PURPOSE:Endothelial function is highly regulated by the interaction between blood flow and the endothelium. Endothelial shear stress (ESS) is defined as the dragging force generated by this interaction and it has been reported that low ESS affects nitric oxide bioavailability which in turn might increase blood pressure. Exercise programs are one of the best suited approaches to prevent high blood pressure, however, there are no studies describing changes on ESS in the common carotid artery during specific modalities of exercise, such as boxing training. Therefore, the purpose of this study was to quantify ESS in the common carotid artery during maximal and submaximal boxing training in normotensive and pre-hypertensive subjects.
METHODS:A cohort of 5 healthy normotensive and 5 pre-hypertensive subjects matched by age, gender, height, and weight were recruited for this study. All 10 subjects performed two boxing tests. The first was a graded maximal boxing test to estimate their maximal oxygen uptake (VO₂max). The second one, performed 48 hours after the first evaluation, was a 2-workload steady-state boxing test at 60%VO2max and at 95%VO2max for 3 minutes each. A high-definition Doppler ultrasound recorded common carotid artery diameters and blood flow velocities throughout each steady-state condition. ESS was estimated using Womersley’s approximation.
RESULTS: There was a significant increase in antegrade ESS with higher workloads in both groups (p < 0.05 for all). No difference were found in anterograde ESS at baseline (Normotensive: 33.9±13.9 dynes/cm², Pre-HTA: 34.7±5.5 dynes/cm²; p = 0.936), at 60%VO₂max (Normotensive: 51.3±19.1 dynes/cm², Pre-HTA: 49.6±7.6 dynes/cm²; p = 0.894, and at 95%VO₂max (Normotensive: 72.9±30.9 dynes/cm² , Pre-HTA: 85.2±12.5 dynes/cm²; p = 0.560) between both groups. Meanwhile, no retrograde blood flow was present at baseline for either groups, but it was identified at 60%VO₂max (Normotensive: 8.1±0.7 dynes/cm², Pre-HTA: 7.8±7.8 dynes/cm²; p = 0.971) and 95%VO₂max (Normotensive: 22.5±18.9 dynes/cm² , Pre-HTA: 20.8±5.6 dynes/cm²; p = 0.891).
CONCLUSIONS:ESS increases in an exercise-intensity manner during boxing training in normotensive and prehypertensive population. Boxing training might be beneficial in high blood pressure prevention due to increments on ESS.