Resistance training-induced changes in muscle proteolysis and extracellular matrix remodeling biomarkers in the untrained and trained states.

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.

Effects of Resistance Training Overload Progression Protocols on Strength and Muscle Mass.

The aim of this study was to compare the effects of progressive overload in resistance training on muscle strength and cross-sectional area (CSA) by specifically comparing the impact of increasing load (LOADprog) versus an increase in repetitions (REPSprog). We used a within-subject experimental design in which 39 previously untrained young persons (20 men and 19 women) had their legs randomized to LOADprog and REPSprog. Outcomes were assessed before and after 10 weeks of training. Muscle strength was assessed using the one repetition maximum (1RM) test on the leg extension exercise, and the CSA of the vastus lateralis was assessed by ultrasonography. Both protocols increased 1RM values from pre (LOADprog: 52.90±16.32 kg; REPSprog: 51.67±15.84 kg) to post (LOADprog: 69.05±18.55 kg, REPSprog: 66.82±17.95 kg), with no difference between them (P+>+0.05). Similarly, both protocols also increased in CSA values from pre (LOADprog: 21.34±4.71 cm²; REPSprog: 21.08±4.62 cm²) to post (LOADprog: 23.53±5.41 cm², REPSprog: 23.39±5.19 cm²), with no difference between them (P+>+0.05). In conclusion, our findings indicate that the progression of overload through load or repetitions can be used to promote gains in strength and muscle hypertrophy in young men and women in the early stages of training.

Low-Load Resistance Training Performed to Muscle Failure or Near Muscle Failure Does Not Promote Additional Gains on Muscle Strength, Hypertrophy, and Functional Performance of Older Adults.

ABSTRACT: Bergamasco, JGA, Gomes da Silva, D, Bittencourt, DF, Martins de Oliveira, R, Júnior, JCB, Caruso, FC, Godoi, D, Borghi-Silva, A, and Libardi, CA. Low-load resistance training performed to muscle failure or near muscle failure does not promote additional gains on muscle strength, hypertrophy, and functional performance of older adults. J Strength Cond Res 36(5): 1209-1215, 2022-The aim of the present study was to compare the effects of low-load resistance training (RT) protocols performed to failure (FAI), to voluntary interruption (VOL), and with a fixed low repetitions (FIX) on muscle strength, hypertrophy, and functional performance in older adults. Forty-one subjects (60-77 years) were randomized into one of the RT protocols (FAI, VOL, or FIX) and completed 12 weeks of RT at 40% of 1 repetition maximum (1RM), twice a week. The assessments included 1RM test, muscle cross-sectional area (CSA), rate of torque development (RTD), and functional performance (chair stand [CS], habitual gait speed [HGS], maximal gait speed [MGS], and timed up-and-go [TUG]). All protocols significantly increased 1RM values from Pre (FAI: 318.3 ± 116.3 kg; VOL: 342.9 ± 93.7 kg; FIX: 328.0 ± 107.2 kg) to Post (FAI: 393.0 ± 143.1 kg, 23.5%; VOL: 423.0 ± 114.5 kg, 23.3%; FIX: 397.8 ± 94.6 kg, 21.3%; p < 0.0001 for all groups). Regarding CS, all protocols showed significant improvements from Pre (FAI: 11.5 ± 2.4 seconds; VOL: 12.1 ± 2.5 seconds; FIX: 11.3 ± 1.1 seconds) to Post (FAI: 10.5 ± 1.1 seconds, -8.5%, p = 0.001; VOL: 10.3 ± 1.5 seconds, -15.1%, p = 0.001; FIX: 11.0 ± 1.1, -3.2%, p = 0.001). Habitual gait speed values increased significantly from Pre (FAI: 1.3 ± 0.2 m·s-1; VOL: 1.3 ± 0.1 m·s-1; FIX: 1.3 ± 0.1 m·s-1) to Post (FAI: 1.4 ± 0.2 m·s-1, 2.5%, p = 0.03; VOL: 1.4 ± 0.2 m·s-1, 5.2%, p = 0.036; FIX: 1.4 ± 0.1 m·s-1, 5.7%, p = 0.03). No significant differences between protocols were found (p > 0.05). In addition, there were no significant changes in CSA, RTD, MGS, and TUG for any protocols (p > 0.05). In conclusion, low-load RT performed without muscle failure promotes significant improvements in muscle strength and some parameters of functional performance in older adults.

Acute and Chronic Changes in Muscle Androgen Receptor Markers Are Not Associated with Muscle Hypertrophy in Women and Men.

PURPOSE: Androgen receptor (AR) expression and signaling has been regarded as a mechanism for regulating muscle hypertrophy. However, little is known about the associations between acute and chronic changes in skeletal muscle total AR, cytoplasmic AR (cAR), nuclear AR (nAR) and AR DNA-binding (AR-DNA) induced by resistance training (RT) and hypertrophy outcomes in women and men. This study aimed to investigate the acute and chronic effects of RT on skeletal muscle total AR, cAR, nAR contents and AR-DNA in women and men. Additionally, we investigated whether these acute and chronic changes in these markers were associated with muscle hypertrophy in both sexes. METHODS: Nineteen women and 19 men underwent 10 weeks of RT. Muscle biopsies were performed at baseline, 24 h after the first RT session and 96-120 h after the last session. AR, cAR and nAR were analyzed using Western blotting, and AR-DNA using an ELISA-oligonucleotide assay. Fiber cross-sectional area (fCSA) was analyzed through immunohistochemistry and muscle cross-sectional area (mCSA) by ultrasound. RESULTS: At baseline, men demonstrated greater nAR than women. Baseline cAR was significantly associated with type II fCSA hypertrophy in men. Acutely, both sexes decreased AR and cAR, whereas men demonstrated greater decreases in nAR. After 10 weeks of RT, AR and nAR remained unchanged, men demonstrated greater cAR compared to women, and both sexes decreased AR-DNA activity. Acute and chronic changes in AR markers did not correlate with muscle hypertrophy (type I/II fCSA and mCSA) in women or men. CONCLUSIONS: Baseline cAR content may influence hypertrophy in men, while neither RT-induced acute nor chronic changes in AR, cAR, nAR, and AR-DNA are associated with muscle hypertrophy in women or men.

Effect of individualized resistance training prescription with heart rate variability on individual muscle hypertrophy and strength responses.

The aim of the present study was to investigate if resistance training (RT), performed with individualized recovery between sessions (RT-IND), promotes greater gains in strength and muscle mass and reduces the variability on adaptations compared to RT with fixed recovery intervals (RT-FIX). Twenty young men (age 21.9 ± 3.3 years) were randomized in the RT-IND and RT-FIX groups. Five days before the beginning of the training, measurements of the root mean square of successive R-R intervals differences (RMSSD) values of each individual were performed to establish the baseline values. Before each RT session, the RMSSD values determined whether the participants from RT-IND protocol were recovered from the previous session. Participants performed the RT session only if RMSSD values had returned to the baseline, otherwise they had to wait for an additional 24 h. RT-FIX performed an RT session every 48 h. Muscle strength was measured by one-maximal repetition (1-RM) test and muscle cross-section area (CSA) of the vastus laterals by ultrasonography were assessed pre- and post-training. 1-RM values increased significantly from pre to post-training for both groups (RT-IND: 30% and RT-FIX: 42%, main time effect, P < 0001), with no significant difference between groups. Muscle CSA increased significantly from pre to post-training (RT-IND: 15.7% and RT-FIX: 15.8%, main time effect, P < 0001), with no significant difference between groups. In conclusion, RT-IND did not increase the gains in muscle strength and mass neither reduce the variability in muscle adaptations when compared to the RT-FIX.