Karuna Yoga

Properties of skeletal muscle:

  1. Excitability and irritability: It’s the property of a muscle to respond to a stimulus. If the response occurs in the front of a contraction. It’s called as contractility.
  2. Tonicity: Muscles of a living organism are in the partially contracted state, even at rest. They are never fully relaxed and they will resist being stretched the resistance to stretch is called as tonicity.
  3. All or none response: When a stimulus is given to a muscle, the muscle either contracts to the maximum or it doesn’t contract at all. When a weak stimulus is applied to a muscle, it doesn’t produce any response. But when the stimulus is gradually increased, the muscle contracts at a point to the maximum level. Later even a greater degree of stimulus does not increase the degree of contraction.

  1. Summation: When a second stimulus is given to a muscle even while it’s contracting due to the first stimulus, the degree of contraction is more. This phenomenon is called as a summation. The increased response is due to stimulation of more and more motor units by repetitive stimuli.
  2. Treppe or staircase phenomenon: Stimulation of a muscle at regular short intervals increases the amplitudes of contraction *which goes on increasing like the steps of a staircase*. This occurs due to increased irritability of the muscle produced by chemical products of the earlier contractions.
  3. Tetanus: When a muscle is stimulated repeatedly at a very faster rate, the muscle contracts maximally. The muscle remains at this maximal state of contraction till 1- the stimulus continues or 2- it gets fatigued. This sustained maximal contraction is called tetanus.
  4. Refractory period: Muscle, like other excitable tissues, has a period following its action potential during which the membrane will not respond to stimulation regardless of the strength.
  5. Isotonic contraction: It’s the contraction in which the muscle shortens under constant load. It occurs in muscles during walking, running or lifting.

  1. Isometric contraction: In this type of contraction, the muscle develops tension but it does not shorten in length e.g. maintaining the posture against gravity.
  2. Fatigue: It’s a state of reduced excitability and contractility of a muscle. It’s produced by rapid and repeated stimulation of the muscle. Fatigue may occur due to depletion of energy and accumulation of metabolites like lactic acid.


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