Grip strength is important for daily activities -- from basic tasks to high-level sports performance. Athletes depend on a strong grip for optimal performance, and grip weakness puts other muscles at risk for injury. For example, grip weakness in tennis players causes forearm and elbow muscles to work harder, increasing the risk of injury. Grip strength is determined by an isometric muscle contraction using a specialized device.
Grip strength is tested using a dynamometer -- a calibrated device with a handle that measures the amount of force applied to it. The handle of the dynamometer does not move -- the device measures an isometric contraction as you grip against the resistance of the stationary handle. Grip strength is determined by the position of a needle inside a hydraulic gauge. Digital dynamometers automatically display results on a screen during the testing process.
Proper positioning is important to ensure valid test results. Grip testing is performed in a standing position, shoulders relaxed and elbow bent to 90 degrees. Hold the dynamometer vertically with the gauge or screen facing away from you. Keep your arm in this position when you squeeze the handle to eliminate assistance of other muscles.
Grip strength is commonly tested using the average of three separate trials. Standard protocol requires a second person to administer the test and read the results. Stand up in the proper test position, grip the dynamometer and squeeze as hard as you can for two to three seconds. Record the result and reset the needle or digital screen. Repeat two more times. Add the three numbers together and divide by three to calculate the average. Switch hands and repeat the test on the opposite side. Grip strength normative data for males and females in various age ranges have been published. These data can be used as a guideline; however, grip strength requirements vary based on your activities.
Several factors can affect grip strength test results. Perform grip testing before exercise -- muscle fatigue will lower your results. Research has shown that grip strength varies at different times of the day. Keep subsequent testing times consistent to measure true progress. Test both sides to obtain the best results -- grip strength is typically higher on your dominant side.