Raised CPK means the muscle cells are dying in this case due to excessive use. This is a usual scenario with a sudden burst of activities in limited time. Excessive CPK don't have any consequences but dying muscle has. They may release Myoglobin
can damage kidneys, can cause compartment syndrome(increased pressure in a group of muscle), Increased potassium in the blood can cause serious side effects.
Hope you find my answers upto date. Any more questions are welcome.