One study that shows the effects of improved cardiovascular fitness with HIIT researched the effects of low volume HIIT versus all-out sprint interval training. They study had 24 young males, age 24 to 26 that were then separated into three groups of 8: the sprint interval training group which, completed three to five cycling rounds of 30 seconds all-out and 4 minutes of recovery in between, the low volume HIIT group which completed six to ten cycling rounds with two minutes of recovery in between and the control group with no training. The training lasted four weeks and the methods of Volume Oxygen consumption max test (VO2 max tests the maximum capacity of an individual's body to transport and use oxygen during incremental exercise), time to exhaustion, and Wingate test to measure power output were compared before and after the four weeks of training. This study found that there was only significant improvement in power output with the all out sprint interval
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