Female
cyclists health and nutrition: A guide to the proper
care and feeding of female cyclists.
By Auriel Forrester and Pirkko Korkia from peak
performance
The
sex of skeletons can be determined from the shape of
the forehead and the width of the pelvis and lower
vertebrae. While the first does not affect athletic
performance, the second certainly does. A girl's
gait and ability to run fast alters dramatically
after puberty because of the widening of the pelvis
and the change in orientation of the hip muscles. In
cycling terms, this means women may require
different saddles and a different angle of saddle
tilt. Furthermore, the obvious anatomical
differences in this area need appropriate
consideration in terms of position and clothing.
Women tend to have relatively longer legs compared
to their height than men, with the thigh often
accounting for a greater percentage of leg length.
These factors need to be taken into account when
setting up a female cyclist's position or ordering a
frame. Long thigh bones mean the saddle will need to
be further back and the seat angle shallow. However,
women with short legs (relative to their height)
will need a steeper frame angle and the seat further
forward. Women also tend to have a shorter reach and
weaker upper body than men of similar height. This
means that they need a relatively smaller frame size
to allow for a reasonable stem length to be fitted
(8-10cm minimum). As women are naturally more
flexible, a greater seat-to-bar height difference
can usually be accommodated. Too many women cyclists
are wrongly advised, buy too large a frame and are
forced to compensate by pushing their saddle forward
and using a short stem. Thus the handling of the
bike and the potential power output are impaired.
Foot
size is important
Women also tend to have smaller feet than men. As
the foot forms part of the functional lever system
when cycling, the '109% of inside-leg length' rule
for saddle height cannot be applied (Gregor and Rugg,
1986). Indeed, in one of the rare studies on female
cyclists, the optimum saddle height was found to be
107% of pubic symphysis. This may not seem much, but
computes to around 1.5cm for the 'average ' female.
This study (Nordeen-Synder, 1977) only looked at ten
women and foot size was not recorded. A woman with a
28in inside leg and small feet would need the saddle
considerably lower than a male with a similar leg
length and size 10 feet! Very little work has been
published on the role of foot size in cycling, but
it certainly has an effect on rider position.
Similarly, crank length may need to be adjusted for
smaller women with little feet - they may benefit
from 165mm cranks instead of the standard 170mm.
The key muscles involved in the flexion and
extension of the ankle, and thus in transmitting
force along the foot lever to the pedal interface,
are the calf (gastrocnemius) and shin (tibialis
anterior) muscles. The shorter the distance from the
ankle to the pedal interface (ball of the foot), the
greater the force required in these muscles. Thus
the rider with larger feet has a mechanical
advantage over the small-footed rider.
Because of this mechanical disadvantage, the fore
and aft positioning of the saddle for female
cyclists is even more critical. The saddle should be
positioned so that maximum efficiency is attained in
the transfer of muscle power from the knee extensor
muscles (the quadricep group) to the pedal.
Positioning the saddle so that a point just behind
the patella (kneecap) is vertically above the pedal
spindle has been shown to be the most effective.
Similarly, a smooth pedalling action with minimum
resistance applied to the up-pedal stroke is
required.
Small riders score in the hills
Women tend to be physically smaller than men. Larger
cyclists have a lower oxygen requirement relative to
body height than smaller cyclists at a given speed,
meaning that women are disadvantaged even in flat
time trials (Swain et al, 1988). In the hills,
percentage body fat and absolute body weight are
more important, so most women are handicapped once
again. Like their male counterparts, small, lightly
built women are more suited to hilly courses than
taller, heavier riders who tend to excel at events
on level ground.
The key physiological differences between men and
women relate to the fact that the male hormone
testosterone is a much more potent anabolic agent
than female oestrogen. Thus men tend to have larger,
stronger muscles and less subcutaneous fat than
women. On average, women are 7-10% fatter than men.
Top female runners tend to have 12-20% body fat
compared to 5-10% for their male counterparts, while
the figure for elite female cyclists is 18-25% and
10-15% for elite males. This additional body fat is
simply a consequence of being female, a fact which
needs to be accepted by female athletes in general.
In cycling body weight is supported, so fat doesn't
represent such a drawback as it does in running, but
it does account for the greater differences between
men and women in hilly events as compared to flatter
ones.
Is the fat any use?
The extra body fat does not seem to offer any
benefits to women in endurance events even though up
to 50% of the energy requirements may be met through
fat metabolism. The reason for this is that a
woman's additional body fat is stored in localized
deposits or subcutaneously rather than intra-muscle.
The difference between male and female world records
in endurance running events is greater than in the
speed events, although there have been instances
where females have outperformed males. For example,
in cross-channel swimming several of the records are
held by women, while the late, great Beryl Burton
OBE held the 12hr cycling record outright. In both
these events, weight bearing is less than in
running, and, in swimming, the higher body fat of
women improves insulation and buoyancy and reduces
drag. However, in general, there is no scientific
evidence to suggest that body fat offers women any
advantages in endurance events such as cycle racing.
Fatty tissue provides a site for steroid hormone
inter-conversion, thus maintaining sufficient
circulating levels of oestrogen. Early research
suggested that low levels of body fat (below 17-18%)
were responsible for disruption of menstruation.
Presently, there are no well-defined limits for body
fat, and inter-personal differences are great. It is
likely that there are many factors that may
influence disruption of menses, including weight
loss, low weight, nutritional inadequacy, physical
or emotional stress, and levels of certain hormones
such as endogenous opiates and cortisol.
Menstrual dysfunction does not only involve total
absence or irregular menstruation but also luteal-phase
deficiency and anovulation, both of which influence
fertility. Lack of oestrogen and menstrual
dysfunction may lead to a number of other problems,
including:
1. loss of bone density, possibly provoking stress
fractures in the short term and increasing the risk
of osteoporosis in later life
2. possible increased risk of breast and endometrial
cancer.
Furthermore,
being underweight and restriction of calories can
lead to:
3. reduced immunity from bacterial and viral
infections
4. increased recovery time after training
5. reduced effectiveness of training.
To summarize, while women cyclists should endeavour
to keep their body fat down to a reasonable level,
they must ensure that their diet contains enough
calories and carbohydrate to support the rigours of
training and competition (Shangold and Mirkin,
1993).
Menstruation and performance
Girls tend to reach puberty earlier than boys. This
means that the advantages of early maturity seen in
junior boy athletes are less prevalent in girls'
events. It also means that while 13-year-old girls
will often be able to beat boys of the same age in
races, by 14 or 15 when the boys have started to go
through puberty, the advantage has been lost.
Excessive exercise tends to delay puberty by about
five months for every year of training, with the
associated medical, physical and psychological
problems. At the other end of the scale, there is no
evidence that exercise has any effect on the date of
the menopause. However, exercise will protect
against some of the side effects of the menopause
such as fatigue and bone loss, although overtraining
may exacerbate them.
There is no evidence that exercise of any type
during menstruation is harmful or that menstruation
causes a drop in performance. Indeed, some women
feel that they perform better at this time. Heavy
bleeding may lead to anaemia, which will cause
lethargy and tiredness, and the hormonal changes
prior to menstruation may lead to bloating and
fatigue. The symptoms of PMS have been largely
attributed to a drop in the brain levels of
serotonin or 5HT (Shangold and Mirkin, 1993).
Exercise itself increases brain levels of 5HT, as
does carbohydrate ingestion. A craving for chocolate
is related to this but, sadly, its high-fat content
has the wrong effect, so reach instead for fruit or
a jam sandwich!
The contraceptive pill offers women some protection
against hormonal fluctuations caused by increased
levels of training. It also alleviates PMS symptoms
and can, in special circumstances, be used to
manipulate periods - but this should only be carried
out with the consent of a doctor. The reduced blood
loss during periods will also benefit athletes who
often suffer from anaemia. Although a few women may
experience mild side effects (most of which can be
alleviated by changing formulations), both the
contraceptive pill and hormone replacement therapy
offer female athletes numerous benefits. There is no
evidence to suggest that these hormonal therapies
have a deleterious effect on athletic performance.
What about diet?
Despite the observed fact that women tend to
perspire less than men, there is no evidence that
they need less fluid or that they can tolerate heat
better. Women also need as much protein and fat as
men relative to their body weight. The dietary
requirements for men and women are broadly similar
with a few exceptions:
1. fewer total calories
2. extra iron and calcium to prevent anaemia and
maintain or promote bone density
3. athletes on the contraceptive pill should take a
multivitamin/mineral supplement as these drugs may
affect absorption and metabolism of certain
vitamins.
The absolute amount of carbohydrate needed will
depend on the individual and the duration and
intensity of training/competition. Total
carbohydrate requirements of 2000 calories per day
are not uncommon, even for women endurance cyclists.
However, experience has shown that most female
cyclists (in common with many other female athletes)
are over-preoccupied with their weight and
underestimate their nutritional needs. Like most
endurance athletes, women cyclists are often guilty
of eating far too little carbohydrate and would
benefit from additional intake without the risk of
gaining weight. This is caused by an increase in the
training potential of the body and a resultant
increase in metabolic rate (Anderson, 1997).
Training and recovery
The differences between the performances of men and
women athletes are greatest in the lower ranks. This
can be explained by the differences in lean body
mass and muscle fibre size. Interestingly, the
differences between the VO2max of elite men and
women athletes can almost all be accounted for by
the differences in lean body mass, red blood cell
number and physique. Absolute maximal oxygen
consumption (L.min-1) is typically 40% or more
greater in men than in women of similar athletic
standing. When body weight is taken into
consideration (ml.min.kg-1) this difference is
reduced to 20%. It decreases to less than 10% if
expressed relative to LEAN body weight. Thus body
fat accounts for almost all of the differences in
VO2max between elite men and women. The remaining
differences are accounted for by physical (eg, gait)
and haematological factors (Shangold and Mirkin,
1993).
Women use the same number of calories per hour of
exercise as men (relative to lean body weight) and
have similar ratios of Type I and Type II muscle
fibres. The production and clearance of lactic acid
is also the same. Women, however, tend to have
smaller hearts than men and higher heart rates at
the same level of exertion, even when expressed as a
percentage of maximum attainable. This needs to be
taken into consideration when prescribing training
levels purely on heart rate (vis-a-vis BCF
guidelines, which were based on a male). Using
perceived rate of intensity as an additional tool is
advisable. A number of texts recommend the equation
226 minus age for predicting maximal heart rates in
women, although, as with 220 minus age, this rule
only applies in about 55% of cases. The variation in
maximum heart rate and the relationship between
VO2max and heart rate varies considerably between
individuals even of the same sex. For this reason
athletes must learn to listen to their own bodies
and train accordingly.
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