OXYGEN UPTAKE

Oxygen Uptake

Abtract

The aim of this study was to examine the effects of maximal oxygen (O2) uptake on heart rate variability (HRV) responses during moderate and severe exercise intensities until exhaustion. Ten healthy males (age, 26.5 ± 6.7 years; body mass, 78.4 ± 7.7 kg; body fat %, 11.3 ± 4.5%; 39.5 ± 6.6 mL kg-1 min-1) volunteered for this study. All tests were performed in the morning, after 8-12 h overnight fasting, at a moderate intensity corresponding to 50% of the difference between the first (VT1) and second (VT2) ventilatory breakpoints and at a severe intensity corresponding to 25% of the difference between the maximal power output and VT2. Forty-eight hours before each experimental session, the subjects performed a 90-min cycling exercise followed by 5-min rest periods and subsequent 1-min cycling bouts at 125% (with 1-min rest periods) until exhaustion, in order to deplete muscle glycogen. A diet providing 10% (O2max) or 65% (O2control) of energy as carbohydrates was consumed for the following 2 days until the experimental test. The Poicaré plots (standard deviations 1 and 2: SD1 and SD2, respectively) and spectral autoregressive model (low frequency LF, and high frequency HF) were applied to obtain HRV parameters. The O2 uptake had no effect on the HRV parameters or ventilation during moderate-intensity exercise. However, the SD1 and SD2 parameters were significantly higher in O2max than in O2control, as taken at exhaustion during the severe-intensity exercise (P < 0.05). The HF and LF frequencies (ms2) were also significantly higher in O2max than in O2control (P < 0.05). In addition, ventilation measured at the 5 and 10-min was higher in O2max (62.5 ± 4.4 and 74.8 ± 6.5 L min-1, respectively, P < 0.05) than in O2control (70.0 ± 3.6 and 79.6 ± 5.1 L min-1, respectively; P < 0.05) during the severe-intensity exercise. These results suggest that the O2 uptake alters the HRV parameters during severe-, but not moderate-, intensity exercise, and this was associated with an increase in ventilation volume.

Lab Report

1. Introduction

The maximal rate of oxygen uptake (VO2max) is considered as a gold standard for measurement of cardiorespiratory fitness. Cardiorespiratory fitness is a direct marker of physiological status and reflects the overall capacity of the cardiovascular and respiratory systems and the ability to carry out prolonged exercise . In addition, recent reports suggest that cardiorespiratory fitness is also an important health marker in young individuals and . High-cardiorespiratory fitness during childhood and adolescence has been associated with a favourable plasma lipid profile in both overweight and non-overweight adolescents , with total and central body fat and , features of the metabolic syndrome and , blood pressure , novel cardiovascular disease risk factors , and with arterial compliance in young people . These findings support the concept that cardiorespiratory fitness may exert a protective effect on the cardiovascular system from an early age .

It seems viable to develop a more accurate VO2max equation for the adolescent period, while taking those variables which have been shown to have an impact on the level of cardiorespiratory fitness into account. Published equations for VO2max have the shape of a linear or quasi-linear expression on different input variables (sex, age, body weight, and stage) (Table ...