Re: What causes muscle tissue to bulk up after weight training.

Hello Judy,

In the short term during and shortly after training the muscles will 
temporarily increase in size due to increased blood flow through the 
muscles to provide them with the necessary oxygen and glucose to keep 
working.  Increasing the blood flow through the muscles is one of the first 
adaptations that takes place during training and should be the first 
noticeable effect within a few weeks that the muscles apparently increase 
in size during training due to this increase blood flow.

In the longer term muscles that are trained regularly will increase in size 
due to an increase in the size of the muscle fibres.  Muscle fibres will 
increase their quantity of contractile proteins including actin and myosin, 
which will enlarge the muscle mass.  The number of muscle fibres does not 
change since they are not able to divide and replicate.  Therefore all the 
increases in muscle mass are due to enlargement of the muscle fibres.

Following training the muscles need time to recover.  Training should not 
cause any damage to the muscles or tendons.  But the muscles need to 
replenish their stores of energy producing enzymes in the muscle cells and 
their stores of carbohydrates and glycogen.  This recovery time also gives 
the muscles time to increase in size.

An interesting web site that is packed full of information on training tips 
and advice can be found here.


Thank you for your interest

David Burton