The formula makes it is clear that efficiency can be increased by
increasing the physical effort and, at the same time, using the same amount of
energy, or by using less energy during a given physical effort. The advantage
of this formula is that it takes into account the minimum amount of energy
required to move the legs (i.e., the energy required to cycle without any
resistance). In this way, the efficiency of the muscles is accurately
determined because the energy needed to keep the body in motion is deducted
from the total use of energy. How is this formula applied? The use of energy
can be measured in a laboratory through the intake of oxygen. The intake of one
liter of oxygen (not air) equals the use of 5 kcal. In other words, a given
person first starts to cycle without any resistance and afterwards with a
certain resistance. In both cases, the intake of oxygen is measured, after
which the results are put into the formula. Physical effort is expressed in
Joule. In order to convert Joule to kcal, the figure expressed in Joules has to
be divided by 4.19.
Another method to determine the efficiency is the cost function. This is a
mathematical expression which provides a description of a certain physical
effort by giving it a numerical value. Or to put it more simply, the cost
function describes the relative efficiency of a movement with only one number.
The determination of this cost function is based on the moments in the joints
during the cycling movement. It is an established fact that these moments
correlate directly with the tension in the muscles. Subsequently, the tension
in the muscles is a criterion for the efficiency of a contraction. If the sum
of the moments in the ankle, knee and hip is minimal, then the position in
which this is the case is the most efficient one.
The formula mentioned above, however, does not take into consideration one
important element which is inherent in sport, in general: the aspect of
competition. This implies that the distances are covered at a relatively high
speed or, alternatively, within a certain time frame. When we introduce the
time element into the formula, we no longer speak of physical effort, but of
power. The best cyclist will be the one who burns the most calories within a
given time frame, thereby taking for granted that all cyclists expand the same
amount of energy at a certain speed. In reality, this is not the case because
not all cyclists adopt an equally efficient position on the bicycle. So there
are a number of cyclists who use up more energy than others in order to arrive
at a certain speed.
What are the factors on which efficiency depends when looking at it from a
biomechanical perspective? Gonzales and Hull (1989) conducted a survey into
this matter, and they came to the conclusion that there are five factors that
determine the efficiency in cycling. In their research they also come to the
conclusion that these factors are interrelated. A logical result of this
conclusion is that these factors should be adjusted accordingly, in order to
arrive at an optimal combination. Hence the use of the term multi-variable
measuring method.