Training4cyclists

Cycling Training Tips

muscle

How a muscle develop force

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This is a short description of how a muscle can develop force:

What is a motor unit

A motor unit is a functional unit that contains a single nerve and all the muscle fibres innervated by the nerve. All muscle fibres are grouped together as motor units and have an average of 150 fibres pr motor neuron.

Hypertrophy

Larger muscle cells (that will say larger square diameter) can generate more power. That is the most commonly known way to increase power, though it is not desirable for cyclists. The problem is that a large muscle mass is heavy to carry and there is a dilution of mitochondrias. Thus, an increment of maximal strength made through hypertrophy will probably not result in a better overall cycling performance.

Nervous regulation of force

Basically there are two ways to control a muscle’s force.

One way is to recruit more motor unit, which will activate more motor units. You can think of this as the brain tells the muscle to use a larger percentile of the muscle’s fibres to generate power. Motor units are recruited to in order of size. Small motor units are recruited before large motor units. This is called the size principle of recruitment.

The second way to regulate force production is through rate coding. It is an increment of the frequency of impulse signals to the motor unit. When a motor unit is stimulated more frequently, the twitches begin to overlap each other, which will generate a larger force.

So now we know the basic physiology behind the mechanisms used to increase the force. It is either to build larger muscle mass, make a better recruitment of motor units or fire a higher frequency of stimuli to the motor neurons.

 

Peripheral Adaptations to Cycling Training

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As a cyclist you are interested in a perfect working aerobic system and the skeletal muscle is certainly a part of this. Fortunately skeletal muscles are very adaptive to training.

A weight lifter will not gain the same changes as a cyclist would. The specific requirements are different and so are the peripheral adaptations in the skeletal muscle.

Increased capillary density

The capillary density increases after periods of cycling training, probably due to a greater demand for oxygen. This oxygen demand stimulates the growth of the capillary bed.

This is a unique adaptation that prepares your body for new challenges.

The diffusing distance between blood and cells is reduced when the capillary density is increased. A shorter diffusing distance makes the exchange of O2, CO2, substrates and metabolites faster.

The increased capillary density also results in a larger surface area available for this exchange, which gives a faster flow rate through the muscle.

During maximal cycling the trained musclue will receive a larger blood volume/min than the untrained muscle will.

More myoglobin

Like hemoglobin, myoglobin is able to bind, store and release oxygen. Myoglobin facilitates oxygen diffusion in muscle fibers that depend on aerobic metabolism.

Cycling training increases the content of myoglobin. More myoglobin means more diffusing forces, which results in a higher oxygen delivery in the skeletal muscle.

More mitochondrias

Increased number and size of the mitochondrias in the skeletal muscle shows us how important these small power fields are for the oxygen transport.

There are also at the same time an increase in a wide range of oxidative enzymes including those in the citric acid cycle.

Better use of free fatty acids as fuel

It is wellknown that the welltrained cyclist is able to cover a larger percentage of the energy demand with free fatty acids and triglycerids as fuel. This gives the welltrained cyclist an advantage because he saves his limited stores of glycogen for later use.

Even for welltrained cyclists with a low fat percent, the amounts of fat available as fuel is more than enough. In fact there is enough fuel for a very long time without hitting a gas station.

The degree of free fatty acids used is changed in the trained part of the body, for cyclists that is primarily the legs. Other parts of the body uses the same amount of free fatty acids as before training.

Larger glycogen stores

With training glycogen stores in the skeletal muscle will increase. It is though important to notice that glycogen stores is very close related to training status and dietary status.

If you train very intense your glycogen stores might be very low afterwards. If you eat a very carbohydrate-rich diet like pasta, rice or bread, your glycogen stores will increase. Carbohydrates are stored in the liver (25%) and the rest is stored in the skeletal muscles (75%).