The handgrip maneuever is performed by clenching one's fist forcefully for a sustained time until fatigued. Variations include squeezing an item such as a rolled up washcloth.

Physiological Response

The handgrip maneuver increases afterload by squeezing the arterioles and increasing
Total Peripheral Resistance

Total peripheral resistance

Vasculature throughout the entire body can be thought of as two separate circuits - one is the systemic circulation, while the other is the pulmonary circulation. Total peripheral resistance is the sum of the resistance of all peripheral vasculature in the systemic circulation...

. This is similar to the squatting maneuver (which also increases afterload). The main difference is that the hand grip test does not increase venous return.

Cardiology

Since increasing afterload will prevent blood from flowing in a normal forward path, it will increase any murmurs that are due to backwards flowing blood.
This includes Aortic Regurgitation (AR), Mitral Regurgitation (MR) and Ventricular Septal Defects (VSD) (murmur increases in intensity).

Murmurs that are due to forward flowing blood such as Aortic Stenosis, Mitral Stenosis, Hypertrophic Cardiomyopathy and Mitral valve prolapse are improved (murmur decreases in intensity)

The effect of reducing the intensity in forward flowing murmurs is much more evident in Aortic stenosis rather than Mitral Stenosis. The reason for this is that there is a larger pressure gradient across the Aortic valve. A complementary maneuver for differentiating disorders is the Valsalva maneuver

Valsalva maneuver

The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut...

, which decreases preload.

Effect	Cardiac Finding
Increased
	Aortic Regurgitation Aortic insufficiency Aortic insufficiency , also known as aortic regurgitation , is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle....
	Mitral Regurgitation
	Ventricular Septal Defect Ventricular septal defect A ventricular septal defect is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.The membranous...
Decreased
	Aortic Stenosis
	Mitral Stenosis Mitral stenosis Mitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.-Signs and symptoms:Symptoms of mitral stenosis include:...
	Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy Hypertrophic cardiomyopathy is a disease of the myocardium in which a portion of the myocardium is hypertrophied without any obvious cause...