The Science of Canoeing By Richard Cox

The number of fibres present in a particular muscle is pre- determined and cannot be increased by drugs or
through training. It is largely an inherited factor and will vary from one individual to another. The size of the
individual fibres is generally a reflection of the amount of actomyosin present in the cells. This is the protein
element in the muscles that brings about contraction when activated (see p. 26).
By stressing the muscle fibres against a significant resistance they will gradually increase the volume of
actomyosin present in the cell and as a consequence also increase in size. During the recovery period between
training sessions the body then rebuilds the muscle tissue but to a new strength; to a level that will tolerate the
stresses imposed on it during exercise. (1)
Finally, not all individuals are capable of activating as many fibres to contract at the same time in a co-ordinated
fashion. This depends upon qualities of the nervous system (see p. 110).
There are two basic types of muscle fibre: red (slow twitch) and white (fast twitch) (2). Every individual is born
with a certain mix or proportionality of these fibres which cannot be changed by training or any other means.
The white fibres are well adapted for fast movements but tire quickly. Red fibres, because of their chemical
nature are slow to respond but are well adapted for endurance work. A summary of the characteristics of these
two types is given in table. Unfortunately, some of these characteristics will be not be very meaningful to the
reader until the Chapter has been read as a whole.
Table 5.1: Functional Characteristics of Slow-Twitch and Fast-Twitch Muscle Fibres
Functional Characteristics Slow Twitch Fast Twitch
(ST) (FT)
Myoglobin Content High Low
Triglyceride stores High Low
Glycogen stores High High
Mitochondrial density High Low
Oxidative (aerobic) enzyme activity High Low
Capillary density High Low
PC Stores Low High
Relaxation time ' Slow Fast
Twitch (contraction) time Slow Fast
Glycoly tic enzyme activity 'LOW High
Fatigability
(From E.L.Fox and Matthews, 1974)
LOW High
(1) Obviously there are limits in the extent to which improvements can be made. Although it is unlikely that
human beings
will ever be capable of lifting their own weight considerable gains in maximum strength can be made. The rate
of improvement will depend upon the training program, the individual’s personality and their physical makeup.
Whilst hereditary factors play a role in determining these qualities, overall improvement in firing co-ordination
cm result from frequent practice of the movement against a significant resistance.
In Canoe Racing maximum strength is not as important as strength endurance, (that is the ability to sustain
repeated muscular contractions against a sub-maximal resistance over a period of time) or power (that is the
ability to execute sub-maximal contractions at speed). The speed and endurance of a muscle is determined by
the types of muscle fibre from which it is composed and the fuel supply to, removal of waste products from, these
fibres.
(2) At least 8 types of different muscle fibres have been identified by researchers, but for the purposes of this text
it is really only necessary to know the existence of the two main types.
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