Repeatability of Respiratory Exchange Ratio Time Series Analysis

Advice to people with Parkinson's in my clinic: Get a cardiopulmonary exercise test

Aerobic (cardiopulmonary) exercise training improves fitness and limits the progression of motor signs in Parkinson's disease. Individualized development of exercise prescriptions relies upon accurately measured peak heart rate (HR). Cardiopulmonary exercise testing (CPET) is the only methodology to objectively confirm an individual's peak HR. This test is important in individuals who may have autonomic dysfunction, which may manifest as chronotropic incompetence. Without CPET's confirmation of maximal effort, there is no way of knowing whether exercise prescription in those with chronotropic incompetence is accurate. CPET also provides information regarding cardiorespiratory fitness, which can motivate patients to exercise to prolong health.

Are anti-gravity treadmills reliable to explore exercise energy metabolism at low degrees of alleviation in normal-weight male individuals?

BACKGROUND

Exploring the independent effect of mechanical discharge in response to weight loss (WL) seems necessary but remains highly challenging from a methodological point. Anti-gravity treadmills could be relevant to simulate a mechanical WL by body weight support (BWS), but their reliability remains unclear to properly explore exercise energy metabolism, especially at low degrees of alleviations.

OBJECTIVE

The study aimed to evaluate the accuracy and reproducibility of an anti-gravity treadmill to generate BWS, and the reproducibility of cardiometabolic responses to an exercise performed at low degrees of BWS on this device.

METHODS

Observed BWS of 18 normal-weight males was obtained twice at seven degrees of target BWS (i.e., 0, 3, 6, 9, 12, 15, 18%) using a digital scale inside the anti-gravity treadmill, and was compared to the expected BWS. Then, 15 of them performed 5-min bout of low-intensity walking exercise at these degrees of BWS in a randomized order, separated by 4-min rest. The exercise was identically repeated on three occasions separated by a minimum of 3 days. Energy metabolism and heart rate (HR) were measured throughout the exercise by indirect calorimetry and a HR monitor, respectively.

RESULTS

The observed BWS were significantly different from the expected BWS (p< 0.001), and there was a high inter- and intra-individual variability in BWS generated by the anti-gravity treadmill. Results showed an overall good reliability of VO2 (intraclass correlation coefficients (ICC) values ranging from 0.67 to 0.85) and HR (ICC > 0.8) in response to exercise. An effect of the degree of BWS was observed for VO2 (p< 0.001), illustrating reduced values at 15% and 18% of BWS compared to 0, 3, and 6%.

CONCLUSIONS

Such device might not be adapted to simulate low degrees of WL in normal-weight males, particularly when it comes to the exploration of energy metabolism.

Factors Influencing Substrate Oxidation During Submaximal Cycling: A Modelling Analysis

BACKGROUND

Multiple factors influence substrate oxidation during exercise including exercise duration and intensity, sex, and dietary intake before and during exercise. However, the relative influence and interaction between these factors is unclear.

OBJECTIVES

Our aim was to investigate factors influencing the respiratory exchange ratio (RER) during continuous exercise and formulate multivariable regression models to determine which factors best explain RER during exercise, as well as their relative influence.

METHODS

Data were extracted from 434 studies reporting RER during continuous cycling exercise. General linear mixed-effect models were used to determine relationships between RER and factors purported to influence RER (e.g., exercise duration and intensity, muscle glycogen, dietary intake, age, and sex), and to examine which factors influenced RER, with standardized coefficients used to assess their relative influence.

RESULTS

The RER decreases with exercise duration, dietary fat intake, age, VO2max, and percentage of type I muscle fibers, and increases with dietary carbohydrate intake, exercise intensity, male sex, and carbohydrate intake before and during exercise. The modelling could explain up to 59% of the variation in RER, and a model using exclusively easily modified factors (exercise duration and intensity, and dietary intake before and during exercise) could only explain 36% of the variation in RER. Variables with the largest effect on RER were sex, dietary intake, and exercise duration. Among the diet-related factors, daily fat and carbohydrate intake have a larger influence than carbohydrate ingestion during exercise.

CONCLUSION

Variability in RER during exercise cannot be fully accounted for by models incorporating a range of participant, diet, exercise, and physiological characteristics. To better understand what influences substrate oxidation during exercise further research is required on older subjects and females, and on other factors that could explain additional variability in RER.

Yo-Yo Intermittent Recovery Level 1 Test for Estimation of Peak Oxygen Uptake: Use Without Restriction?

Purpose: This study analyzed the physiological response during Yo-Yo Intermittent Recovery Level 1 (YYIR1) test and re-test by in-field ergospirometry and time-series analyses of respiratory parameters. Methods: Ten moderately trained males (23.4 ± 2.01 years, VO_2peak= 56.81 ± 10.75 mL·kg^-1·min^-1) completed three running trials including two separate YYIR1 tests and an independent maximal performance running test with time-series analyses of gas exchange parameters. Physiological response was assessed during all tests by determination of blood lactate levels (including calculation of individual lactate threshold), heart rate, oxygen consumption and respiratory exchange ratio (RER). Results: Modeling of YYIR1 test mean VO₂ uptake kinetics over all participants revealed that VO₂ increased rapidly after the individual lactate threshold (11.49 ± 0.66 km∙h^-1 at 3.83 ± 0.42 mmol∙L^-1) was reached with ~95% VO_2peak at ~50% of the test duration (test, VO₂ ^50%= 95.17 ± 8.74% of VO_2peak; re-test, VO₂ ^50%= 96.78 ± 7.04% of VO_2peak). However, and despite identical YYIR1 test performance (1568 ± 364.6 m vs. 1568 ± 449.7 m, CV = 4.59%), mean VO_2peak during YYIR1 test was 8.81 ± 5.6% higher than YYIR1 re-test (p = .027). Importantly, correlation of VO_2peak with YYIR1 test performance was weak (R² = 0.28, p = .115). Conclusions: We conclude that the YYIR1 test should not be used to estimate VO_2peak. Further studies on direct determination of gas exchange parameters during different YYI test variants are warranted.

Efficacy and Safety of Whey Protein Supplements on Vital Sign and Physical Performance Among Athletes: A Network Meta-Analysis

Introduction: Athletes train physically to reach beyond their potential maximum aerobic threshold. Whey protein supplements (WPS) are often used in conjunction with physiotherapy and psychotherapy to regain better vital sign and physical performances. This review aimed to explore the clinical evidence on the efficacy and safety of WPS in sports performance and recovery among athletes.

Methodology: A comprehensive literature search was performed to identify relevant randomized control trials (RCTs) that investigated the efficacy and safety of WPS on the vital sign and physical performance among athletes. The Cochrane Risk of Bias (ROB) Assessment tools were used to assess the quality of the studies. Meta-analysis was conducted using the frequentist model with STATA version 14.2®.

Results: A total of 333,257 research articles were identified out of which 20 RCTs were included for qualitative synthesis and network meta-analysis with 351 participants. Among the studies, 7 had low ROB and 3 RCTs had high ROB. Of these 20 trials, 16 trials were randomized clinical trials which compared whey protein supplements (WPS) with various comparators i.e., L-alanine, bovine colostrum, carbohydrate, casein, leucine, maltodextrin, rice, protein + caffeine were compared with placebo. Analysis from the pairwise meta-analysis revealed that for respiratory exchange ratio (RER) WPS was found to be significantly improving compared to maltodextrin (WMD = 0.012; 95%CI = 0.001, 0.023). Similarity to RPE (Rate Perceived Exertion), slight difference between WPS and the comparators, however, when the estimation was favorable to the comparators, there was moderate-high heterogeneity. For VO_2max, high heterogeneity appeared when WPS compared to maltodextrin with the I² = 97.8% (WMD = 4.064; 95% CI = −4.230, 12.359), meanwhile bovine colostrum (WMD = −2.658; 95%CI = −6.180, 0.865) only comparator that was better than WPS. According to the estimated effect of the supplements on physical performance outcome results, maximum power (8 studies, 185 athletes), highest ranked was bovine colostrum (SUCRA = 70.7%) and the lowest ranked was placebo (SUCRA = 17.9%), yet all insignificant. Then again, on average power (nine studies, 187 athletes), WPS was the highest ranked (SUCRA = 75.4 %) about −112.00 watt (−187.91, −36.08) and most of the estimations were significant. Body mass was reported in 10 studies (171 athletes), carbohydrate may be at the highest ranked (SUCRA = 66.9%) but it is insignificant. Thought the second highest ranked was WPS (SUCRA = 64.7%) and it is significant (WMD = −6.89 kg; CI = −8.24, −5.54).

Conclusion: The findings of this review support the efficacy and safety of WPS as an ergogenic aid on athletes' sports performance and recovery. The overall quality of clinical evidence was found to be valid and reliable from the comprehensive search strategy and ROB assessment.