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PURPOSE: Resistance training (RT) induces muscle growth at varying rates across RT phases, and evidence suggests that the muscle-molecular responses to training bouts become refined or attenuated in the trained state. This study examined how proteolysis-related biomarkers and extracellular matrix (ECM) remodeling factors respond to a bout of RT in the untrained (UT) and trained (T) state. METHODS: Participants (19 women and 19 men) underwent 10 weeks of RT. Biopsies of vastus lateralis were collected before and after (24 h) the first (UT) and last (T) sessions. Vastus lateralis cross-sectional area (CSA) was assessed before and after the experimental period. RESULTS: There were increases in muscle and type II fiber CSAs. In both the UT and T states, calpain activity was upregulated and calpain-1/-2 protein expression was downregulated from Pre to 24 h. Calpain-2 was higher in the T state. Proteasome activity and 20S proteasome protein expression were upregulated from Pre to 24 h in both the UT and T. However, proteasome activity levels were lower in the T state. The expression of poly-ubiquitinated proteins was unchanged. MMP activity was downregulated, and MMP-9 protein expression was elevated from Pre to 24 h in UT and T. Although MMP-14 protein expression was acutely unchanged, this marker was lower in T state. TIMP-1 protein levels were reduced Pre to 24 h in UT and T, while TIMP-2 protein levels were unchanged. CONCLUSION: Our results are the first to show that RT does not attenuate the acute-induced response of proteolysis and ECM remodeling-related biomarkers.
RESUMO
ABSTRACT: Nóbrega, SR, Scarpelli, MC, Barcelos, C, Chaves, TS, and Libardi, CA. Muscle hypertrophy is affected by volume load progression models. J Strength Cond Res 37(1): 62-67, 2023-This exploratory secondary data analysis compared the effects of a percentage of 1 repetition maximum (%1RM) and a repetition zone (RM Zone) progression model carried out to muscle failure on volume load progression (VLPro), muscle strength, and cross-sectional area (CSA). The sample comprised 24 untrained men separated in 2 groups: %1RM (n = 14) and RM Zone (n = 10). Muscle CSA and muscle strength (1RM) were assessed before and after 24 training sessions, and an analysis of covariance was used. Volume load progression and accumulated VL (VLAccu) were compared between groups. The relationships between VLProg, VLAccu, 1RM, and CSA increases were also investigated. A significance level of p ≤ 0.05 was adopted for all statistical procedures. Volume load progression was greater for RM Zone compared with %1RM (2.30 ± 0.58% per session vs. 1.01 ± 0.55% per session; p < 0.05). Significant relationships were found between 1RM and VLProg (p < 0.05) and CSA and VLProg (p < 0.05). No between-group differences were found for VLAccu (p > 0.05). Analysis of covariance revealed no between-group differences for 1RM absolute (p < 0.05) or relative changes (p < 0.05). However, post hoc testing revealed greater absolute and relative changes in CSA for the RM Zone group compared with the %1RM group (p < 0.001). In conclusion, RM Zone resulted in a greater VLPro rate and muscle CSA gains compared with %1RM, with no differences in VLAccu and muscle strength gains between progression models.
