Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
©Journal of Sports Science and Medicine (2023) 22, 559 - 570   DOI:

Research article
Effects of Acute Loading Induced Fatigability, Acute Serum Hormone Responses and Training Volume to Individual Hypertrophy and Maximal Strength during 10 Weeks of Strength Training
Aapo Räntilä , Juha P. Ahtiainen, Keijo Häkkinen
Author Information
Faculty of Sport and Health Sciences, Neuromuscular Research Center, University of Jyväskylä, Finland

Aapo Räntilä
✉ Faculty of Sport and Health Sciences, Neuromuscular Research Center, University of Jyväskylä, P.O. Box 35, FI-40014, Finland
Publish Date
Received: 03-07-2023
Accepted: 23-08-2023
Published (online): 01-09-2023
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This study investigated whether a strength training session-induced acute fatigue is related to individuals’ strength training adaptations in maximal force and/or muscle hypertrophy, and whether acute responses in serum testosterone (T) and growth hormone (GH) concentrations during the training sessions would be associated with individual neuromuscular adaptations. 26 males completed the 10-week strength-training intervention, which included fatiguing dynamic leg press acute loading bouts (5 x 10 RM) at weeks two, four, six, and ten. Blood samples were collected before and after the loading and after 24h of recovery for serum T, GH, and cortisol (C) concentrations at weeks 2, 6, and 10. The cross-sectional area of the vastus lateralis was measured by ultrasonography. Isometric force measurements were performed before and immediately after loadings, and loading-induced acute decrease in maximal force was reported as the fatigue percentage. The subjects were split into three groups according to the degree of training-induced muscle hypertrophy after the training period. Increases in isometric force were significant for High Responders (HR, n = 10) (by 24.3 % ± 17.2, p = 0.035) and Medium Responders (MR, n = 7) (by 23.8 % ± 5.5, p = 0.002), whereas the increase of 26.2 % (±16.5) in Low Responders (LR, n = 7) was not significant. The amount of work (cm + s) increased significantly at every measurement point in all the groups. A significant correlation was observed between the fatigue percentage and relative changes in isometric force after the training period for the whole group (R = 0.475, p = 0.022) and separately only in HR (R = 0.643, p = 0.049). Only the HR group showed increased acute serum GH concentrations at every measurement point. There was also a significant acute increase in serum T for HR at weeks 6 and 10. HR showed the strongest correlation between acute loading-induced fatigue and isometric force gains. HR was also more sensitive to acute increases in serum concentrations of T and GH after the loading. Acute fatigue and serum GH concentrations may be indicators of responsiveness to muscle strength gain and, to some extent, muscle hypertrophy.

Key words: Strength training, muscle hypertrophy, strength gains, individual differences, acute loading-induced fatigue, serum responses of testosterone and growth hormone

           Key Points
  • High responders to strength training showed a strong correlation with acute fatigue and training-induced gains in isometric force
  • High responders were more sensitive to acute increases in serum hormone concentration compared to other subgroups
  • Low responders did more work compared to High responders, but high responders increased their workload more throughout the intervention.
  • Progression in the amount of work might be more important than the overall workload
  • Force production ability decreased during the acute loading tests from the first test of -16.8% to all the way down to -26.3%, while optimal fatigue range for muscle hypertrophy needs further investigation.
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