Because most of the time they are not properly warming up the muscles necessary for the physical activity your partaking in.
I would say bicycling because jogging and jumping jacks can be bad on your knees because of the impact. Biking is pretty smooth though and wouldn't have much of an impact. Hope this helps :)
Low my opion thanks ( I could be wrong )
Beans,watermelon and strawberries
I hope this helps, have a great day!
