes occurred in CON. Detraining decrements in strength and aCSA were greater in SL than LL muscles (P < 0.05). Conclusions: Enhanced muscle in vivo (and somewhat IGF-1) adaptations to resistance training are concurrent with muscle stretch, which warrants its inclusion within training. Muscle Nerve 49: 108–119, 2014

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