Molecular Differences in Skeletal Muscle After 1 Week of Active vs. Passive Recovery From High-Volume Resistance Training

Effects of Physical Exercise on MuRF-1/TRIM63 mRNA Expression in Humans: A Systematic Review

BACKGROUND/OBJECTIVES

Muscle-specific RING finger protein 1 (MuRF-1) is a pivotal regulator of muscle protein breakdown, an essential process for post-exercise muscle adaptation. This systematic review aimed to evaluate the effects of physical exercise on MuRF-1 mRNA expression in humans.

METHODS

A literature search was conducted in PubMed, Scopus, Cochrane Library, Google Scholar, and Web of Science following the PRISMA guidelines. The search was limited to studies published from 1 January 2001 to 1 December 2024. The inclusion and exclusion criteria were defined using the PICOS strategy. Two investigators independently performed the study selection, data extraction, and assessment of methodological quality, with any disagreements resolved by a third investigator. The PEDro scale was used to evaluate the risk of bias.

RESULTS

Forty-six studies met the eligibility criteria and were included. The findings evidenced that physical exercise significantly modulates MuRF-1 mRNA expression in humans. Resistance exercise induces transient increases, typically peaking between 1 and 4 h, whereas endurance exercise elicits similar responses within 40 min to 4 h post-exercise. Combined exercise protocols that include resistance and endurance exercises significantly increased MuRF-1 mRNA expression at 3 h post-exercise. The effects of physical exercise on MuRF-1 mRNA expression are influenced by factors such as exercise order, intensity, contraction mode, age, sex, and fitness level.

CONCLUSIONS

This systematic review shows that MuRF-1 mRNA expression is significantly modulated by physical exercise in humans and is sensitive to different exercise modalities. These findings suggest that this key protein involved in muscle protein breakdown and turnover is essential for exercise-induced adaptations, contributing to skeletal muscle recovery and remodeling after exercise.

Gaining more from doing less? The effects of a one-week deload period during supervised resistance training on muscular adaptations

Background

Based on emerging evidence that brief periods of cessation from resistance training (RT) may re-sensitize muscle to anabolic stimuli, we aimed to investigate the effects of a 1-week deload interval at the midpoint of a 9-week RT program on muscular adaptations in resistance-trained individuals.

Methods

Thirty-nine young men (n = 29) and women (n = 10) were randomly assigned to 1 of 2 experimental, parallel groups: An experimental group that abstained from RT for 1 week at the midpoint of a 9-week, high-volume RT program (DELOAD) or a traditional training group that performed the same RT program continuously over the study period (TRAD). The lower body routines were directly supervised by the research staff while upper body training was carried out in an unsupervised fashion. Muscle growth outcomes included assessments of muscle thickness along proximal, mid and distal regions of the middle and lateral quadriceps femoris as well as the mid-region of the triceps surae. Adaptions in lower body isometric and dynamic strength, local muscular endurance of the quadriceps, and lower body muscle power were also assessed.

Results

Results indicated no appreciable differences in increases of lower body muscle size, local endurance, and power between groups. Alternatively, TRAD showed greater improvements in both isometric and dynamic lower body strength compared to DELOAD. Additionally, TRAD showed some slight psychological benefits as assessed by the readiness to train questionnaire over DELOAD.

Conclusion

In conclusion, our findings suggest that a 1-week deload period at the midpoint of a 9-week RT program appears to negatively influence measures of lower body muscle strength but has no effect on lower body hypertrophy, power or local muscular endurance.

Integrating Deloading into Strength and Physique Sports Training Programmes: An International Delphi Consensus Approach

BACKGROUND

Deloading is a ubiquitous yet under-researched strategy within strength and physique training. How deloading should be integrated into the training programme to elicit optimal training outcomes is unknown. To aid its potential integration, this study established consensus around design principles for integrating deloading in strength and physique training programmes using expert opinion and practical experience.

METHODS

Expert strength and physique coaches were invited to an online Delphi consisting of 3 rounds. Thirty-four coaches completed the first round, 29 completed the second round, and 21 completed the third round of a Delphi questionnaire. In the first round, coaches answered 15 open-ended questions from four categories: 1: General Perceptions of Deloading; 2: Potential Applications of Deloading; 3: Designing and Implementing Deloading; and 4: Creating an Inclusive Deloading Training Environment. First-round responses were analyzed using reflexive thematic analysis, resulting in 138 statements organized into four domains. In the second and third rounds, coaches rated each statement using a four-point Likert scale, and collective agreement or disagreement was calculated.

RESULTS

Stability of consensus was achieved across specific aspects of the four categories. Findings from the final round were used to develop the design principles, which reflect the consensus achieved.

CONCLUSIONS

This study develops consensus on design principles for integrating deloading into strength and physique sports training programmes. A consensus definition is proposed: "Deloading is a period of reduced training stress designed to mitigate physiological and psychological fatigue, promote recovery, and enhance preparedness for subsequent training." These findings contribute novel knowledge that might advance the current understanding of deloading in strength and physique sports.

"You can't shoot another bullet until you've reloaded the gun": Coaches' perceptions, practices and experiences of deloading in strength and physique sports

Deloading refers to a purposeful reduction in training demand with the intention of enhancing preparedness for successive training cycles. Whilst deloading is a common training practice in strength and physique sports, little is known about how the necessary reduction in training demand should be accomplished. Therefore, the purpose of this research was to determine current deloading practices in competitive strength and physique sports. Eighteen strength and physique coaches from a range of sports (weightlifting, powerlifting, and bodybuilding) participated in semi-structured interviews to discuss their experiences of deloading. The mean duration of coaching experience at ≥ national standard was 10.9 (SD = 3.9) years. Qualitative content analysis identified Three categories: definitions, rationale, and application. Participants conceptualised deloading as a periodic, intentional cycle of reduced training demand designed to facilitate fatigue management, improve recovery, and assist in overall training progression and readiness. There was no single method of deloading; instead, a reduction in training volume (achieved through a reduction in repetitions per set and number of sets per training session) and intensity of effort (increased proximity to failure and/or reduction in relative load) were the most adapted training variables, along with alterations in exercise selection and configuration. Deloading was typically prescribed for a duration of 5 to 7 days and programmed every 4 to 6 weeks, although periodicity was highly variable. Additional findings highlight the underrepresentation of deloading in the published literature, including a lack of a clear operational definition.

Effects of Peanut Protein Supplementation on Resistance Training Adaptations in Younger Adults

Protein supplementation is a commonly employed strategy to enhance resistance training adaptations. However, little research to date has examined if peanut protein supplementation is effective in this regard. Thus, we sought to determine if peanut protein supplementation (PP; 75 total g/d of powder providing 30 g/d protein, >9.2 g/d essential amino acids, ~315 kcal/d) affected resistance training adaptations in college-aged adults. Forty-seven college-aged adults (n = 34 females, n = 13 males) with minimal prior training experience were randomly assigned to a PP group (n = 18 females, n = 5 males) or a non-supplement group (CTL; n = 16 females, n = 8 males) (ClinicalTrials.gov trial registration NCT04707963; registered 13 January 2021). Body composition and strength variables were obtained prior to the intervention (PRE). Participants then completed 10 weeks of full-body resistance training (twice weekly) and PP participants consumed their supplement daily. POST measures were obtained 72 h following the last training bout and were identical to PRE testing measures. Muscle biopsies were also obtained at PRE, 24 h following the first exercise bout, and at POST. The first two biopsy time points were used to determine myofibrillar protein synthesis (MyoPS) rates in response to a naïve training bout with or without PP, and the PRE and POST biopsies were used to determine muscle fiber adaptations in females only. Dependent variables were analyzed in males and females separately using two-way (supplement × time) repeated measures ANOVAs, unless otherwise stated. The 24-h integrated MyoPS response to the first naïve training bout was similar between PP and CTL participants (dependent samples t-test p = 0.759 for females, p = 0.912 for males). For males, the only significant supplement × time interactions were for DXA-derived fat mass (interaction p = 0.034) and knee extensor peak torque (interaction p = 0.010); these variables significantly increased in the CTL group (p < 0.05), but not the PP group. For females, no significant supplement × time interactions existed, although interactions for whole body lean tissue mass (p = 0.088) and vastus lateralis thickness (p = 0.099) approached significance and magnitude increases in these characteristics favored the PP versus CTL group. In summary, this is the second study to determine the effects of PP supplementation on resistance training adaptations. While PP supplementation did not significantly enhance training adaptations, the aforementioned trends in females, the limited n-size in males, and this being the second PP supplementation study warrant more research to determine if different PP dosing strategies are more effective than the current approach.

Skeletal Muscle Adaptations and Performance Outcomes Following a Step and Exponential Taper in Strength Athletes

Before major athletic events, a taper is often prescribed to facilitate recovery and enhance performance. However, it is unknown which taper model is most effective for peaking maximal strength and positively augmenting skeletal muscle. Thus, the purpose of this study was to compare performance outcomes and skeletal muscle adaptations following a step vs. an exponential taper in strength athletes. Sixteen powerlifters (24.0 ± 4.0 years, 174.4 ± 8.2 cm, 89.8 ± 21.4 kg) participated in a 6-week training program aimed at peaking maximal strength on back squat [initial 1-repetition-maximum (1RM): 174.7 ± 33.4 kg], bench press (118.5 ± 29.9 kg), and deadlift (189.9 ± 41.2 kg). Powerlifters were matched based on relative maximal strength, and randomly assigned to either (a) 1-week overreach and 1-week step taper or (b) 1-week overreach and 3-week exponential taper. Athletes were tested pre- and post-training on measures of body composition, jumping performance, isometric squat, and 1RM. Whole muscle size was assessed at the proximal, middle, and distal vastus lateralis using ultrasonography and microbiopsies at the middle vastus lateralis site. Muscle samples (n = 15) were analyzed for fiber size, fiber type [myosin-heavy chain (MHC)-I, -IIA, -IIX, hybrid-I/IIA] using whole muscle immunohistochemistry and single fiber dot blots, gene expression, and microRNA abundance. There were significant main time effects for 1RM squat (p < 0.001), bench press (p < 0.001), and deadlift, (p = 0.024), powerlifting total (p < 0.001), Wilks Score (p < 0.001), squat jump peak-power scaled to body mass (p = 0.001), body mass (p = 0.005), fat mass (p = 0.002), and fat mass index (p = 0.002). There were significant main time effects for medial whole muscle cross-sectional area (mCSA) (p = 0.006) and averaged sites (p < 0.001). There was also a significant interaction for MHC-IIA fiber cross-sectional area (fCSA) (p = 0.014) with post hoc comparisons revealing increases following the step-taper only (p = 0.002). There were significant main time effects for single-fiber MHC-I% (p = 0.015) and MHC-IIA% (p = 0.033), as well as for MyoD (p = 0.002), MyoG (p = 0.037), and miR-499a (p = 0.033). Overall, increases in whole mCSA, fCSA, MHC-IIA fCSA, and MHC transitions appeared to favor the step taper group. An overreach followed by a step taper appears to produce a myocellular environment that enhances skeletal muscle adaptations, whereas an exponential taper may favor neuromuscular performance.