Half Jacks work out your legs and calves in particular. This workout is great for tennis players since we do a lot of split steps and this session will help you get quick on your feet.
Disclaimer: Do not perform these exercises if you have any injury, get rehabilitation first. If you get short of breath, feel fatigued or tired during any of these workouts, stop and take a break. Consult a doctor/trainer if necessary before starting any workout session. Children should do them under supervision of an adult.
These workouts are taken from the Darebee 30 days of HIIT program.