This study investigated the effects of increasing resistance training volume on muscle hypertrophy and strength in trained males. All groups showed significant increases in regional fat-free mass (ROI-FFM) and muscle thickness (MT), with no significant differences between groups. The control group (CON) surprisingly demonstrated the highest overall 1RM back squat strength gains (p < 0.05), while the group with a 30% volume increase (G30) showed the greatest improvement in repetitions to failure (RTF). These findings suggest that maintaining a moderate training volume can be sufficient for muscle growth and may be superior for maximal strength gains in trained individuals, while a 30% increase in volume might benefit strength-endurance.
The study provides valuable insights into the effects of individualized resistance training volume increases on muscle hypertrophy and strength adaptations in trained males. While the results indicate that all groups experienced similar muscle growth, the control group demonstrated superior maximal strength gains, and the 30% increase group showed improved strength-endurance. These findings suggest a complex relationship between training volume and adaptations, highlighting the potential limitations of simply increasing volume for trained individuals and emphasizing the importance of considering individual responses and training goals.
The study's practical utility is somewhat limited by its specific focus on resistance-trained males and the relatively short intervention period. However, the findings challenge the conventional wisdom that "more is always better" when it comes to training volume, suggesting that a moderate volume may be sufficient for muscle growth and even optimal for strength gains in this population. These results are placed within the context of existing literature, although a more thorough comparison with studies on individualized volume increases would further strengthen the discussion.
Practitioners can use these findings to inform their training recommendations, particularly for experienced lifters. Maintaining a moderate training volume (around 12 weekly sets per muscle group) appears to be a viable strategy for promoting muscle growth and strength gains. While a 30% increase in volume may enhance strength-endurance, further increases may not provide additional benefits and could even hinder strength development. However, it is crucial to acknowledge the study's limitations, including the specific population studied, the short-term nature of the intervention, the lack of nutritional control, and the high dropout rate. These factors may limit the generalizability of the findings and warrant caution in their interpretation.
Several critical questions remain unanswered. The study's design does not allow for a definitive determination of the optimal training volume for different populations or training goals. Additionally, the mechanisms underlying the unexpected strength gains in the control group are not fully understood. While the methodological limitations, particularly the high dropout rate and lack of nutritional control, do not fundamentally invalidate the conclusions, they do highlight the need for further research with larger sample sizes, longer intervention periods, and more diverse populations. Future studies should also investigate the long-term effects of individualized volume increases and explore the potential influence of other training variables.
The abstract effectively summarizes the study's purpose, methodology, key findings, and implications. It provides a concise overview of the research conducted, including the participant group, intervention, and main outcome measures.
This is a medium-impact suggestion to enhance the clarity and context of the abstract by explicitly stating the practical implications of the findings. While the abstract mentions the implications for training, directly stating the benefit for athletes or fitness enthusiasts would broaden the appeal and relevance of the research. Providing a clear takeaway message about the optimal training volume for muscle growth and strength in trained individuals would enhance the abstract's impact and encourage further reading. This would make the research more accessible to a wider audience and highlight its practical value. Explicitly stating the practical implications would strengthen the abstract by making the research findings more impactful and relevant to practitioners in the field.
Implementation: Add a sentence at the end of the abstract summarizing the practical implications. For example: "These findings provide practical guidance for resistance-trained individuals seeking to optimize their training volume for muscle growth and strength gains."
The introduction effectively establishes the context and importance of resistance training volume for muscle growth and strength adaptations. It clearly defines the key terms and concepts used in the study, such as RT volume and the dose-response relationship. This clarity ensures that readers have a shared understanding of the research focus.
This is a high-impact suggestion to strengthen the introduction by providing a more focused and explicit research gap and hypothesis. While the introduction discusses previous research and highlights conflicting findings, it does not explicitly state the specific gap that this study aims to address. Clearly articulating the research gap would enhance the rationale for the current study and highlight its novel contribution. A more focused research gap would strengthen the introduction by providing a clear justification for the study's design and methodology. It would also help readers understand the specific contribution of this research to the existing literature. Explicitly stating the research gap would improve the introduction by providing a more compelling rationale for the study.
Implementation: Add a distinct paragraph after the literature review that explicitly states the unanswered question or research gap being addressed. For example: "Despite the existing research on RT volume, there is still a lack of clarity regarding the optimal approach to individualizing volume increases for trained individuals. Specifically, it remains unclear how different percentage increases in previous training volume affect muscle growth and strength adaptations in this population."
This is a high-impact suggestion to enhance the introduction by providing a more concise and focused hypothesis statement. While the introduction mentions the study's hypotheses, they are embedded within a paragraph and not clearly separated. Presenting the hypotheses as a distinct, numbered list would improve their clarity and emphasis. A more structured presentation of the hypotheses would strengthen the introduction by making the study's aims more explicit and testable. This would also enhance the overall clarity and organization of the introduction, making it easier for readers to understand the study's objectives. Ultimately, a concise and focused hypothesis statement would significantly improve the introduction by making the study's aims more prominent and accessible to readers.
Implementation: Present the hypotheses as a separate, numbered list after stating the research gap. For example:"Therefore, we hypothesized that: 1. Individualized volume increases of 30% and 60% would enhance regional-of-interest fat-free mass accretion and muscle thickness adaptations compared to the control group. 2. The 30% individualized increase would elicit superior maximum strength adaptation. 3. The 60% increase would elicit superior strength-endurance adaptations."
The methods section clearly defines the study's design as a parallel-group repeated-measures design with counterbalanced randomization. This is a strength as it enhances the internal validity of the study by controlling for potential confounding variables and ensuring that the groups are comparable at baseline.
The inclusion and exclusion criteria for participants are well-defined, ensuring the selection of a homogenous sample of resistance-trained males. This strengthens the study's internal validity and allows for more precise conclusions about the effects of the intervention on the target population.
The procedures for data collection are described in detail, including specific equipment, measurement protocols, and timing of assessments. This level of detail strengthens the study's reproducibility, allowing other researchers to replicate the methods and verify the findings.
This is a high-impact suggestion to enhance the methodological rigor and transparency of the study by providing a rationale for the chosen sample size. While the section mentions a post-hoc power analysis, it lacks a clear justification for the initial recruitment target. The Materials & Methods section needs this justification to address potential concerns about underpowering and to provide context for the post-hoc analysis. Adding a rationale for the initial sample size target, even if it was not based on a formal a priori power analysis, would strengthen the paper by demonstrating a thoughtful approach to study design and increasing confidence in the reported findings. It would also address potential reviewer concerns about the study's power and generalizability. Ultimately, providing this rationale would significantly improve the study's methodological rigor by ensuring transparency and justifying the chosen sample size.
Implementation: Include a statement explaining the rationale for the initial sample size target. For example: "Due to the exploratory nature of the study and the limited available data on the effects of individualized volume increases in trained individuals, a formal a priori power analysis was not conducted. However, a sample size of 55 participants was initially targeted based on previous research in similar populations and feasibility considerations."
This is a medium-impact suggestion to improve the clarity and reproducibility of the training intervention description by providing more details about the exercise selection rationale. While the section lists the exercises used, it doesn't explain why these specific exercises were chosen. The Materials & Methods section needs this information to allow other researchers to understand the rationale behind the training program and potentially replicate it. Providing a rationale for the exercise selection would strengthen the paper by enhancing the transparency of the training intervention and allowing for better comparisons with other studies. It would also help readers understand the specific muscle groups targeted and the overall training stimulus applied. Ultimately, including this rationale would improve the study's methodological rigor and facilitate future research in this area.
Implementation: Add a sentence or two explaining the rationale for choosing the squat, leg press, and leg extension exercises. For example: "These exercises were selected to target the quadriceps muscle group comprehensively, incorporating compound and isolation movements with varying biomechanical demands."
This is a medium-impact suggestion to enhance the clarity and reproducibility of the study by providing more detail about the volume load calculations for the posterior chain exercises. While the section mentions that volume load was calculated and presented only for quadriceps exercises, it lacks specific details about how the volume load for the posterior chain exercises was handled. The Methods section needs this clarification to ensure transparency and allow for a complete understanding of the training protocol. Providing more details about the volume load calculations for the posterior chain exercises, even if they are not presented in the results, would strengthen the paper by ensuring methodological transparency and enabling other researchers to replicate the study more accurately. It would also address potential questions about the overall training stimulus applied to the posterior chain muscles. Ultimately, clarifying this aspect would improve the study's methodological rigor and reproducibility.
Implementation: Add a sentence or two explaining how the volume load for the Romanian deadlifts and glute-ham raises was calculated and whether it was included in any analyses. For example: "Volume load for Romanian deadlifts and glute-ham raises was calculated similarly to the quadriceps exercises but was not included in the primary analyses to maintain the focus on the quadriceps muscle group."
Figure 2. Overview of the region-of-interest fat-free mass (ROI-FFM) and anterior thigh muscle thickness: RF- Rectus femoris, VI- Vastus intermedius. A- ROI-FFM, B- proximal muscle thickness, and (C) distal muscle thickness assessments.
The results section effectively presents the findings of the study, including the changes in ROI-FFM, muscle thickness, 1RM, and RTF. The data is presented clearly in tables and figures, allowing readers to easily understand the main outcomes of the intervention.
This is a high-impact suggestion to enhance the clarity and interpretability of the results by providing effect sizes for all outcome measures. While the section reports p-values and confidence intervals, it lacks effect sizes, which are crucial for understanding the magnitude of the observed effects. The Results section needs effect sizes to allow readers to assess the practical significance of the findings and compare them with other studies. Adding effect sizes would strengthen the paper by providing a more complete picture of the intervention's impact and facilitating meta-analyses. This would enhance the study's contribution to the field and improve the overall quality of the results. Ultimately, reporting effect sizes is essential for enhancing the interpretability and practical relevance of the findings.
Implementation: Calculate and report appropriate effect sizes (e.g., Cohen's d, eta squared) for all outcome measures, including ROI-FFM, muscle thickness, 1RM, and RTF. Include these effect sizes in the tables and/or text describing the results.
This is a medium-impact suggestion to improve the clarity and interpretability of the results by providing a more detailed explanation of the statistical findings. While the section reports the main effects and interactions, it lacks a clear explanation of what these findings mean in the context of the study's hypotheses. The Results section needs a more interpretive approach to help readers understand the implications of the statistical analyses. Explaining the findings in plain language and connecting them back to the hypotheses would strengthen the paper by making the results more accessible and meaningful to a wider audience. It would also enhance the overall clarity and impact of the results section. Ultimately, providing a more detailed explanation of the statistical findings would significantly improve the study's clarity and facilitate a deeper understanding of the results.
Implementation: For each significant main effect or interaction, provide a brief explanation of what it means in the context of the study. For example, for the main time effect for ROI-FFM, state: "This indicates that ROI-FFM increased significantly from pre- to post-training in all groups." Connect these explanations back to the original hypotheses. For example: "This finding supports our first hypothesis that individualized volume increases would enhance ROI-FFM accretion."
Figure 3. The average weekly volume load for the intervention exercises throughout 16 sessions across experimental groups. Control group (CON – blue line), 30% increase in the number of sets (G30 - orange line), and 60% increase in the number of sets (G60 – green line).
Figure 4. Delta-change in fat-free mass and muscle thickness per participant. Scatterplot of individual changes in muscle thickness plotted against the change in region-of-interest fat-free mass. The size of the marker indicates the subject's volume load. Density plots for the responses are plotted on respective axis spines.
Figure 5. Delta change in repetition to failure and 1RM per participant. Scatterplot of individual changes in one-repetition-maximum plotted against the change in repetitions-to-failure. The size of the marker indicates the subject's volume load. Density plots for the responses are plotted on respective axis spines.
Table 2. Region-of-interest fat-free mass and muscle thickness assessments (mean ± SD)
The discussion effectively summarizes the main findings of the study, including the observed changes in muscle hypertrophy, maximal strength, and strength-endurance. This provides a clear overview of the key outcomes and allows readers to quickly grasp the main takeaways.
This is a high-impact suggestion to enhance the discussion by providing a more in-depth analysis of the unexpected findings regarding maximal strength. While the discussion acknowledges the unexpected superior performance of the CON group in 1RM, it lacks a thorough exploration of potential underlying mechanisms. The Discussion section needs to delve deeper into these unexpected results to provide a more nuanced interpretation and stimulate further research. Expanding on this analysis would strengthen the paper by demonstrating a critical evaluation of the results and offering potential explanations for the observed discrepancies. This would enhance the study's scientific contribution and provide valuable insights for future research. Ultimately, a more in-depth analysis of the unexpected strength findings would significantly improve the discussion by fostering a deeper understanding of the complex relationship between training volume and strength adaptations.
Implementation: Add a paragraph discussing potential reasons for the CON group's superior 1RM gains. Consider factors like the potential for overtraining in the higher volume groups, individual differences in training responsiveness, and the specific training status of the participants. For example: "The unexpected superior 1RM gains in the CON group warrant further investigation. It is possible that the higher volume groups experienced greater fatigue accumulation or surpassed their maximal recoverable volume, hindering strength gains. Additionally, the specific training history of the participants, such as their previous exposure to higher volumes, could have influenced their responsiveness to the volume increases."
This is a medium-impact suggestion to improve the discussion by providing a more thorough comparison of the study's findings with the existing literature. While the discussion cites some relevant studies, it lacks a comprehensive and systematic comparison of the current results with previous research on individualized volume increases. The Discussion section needs to provide a more detailed comparison to highlight the study's novel contributions and contextualize its findings within the broader literature. A more thorough comparison would strengthen the paper by demonstrating a comprehensive understanding of the existing literature and clarifying the study's unique contribution. This would enhance the study's impact and facilitate future research. Ultimately, a more detailed comparison with the existing literature would significantly improve the discussion by providing a more nuanced and contextualized interpretation of the findings.
Implementation: Expand the discussion to include a more systematic comparison of the current results with previous studies on individualized volume increases, specifically focusing on studies that have accounted for participants' previous training volume. Discuss similarities and differences in findings, methodological approaches, and participant characteristics. For example: "Our findings partially align with those of Scarpelli et al. (13), who observed greater hypertrophic adaptations with individualized volume increases. However, unlike their within-subject design, our parallel group design may have limited the precision of our estimates, potentially explaining the lack of significant differences between groups in the current study."
This is a medium-impact suggestion to enhance the discussion by providing more specific and actionable recommendations for future research. While the discussion mentions the need for further research, it lacks concrete and specific directions for future studies. The Discussion section needs to provide clear guidance for future research to build upon the current findings and address remaining questions. Adding specific recommendations would strengthen the paper by guiding future research efforts and maximizing the impact of the current study. This would contribute to a more efficient and focused advancement of knowledge in the field. Ultimately, providing more specific recommendations for future research would significantly improve the discussion by facilitating the development of new research questions and methodologies.
Implementation: Add a paragraph outlining specific directions for future research. Include recommendations for study design, participant populations, training interventions, and outcome measures. For example: "Future research should investigate the effects of individualized volume increases in different populations, such as untrained individuals or women, to determine the generalizability of the current findings. Longitudinal studies with larger sample sizes and more frequent assessments are also needed to examine the long-term effects of individualized volume increases on muscle growth and strength adaptations. Additionally, future studies should explore the potential influence of other training variables, such as exercise selection and training frequency, on the effectiveness of individualized volume approaches."
The limitations section transparently acknowledges the specific constraints of the study, such as the focus on lower-body training in young, resistance-trained males, and the short-term nature of the intervention. This strengthens the study by providing context for interpreting the results and acknowledging the boundaries of generalizability.
This is a high-impact suggestion to enhance the discussion of limitations by providing a more thorough analysis of the potential impact of the high dropout rate. While the section mentions the dropout rate, it does not fully explore how this attrition might have affected the study's findings and conclusions. The Limitations section needs a more in-depth discussion of the dropout rate to address potential concerns about selection bias and reduced statistical power. Expanding on this analysis would strengthen the paper by demonstrating a critical evaluation of the study's limitations and their potential influence on the results. This would enhance the study's scientific rigor and provide valuable insights for future research. Ultimately, a more thorough analysis of the dropout rate's impact would significantly improve the limitations section by fostering a deeper understanding of the study's constraints and their potential implications.
Implementation: Add a paragraph discussing the potential impact of the high dropout rate on the study's findings. Consider factors like selection bias, reduced statistical power, and the representativeness of the final sample. For example: "The high dropout rate (approximately 45%) due to the COVID-19 pandemic is a significant limitation of this study. This attrition may have introduced selection bias, as participants who dropped out may have differed systematically from those who completed the study. The reduced sample size also likely decreased the study's statistical power, potentially leading to Type II errors. Furthermore, the final sample may not be fully representative of the original population, limiting the generalizability of the findings."
This is a medium-impact suggestion to enhance the clarity and comprehensiveness of the limitations section by providing a more detailed discussion of the limitations related to the lack of nutritional control. While the section mentions this as a limitation, it doesn't fully explore the potential implications for the study's findings. The Limitations section needs more detail about the potential impact of uncontrolled nutrition to ensure transparency and allow readers to fully assess the study's limitations. Expanding on this discussion would strengthen the paper by demonstrating a thorough understanding of the potential confounding factors and their possible influence on the results. This would enhance the study's scientific rigor and provide valuable insights for future research. Ultimately, a more detailed discussion of the nutritional control limitation would significantly improve the limitations section by fostering a deeper understanding of the study's constraints and their potential implications.
Implementation: Expand the discussion of the nutritional control limitation to include specific examples of how uncontrolled nutrition might have affected the outcome measures. For example: "The lack of nutritional control is another limitation of this study. Participants' protein and calorie intake were not monitored or controlled, which could have influenced their muscle growth and strength adaptations. Some participants may have consumed insufficient protein or calories to support optimal muscle growth, while others may have overconsumed, potentially leading to increased fat mass. This variability in nutritional intake could have confounded the effects of the training intervention, making it difficult to isolate the specific impact of the volume increases."
The conclusion effectively synthesizes the study's main findings regarding muscle hypertrophy, maximal strength, and strength-endurance. It accurately reflects the results presented in the previous section, providing a concise summary of the key outcomes.
This is a high-impact suggestion to enhance the conclusion by providing a more nuanced and comprehensive interpretation of the findings in light of the study's limitations. While the conclusion summarizes the results, it doesn't fully integrate the limitations discussed in the preceding section. The Conclusion section needs to explicitly address the limitations to avoid overgeneralizing the findings and to provide a more balanced perspective. Integrating the limitations into the conclusion would strengthen the paper by demonstrating a critical awareness of the study's constraints and their potential impact on the interpretation of the results. This would enhance the study's scientific rigor and provide a more cautious and contextualized conclusion. Ultimately, acknowledging the limitations within the conclusion would significantly improve the paper by ensuring a more accurate and balanced interpretation of the findings.
Implementation: Add a sentence or two acknowledging the limitations and their potential impact on the interpretation of the findings. For example: "However, these findings should be interpreted cautiously considering the study's limitations, such as the specific population studied, the short-term intervention period, and the lack of nutritional control. Future research addressing these limitations is needed to confirm and generalize these findings."
This is a medium-impact suggestion to strengthen the conclusion by providing more specific and actionable recommendations for practitioners. While the conclusion mentions practical implications, it lacks concrete guidance for coaches and athletes. The Conclusion section needs to offer more specific recommendations to bridge the gap between research and practice. Providing actionable recommendations would strengthen the paper by enhancing its practical relevance and impact. This would make the study's findings more applicable to real-world training scenarios and provide valuable guidance for practitioners in the field. Ultimately, including specific recommendations for practitioners would significantly improve the conclusion by increasing its practical value and facilitating the translation of research into practice.
Implementation: Add a sentence or two providing specific recommendations for practitioners. For example: "Based on these findings, resistance-trained individuals seeking to maximize muscle growth and strength may benefit from maintaining a moderate training volume of approximately 12 weekly sets per muscle group, ensuring a high level of effort (0-2 RIR) in each set. Moderate increases in volume (e.g., 30%) may be beneficial for enhancing strength-endurance."