programme (Faulkner & White 1990). Strength
training with high loads leads to an increase in
the cross-sectional area of the muscle without
any appreciable change in muscle length, and
changes in cross-sectional area of the muscle can
be used as an index of the gain in muscle mass.
Both type I and type II fibres increase in size in
response to this type of training stimulus, and
increases in cross-sectional area of 39% for type I
fibres and 31% for type II fibres have been
reported after a programme of heavy resistance
exercise (MacDougall et al. 1980). Increases in
force-generating capacity after strength training
may be large (30–40%) in the early stages of a
training programme, and are invariably greater
than the increase in cross-sectional area
(Maughan 1984). Some of the increase in muscle
strength is therefore likely to be the result of
changes in the muscle recruitment pattern and in
neural drive. In pennate muscles, where the indi-
vidual fibres lie at an angle to the long axis of the
muscle, increases in the size of the individual
fibres will result in an increase in the angle of
pennation, which will have the effect of decreas-
ing the force relative to the anatomical cross-
sectional area (Maughan 1984).
Release of a variety of hormones is stimulated
during and after high resistance training: these
include growth hormone, testosterone, cate-
cholamines and cortisol (Sutton et al. 1990). The
release of these hormones will be influenced by
the intensity of training, the length of rest periods
allowed, and the level of training of the athlete.
The response to training is specific to the muscle,
so there must be a change in the sensitivity of the
active muscle to the circulating hormones and
growth factors so that changes in the systemic
concentration results in specific changes in
protein synthesis. This may involve a change in
receptor number or sensitivity and/or release of
local growth factors (including insulin-like
growth factor) in the working muscle in response
to hormonal stimulation.
Increases in muscle strength and muscle
hypertrophy have been shown to be greater after
prolonged fatiguing contractions than after
626 sport-specific nutrition
short, intermittent contractions (Schott et al.
1995). The authors speculated that the enhanced
response after fatiguing contractions indicated
an involvement of changes in intracellular
metabolite levels and pH in determining the
response of the muscle.
In addition to the changes in muscle size and
strength, weight training will have a significant
effect on bone mass. Peak bone mass, which is
normally reached in the third decade of life, can
be increased by any form of weight-bearing exer-
cise, and will help to protect the skeleton against
the stresses imposed on it. These processes are
described in detail in Chapter 23.
As the muscle becomes stronger with training
and the load that can be applied increases, so the
stimulus for new bone formation should also
be increased to a degree consistent with the
imposed load or relative intensity of the exercise.
The imposed load is more important for deter-
mining the response of bone than the number of
loading cycles completed. Progressive resistance
training should therefore allow the bone mass to
increase until it reaches the genetically deter-
mined peak bone mass. Given the greater length
of time required for new bone formation relative
to the adaptation of skeletal muscle, which is
apparent within a few days of training begin-
ning, changes in bone mass require long-term
adherence to a training programme that will
effectively load the skeleton.Training diet
The adaptive changes that occur in the various
organs and tissues of the athlete in response to
the training load occur in a phasic manner. The
acute responses to a single bout of exercise are
translated into a permanent (at least as long as
the training persists) condition by a series of
events that may be described as fatigue, restora-
tion and supercompensation. The adaptations
which occur in response to training result in an
increased capacity for force generation, power
output or endurance, depending on the type of
training. This will be manifested during the