Effects of aging and training status on ventilatory response during incremental cycling exercise

The Ratio of Oxygen Uptake From Ventilatory Anaerobic Threshold to Respiratory Compensation Point Is Maintained During Incremental Exercise in Older Adults

Introduction

The period from ventilatory anaerobic threshold (VAT) to respiratory compensation point (RCP) during incremental exercise (isocapnic buffering phase) has been associated with exercise tolerance and skeletal muscle composition. However, several reports compare younger and older healthy adults, and specific age-related changes are unclear. This study aimed to examine the oxygen uptake (VO₂) from VAT to RCP and its change over time in younger and older healthy adults.

Methods

A total of 126 consecutive participants were divided into two groups (95 younger and 31 older than 50 years of age) who underwent cardiopulmonary exercise testing, and VAT and RCP were determined. The ratio (RCP/VAT) and difference (ΔVO₂ RCP-VAT) were calculated from the VO₂ of VAT and RCP and compared between groups and ages. Statistical analyses included t-tests and Spearman’s correlation tests, and the significance level was set at <5%.

Results

RCP/VAT was not significantly different (1.40 ± 0.19 vs. 1.59 ± 0.24, p = 0.057) but weakly correlated with age (r = −0.229, p = 0.013, y = −0.0031x + 1.7588, lowering rate: 0.185%/year). Conversely, ΔVO₂ RCP-VAT was significantly lower in the older group (7.7 ± 3.1 vs. 13.8 ± 4.9 ml/kg/min, p < 0.001) and correlated significantly with age (r = −0.499; p < 0.001; y = −0.1303x + 16.855; lowering rate, 0.914%/year).

Conclusion

ΔVO₂ RCP-VAT was considered to be a poor indicator of lactate buffering capacity in the IB phase because both VAT and RCP were greatly affected by age-related decline. Conversely, RCP/VAT was suggested to be an index not easily affected by aging.

EFFECTS OF REPEATED SPRINT TRAINING ON ISOCAPNIC BUFFERING PHASE IN VOLLEYBALL PLAYERS

ABSTRACT Introduction: The region between the ventilatory threshold (VT) and respiratory compensation point (RCP) is defined as the isocapnic buffering (ICB) phase and represents a phase of compensation for exercise-induced metabolic acidosis. There is sparse literature examining the effects of physical training on ICB phase in athletes. Objectives: The purpose of this study was to examine the effects of a repeated sprint training program on the ICB phase of college volleyball players. Methods: Eighteen male volleyball players were randomly assigned to either an experimental group (n=9) or a control group (n=9) and followed a traditional volleyball training program three times per week for six weeks. The experimental group additionally performed a repeated sprint training protocol immediately before each volleyball training session. Before and after the 6-week training period, all participants performed an incremental treadmill test to determine VT, RCP, and maximal oxygen uptake (VO2max). The ICB phases were calculated as VO2 (ml/kg/min) and sprint speed (km/h). Results: The experimental group showed significant improvements in ICB phase, RCP, VO2max and maximal sprint speed after training (p<0.01). There were no significant changes in VT after training in the experimental group (p>0.05). None of these variables changed significantly in the control group (p>0.05). Conclusions: These findings indicate that repeated sprint training can enhance the ICB phase of volleyball players, which may be attributable to an improvement in buffering capacity leading to a shift in RCP towards higher intensities without any change in VT. The increase in the ICB phase may an important factor in terms of improvement in the high-intensity exercise tolerance of athletes. Level of Evidence II; Therapeutic studies - Investigating the results of treatment.

Isocapnic buffering phase: a useful indicator of exercise endurance in patients with coronary artery disease

OBJECTIVES

The significance of the isocapnic buffering (IB) phase - the period between the first ventilatory threshold (1^st VT) and respiratory compensation point (RCP) - has not been adequately established in patients. This study aimed to determine the clinical significance of the IB phase in patients with coronary artery disease (CAD).

METHODS

This retrospective study included data of sixty-two CAD patients after coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI) performed in a single medical center between 2010 - 2014. According to their physical conditions, the patients performed incremental cardiopulmonary exercise test (CPET) using a cycle ergometer by the ramp of 5-20 W/min. Correlations between the corrected IB phase duration and age, body mass index (BMI), left ventricular ejection fraction (LVEF), and CPET parameters were evaluated using Pearson correlation coefficients. Variables predicting peak oxygen consumption (VO₂) were evaluated using multiple regression.

RESULTS

Peak VO₂ (p < 0.001), VO₂ at RCP (p < 0.001), ∆O₂/∆WR slope (p < 0.001), maximal partial pressure of end tidal CO₂ (PetCO₂) (p = 0.0012), VE/VCO₂ slope (p = 0.010), BMI (p = 0.012), and age (p = 0.017) were significantly correlated, whereas LVEF (p = 0.246) and VO₂ at 1^st VT (p = 0.179) were not significantly correlated with the corrected IB phase duration. In multiple regression analysis, the corrected IB phase duration, VO₂ at 1^st VT, and ∆O₂/∆WR slope were significantly associated with peak VO₂.

CONCLUSION

The findings indicate that the IB phase duration is a useful indicator of peripheral cardiopulmonary function and endurance performance in CAD patients. These findings could assist the exercise prescription of cardiac rehabilitation for patients with CAD.

Influence of ACTN3 R577X polymorphism on ventilatory thresholds related to endurance performance

The purpose of this study was to verify the association between ACTN3 polymorphism and physiological parameters related to endurance performance. A total of 150 healthy male volunteers performed a maximal incremental running test to determine the speeds corresponding to ventilatory threshold (VT) and respiratory compensation point (RCP). Participants were genotyped and divided into terciles based on the analysed variables. Genotype frequencies were compared through χ(2) test between lower and higher terciles, with the lowest or highest values of each analysed variable. ACTN3 XX genotype was over-represented in higher tercile for VT and RCP. Odds ratio also showed significantly higher chances of XX individuals to be in higher tercile compared to RR (7.3) and RR + RX (3.5) for VT and compared to RR genotype (8.1) and RR + RX (3.4) for RCP. Thus, XX individuals could attain the VT and RCP at higher speeds, suggesting that they are able to sustain higher running speeds in lower exercise intensity domains. It could result in higher lipid acids oxidation, saving muscle glycogen and delaying the fatigue during prolonged exercises, which could be the advantage mechanism of this genotype to endurance performance.

Cardio-respiratory reference data in 4631 healthy men and women 20-90 years: the HUNT 3 fitness study

PURPOSE

To provide a large reference material on key cardio-respiratory variables in a healthy population of Norwegian men and women aged 20-90 years.

METHODS

Sub maximal and peak levels of cardio-respiratory variables were measured using cardiopulmonary exercise testing during treadmill running.

RESULTS

The highest peak ventilation among men (141.9±24.5 L·min-1) and women (92.0±16.5 L·min-1) was observed in the youngest age group (20-29 years, sex differences p<0.001) with an average 7% reduction per decade. The highest tidal volumes were observed in the 30-39 and 40-49 year age groups among men (2.94±0.46 L) and women (2.06±0.32 L) (sex differences p<0.001), with a subsequent average 6% reduction per decade. Ventilatory threshold and respiratory compensation point were observed at approximately 77% and 87% of peak oxygen uptake (VO2peak) among men and women, respectively. The best ventilatory efficiency (EqVCO2Than) was observed in the youngest age group (20-29 years) in both men (26.2±2.8) and woman (27.5±2.7) (sex differences p<0.001) with an average 3% deterioration in ventilatory efficiency per decade.

CONCLUSION

This is the largest European reference material of cardio-respiratory variables in healthy men and women aged 20-90 years, establishing normal values for, and associations between key cardio-respiratory parameters. This will be useful in clinical decision making when evaluating cardiopulmonary health in similar populations.