Intermittent versus continuous handgrip exercise and peripheral endothelial function: impact of shear rate...

Area of Science:

• Physiology
• Cardiovascular Health
• Exercise Science

Background:

• Sustained exercise-induced elevations in shear rate (SR) are known to benefit endothelial function.
• The impact of intermittent SR fluctuations on peripheral endothelial function remains unclear.

Purpose of the Study:

• To compare the effects of intermittent versus sustained SR elevations on peripheral endothelial function.
• To investigate the acute impact of different exercise protocols on brachial artery flow-mediated dilation (FMD).

Main Methods:

• 13 healthy adults performed three 30-minute handgrip exercise protocols: intermittent at 25% MVC (INT-25%), intermittent at 15% MVC (INT-15%), and continuous at 15% MVC.
• Brachial artery diameter and velocity were measured using Doppler ultrasound to assess SR and FMD.
• FMD was assessed before and after each exercise intervention.

Main Results:

• All exercise protocols increased FMD, but the increase was significantly greater following INT-25% compared to INT-15% and continuous exercise.
• Normalized FMD to shear rate area under the curve increased significantly with intermittent exercises (INT-25% and INT-15%) but not with continuous exercise.
• Intermittent elevations in SR produced a greater acute improvement in endothelial function compared to continuous elevations, despite similar total SR increases.

Conclusions:

• Intermittent fluctuations in shear rate during handgrip exercise may be a more effective stimulus for acute improvements in peripheral endothelial function than sustained elevations.
• Novel findings suggest intermittent exercise protocols could be a superior strategy for enhancing endothelial function.