Chapter 4 Summary
- Skeletal muscle structure, function and
metabolism is a key area in our understanding of sport and
exercise science, with this dispersed ‘organ’
accounting for around 50% of the body mass of most individuals.
- Muscle and nerve meet at the neuromuscular
junction, a chemical synapse that allows action potentials
to cross the synaptic cleft, the endplate potential depolarises
adjacent areas of muscle membrane, and the action potential
initiates muscle excitation-contraction (EC) coupling.
- Sarcomeres are the basic functional units
of the muscle fibre and contain structural and contractile
proteins which maintain integrity of the functional unit
and allow for the molecular mechanism that is the basis
of the sliding filament model of muscle action.
- ATP production is maintained as a result
of ADP rephosphorylation (using PCr), through glycolysis,
and by oxidative phosphorylation, and the relative contribution
of these routes is dependent on the physiological state
of the body (e.g. rest, light exercise, high-intensity exercise).
- Key pathways of energy metabolism are
glycolysis, the TCA cycle, and the electron transport chain/oxidative
- The body has a number of mechanisms to
control acid-base balance, and these are challenged severely
as a result of high-intensity exercise which results in
a decline in muscle pH.
- There are two principal muscle cell or
fibre types, type I and type II, with different contractile,
histochemical and metabolic properties.
- Muscle fibre type proportions have been
compared with exercise performance capability to indicate
a dominance of type I muscle fibres in endurance trained
humans, and a dominance of type II fibres in sprint trained
- Tension (Force) is generated by
muscle and there are distinct relationships between the
length of muscle and tension, and, between force and velocity.