Hand-Grip dynamometer are used to measure the strength and endurance of the muscles in your forearm, and to a lesser extent your hand. Using a handgrip dynamometer will increase your performance at work, improve posture, decrease chances for injury, and prevent low back pain. Endurance is the ability of a muscle to work for long periods of time without extreme fatigue. It prevents unwanted fatigue from daily activities, sport and recreation. For the elderly person, good hand grip strength may prevent a fall down stairs or in bathtubs and may help people from dropping jars. It could help the elderly with opening jars as well.
Three areas of rationale are used to measure strength-anatomical, physiological, and biochemical. These are all interrelated. The first area Anatomical Rationale-Hand grip strength is mainly a function of the muscles in the forearm, and hand. Eight muscles serve as the prime movers and stabilizers in hand grip strength. Eleven other muscles assist in contraction of the hand.
The second is physiological Rationale which has six categories. Six of the most common measurement terms in physiology are mass, force, work, velocity, power and energy.
The third area is biochemical rationale exercise may be divided into three categories based upon the predominant metabolic pathway. The primary biochemical reaction for strength, or any muscle contraction is ATP ( Adenosine Triphosophate).
The muscular strength is highly affected by the nervous system. Emotional and mental factors play important part in strength testing. If a subject is consistent with motivation strength variability should be minimized. In women a daily variation in strength range is between 2 and 12% and 5 to 9% in men.
Instruments used to measure muscle strength are cable tensiometer, dymameter, free weights, barbells, isokinetics devices and load cells or elechromechanical devices. Strength is usually measured in units of force or torque. Kilogram (kg), and pounds (lb), is the force unit. The torque unit may be expressed as a foot-pounds (fl-lb) or Newton meters (nm).
The procedures for handgrip strength testing are:
1.The subject should be in the standing position.
2.The subjects head should be in the midposition (facing straight ahead).
3.The grip size should be adjusted so that the middle fingers midportion is approximatrely at a right angle.
4.The subjects forearm may be placed at any angle between 90 degrees and 180 degrees of the upper arm; the upper arm is in a vertical position.
5.The subjects wrist and forearm should be at the midprone position.
6.The subject should exert maximally and quickly.
7.The subject should perform two or three trials alternately with each hand, with at least 30s between trials for the same hand.
The norms in Table 4.1 and 4.2 are based on a study made by 6,000 persons. In Table 4.2 it provides the strength / body weight ratios, the sum of the right and left grip strength scores is divided by the individuals body weight (kg/ kg body weight). The Canadian norms in Table 4.3 are based on data from 1981 Canada Fitness Survey.
In order to evaluate a good criteria to use: 0.90 To 0.99 high reliability, 0.80 to 0.89 good reliability, 0.70 to 0.79 fair reliability, and 0.69 and below poor reliability.
For comparable results, it is important that all persons use the dynamometer in the same way. While standing, hold the dynamometer at right angles to the floor, with the elbow held against the body and bent at 90 degrees. When squeezing the dynamometer do not turn or bend the head, or otherwise move the rest of the body. Squeeze quickly, giving maximum effort. In Part 1, rest at least one minute between same-hand trials take turns with partner. Strength is defined as the force that can be achieved with maximum effort with the stronger arm for one repetition. It is generally abbreviated as 1 RM (one repetition maximum). An older term sometimes used is maximum voluntary contraction (MVC).