Rationale. The 'Dead Bug' is a popular 'core' exercise for runners, used to target the trunk muscles (erector spinae, obliques, rectus abdominis, transverse abdominis) which together provide a strong base for our moving limbs so we can maintain good form whilst running.
How to do it: Lie on your back with hands above you and feet up so your knees are at 90 degrees. Straighten your leg until your heel is an inch from the floor and then return to the start position. Repeat with the other leg.