Physiological effects of micropauses in isometric handgrip exercise

Area of Science:

• Physiology
• Exercise Science
• Sports Medicine

Background:

• Understanding physiological responses to different exercise protocols is crucial for optimizing training and recovery.
• Handgrip exercise is a common model for studying muscle fatigue and physiological adaptations.

Purpose of the Study:

• To compare the physiological responses to continuous handgrip (CH) versus intermittent handgrip (IH) exercise.
• To investigate the effect of electrical stimulation (ES) during intermittent handgrip (IHES) on exercise performance and physiological parameters.

Main Methods:

• Three experiments were conducted until exhaustion at 25% of maximal voluntary contraction (MVC): CH, IH (10-s rest every 3 min), and IHES.
• Physiological measures included heart rate (HR), blood pressure (BP), forearm blood flow, venous potassium [K+] and lactate [La-], electromyogram (EMG), and perceived exertion.
• Maximal voluntary contraction (MVC) and EMG responses were assessed before and up to 24 hours post-exercise.

Main Results:

• Maximal endurance time (tlim) was significantly longer in IH (23.1 min) than in CH (16.2 min); ES did not significantly affect tlim.
• No significant differences in blood flow, venous [K+], [La-], or EMG response were observed between CH and IH during exercise.
• HR and BP increased similarly during exercise, but reached higher levels at exhaustion in IH due to longer duration. Subjective fatigue was lower in IH.

Conclusions:

• Intermittent handgrip exercise enhances endurance capacity and reduces perceived fatigue compared to continuous handgrip.
• Recovery of maximal voluntary contraction is faster following intermittent handgrip exercise.
• Electrical stimulation during the rest intervals of intermittent handgrip did not further improve endurance time.