OK my friend I believe the best answer for this would be that During exercise the amount of Oxygen carried in the blood to the muscles increases
Answer:
If the heart rate monitor says you're working at 50 to 60% of your max heart rate, then the exercise is considered moderate. If the heart rate monitor shows that you're working at 70 to 85% of your heart rate then it's vigorous exercise. To find your maximum heart rate, subtract your age from 220.
Explanation:
Skeletal muscles are attached to the skeleton by tough connective tissues called tendons(see Figure above). Many skeletal muscles are attached to the ends of bones that meet at a joint. The muscles span the joint and connect the bones. When the muscles contract, they pull on the bones, causing them to move.
Vitamin D I think not sure check google
