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Class 12
Physical Education
Notes
Ch-7(Physiology and Sports Injuries)

Physiological factors for determining strength.
The following are the factors for determining strength:
Muscle composition: There are two types of fibres in muscles i.e. fast twitch fibres
and slow twitch fibres. The muscles which consist of more percentage of fast twitch
fibres will produce more strength.
Size of the muscle: The strength of an individual depends on the size of muscle. As
larger and bigger muscle produce more force and with the help of different methods
of strength training , the size of the muscle can be increased.
Body weight: there is a positive relation between body weight and strength. The
individuals who are heavier are stronger than the individuals who are lighter in
weight.
Intensity of nerve impulse: A muscle is composed of no. of motor units. The total
force of muscle depends upon the number of contracting motor units. Whenever, a
stronger nerve impulse from central nervous system excite more number of motor
units , the muscle will contract more stongly or it can be said that the muscle will
produce more force or strength.
Physiological factors for determining speed.
The following are the factors for determining speed:
Muscle composition: The muscles which consist of more percentage of fast twitch
fibrescontract with morespeed and produce a greater speed. Different muscles of the
body have different percentage of fast twitch fibres.
Explosive strength: it depends on the shape, size and coordination of muscles. For
very quick and explosive movement, explosive strength is required. The related
proportion of fast twitch fibres and slow twitch fibres determines the maximum
possible speed with which the muscle can contract.
Flexibility: It also determines the speed. Good flexibility allows maximum range of
movements and also enables complete utilization of explosive strength.
Biochemical reserves and metabolic power: muscles requires more amount of
energy and high rate of consumption for maximum speed performance. For this
purpose the stores of ATP & CP in the muscles should be enough. If the store is
less, the working process of the muscles slows down after short time.
Physiological factors for determining flexibility.
The physiological factors for determining flexibility are:
Muscle strength: Flexibility depends on the level of strength. Weak muscles can
become a limiting factor for achieving higher range of movement. Muscle strength is
highly trainable therefore, it can enhance flexibility.
Joint structure: There are several different types of joints in human body. Some of
the joints intrinsically have a greater range of motion.eg. the ball and socket joint of
the shoulder has the greatest range of motion.
Age and gender: flexibility decreases with the advancement of age. It can be
enhanced with the help of training. Gender also determines the flexibility as females
tends to be more flexible than males.
Internal environment:The internal environment of an athlete influences the
flexibility. If internal temperature increases flexibility increases; if decreases