Evaluating the progressive cardiovascular health benefits of short-term high-intensity interval training.

PURPOSE: High-intensity training is recognised as a time-efficient way of improving aerobic fitness. However, there is a lack of consensus regarding the temporal nature of adaptation response and which peripheral and cardiac changes occur using the same exercise stimulus and protocol. Therefore, this study aimed to evaluate the progression of vascular and cardiac changes over a 6-week training period.

METHODS: Twelve healthy males (age 21 ± 2 years; 42.5 ± 8.3 ml min-1  kg-1 ) participated in a high-intensity training programme consisting of 1-min sprints, interspersed with 2 min active recovery, 3 days/week for 6 weeks on a cycle ergometer. Cardiac, vascular, blood lipids and VO2max measurements were taken at 0, 3 and 6 weeks and compared against a participant-matched control group (age 21 ± 2 years; 37.7 ± 8.3 ml min-1  kg-1 ).

RESULTS: There was a significant improvement in VO2max (42.5 ± 8.3-47.4 ± 8.5 ml min-1  kg-1 ; p = 0.009) in the training group and a significant decrease in systolic blood pressure (8%) from 0 to 6 weeks (p = 0.025). There was a small yet significant decrease in ejection fraction and increased end-systolic volume in both groups over time (p = 0.01) with no significant interaction effect (p > 0.05). A between-group difference in peak velocity of early diastolic mitral annular motion was also observed (p = 0.01). No improvements were seen in blood lipid profiles, central arterial stiffness and cardiometabolic risk score.

CONCLUSIONS: Six weeks of high-intensity training increases aerobic fitness and is enough to stimulate initial reductions in peripheral pressure, but not sufficient to elicit structural and functional cardiac changes, reduce arterial stiffness or lower CV risk.