ECSS Paris 2023: OP-PN24
INTRODUCTION: Many athletes can be at risk of low energy availability (LEA) caused by high exercise energy expenditure (EEE) and/or inadequate energy intake (EI). Accurate calculation of EEE is important for determining energy availability (EA), however, various methods can be used. Currently, it is unclear how different calculation methods affect both EEE and EA, particularly in real world, free-living settings. This study compared the values of EEE (kcal) derived from different calculation and prediction methods and the effects on estimates of EA (kcal/kg/FFM). METHODS: Elite rowers (n=46; Tiers 4-5) attended a 3-week altitude training camp in which day-to-day energy availability was measured. This study focused on six different methods for EEE calculation across all rowing and bike ergometer sessions: (1) measured gross efficiency (GE) for each individual and modality, (2) estimated GE for each modality, (3) heart rate derived calculation, (4) heart rate derived calculation that accounted for VO2max, (5) metabolic equivalent score (METs) estimation and (6) linear regression prediction from GE. Predicted RMR was estimated using three different equations, with basal energy expenditure during exercise either included or excluded to determine its effect. Finally, EA was calculated as EI minus EEE, relative to fat free mass (FFM). Linear mixed models were used to determine the effects of EEE and RMR calculation methods on both EEE and EA. Method 1 was used as a benchmark to which the other methods were compared to. RESULTS: There were significant differences between the values derived from each of the six methods of EEE calculation (p<0.001). Compared to individualised gross efficiency, METs calculations overestimated EEE by 3.2% whereas the heart rate (HR) derived calculations showed 33.5% and 26.8% underestimations of EEE respectively. The removal of RMR significantly affects EEE values (p<0.001). The transfer of EEE values into EA calculations also produced significantly different results (p<0.001). The lowest EA values were derived from METs values (7.4 kcal/kg/FFM lower than benchmark) while the highest EA values came from HR derived EEE calculations (7 kcal/kg/FFM higher than benchmark). CONCLUSION: These results have practical implications for EA calculations in both research and applied settings. The use of METs may overestimate EEE while HR derived calculations (at least in athletic populations) may underestimate EEE compared to power output derived estimates using individualised GE outcomes. Differences in the method to estimate EEE from the same exercise sessions translated into significant differences in calculations of EA, as did the removal of RMR from EEE. Although the results are statistically significant, experts need to decide whether such changes may have a clinical or physiological effect on athletes in a real-world environment.
Read CV Alicia WalkerECSS Paris 2023: OP-PN24
INTRODUCTION: Mitochondria play a pivotal role in cell biology and are essential to overall metabolic health. Skeletal muscle is a highly metabolic tissue, containing a particularly rich volume of mitochondria that can be further enhanced with exercise. While this process is well known, the regulatory mechanisms remain elusive. microRNAs (miRNAs), however, have shown potential as regulators of cellular function, including mitochondrial dynamics. Additionally, miRNAs have been shown to localise to the mitochondria. Though, their function remains elusive. The aim of the MATRX (Mitochondrial And Transcriptomic Response to eXercise) study was to investigate the regulation of miRNAs localised to the skeletal muscle mitochondria of young, healthy males and observe changes in miRNA expression following an acute bout of sub-maximal exercise. METHODS: Ethics was obtained prior to recruitment (2024-191). 13 young, healthy males were included in the study. Participants were required to cycle for 60 minutes at submaximal intensity with muscle biopsies taken before, after and at three hours after exercise. Mitochondria were isolated with Magnetic-Activated Cell Sorting and treated with RNAse-A and Proteinase K prior to RNA extraction (1). Mitochondrial RNA libraries were sequenced and differential expression analysis performed on the resulting transcripts using DEseq2. Wald tests were used for pairwise contrasts to assess acute (post vs pre), recovery (post vs recovery) and sustained (recovery vs pre) responses. P-values were adjusted for multiple testing using the Benjamini-Hochberg false discovery rate procedure with an adjusted p-value < 0.05 considered statistically significant. RESULTS: 314 miRNAs were identified in the mitochondria of skeletal muscle. A subset of these were significantly differentially expressed following an acute bout of endurance exercise. Pairwise Wald contrasts identified three distinct response patterns and included 23 miRNAs that were uniquely regulated in the acute phase, 25 miRNAs that were uniquely regulated in the recovery phase and 59 miRNAs that showed sustained regulation across the exercise-recovery time course. Canonical myomiRs including miR-1, miR-133a, miR-133b and miR-206 were identified, though none were significantly differentially expressed. CONCLUSION: Nuclear-encoded miRNAs localise to skeletal muscle mitochondria in humans and exhibit distinct temporal regulation following acute endurance exercise. The identification of multiple exercise-induced mitochondrial-associated miRNAs highlights a potential regulatory layer underlying mitochondrial adaptation. While the mode of mitochondrial localisation and function of these miRNAs were not addressed in the present study, these findings identify candidate miRNAs for future studies integrating mitochondrial gene expression and functional manipulation. References: 1. Silver et al. FASEB J, 38(23): e70223, 2024.
Read CV Matthew GedyeECSS Paris 2023: OP-PN24
INTRODUCTION: Anaerobic threshold (AT)-based exercise prescription is commonly performed as cycle ergometer exercise at a pedaling rate of 60 rpm. However, patients often request changes in pedaling rate. The effects of different pedaling rates on hemodynamic and metabolic responses remain unclear. Furthermore, to our knowledge, no previous studies have examined the effects of varying pedaling rate while keeping the workload constant at the AT workload determined at 60 rpm, which is commonly used in AT-based exercise prescription. Therefore, this study aimed to clarify the effects of different pedaling rates on hemodynamic and metabolic responses at the AT workload determined at 60 rpm. METHODS: Twelve healthy adults (9 men and 3 women; age 27+/- 3 years) participated. On day 1, the AT workload was determined during cardiopulmonary exercise testing at 60 rpm. On day 2, participants performed constant-load cycle ergometer exercise at the AT workload under three pedaling rate conditions of 40, 60, and 80 rpm in a randomized crossover design. Measurements were obtained at steady state, 3 min after the onset of exercise. Outcomes included respiratory gas analysis, echocardiography, and blood lactate concentration. Repeated-measures analysis of variance (ANOVA) was performed, followed by Holm-corrected multiple comparisons when a significant main effect was detected. RESULTS: Respiratory exchange ratio increased with increasing pedaling rate (40 rpm: 0.93+/-0.04, 60 rpm: 0.99+/-0.04, 80 rpm: 1.03+/-0.05; P<0.001). Cardiac output increased with pedaling rate (40 rpm: 8.7+/-1.3 L/min; 60 rpm: 10.0+/-1.6 L/min; 80 rpm: 12.3+/-2.0 L/min; P<0.001). Oxygen uptake also increased with pedaling rate (40 rpm: 1.17+/-0.26 L/min; 60 rpm: 1.23+/-0.26 L/min; 80 rpm: 1.36+/-0.26 L/min; P<0.001). In contrast, arteriovenous oxygen difference decreased with increasing pedaling rate (40 rpm: 13.8+/-1.7 mL O2/100 mL; 60 rpm: 12.6+/-1.6 mL O2/100 mL; 80 rpm: 11.4+/-2.2 mL O2/100 mL; P<0.001). Holm-corrected multiple comparisons showed significant differences for all pairwise comparisons among the three pedaling rate conditions of 40, 60, and 80 rpm for the respiratory exchange ratio, cardiac output, oxygen uptake, and arteriovenous oxygen difference. CONCLUSION: Increasing pedaling rate was associated with increased cardiac output and decreased arteriovenous oxygen difference, suggesting that oxygen delivery may increase relative to oxygen demand. In contrast, the increase in respiratory exchange ratio suggested that anaerobic metabolism may be recruited even under relatively sufficient oxygen delivery. Therefore, careful consideration may be required when changing pedaling rate during AT-based exercise prescription.
Read CV Daichi TakanoECSS Paris 2023: OP-PN24