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Muscular and systemic correlates of resistance training-induced muscle hypertrophy.
PLoS One. 2013; 8(10):e78636.Plos

Abstract

PURPOSE

To determine relationships between post-exercise changes in systemic [testosterone, growth hormone (GH), insulin like grow factor 1 (IGF-1) and interleukin 6 (IL-6)], or intramuscular [skeletal muscle androgen receptor (AR) protein content and p70S6K phosphorylation status] factors in a moderately-sized cohort of young men exhibiting divergent resistance training-mediated muscle hypertrophy.

METHODS

Twenty three adult males completed 4 sessions•wk⁻¹ of resistance training for 16 wk. Muscle biopsies were obtained before and after the training period and acutely 1 and 5 h after the first training session. Serum hormones and cytokines were measured immediately, 15, 30 and 60 minutes following the first and last training sessions of the study.

RESULTS

Mean fiber area increased by 20% (range: -7 to 80%; P<0.001). Protein content of the AR was unchanged with training (fold change = 1.17 ± 0.61; P=0.19); however, there was a significant correlation between the changes in AR content and fiber area (r=0.60, P=0.023). Phosphorylation of p70S6K was elevated 5 hours following exercise, which was correlated with gains in mean fiber area (r=0.54, P=0.007). There was no relationship between the magnitude of the pre- or post-training exercise-induced changes in free testosterone, GH, or IGF-1 concentration and muscle fiber hypertrophy; however, the magnitude of the post exercise IL-6 response was correlated with muscle hypertrophy (r=0.48, P=0.019).

CONCLUSION

Post-exercise increases in circulating hormones are not related to hypertrophy following training. Exercise-induced changes in IL-6 correlated with hypertrophy, but the mechanism for the role of IL-6 in hypertrophy is not known. Acute increases, in p70S6K phosphorylation and changes in muscle AR protein content correlated with muscle hypertrophy implicating intramuscular rather than systemic processes in mediating hypertrophy.

Authors+Show Affiliations

Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

24130904

Citation

Mitchell, Cameron J., et al. "Muscular and Systemic Correlates of Resistance Training-induced Muscle Hypertrophy." PloS One, vol. 8, no. 10, 2013, pp. e78636.
Mitchell CJ, Churchward-Venne TA, Bellamy L, et al. Muscular and systemic correlates of resistance training-induced muscle hypertrophy. PLoS ONE. 2013;8(10):e78636.
Mitchell, C. J., Churchward-Venne, T. A., Bellamy, L., Parise, G., Baker, S. K., & Phillips, S. M. (2013). Muscular and systemic correlates of resistance training-induced muscle hypertrophy. PloS One, 8(10), e78636. https://doi.org/10.1371/journal.pone.0078636
Mitchell CJ, et al. Muscular and Systemic Correlates of Resistance Training-induced Muscle Hypertrophy. PLoS ONE. 2013;8(10):e78636. PubMed PMID: 24130904.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Muscular and systemic correlates of resistance training-induced muscle hypertrophy. AU - Mitchell,Cameron J, AU - Churchward-Venne,Tyler A, AU - Bellamy,Leeann, AU - Parise,Gianni, AU - Baker,Steven K, AU - Phillips,Stuart M, Y1 - 2013/10/09/ PY - 2013/06/01/received PY - 2013/09/21/accepted PY - 2013/10/17/entrez PY - 2013/10/17/pubmed PY - 2014/6/12/medline SP - e78636 EP - e78636 JF - PloS one JO - PLoS ONE VL - 8 IS - 10 N2 - PURPOSE: To determine relationships between post-exercise changes in systemic [testosterone, growth hormone (GH), insulin like grow factor 1 (IGF-1) and interleukin 6 (IL-6)], or intramuscular [skeletal muscle androgen receptor (AR) protein content and p70S6K phosphorylation status] factors in a moderately-sized cohort of young men exhibiting divergent resistance training-mediated muscle hypertrophy. METHODS: Twenty three adult males completed 4 sessions•wk⁻¹ of resistance training for 16 wk. Muscle biopsies were obtained before and after the training period and acutely 1 and 5 h after the first training session. Serum hormones and cytokines were measured immediately, 15, 30 and 60 minutes following the first and last training sessions of the study. RESULTS: Mean fiber area increased by 20% (range: -7 to 80%; P<0.001). Protein content of the AR was unchanged with training (fold change = 1.17 ± 0.61; P=0.19); however, there was a significant correlation between the changes in AR content and fiber area (r=0.60, P=0.023). Phosphorylation of p70S6K was elevated 5 hours following exercise, which was correlated with gains in mean fiber area (r=0.54, P=0.007). There was no relationship between the magnitude of the pre- or post-training exercise-induced changes in free testosterone, GH, or IGF-1 concentration and muscle fiber hypertrophy; however, the magnitude of the post exercise IL-6 response was correlated with muscle hypertrophy (r=0.48, P=0.019). CONCLUSION: Post-exercise increases in circulating hormones are not related to hypertrophy following training. Exercise-induced changes in IL-6 correlated with hypertrophy, but the mechanism for the role of IL-6 in hypertrophy is not known. Acute increases, in p70S6K phosphorylation and changes in muscle AR protein content correlated with muscle hypertrophy implicating intramuscular rather than systemic processes in mediating hypertrophy. SN - 1932-6203 UR - https://www.unboundmedicine.com/medline/citation/24130904/Muscular_and_systemic_correlates_of_resistance_training_induced_muscle_hypertrophy_ L2 - http://dx.plos.org/10.1371/journal.pone.0078636 DB - PRIME DP - Unbound Medicine ER -