Scott J Dankel1, Minsoo Kang2, Takashi Abe1, Jeremy P Loenneke3. 1. Kevser Ermin Applied Physiology Laboratory, Department of Health, Exercise Science, and Recreation Management, The University of Mississippi, 231 Turner Center, University, MS, 38677, USA. 2. Health and Sports Analytics Laboratory, Department of Health, Exercise Science, and Recreation Management, The University of Mississippi, University, MS, USA. 3. Kevser Ermin Applied Physiology Laboratory, Department of Health, Exercise Science, and Recreation Management, The University of Mississippi, 231 Turner Center, University, MS, 38677, USA. jploenne@olemiss.edu.
Abstract
PURPOSE: Considerable debate exists as to whether increases in strength that occur with resistance exercise are the result of increases in muscle size. Most studies have attempted to answer this question using assessments of whole muscle size and voluntary muscle strength, but examining changes at the individual muscle fiber level may also provide some insight. The purpose of this meta-analysis was to compare adaptations at the whole muscle and individual fiber level. METHODS: A meta-analysis was conducted in February, 2018 including all previously published papers and was analyzed using a random effects model. RESULTS: There were no differences (p = 0.88) when comparing hypertrophy at the whole muscle (4.6%) and individual fiber level (7.0%), but significantly larger (p < 0.001) strength gains were observed at the whole muscle level (43.3%) relative to the individual fiber (19.5%). Additionally, there was an increase in the specific tension of type 1 muscle fibers (p = 0.013), but not type 2 muscle fibers (p = 0.23) which was driven by similar increases in strength (type 1: 17.5%, type 2A: 17.7%), despite differences in muscle size (type 1: 6.7%, type 2A: 12.1%). CONCLUSION: These results support the hypothesis that the neural adaptations play a large role in increasing isotonic whole muscle strength, but also demonstrate that an improvement in specific tension of type 1 muscle fibers is present. These results would suggest that some mechanism intrinsic to the muscle fiber, and independent of muscle growth, may also be contributing to strength increases in response to resistance exercise providing an avenue for future research.
PURPOSE: Considerable debate exists as to whether increases in strength that occur with resistance exercise are the result of increases in muscle size. Most studies have attempted to answer this question using assessments of whole muscle size and voluntary muscle strength, but examining changes at the individual muscle fiber level may also provide some insight. The purpose of this meta-analysis was to compare adaptations at the whole muscle and individual fiber level. METHODS: A meta-analysis was conducted in February, 2018 including all previously published papers and was analyzed using a random effects model. RESULTS: There were no differences (p = 0.88) when comparing hypertrophy at the whole muscle (4.6%) and individual fiber level (7.0%), but significantly larger (p < 0.001) strength gains were observed at the whole muscle level (43.3%) relative to the individual fiber (19.5%). Additionally, there was an increase in the specific tension of type 1 muscle fibers (p = 0.013), but not type 2 muscle fibers (p = 0.23) which was driven by similar increases in strength (type 1: 17.5%, type 2A: 17.7%), despite differences in muscle size (type 1: 6.7%, type 2A: 12.1%). CONCLUSION: These results support the hypothesis that the neural adaptations play a large role in increasing isotonic whole muscle strength, but also demonstrate that an improvement in specific tension of type 1 muscle fibers is present. These results would suggest that some mechanism intrinsic to the muscle fiber, and independent of muscle growth, may also be contributing to strength increases in response to resistance exercise providing an avenue for future research.
Authors: Walter R Frontera; Virginia A Hughes; Lisa S Krivickas; Sang-Kyu Kim; Mona Foldvari; Ronenn Roubenoff Journal: Muscle Nerve Date: 2003-11 Impact factor: 3.217
Authors: Gerson E R Campos; Thomas J Luecke; Heather K Wendeln; Kumika Toma; Fredrick C Hagerman; Thomas F Murray; Kerry E Ragg; Nicholas A Ratamess; William J Kraemer; Robert S Staron Journal: Eur J Appl Physiol Date: 2002-08-15 Impact factor: 3.078
Authors: Derrick W Van Every; Max Coleman; Avery Rosa; Hugo Zambrano; Daniel Plotkin; Xavier Torres; Mariella Mercado; Eduardo O De Souza; Andrew Alto; Douglas J Oberlin; Andrew D Vigotsky; Brad J Schoenfeld Journal: PLoS One Date: 2022-09-01 Impact factor: 3.752