Lie supine, legs tabletop or extended, arms reaching long by sides.
Lift head and shoulders, engage core, gaze toward thighs.
Pump arms vigorously, inhaling five counts, exhaling five counts.
Maintain stable torso and strong abdominals for one hundred counts.
百式(双腿伸直)エクササイズガイド - 腹肌ワークアウト | MuscleWiki