short term effect on the skeletal system

When your exercising your bones are under significant amount of pressure.

Your bones need calcium to survive that pressure. Calcium makes your bone stronger and bigger, so there will be less stress on your bone when your doing weight-bearing exercises. 

Our bodies produce cells called Osteoblasts, which build new bones and make bones stronger and denser and that lowers the risk of Osteoporosis.

If your bone is weak, then your bones will break with the slightest stress on them, so your bones need calcium.

There will be an increase of bone density (bone strength) due to increase in calcium production, Also stronger connectives tissues (Ligaments and Tendons), so more resistant to injury.

 Skeletal muscles adapt to using more oxygen, the muscles and their capillaries become more efficient and can therefore work for a longer period of time.

If you do a lot of high impact activities, it will encourage new bone formation. weight-bearing exercise such as like strength training and running puts stress through your bones. Your bones response to this stress by creating new bones that are stronger so next time when you do the same exercise your bones will cope with the exercise.