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CORRELATION BETWEEN NON-INVASIVE MITOCHONDRIAL CAPACITY ASSESSMENT AND OXYGEN UPTAKE KINETICS FOLLOWING MODERATE INTENSITY EXERCISE

Abstract

Alexis Coleman, Justin P. Guilkey, Timothy R. Rotarius. Coastal Carolina University, Conway, SC.

BACKGROUND: Mitochondrial capacity (mVO2) is important for our understanding of exercise capacity as it plays a vital role in aerobic metabolism. Pulmonary oxygen uptake (pVO2) kinetics have been shown to closely match mVO2. Non-invasive measures of mVO2 using near-infrared spectroscopy (NIRS) have become increasingly popular as it has been found to be a reliable measure of mVO2. The purpose of the present investigation was to assess the relationship between mVO2 and pVO2 on- and off-kinetics following moderate intensity exercise. METHODS: Seven healthy males (24 ± 5 yrs.) performed 2 bouts of moderate intensity (80% of lactate threshold) cycling exercise for 6 minutes followed by a 5-min cooldown at 20W. mVO2 assessment was performed prior to and following each exercise bout. pVO2 was continuously recorded breath-by-breath. Phase II kinetics (on-kinetics) were analyzed using either a 1- or 2-component exponential model after interpolating to 1 s and ensemble averaging each trial. mVO2 was determined from 20 short (5-10 s) arterial occlusions. Deoxyhemoglobin (HHb) was measured at the vastus lateralis and the slope of change in HHb during the first 3-5 seconds of each occlusion was plotted over time as mVO2. pVO2 off-kinetics and mVO2 were analyzed using a mono-exponential decay model. Matched pairs t-tests were used to compare pVO2 on- and off-kinetics and pre- and post-mVO2. Pearson correlation coefficients were computed to assess relationships between pVO2 on- and off-kinetics and pre- and post-mVO2 recovery constants. Significance was established if p < 0.05. RESULTS: pVO2 on- and off-transient kinetics were similar (ON: 44.0 ± 11.0 s; OFF: 34.4 ± 9.5 s). mVO2 recovery kinetics were similar before and after exercise (PRE: 30.4 ± 6.1 s; POST: 28.9 ± 11.5 s). pVO2 off-kinetics were not correlated with mVO2 recovery prior to exercise (r = 0.447), but was strongly correlated with post-exercise mVO2 (r = 0.700). pVO2 on-kinetics were not correlated with mVO2 prior to (r = -0.596) or after (r = -0.293) exercise. CONCLUSION: Non-invasive assessment of mVO2 is not affected by a bout of moderate intensity exercise. mVO2 was not different pre- and post-exercise. pVO2 off-kinetics are positively and strongly correlated to mVO2 post-exercise but not correlated with pre-exercise mVO2. There is no correlation between mVO2 and pVO2 on-kinetics before or after moderate exercise.

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