VPB 121: Veterinary Physiology - II (2+1)

TYPES OF WHOLE MUSCLE CONTRACTION

• Muscle contraction is principally of two types
• Isometric contraction
  • Muscle contraction without shortening in length that occurs during the manifestation of the process of muscle contraction.
  • In isometric contraction, the muscle contracts between two fixed points. Hence during the process of contraction it does not shorten in its length and develops the force of contraction.
  • Therefore in isometric (same length) contraction, there is no work performance, less force of contraction and low Fenn effect due to liberation less energy.
• Isotonic contraction
  • On stimulation, the muscle contracts between one fixed and one moveable points (eg. Lifting the weight) shows shortening in length, but the tension on the muscle remains constant.
• Contractions of muscle in the body
  • In the body, most of the muscular contractions are a mixture of both isometric and isotonic contractions. During standing posture the quadriceps shows isometric contraction, to tighten the knee joint to keep the legs stiff. Contraction of the biceps is isotonic when the hand lifts the weight.
  • Alternate isometric and isotonic contractions of the quadriceps and gastrocnemius (calf muscle) help to effect running or walking. The quadriceps contracts isometrically when the foot hit the ground, while the calf muscle contracts isotonically when the foot is lifted off the ground.