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.
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.
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%).