What is the effect of isometric handgrip (IHG) on venous return to the right atrium?

From the Guidelines

Isometric handgrip exercise increases venous return to the right atrium through several physiological mechanisms, resulting in a moderate increase in cardiac output and blood pressure. When a person performs an isometric handgrip, the sustained muscle contraction increases intramuscular pressure, which compresses nearby veins and propels blood toward the heart. This muscle pump effect is accompanied by a rise in sympathetic nervous system activity, leading to vasoconstriction in non-exercising tissues and increased cardiac output 1. Additionally, the elevated intrathoracic pressure during isometric exercise creates a pressure gradient that further enhances venous return. The increased venous return stimulates baroreceptors in the right atrium, triggering the Bainbridge reflex which increases heart rate.

The magnitude of this effect depends on the intensity of the grip (usually measured as a percentage of maximal voluntary contraction), duration of contraction, and the individual's baseline cardiovascular status. According to the study by the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism 1, the impact of isometric exercise on cardiovascular responses is significant, with increases in heart rate, systolic blood pressure, and diastolic blood pressure nearly proportional to the force exerted relative to the greatest possible force that an individual can evoke.

Key points to consider:

• Isometric handgrip exercise increases intramuscular pressure, which compresses nearby veins and propels blood toward the heart
• The muscle pump effect is accompanied by a rise in sympathetic nervous system activity, leading to vasoconstriction in non-exercising tissues and increased cardiac output
• The elevated intrathoracic pressure during isometric exercise creates a pressure gradient that further enhances venous return
• The increased venous return stimulates baroreceptors in the right atrium, triggering the Bainbridge reflex which increases heart rate
• The magnitude of this effect depends on the intensity of the grip, duration of contraction, and the individual's baseline cardiovascular status.

It is essential to note that the provided evidence does not directly address the effect of isometric handgrip on venous return to the right atrium, but rather discusses the physiological responses to isometric exercise in general. However, based on the available information, it can be inferred that isometric handgrip exercise does have a positive effect on venous return, which in turn contributes to the acute cardiovascular responses observed during isometric exercise.

From the Research

Effect of Isometric Handgrip on Venous Return

• The effect of isometric handgrip (IHG) on venous return to the right atrium is not directly addressed in the provided studies 2, 3, 4, 5, 6.
• However, some studies suggest that IHG training can improve cardiovascular function, including reducing blood pressure and improving vascular function 4, 5, 6.
• One study found that IHG training reduced diastolic blood pressure and improved local vascular function in patients with peripheral artery disease 4.
• Another study found that IHG training lowered resting systolic blood pressure and improved resistance vessel endothelial function in normotensive women 5.
• A systematic review and meta-analysis found that IHG training, but not a single session, reduced blood pressure in individuals with hypertension 6.

Mechanisms of IHG Training

• The mechanisms by which IHG training affects cardiovascular function are not fully understood, but may include improved vagal modulation and increased forearm reactive hyperemic blood flow 3, 5.
• IHG training may also improve heart rate variability (HRV), although the evidence is inconsistent 3, 5.

Limitations of the Evidence

• The provided studies do not directly address the effect of IHG on venous return to the right atrium.
• The studies have varying populations, including patients with coronary artery disease, peripheral artery disease, and hypertension, as well as normotensive women.
• The studies have different methodologies, including varying durations and intensities of IHG training.