Creatine supplementation increased total sleep duration on resistance training days in naturally menstruating women compared to placebo. No significant changes were observed in chronic sleep quality (PSQI), strength gains, or body composition. Both groups experienced a decrease in caloric, protein, and fat intake during the study. The primary finding of increased total sleep duration on training days was specific to the creatine group and suggests a potential benefit for post-exercise recovery.
This study presents moderate evidence for the positive effect of creatine supplementation on acute total sleep duration following resistance training in naturally menstruating women. The randomized, double-blind, placebo-controlled design is a significant strength, minimizing bias and supporting causal inferences. The use of objective sleep measures (Oura ring) and robust statistical analysis (MLM) further strengthens the evidence. However, the study's small sample size, the lack of reported effect sizes, the unexplained dietary changes during the intervention, and the limited 6-week timeframe somewhat limit the generalizability and long-term implications of the findings. While the study effectively demonstrates an acute effect on sleep duration on training days, the lack of significant changes in chronic sleep quality or strength gains warrants further investigation. Overall, the study makes a valuable contribution to the field by exploring the effects of creatine on sleep in a relatively understudied population, but further research is needed to confirm and expand upon these findings, particularly regarding long-term effects, optimal supplementation durations, and the interplay between creatine, sleep, and dietary intake.
The abstract clearly and concisely presents the study's main objective, methodology, key findings, and implications. It adheres to standard abstract conventions, providing a comprehensive overview of the research within a reasonable word count.
This is a medium-impact suggestion to enhance the clarity and precision of the abstract's conclusion. While the abstract mentions the increased sleep duration on training days, it lacks specific details about the magnitude of this increase. Quantifying this improvement would provide readers with a more concrete understanding of the effect size and its practical significance. Including this information in the abstract, the initial point of contact for most readers, would strengthen the paper's impact and facilitate a quicker grasp of the study's key contribution. Adding specific numerical results regarding the increase in sleep duration on training days, such as reporting the average increase in minutes or as a percentage, would make the abstract more informative and compelling. This would allow readers to immediately gauge the practical relevance of the findings and better understand the magnitude of the observed effect. Ultimately, quantifying the sleep duration increase in the abstract would enhance the clarity and impact of the study's main finding.
Implementation: In the abstract's concluding sentence, quantify the increase in total sleep duration on training days for the creatine group. For example, state the average increase in minutes or the percentage increase compared to the placebo group or baseline values. Ensure this numerical data is consistent with the results presented in the main body of the paper.
The introduction effectively establishes the context of the research by highlighting the underrepresentation of naturally menstruating women in creatine and sleep studies. It underscores the relevance of this demographic due to their unique hormonal fluctuations and generally poorer sleep quality compared to men.
The introduction logically connects the known benefits of resistance training on muscle strength and body composition to its potential for improving sleep quality. This connection provides a strong rationale for investigating the combined effects of creatine and resistance training on sleep in this specific population.
This is a high-impact suggestion that would strengthen the introduction by providing a more focused and explicit research question or hypothesis. While the introduction mentions the general aim of examining the effects of creatine on sleep, it lacks a clearly defined research question that guides the study. Explicitly stating the research question would enhance the paper's clarity and focus, allowing readers to immediately understand the study's specific objective. This would also provide a framework for interpreting the results and evaluating the study's overall contribution. Ultimately, formulating a concise research question would significantly improve the introduction by providing a clear direction for the study and enhancing its scientific rigor.
Implementation: Formulate a concise research question that specifically addresses the relationship between creatine supplementation, resistance training, and sleep in naturally menstruating women. For example, "Does creatine supplementation, in conjunction with resistance training, improve sleep quality and/or quantity in naturally menstruating women compared to resistance training alone?" Place this research question at the end of the introduction to clearly guide the reader.
This is a medium-impact suggestion to enhance the clarity and precision of the introduction. While the introduction mentions the use of an Oura ring for sleep assessment, it doesn't explicitly state which sleep parameters will be the primary outcome measures. Defining these parameters upfront would provide readers with a clearer understanding of the study's focus and facilitate interpretation of the results. Specifying the primary sleep outcome measures would strengthen the introduction by ensuring alignment between the study's objectives and the reported findings. This would also prevent potential ambiguity and allow readers to critically evaluate the study's conclusions based on the chosen parameters. Ultimately, clarifying the primary sleep outcome measures would improve the introduction's clarity and ensure that the study's focus is transparent from the outset.
Implementation: Explicitly state the primary sleep parameters that will be analyzed as outcome measures. For example, "The primary sleep outcome measures will be total sleep duration, sleep efficiency, and sleep onset latency." Include this information in the introduction after mentioning the use of the Oura ring.
The participant selection criteria are well-defined and appropriate for the research question. The inclusion of naturally menstruating women or those using a copper IUD, along with the exclusion of those using hormonal birth control, helps control for the potential confounding effects of hormonal variations on sleep.
The study's double-blind, placebo-controlled, randomized design is a strength, minimizing bias and increasing the reliability of the findings. This rigorous approach enhances the internal validity of the study and allows for stronger causal inferences.
The detailed description of the creatine and placebo supplementation protocol, including dosage, timing, and administration method, ensures transparency and reproducibility. This level of detail allows other researchers to replicate the study and strengthens the reliability of the findings.
The use of both objective (Oura ring) and subjective (PSQI) sleep measures provides a more comprehensive assessment of sleep. This multi-faceted approach allows for a deeper understanding of the impact of creatine on various aspects of sleep.
This is a high-impact suggestion to improve the clarity and reproducibility of the resistance training intervention. While the section mentions the use of TONAL and provides general information about the workouts, it lacks specific details about the exercises performed, sets, repetitions, and progression scheme. Providing a comprehensive description of the resistance training protocol is crucial for allowing other researchers to replicate the study and evaluate the generalizability of the findings. This detailed information would also strengthen the study's methodological rigor and enhance the transparency of the intervention. Ultimately, including a detailed resistance training protocol would significantly improve the reproducibility and scientific value of the study.
Implementation: Provide a detailed description of the TONAL resistance training program, including the specific exercises performed during each session, the number of sets and repetitions for each exercise, the resistance used (or how it was determined), and the progression scheme used over the 6 weeks. Consider including a table or supplementary material to present this information clearly.
This is a medium-impact suggestion to enhance the clarity and interpretability of the dietary analysis. The section mentions the use of DHQ III to assess dietary intake but doesn't specify which variables were analyzed or how potential confounding factors were addressed. Providing more detail about the dietary analysis would strengthen the study by allowing readers to better understand the nutritional context of the findings and assess the potential influence of diet on the observed outcomes. This would also enhance the transparency of the study's methodology. Ultimately, clarifying the dietary analysis details would improve the study's rigor and facilitate a more nuanced interpretation of the results.
Implementation: Specify the dietary variables analyzed, including total caloric intake, macronutrient composition (protein, carbohydrates, fat), and micronutrient intake if relevant. Also, describe how potential confounding factors, such as changes in dietary habits during the intervention, were addressed in the analysis.
This is a medium-impact suggestion to improve the clarity and reproducibility of the body composition analysis. While the section mentions the use of DXA and BIA, it lacks specific details about the measurement protocols and data handling. Providing a more comprehensive description of the body composition assessment would strengthen the study's methodological rigor and allow other researchers to replicate the measurements accurately. This would also enhance the transparency of the study and facilitate comparisons with other research. Ultimately, clarifying the body composition assessment details would improve the study's scientific value and contribute to a more robust understanding of the findings.
Implementation: Provide specific details about the DXA and BIA measurement protocols, including the equipment used, the software used for analysis, and the specific variables extracted. Also, describe how data were handled, including quality control procedures and any transformations or adjustments applied.
Figure 1. Experimental Design & Methodology Schematic. PARQ+, Physical Activity Readiness Questionnaire for Everyone; PSQI, Pittsburgh Sleep Quality Index; DHQ III, Diet History Questionnaire III; BIA, bioelectrical impedance analysis; DXA, dual energy x-ray absorptiometry; CR, creatine; PLA, placebo.
The Results section effectively uses statistical methods appropriate for the study's design, including repeated-measures ANOVAs and multilevel modeling (MLM). MLM is particularly suitable for analyzing the daily sleep data due to its nested structure and ability to handle missing values.
The Results section clearly presents the main findings related to sleep duration, with a specific focus on the significant increase in total sleep on training days for the creatine group. This direct presentation of the key result allows readers to quickly grasp the study's primary outcome.
This is a high-impact suggestion that would significantly improve the interpretability and context of the findings. The Results section lacks a clear presentation of the effect sizes for the observed changes in sleep duration. Reporting effect sizes, such as Cohen's d or eta-squared, would provide readers with a standardized measure of the magnitude of the observed effects, allowing for better comparison with other studies and a more nuanced understanding of the practical significance of the findings. Ultimately, including effect sizes would enhance the scientific rigor and interpretability of the results.
Implementation: Calculate and report effect sizes (e.g., Cohen's d or eta-squared) for the significant changes in sleep duration, specifically the group x workout interaction for total sleep duration. Include these effect sizes in the Results section alongside the p-values.
This is a medium-impact suggestion to enhance the clarity and completeness of the reported findings. The Results section mentions the lack of significant changes in chronic sleep quality but doesn't provide the actual PSQI scores. Including these scores would allow readers to fully understand the sleep quality data and assess the potential clinical significance of any observed changes, even if they are not statistically significant. Ultimately, presenting the PSQI scores would improve the transparency and completeness of the results.
Implementation: Report the mean and standard deviation of the PSQI scores for both groups at both pre- and post-intervention time points. Include these data in the Results section when discussing the lack of significant changes in sleep quality.
Figure 2. Model-estimated means (and standard errors) of total sleep duration as a function of workout and group status. Note: The thick lines represent the average effect estimated by the fixed effect and the thinner lines represent the effects by participant (i.e., the random effect).
The discussion effectively connects the primary finding of increased total sleep duration on training days with creatine supplementation to the existing literature on creatine's effects on sleep and cognitive function. This grounding in prior research provides context and strengthens the interpretation of the study's results.
This is a high-impact suggestion that would significantly enhance the discussion's depth and scientific rigor. The discussion acknowledges the limitations of the 6-week intervention period but doesn't fully explore the potential implications of a longer supplementation period, especially regarding the non-significant changes in lean soft tissue (LST) and fat mass (FM). Expanding on this point would strengthen the discussion by providing a more nuanced interpretation of the findings and guiding future research directions. It would allow readers to better understand the potential long-term effects of creatine supplementation and the optimal duration for observing changes in body composition. Ultimately, discussing the potential implications of a longer supplementation period would improve the discussion's scientific contribution by addressing a key limitation and generating hypotheses for future studies.
Implementation: Expand the discussion on the limitations of the 6-week intervention period. Specifically, discuss the potential for observing significant changes in LST and FM with a longer supplementation period, perhaps citing studies with longer creatine interventions. Propose future research directions that explore the optimal supplementation duration for maximizing body composition changes in conjunction with resistance training.
This is a medium-impact suggestion that would enhance the discussion's clarity and address a potential point of confusion for readers. The discussion mentions the lack of significant changes in chronic sleep quality as measured by the PSQI but doesn't fully reconcile this with the observed increase in total sleep duration. Elaborating on this apparent discrepancy would strengthen the discussion by providing a more nuanced interpretation of the findings and clarifying the distinct aspects of sleep being measured. It would help readers understand the difference between acute changes in sleep duration after exercise and overall chronic sleep quality. Ultimately, discussing the relationship between acute sleep duration changes and chronic sleep quality would improve the discussion's clarity and prevent potential misinterpretations of the results.
Implementation: Expand the discussion on the lack of significant changes in chronic sleep quality (PSQI) despite the increase in total sleep duration on training days. Explain that these are distinct aspects of sleep and that acute changes in sleep duration after exercise may not necessarily translate to improvements in overall, chronic sleep quality as measured by the PSQI. Consider discussing the potential mechanisms underlying this discrepancy.
The conclusion effectively summarizes the main finding of the study, which is the increase in total sleep duration on training days for the creatine group. This concise restatement of the primary outcome reinforces the study's key contribution.
This is a high-impact suggestion aimed at strengthening the conclusion's contribution to the field by explicitly stating the clinical or practical implications of the findings. While the conclusion summarizes the main result, it doesn't elaborate on the broader significance of this finding for athletes, coaches, or healthcare professionals working with active women. Expanding on the practical implications would enhance the conclusion's impact by providing readers with a clear understanding of how these findings can be applied in real-world settings. This would also increase the study's relevance to a wider audience beyond the research community. Ultimately, discussing the practical implications of the increased sleep duration would strengthen the conclusion by highlighting the study's translational value and potential to inform practice.
Implementation: Add a sentence or two at the end of the conclusion that explicitly states the practical implications of the findings. For example, "This finding suggests that creatine supplementation could be a valuable strategy for athletes and active women to enhance recovery and improve performance by optimizing sleep duration after training."
This is a medium-impact suggestion to enhance the conclusion's connection to the study's limitations and future research directions. While the conclusion mentions the need for further research, it doesn't specifically link this need to the study's limitations, such as the short intervention period or the lack of significant changes in chronic sleep quality. Connecting future research directions to the study's limitations would strengthen the conclusion by providing a more focused and actionable roadmap for future investigations. This would also demonstrate a critical awareness of the study's boundaries and guide other researchers in building upon this work effectively. Ultimately, linking future research to the study's limitations would improve the conclusion's contribution to the field by providing specific avenues for future research that directly address the current study's limitations.
Implementation: Add a sentence or two that explicitly connects the need for further research to the study's limitations. For example, "Given the short intervention period of this study, future research should investigate the long-term effects of creatine supplementation on sleep in active women. Further studies should also explore the impact of creatine on various aspects of sleep quality, including sleep efficiency and sleep architecture."