VO2 Responses to Running Speeds Above Intermittent Critical Speed

Abstract The aim of this study was to examine whether intermittent critical speed (ICS) is the threshold velocity above which intermittent exercise leads to the attainment of VO 2 max. After an incremental test, 7 active male subjects (49.7±3.74 mL.min − 1 .kg − 1 ) performed 3 intermittent exercises until exhaustion at 100%, 110%, 120% of the velocity associated with VO 2 max to determine ICS. On 4 occasions, the subjects performed intermittent exercise tests until exhaustion at the velocity corresponding to 105% (IE 105 ) and 110% (IE 110 ) of ICS, and at a speed that was initially set at 125%ICS but which then decreased to 105%ICS (IE 125–105 ) in one instance and to 110%ICS (IE 125–110 ) in another. The intermittent exercises consisted of repeated 30-s runs alternated with 15-s passive rest intervals. At IE 125–105 , peak VO 2 was not different from VO 2 max but decreased significantly after the change of speed to 105%ICS. During IE 110 , peak VO 2 value reached VO 2 max and also during the higher speed at IE 125–110 , but did not change when the speed was lowered. These results demonstrated that during intermittent exercise just above ICS (105%) VO 2 max was not elicited, suggesting that ICS might not be the threshold speed above which VO 2 max can be reached.