At the Movement Assessment Technologies, we are big believers that when it comes to upright function against gravity and ground reaction force there is no such thing at Antagonist and Agonist muscles. Just Synergists, that is the whole body working together to achieve the movement goal.
The following study by Rand and Ohtsuki (2000; Gait and Posture) looking at lateral movement in the all important Frontal Plane of motion using a visual stimulus condition-open maneuver (STO), visual stimulus condition-cross maneuver (STC), self-initiated condition-open maneuver (SFO), and self-initiated condition-cross maneuver (SFC). The subjects also performed a condition of straight running (CON) and a condition of running modification to stop (STF) as control conditions.
EMG signals were recorded from them. vastus medialis (VM), m. gastrocnemius (lateralis) (G), m. gluteus medius (anterior portion) (GM) and m. sartorius (SAR).
As demonstrated by the following picture the greatest spikes in all muscle activity occurred during foot strike as the body opposes gravity and ground reaction force to stop it collapsing. This creates an eccentric load to facilitate an efficient concentric contraction. We believe that this eccentric action is the true role of a muscles function. It is during this important phase that an inability to load efficiently either due to a structural or movement skill problem could lead to injury or performance loss.
Next time you are treating or training a patient or client consider the role of all muscles in the kinetic chain and what their eccentric function may be.
If you would like to learn more about the Movement Assessment Technologies approach to treatment and training eccentric load in the Frontal Plane of motion check out: https://www.matassessment.com
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