Mechanics of a Push Up

Question:

I am wondering if you could tell me in what planes and axis of motion are push ups? And what are the synergistic muscles and their actions?

Answer:

Anatomically, the fixed prone push up is horizontal ab/adduction and functions around a transverse axis. Your question regarding synergistic muscles is well put. When performing movement tasks such as push ups, the body ALWAYS works in synergistic relationships as opposed to agonist/antagonist relationships (for a very in depth look, please refer to "Muscles Alive" by Basmajian or any of the work by Andrews, Zajac and Gordon). The fixed prone push up involves dynamic actions of mobile stabilization and force generation from some of the following muscles, all in synergy. The following is by no means a complete list, but touches on the major myofascial structures:

• Pec. Minor – To assist in dynamic stabilization of the shoulder girdle (rib cage and scapula), as well as scapular depression (deceleration) and scapular elevation (acceleration).
• Pec. Major (both the sternal and clavicular portions) - To assist in deceleration and acceleration of horizontal ab/adduction primarily at the gleno-humeral joint.
• Cervical Extensors – To collectively assist in maintaining a straight head position.
• Deltoids (the anterior portion will have a mechanical advantage in the push up) - To assist in dynamic stability and deceleration/acceleration of shoulder complex movement.
• Triceps group – To assist in movements at the elbow complex and shoulder complex (via the action of the long head); decelerates elbow flexion and shoulder horizontal abduction, accelerates elbow extension and shoulder horizontal adduction.
• Coracobrachalis – To assist in decelerating horizontal abducting and accelerating horizontal adduction.
• Biceps group – Similar to the hamstrings during a squat (Lombard’s paradox), the biceps assist synergistically to help accelerate the elbow complex into extension, and the long head of the biceps assists the gleno-humeral joint to accelerate into horizontal adduction (because of the position of the upper arm).
• Serratus Anterior – To assist in dynamically stabilizing the scapulo-thoracic joint and assists in accelerating the approximation of the scapula to the rib cage (working with the rhomboids and trapezius).
• Rhomboids and Trapezius – To dynamically stabilize the scapula (via the scapulo-thoracic joint) in motion.
• Trunk muscles (this includes all of the abdominal muscles and spinal erectors as well as the hip flexors) – To dynamically stabilize the lumbo pelvic hip complex.

To successfully perform a fixed prone push up, all of these muscles (and more) must operate synergistically and be timed properly by the nervous system. To successfully challenge the neuro-muscular system, progressions into moving push ups (i.e., ones that involve a push up and a crawl pattern – see the PTontheNET.com Exercise Library) may be given to more advanced clients/athletes. This MUST be a progression. Proper dynamic stabilization and strength must clearly be observed before progression occurs. This progression challenges both the nervous system and myofascial structures in all three planes, ultimately creating higher levels of skilled movement.

References:

1. Basmajian, J. "Muscles Alive." 1978
2. Andrews, JG. "A general method for determining the functional role of a muscle." 1985, J Biomech Eng 107: 348-353
3. Zajac, F. and Gordon, M. "Determining Muscle’s Force and Action in Multi-Articular Movement." 1989, Exerc Sport Sci Revs 17: 187-230