נק' מוניטין:
58,705
Commentaries on Viewpoint: What is the relationship between acute measure of muscle protein synthesis and changes in muscle mass?
Philip J. Atherton , Benjamin F. Miller , Nicholas A. Burd , Lindsay S. Macnaughton , Andrew J. Murton , Donny M. Camera , Adelina V. Pancheva , Xiaonan Wang , Mary C. Vagula , B.E. Phillips , M.S. Brook , D.J. Wilkinson , K. Smith , T.E. Etheridge , Karyn L. Hamilton , Joseph W. Beals , Stephan van Vliet , Luc J.C. van Loon , Sophie L. Wardle , Kevin D. Tipton , F.B. Stephens , R. Billeter , B.T. Wall , John A. Hawley , Vladimir S. Panchev , Marieta V. Pancheva
Journal of Applied Physiology Published 15 February 2015 Vol. 118 no. 4, 498-503 DOI: 10.1152/japplphysiol.01069.2014
COMMENTARY RESPONSE TO VIEWPOINT: “WHAT IS THE RELATIONSHIP BETWEEN ACUTE MEASURES OF MUSCLE PROTEIN SYNTHESIS AND CHANGES IN MUSCLE MASS?”
TO THE EDITOR: Mitchell et al. (3) critique putative links between acute muscle protein synthesis (MPS) and ensuing hypertrophy after resistance exercise (RE) training (RT). Just two papers have addressed this longitudinally. The first reports that young but not older individuals exhibit acute (fasted mixed muscle MPS, 24 h post-RE) increases in MPS (2); yet hypertrophy gains, assessed by DXA and fiber area, were equal. Similarly, poor quantitative MPS linkages were reported 1–6 h post-RE (myofibrillar muscle, fed state) with ensuing hypertrophy (4), i.e., two study's suggesting bona fide dissociation. However, for (2), prior reports of age-related temporal differences in acute MPS responses to RE (1) and lack of intra/inter age group correlations (2) mitigate such resounding conclusions. Also, in (4), RE was under fed state conditions; this is significant because consumption of protein feeds extends (not amplifies) elevations in MPS post-RE (5). Therefore, MPS responses 1–6 h post-RE were chiefly predominated by feeding, i.e., the coupling of which to RE may not aptly reflect interindividual variation (5), e.g., due to isolated mechano-auto/paracrine responses to RE. Yet, acute MPS can/does inform on group interventions for RT-induced muscle hypertrophy, signifying it a practicable, informative end-point. But, could quantitative relationships still exist and what defines “acute” post-RE MPS? Fasted/fed? Immediately (<6 h?)/later (>24?) What muscle fraction(s)? Is there an applicable “snapshot”? Without defining acute this is indiscernible. The authors justifiably raise potential technical, temporal, methodological confounder(s). Because hypertrophy is a heterogeneous and temporally dynamic process we hypothesize that (coupled to not isolating/fractionating/holistically capturing “acute” MPS) interindividual trajectories and plateauing hypertrophy in the face of fixed study end-points are the major barriers to defining quantitative links between acute MPS and RT-induced hypertrophy.
Philip J. Atherton , Benjamin F. Miller , Nicholas A. Burd , Lindsay S. Macnaughton , Andrew J. Murton , Donny M. Camera , Adelina V. Pancheva , Xiaonan Wang , Mary C. Vagula , B.E. Phillips , M.S. Brook , D.J. Wilkinson , K. Smith , T.E. Etheridge , Karyn L. Hamilton , Joseph W. Beals , Stephan van Vliet , Luc J.C. van Loon , Sophie L. Wardle , Kevin D. Tipton , F.B. Stephens , R. Billeter , B.T. Wall , John A. Hawley , Vladimir S. Panchev , Marieta V. Pancheva
Journal of Applied Physiology Published 15 February 2015 Vol. 118 no. 4, 498-503 DOI: 10.1152/japplphysiol.01069.2014
COMMENTARY RESPONSE TO VIEWPOINT: “WHAT IS THE RELATIONSHIP BETWEEN ACUTE MEASURES OF MUSCLE PROTEIN SYNTHESIS AND CHANGES IN MUSCLE MASS?”
TO THE EDITOR: Mitchell et al. (3) critique putative links between acute muscle protein synthesis (MPS) and ensuing hypertrophy after resistance exercise (RE) training (RT). Just two papers have addressed this longitudinally. The first reports that young but not older individuals exhibit acute (fasted mixed muscle MPS, 24 h post-RE) increases in MPS (2); yet hypertrophy gains, assessed by DXA and fiber area, were equal. Similarly, poor quantitative MPS linkages were reported 1–6 h post-RE (myofibrillar muscle, fed state) with ensuing hypertrophy (4), i.e., two study's suggesting bona fide dissociation. However, for (2), prior reports of age-related temporal differences in acute MPS responses to RE (1) and lack of intra/inter age group correlations (2) mitigate such resounding conclusions. Also, in (4), RE was under fed state conditions; this is significant because consumption of protein feeds extends (not amplifies) elevations in MPS post-RE (5). Therefore, MPS responses 1–6 h post-RE were chiefly predominated by feeding, i.e., the coupling of which to RE may not aptly reflect interindividual variation (5), e.g., due to isolated mechano-auto/paracrine responses to RE. Yet, acute MPS can/does inform on group interventions for RT-induced muscle hypertrophy, signifying it a practicable, informative end-point. But, could quantitative relationships still exist and what defines “acute” post-RE MPS? Fasted/fed? Immediately (<6 h?)/later (>24?) What muscle fraction(s)? Is there an applicable “snapshot”? Without defining acute this is indiscernible. The authors justifiably raise potential technical, temporal, methodological confounder(s). Because hypertrophy is a heterogeneous and temporally dynamic process we hypothesize that (coupled to not isolating/fractionating/holistically capturing “acute” MPS) interindividual trajectories and plateauing hypertrophy in the face of fixed study end-points are the major barriers to defining quantitative links between acute MPS and RT-induced hypertrophy.
@יהושע60
