Planks work out your core, shoulders and overall endurance.
Try this workout. Beginners can do 1 set, intermediate 2 and advanced can do 3.
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.