Dynamic stabilizer: Biceps Brachii (short head only)
Important stabilizers of supporting leg and core: Obliques, Quadriceps, Iliopsoas, Sartorius, Tensor Fasciae Latae
Stabilizers of raised leg: Hamstrings, Gluteus Maximus
Get on your hands and knees, with your arms positioned a little wider than shoulder width.
Extend your feet backward and straighten your body.
Raise one foot off the floor.
Keeping your body straight and rigid, inhale as you lower your chest to the floor by flexing your elbows.
Exhale as you extend your elbows and push your body back up to the starting position.
Repeat for more repetitions.
Repeat the repetitions with your opposite foot raised off the floor.
Comments and tips
To preserve shoulder health, keep your elbows slightly tucked into your body.
The point of raising one leg off the floor with the one-leg push-up is to put the body out of balance and force the recruitment of more stabilizer muscles, especially in the core.
Two of the target muscles, the iliopsoas and obliques, are exercised isometrically (they contract and stay contracted without changing shape). The other target muscle, the sternal pectoralis major, is exercised dynamically (it does change shape).