During exercise energy demand in muscles increase which other system directly provide for this demand

In short, during normal exercise, muscle will utilise your blood glucose and glycogen (liver glycogen, muscle glycogen can't be used directly) storage to make Adenosine Triphosphate (ATP).

However, this storage runs out fast.

After that, you will start to burn your fat storage to power your muscles, by the process, if beta-oxidation reaction of the fatty acid chain of fat can't be carried out fully (you might have heard the term:aerobic exercise, which focuses on your overall health), keton bodies will inevitably accumulate.

Though keton bodies accumulation is harmful in many ways, there are pathways to utilise these metabolites to make the last bit of energy.