@article{0074f83163b84e4199369ff00c0e01d7,
title = "Physiological adaptations to resistance training in rats selectively bred for low and high response to aerobic exercise training.",
abstract = "New Findings: What is the central question of this study? Can phenotypic traits associated with low response to one mode of training be extrapolated to other exercise-inducible phenotypes? The present study investigated whether rats that are low responders to endurance training are also low responders to resistance training. What is the main finding and its importance? After resistance training, rats that are high responders to aerobic exercise training improved more in maximal strength compared with low-responder rats. However, the greater gain in strength in high-responder rats was not accompanied by muscle hypertrophy, suggesting that the responses observed could be mainly neural in origin. Abstract: The purpose of this study was to determine whether rats selectively bred for low and high response to aerobic exercise training co-segregate for differences in muscle adaptations to ladder-climbing resistance training. Five high-responder (HRT) and five low-responder (LRT) rats completed the resistance training, while six HRT and six LRT rats served as sedentary control animals. Before and after the 6 week intervention, body composition was determined by dual energy X-ray absorptiometry. Before tissue harvesting, the right triceps surae muscles were loaded by electrical stimulation. Muscle fibre cross-sectional areas, nuclei per cell, phosphorylation status of selected signalling proteins of mTOR and Smad pathways, and muscle protein, DNA and RNA concentrations were determined for the right gastrocnemius muscle. The daily protein synthesis rate was determined by the deuterium oxide method from the left quadriceps femoris muscle. Tissue weights of fore- and hindlimb muscles were measured. In response to resistance training, maximal carrying capacity was greater in HRT (∼3.3 times body mass) than LRT (∼2.5 times body mass), indicating greater improvements of strength in HRT. However, muscle hypertrophy that could be related to greater strength gains in HRT was not observed. Furthermore, noteworthy changes within the experimental groups or differences between groups were not observed in the present measures. The lack of hypertrophic muscular adaptations despite considerable increases in muscular strength suggest that adaptations to the present ladder-climbing training in HRT and LRT rats were largely induced by neural adaptations.",
keywords = "fibre contractility, muscle hypertrophy, muscle stimulation, protein synthesis",
author = "Ahtiainen, {Juha P.} and Sanna Lensu and Ilona Ruotsalainen and Moritz Schumann and Ihalainen, {Johanna K.} and Vasco Fachada and Mendias, {Christopher L.} and Brook, {Matthew S.} and Kenneth Smith and Atherton, {Philip J.} and Koch, {Lauren G.} and Britton, {Steven L.} and Heikki Kainulainen",
note = "Funding Information: This work was supported by the Academy of Finland (grant no. 274098 to H.K.) and META-PREDICT within the European Union Seventh Framework Program (HEALTH-F2-2012-277936 to H.K.). This work was also supported by the Medical Research Council (grant no. MR/K00414X/1) and Arthritis Research UK (grant no. 19891) as part of the MRC-ARUK Centre for Musculoskeletal Ageing Research; the Physiological Society (awarded to P.J.A. and K.S.); the Dunhill Medical Trust (R264/1112 to K.S. and P.J.A.); and a Medical Research Council Confidence in Concept award (CIC12019 to P.J.A. and K.S.). The LRT-HRT rat model system was supported by the Office of Research Infrastructure Programs/OD grant ROD012098A(toL.G.K.andS.L.B.)fromthe National Institutes of Health (USA). Contact L.G.K.(lauren.koch2@utoledo.edu)orS.L.B. (brittons@umich.edu) for information on the LRT and HRT rats; these rat models are maintained as an international collaborative resource at the University of Toledo, Toledo, OH, USA. Funding Information: information This work was supported by the Academy of Finland (grant no. 274098 to H.K.) and META-PREDICT within the European Union Seventh Framework Program (HEALTH-F2-2012-277936 to H.K.). This work was also supported by the Medical Research Council (grant no. MR/K00414X/1) and Arthritis Research UK (grant no. 19891) as part of the MRC-ARUK Centre for Musculoskeletal Ageing Research; the Physiological Society (awarded to P.J.A. and K.S.); the Dunhill Medical Trust (R264/1112 to K.S. and P.J.A.); and a Medical Research Council Confidence in Concept award (CIC12019 to P.J.A. and K.S.). The LRT-HRT rat model system was supported by the Office of Research Infrastructure Programs/OD grant ROD012098A (to L.G.K. and S.L.B.) from the National Institutes of Health (USA). Contact L.G.K. (lauren.koch2@utoledo.edu) or S.L.B. (brittons@umich.edu) for information on the LRT and HRT rats; these rat models are maintained as an international collaborative resource at the University of Toledo, Toledo, OH, USA.We acknowledge Satu Koskinen, Elina M{\"a}kinen, Eliisa Kiukkanen, Janne Paajala, Petri Jalanko, Mervi Matero, Leena Tulla, Bernardo Soares Oliveira and Jevgenia Lasmanova (University of Jyv{\"a}skyl{\"a}, Finland) for their valuable help with data collection and analyses. Publisher Copyright: {\textcopyright} 2018 The Authors. Experimental Physiology {\textcopyright} 2018 The Physiological Society",
year = "2018",
month = nov,
day = "1",
doi = "10.1113/EP087144",
language = "English",
volume = "103",
pages = "1513--1523",
journal = "Experimental Physiology",
issn = "0958-0670",
publisher = "Wiley-Blackwell",
number = "11",
}