Harris, E., Rakobowchuk, M., & Birch, K. M. (2012). Sprint interval and sprint continuous training improve aerobic fitness but not vascular function or repair. Presentation 2828 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

"Shear stress is cited as a mechanism for exercise mediated improvements in vascular function. Sprint interval training (SIT) has been shown to be a time-efficient method for improving skeletal muscle oxidative capacity. However, little is known about the effects of repeated increments in shear stress during SIT on vascular function and repair, especially when compared to a continuous high intensity shear stress stimulus."

This study determined whether two types of sprint-training programs (interval vs. continuous) matched for total work can improve markers of vascular function and repair. Females completed four weeks of either sprint-interval (N = 6) or continuous-sprint training (N = 6) three days per week. Sprint-interval training consisted of four 30-second Wingate tests separated by 4.5 minutes of recovery. Continuous-sprint training involved sprint cycling for ~3-4 minutes, until the S reached the equivalent work achieved in four 30-second Wingate tests performed in the first training session. Before and after the training period, VO2peak and lactate threshold were estimated from a cycling incremental exercise test. Vascular function was assessed from brachial artery flow-mediated dilation and total vessel reactivity. Circulating progenitor cells, an index of vascular repair, were defined as triple positive cells (CD45dimCD34+KDR+).

Four weeks of sprint-interval or continuous-sprint training improved VO2peak and increased lactate threshold in both groups (no group x time interaction). Circulating progenitor cells did not increase across the duration of the study. Brachial artery flow-mediated dilation and total vessel reactivity did not change during training in either group.

Implication. Despite the differences in the shear stress profile and training time, sprint-interval and continuous-sprint training produced similar results in females. The improvement in aerobic fitness is consistent with previous studies and is suggestive of enhanced skeletal muscle metabolism. Training had minimal effect on vascular function and repair.

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