Effects of High Intensity Interval Exercise on Peripheral Blood Flow and Muscle Tissue Oxygenation

Abstract

Intense physical exercise has profound effects on muscle metabolism. Previous studies have looked at muscle oxygenation changes with intense exercise. However, this study is unique in that its purpose is to look at the relationship between tissue oxygenation and blood flow delivery in response to a high intensity training protocol. Six subjects (Age = 20.5 ± 0.8 yrs, Weight = 68.6 ± 12.6 kgs) participated in four trials. During the first trial, a maximum cycle ergometer test was performed to determine the maximum power output for each participant. In the second trial, either condition one or condition two was performed in a random order. Condition one consisted of six bouts of high intensity exercise (HIE) followed by a one‐hour rest period. Each bout consisted of 30 seconds pedaling at the subject's maximum resistance followed by one minute pedaling without resistance (active recovery). Condition two consisted of two series of six HIE bouts separated by a 30 minute rest period followed by a one hour rest period. Near‐infrared spectroscopy (Portamon, Artinis Inc.) in the left gastrocnemius muscle was used to assess tissue saturation index (TSI). Slope of the TSI response was then calculated. Forearm blood flow was measured every ten minutes during the rest periods using venous occlusion plethysmography. Heart rate (HR) and beat‐to‐beat blood pressure were continuously recorded (CNAP 500, CNS Systems) throughout exercise and rest periods. In the third trial, baseline measurements of NIRS, forearm blood flow, and HR were taken. In the last trial, each subject completed whichever condition they did not complete on day two. TSI slope was consistently negative during the maximum resistance portions of exercise and was consistently positive during the active recovery portion of exercise. Slope of TSI % during the first bout of maximum resistance (Condition 1: −0.015 ± 0.007, Condition 2: −0.032 ± 0.046) declined at a greater rate than the following five bouts of exercise. Furthermore, slope of TSI % during the one‐hour rest in both conditions was highest one minute into the rest period (Condition 1: 0.0011 ± 0.0015, Condition 2: 0.0020 ± 0.0023) and then returned to baseline by 11 minutes into the rest period. Forearm blood flow during the one‐hour rest in both conditions was also highest one minute into the rest period (Condition 1: 11.4 ± 6.3 ml/100 ml/min, Condition 2: 10.3 ± 2.8 ml/100 ml/min) and then returned to baseline by 11 minutes into the rest period. In conclusion, muscle oxygenation declined at a high rate during HIE and was partially restored during active recovery. Most of the deoxygenation occurred during the first HIE bout, suggesting that increased blood flow in subsequent bouts facilitated an increase in oxygen delivery