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Biomechanics: Muscle contractions

Notes

Notes

Introduction to OMM

Biomechanics: Muscle contractions

A contraction is defined simply as the generation of tension within a muscle fiber. Muscle fibers generate tension through actin and myosin cross-bridge cycling. Under tension, a muscle belly can either lengthen, shorten, or remain the same length. The names of contractions are based upon how the muscle belly length changes during this tension.

Isokinetic contractions are those in which there is a consistent rate of speed.

Isotonic contractions are those in which there is consistent tension as the muscle length changes. These can be either concentric (muscle shortening) or eccentric (muscle elongation).

Isometric contractions are those in which the length of the muscle does not change.
TYPES OF MUSCLE CONTRACTIONS
TYPE OF CONTRACTION
DEFINITION / CHARACTERISTICS
EXAMPLE
Isokinetic
When the velocity of the muscle contraction remains constant while muscle length changes

Riding a stationary bike
Concentric (isotonic)

When a muscle is activated and required to lift a load which is less than the maximum tension it can generate, resulting in muscle shortening
Raising a dumbbell with a bicep curl
Eccentric (isotonic)

When the external force on a muscle is greater than the maximal force it can generate, resulting in muscle lengthening
Walking down stairs
Isometric
When a muscle is activated at a constant length
Holding a shopping bag

Figure 1. Riding a stationary bike, raising a dumbbell with a bicep curl, and holding a weight at a constant height are examples of isokinetic, isotonic, and isometric contractions, respectively.