Isometric handgrip exercise improves acute neurocardiac regulation

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Regulation
• Nonlinear Dynamics in Physiology

Background:

• Isometric handgrip (IHG) training is known to reduce resting arterial blood pressure (ABP) and improve cardiac autonomic modulation over weeks.
• The acute effects of a single IHG session on neurocardiac regulation, particularly heart rate dynamics, are not well understood.

Purpose of the Study:

• To investigate the immediate impact of a single bout of IHG exercise on nonlinear heart rate dynamics and cardiac vagal activity in older adults.
• To assess changes in measures of heart rate complexity and vagal tone following acute IHG exposure.

Main Methods:

• A randomized crossover design was employed with 18 older adults (mean age 70 years).
• Participants underwent a single session of bilateral IHG exercise (four 2-min contractions at 30% maximal voluntary contraction) and a time-matched control condition.
• Nonlinear heart rate dynamics were analyzed using sample entropy and detrended fluctuation analysis (alpha(1)). Cardiac vagal activity was assessed via the cardiac vagal index (CVI) using a 4-second test.

Main Results:

• A single IHG bout resulted in a small but significant reduction in systolic blood pressure.
• Significant improvements in acute cardiac autonomic modulation were observed, including a decrease in alpha(1) and an increase in sample entropy, indicating enhanced heart rate variability.
• Cardiac vagal activity, measured by the CVI, also significantly increased post-IHG exercise.

Conclusions:

• A single session of isometric handgrip exercise acutely enhances cardiac autonomic modulation in older adults.
• These findings suggest that IHG exercise may have immediate physiological benefits on neurocardiac regulation.
• The observed acute effects warrant further investigation for potential clinical applications in managing cardiovascular health.