The effect of high intensity interval training on cardio-respiratory fitness levels, endothelin-1 and Nitric oxide levels in obese individuals

Obesity is one of the biggest barriers to health in today's society. Endothelial dysfunction is more common in obese people than in other people and cardiorespiratory fitness is also low in these people. The aim of this study was to evaluate the effect of HIIT training with weight bearing, without weight bearing, and combined on the levels of ET-1, Nox, and cardiorespiratory fitness in obese population.

The present study was a semi-experimental study. 100 obese subjects (based on body mass index) who referred to Shariati Hospital in Tehran were randomly divided into four groups of High Intensity Interval training (HIIT), Treadmill (TR), Bicycle (CY), Combined (CO), and Control (CTR). The subjects in the training groups trained for 12 weeks. Blood samples and cardiovascular fitness tests of the subjects were measured in two rounds before and after the test. ELISA method was used to measure the levels of nitric oxide (NOx) and endothelin-1 (ET-1) and one-way and two-way methods were used to study the data changes.

The results of the present study indicated that after 12 weeks of training, the VO2peak in the training groups improved compared to the control group (p<0.001) and it increased in the HIIT-TR group more than the HIIT-CO group (p<0.01). In the TR group, the rate of NOx increase was higher than other exercise groups (p<0.01). It was also indicated that training decreased plasma levels of ET-1 in the TR and CO exercise groups, while ET-1 levels in the CY group did not differ significantly from the CTR group (p>0.05).

It is possible that HIIT training improves VO2peak (especially in the HIIT group with weight bearing and combination) and the duration of training and also raises the mean maximum heart rate by increasing the biochemical factors of vasodilation and reducing the factors of vasoconstriction in obese patient in the training groups compared to the control group.