Day-to-day variability in resting metabolic rate in strength athletes.
RMR measurements in strength-trained athletes show notable day-to-day variability, and session averaging can improve measurement consistency.
Where it sits
this study against the rest of the kisspeptin (kp-10) corpusSummary and findings
This study measured resting metabolic rate (RMR) in 13 weight-stable strength-trained athletes over five consecutive mornings. The mean RMR was 26.9 ± 1.4 kcal·kgFFM⁻¹·day⁻¹ for males and 29.1 ± 1.7 kcal·kgFFM⁻¹·day⁻¹ for females. The study aimed to quantify intra-individual variability and establish least significant change thresholds.
Abstract
<h4>Background</h4>Resting Metabolic Rate (RMR) is measured in sport settings for health monitoring and nutrition planning; however, interpreting repeated measures requires an understanding of typical day-to-day variability under habitual, free-living conditions. This study quantified intra-individual variability in RMR among weight-stable strength-trained athletes, examined the impact of data processing approaches, and established protocol-specific least significant change (LSC) thresholds under ecological conditions.<h4>Methods</h4>A repeated-measures design was used to quantify intra-individual variability in RMR in 13 weight-stable strength-trained athletes (8 male, 5 female). RMR was measured on five consecutive mornings using the Parvo Medics TrueOne 2400 metabolic cart with a Hans Rudolph mouthpiece under standardized conditions. Breath-by-breath data were processed using multiple cleaning approaches to evaluate their impact on RMR estimates, with the most reliable method retained for analysis. Intra-individual variability was quantified and used to derive protocol-specific LSC thresholds.<h4>Results</h4>Session averaging produced the lowest intra-individual variability in RMR (CV: 3.4 ± 1.4%) compared with alternative data cleaning approaches. Mean RMR was 26.9 ± 1.4 and 29.1 ± 1.7 kcal·kgFFM<sup>-1</sup>·day<sup>-1</sup> in males and females, respectively. The group-level LSC was 2.9 ± 1.2 kcal·kgFFM<sup>-1</sup>·day<sup>-1</sup> (10.4 ± 4.2%), representing the magnitude of change required to exceed expected within-subject variability under the conditions of this protocol. Fat-free mass (FFM) was positively associated with both absolute RMR and day-to-day variability, whereas prior-day training load and protein intake showed no clear association with RMR variability.<h4>Conclusions</h4>Notable intra-individual variability occurs in repeated RMR measurements in strength-trained athletes under applied conditions. Meaningful interpretation of change requires protocol-specific reliability estimates to distinguish true physiological change from expected day-to-day variation. Session averaging improves measurement consistency and is recommended for mouthpiece-based indirect calorimetry systems. RMR should be interpreted relative to individual and context-specific variability rather than universal thresholds.
Background
This paper addresses the variability in resting metabolic rate (RMR) among strength-trained athletes, a topic of interest for health monitoring and nutrition planning. Previous research has indicated that RMR can fluctuate based on various factors, but there is limited understanding of day-to-day variability in free-living conditions. This study is significant as it aims to quantify this variability and establish reliable thresholds for interpreting changes in RMR.
Methods
The study utilized a repeated-measures design involving 13 weight-stable strength-trained athletes (8 male, 5 female). RMR was measured over five consecutive mornings using the Parvo Medics TrueOne 2400 metabolic cart. The primary outcome measure was the intra-individual variability in RMR, with data processed using multiple cleaning approaches to determine the most reliable method.
Results
The primary finding was that session averaging produced the lowest intra-individual variability in RMR, with a coefficient of variation (CV) of 3.4 ± 1.4%. Mean RMR values were reported as 26.9 ± 1.4 kcal·kgFFM⁻¹·day⁻¹ for males and 29.1 ± 1.7 kcal·kgFFM⁻¹·day⁻¹ for females. The group-level least significant change (LSC) was calculated to be 2.9 ± 1.2 kcal·kgFFM⁻¹·day⁻¹, representing a 10.4 ± 4.2% change.
Interpretation
These findings suggest that there is notable intra-individual variability in RMR measurements among strength-trained athletes, which aligns with previous literature on metabolic variability. While the statistical significance of the results is clear, the clinical significance may be limited due to the small effect sizes and sample size. The study's reliance on a small cohort and specific measurement protocols may confound the applicability of these results to broader populations.
Key findings
- Mean RMR was 26.9 ± 1.4 kcal·kgFFM⁻¹·day⁻¹ in males.
- Mean RMR was 29.1 ± 1.7 kcal·kgFFM⁻¹·day⁻¹ in females.
- Session averaging produced the lowest intra-individual variability in RMR (CV: 3.4 ± 1.4%).
- Group-level LSC was 2.9 ± 1.2 kcal·kgFFM⁻¹·day⁻¹ (10.4 ± 4.2%).
- Fat-free mass (FFM) was positively associated with both absolute RMR and day-to-day variability.
Limitations
- small n=13
- limited generalizability due to sample size
- no clear associations reported with prior-day training load and protein intake