Physical strength is the measure of an

individual An individual is one that exists as a distinct entity. Individuality (or self-hood) is the state or quality of living as an individual; particularly (in the case of humans) as a person unique from other people and possessing one's own needs or g ...

's exertion of

force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...

physical object In natural language and physical science, a physical object or material object (or simply an object or body) is a contiguous collection of matter, within a defined boundary (or surface), that exists in space and time. Usually contrasted with ...

s. Increasing physical strength is the goal of

strength training Strength training, also known as weight training or resistance training, is exercise designed to improve physical strength. It is often associated with the lifting of Weightlifting, weights. It can also incorporate techniques such as bodyweigh ...

Overview

An individual's physical strength is determined by two factors: the cross-sectional area of muscle fibers recruited to generate force and the intensity of the recruitment. Individuals with a high proportion of type I slow twitch muscle fibers will be relatively weaker than a similar individual with a high proportion of type II fast twitch fibers, but would have greater endurance. The genetic inheritance of muscle fiber type sets the outermost boundaries of physical strength possible (barring the use of enhancing agents such as

testosterone Testosterone is the primary male sex hormone and androgen in Male, males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testicles and prostate, as well as promoting se ...

), although the unique position within this envelope is determined by training. Individual muscle fiber ratios can be determined through a muscle biopsy. Other considerations are the ability to recruit muscle fibers for a particular activity, joint angles, and the length of each limb. For a given cross-section, shorter limbs are able to lift more weight. The ability to gain muscle also varies person to person, based mainly upon genes dictating the amounts of hormones secreted, but also on sex, age, health of the person, and adequate nutrients in the diet. A

one-repetition maximum One-repetition maximum (one-rep max or 1RM) in weight training is the maximum amount of weight that a person can possibly lift for one repetition. It may also be considered as the maximum amount of force that can be generated in one maximal contr ...

test is the most accurate way to determine maximum muscular strength.

Strength capability

There are various ways to measure physical strength of a person or population. Strength capability analysis is usually done in the field of

ergonomics Ergonomics, also known as human factors or human factors engineering (HFE), is the application of Psychology, psychological and Physiology, physiological principles to the engineering and design of products, processes, and systems. Primary goa ...

where a particular task (e.g., lifting a load, pushing a cart, etc.) and/or a posture is evaluated and compared to the capabilities of the section of the population that the task is intended towards. The external reactive moments and forces on the joints are usually used in such cases. The strength capability of the joint is denoted by the amount of moment that the muscle force can create at the joint to counter the external moment. Skeletal muscles produce reactive forces and moments at the joints. To avoid injury or fatigue, when person is performing a task, such as pushing or lifting a load, the external moments created at the joints due to the load at the hand and the weight of the body segments must be ideally less than the muscular moment strengths at the joint. One of the first sagittal-plane models to predict strength was developed by Chaffin in 1969. Based on this model, the external moments at each joint must not exceed the muscle strength moments at that joint. Where, S_j is the muscle strength moment at joint, j, and M_j/L is the external moment at the joint, j, due to load, L and the body segments preceding the joint in the top-down analysis. Top-down analysis is the method of calculating the reactive moments and forces at each joint starting at the hand, all the way till the ankle and foot. In a 6-segment model, the joints considered are elbow, shoulder, L5/S1 disc of the spine, hip, knee and ankle. It is common to ignore the wrist joint in manual calculations. Software intended for such calculation use the wrist joint also, dividing the lower arm into hand and forearm segments.

Prediction of static strength

Static strength prediction is the method of predicting the strength capabilities of a person or a population (based on anthropometry) for a particular task and/or posture (an isometric contraction). To predict capability, manual calculations are usually performed using the top-down analysis on a six or seven-link model, based on available information about the case and then compared to standard guidelines, such as the one provided by the National Institute for Occupational Safety and Health.

References

{{Authority control Athletic training Physical exercise Physical fitness

Overview

Strength capability

Prediction of static strength

See also

References