The Impact of Sprint Interval Training on Arterial Compliance and Brachial Endothelial Function in Young Healthy Males

Abstract

<p> Increased arterial stiffness and vascular endothelial dysfunction have been identified as independent risk factors for the development and progression of cardiovascular disease. Traditional endurance training has been associated with elevated levels of central arterial compliance and an attenuation of cardiovascular events. As well, the positive benefits of aerobic-based training have been acknowledged as effective modulators of vascular endothelial function. To date, the impact of sprint interval training on cardiovascular health has not been evaluated. Furthermore, the mechanisms responsible for previously observed enhancements in endurance (750 kJ) performance following two weeks of sprint interval training remain unclear, but may be related to changes in vascular structure and function.</p> <p> Nine young healthy males [age: 22 ± 0.5 (mean± SEM)] participated in a two week sprint interval training program consisting of 4-6 30 second maximum effort exercise bouts performed every other day on a cycle ergometer. In addition, each participant was required to complete a 750 kJ time trial on a cycle ergometer as a measure of aerobic exercise performance before (PRE) and after (POST) training. Measurements of supine, resting carotid pulse pressure, carotid cross-sectional compliance, and brachial vascular endothelial function (using flow mediated dilation) were also acquired PRE and POST training.</p> <p> Resting pulse pressure did not show any significant changes with exercise training (PRE= 48.6±1.6, POST= 52.4±2.5 mmHg, p>0.05). Mean brachial artery diameter was not changed with sprint interval training (PRE= 4.29±0.17, POST= 4.38±0.18 mm, p>0.05); however, mean carotid artery diameter increased significantly PRE to POST (PRE= 6.40±0.15, POST= 6.49±0.14 mm, p=0.008). Carotid cross-sectional compliance did not change PRE to POST training (PRE= 0.164±0.010, POST= 0.162±0.007 mm^2/mmHg, p>0.05). Brachial vascular endothelial function measured using flow-mediated dilation did not show a significant change with sprint interval training, however a trend towards improvement was noted (PRE= 4.6±1.8, POST= 6.4±1.0 %, p=0.296). When normalized for shear rate (which was also unaltered with sprint interval training) there were no changes in endothelial function (PRE = 0.158±0.068, POST= 0.198 ± 0.034 %/S^-1, p>0.05). Average brachial post-occlusion blood flow was significantly enhanced following training possibly revealing enhanced resistance vessel function (PRE= 296.0±37.4, POST= 324.8±38.8 ml/min, p=0.04), despite no change in peak brachial blood flow (PRE= 332.0±42.3, POST= 362.6±45.7 ml/min, p>0.05). 750 kJ time trial performance was significantly enhanced with training (PRE = 62.8±4.9; POST= 55.84±3.55 min; p=0.006).</p> <p> In conclusion, sprint interval training did not change resting carotid compliance or brachial endothelial function, despite significant improvements in aerobic performance (750 kJ). However, carotid resting diameters and brachial post occlusion blood flow were significantly increased PRE to POST and a trend towards improvement was seen for brachial flow mediated dilation. The exact mechanisms responsible for such changes remain unknown and require further investigation.</p>