Grip Strength: Measurement Units, Tools, and Importance

What is grip strength measured in?

Grip strength is primarily measured in units of force, most commonly kilograms (kg) or pounds (lbs), using a specialized device called a hand dynamometer.

Understanding Grip Strength

Grip strength refers to the force generated by the muscles of the hand and forearm. It's a critical component of overall physical strength and functional capacity, essential for countless daily activities, athletic performance, and even as a robust biomarker for health. While often thought of as a single entity, grip strength can be categorized into three main types:

• Crush Grip: The ability to squeeze an object, like shaking hands or gripping a barbell. This is the most common type measured in clinical and fitness settings.
• Pinch Grip: The ability to hold an object between the thumb and fingers, such as picking up a coin.
• Support Grip: The ability to hang onto an object for an extended period, like during a farmer's carry or pull-up.

When discussing general grip strength measurement, the focus is almost exclusively on the crush grip.

Primary Units of Measurement

The measurement of grip strength quantifies the maximum isometric force an individual can exert. This force is recorded in specific units:

• Kilograms (kg): This is the most widely adopted unit in clinical research, sports science, and healthcare settings globally. It aligns with the International System of Units (SI) for mass, which, when combined with gravity, represents force.
• Pounds (lbs): Commonly used in the United States and some other regions, pounds represent a unit of force (pound-force).
• Newtons (N): As the SI unit of force, Newtons are fundamental in physics and biomechanics. While less common in standard clinical or gym settings, some advanced dynamometers may offer readings in Newtons, or data may be converted to Newtons for scientific analysis. (1 kg-force ≈ 9.81 N; 1 lb-force ≈ 4.45 N).

The choice of unit often depends on geographical location, the specific dynamometer used, and the context of the assessment (e.g., clinical, research, or athletic performance).

Common Measurement Tools

The primary instrument for measuring grip strength is the hand dynamometer. Several types exist, but the most recognized and validated for assessing crush grip strength is the hydraulic hand dynamometer.

• Hydraulic Hand Dynamometer (e.g., Jamar Dynamometer): Considered the gold standard, this device features an adjustable handle to accommodate different hand sizes and a hydraulic system that measures the force applied when squeezed. The force reading is displayed on a gauge, typically in kilograms and/or pounds.
• Electronic Hand Dynamometer: These devices use strain gauges to measure force and display readings digitally. They often offer more features, such as peak hold, average calculations, and connectivity to computers for data logging.
• Pinch Dynamometers: Specifically designed to measure pinch strength, these are distinct from hand dynamometers used for crush grip.
• Sphygmomanometer (Modified): Less precise and primarily used in resource-limited settings or for very basic assessments, a blood pressure cuff can be rolled up and squeezed, with the pressure reading providing a rudimentary measure of force. However, it lacks standardization and accuracy compared to dedicated dynamometers.

Standardized Testing Protocols

For grip strength measurements to be reliable and comparable, standardized protocols are crucial. These typically include:

• Body Position: The individual usually sits in a chair with their feet flat on the floor, or stands upright.
• Arm Position: The elbow is typically flexed at a 90-degree angle, with the forearm in a neutral position (neither pronated nor supinated) and the wrist in slight extension (0-30 degrees). The arm should be unsupported and not touching the body.
• Handle Position: The dynamometer's handle is adjusted to fit the individual's hand size, ensuring optimal mechanical advantage (usually the second or third position on a Jamar dynamometer).
• Effort: The individual is instructed to squeeze the dynamometer as hard as possible for 3-5 seconds.
• Number of Trials: Typically, three trials are performed for each hand, with a brief rest period (e.g., 30-60 seconds) between trials. The highest reading from the three trials is usually recorded as the individual's grip strength for that hand.
• Alternating Hands: It's common practice to alternate between the dominant and non-dominant hand to prevent fatigue from affecting subsequent measurements.

Why Measure Grip Strength?

Beyond its direct relevance to hand and forearm function, grip strength serves as a powerful indicator for several broader aspects of health and fitness:

• Overall Strength Indicator: Grip strength correlates strongly with total body strength and muscle mass.
• Health Biomarker: It is recognized as a robust predictor of various health outcomes, including:
  • All-cause mortality: Lower grip strength is associated with an increased risk of death from any cause.
  • Cardiovascular disease: It's an independent predictor of heart attack and stroke.
  • Functional decline: In older adults, declining grip strength is linked to increased risk of falls, frailty, and loss of independence.
  • Cognitive function: Emerging research suggests a link between grip strength and cognitive health.
• Rehabilitation Progress: It's a key metric for assessing recovery following injuries to the hand, wrist, or arm, and for tracking the effectiveness of rehabilitation programs.
• Athletic Performance: Essential for sports requiring strong grasping, pulling, or holding, such as weightlifting, climbing, martial arts, and various ball sports.
• Nutritional Status: Can reflect overall nutritional status, as malnutrition can lead to muscle wasting and reduced strength.

Factors Influencing Grip Strength

Numerous factors can influence an individual's grip strength, including:

• Age: Grip strength typically peaks in young adulthood (20s-30s) and gradually declines with age.
• Sex: Men generally have higher absolute grip strength than women.
• Hand Dominance: The dominant hand usually exhibits slightly higher strength.
• Body Size and Composition: Taller individuals and those with greater muscle mass tend to have stronger grips.
• Physical Activity Level: Regular strength training and physical activity can significantly improve and maintain grip strength.
• Health Conditions: Neurological disorders, arthritis, carpal tunnel syndrome, and other medical conditions can impair grip strength.

Improving Grip Strength

Improving grip strength often involves a combination of general strength training and targeted exercises:

• Compound Lifts: Exercises like deadlifts, rows, and pull-ups inherently challenge grip strength.
• Farmer's Carries: Walking while holding heavy dumbbells or kettlebells is excellent for support grip.
• Plate Pinches: Holding weight plates together with just your fingers and thumb targets pinch strength.
• Thick Bar Training: Using fatter barbells or dumbbells (or adding thick grips) increases the demand on your hands and forearms.
• Grip Strengtheners: Hand grippers provide a convenient way to directly train crush grip.
• Forearm Exercises: Wrist curls and extensions can strengthen the muscles that contribute to grip.

Conclusion

Grip strength is a fundamental measure of force, most accurately quantified in kilograms or pounds using a hand dynamometer under standardized testing conditions. Its importance extends far beyond the hands themselves, serving as a vital indicator of overall strength, functional capacity, and a significant biomarker for general health and longevity. Regular assessment and targeted training can contribute significantly to maintaining and improving this crucial aspect of physical fitness.