Human Movement, Flexibility and Balance

In human movement, flexibility and balance have a close relationship. The balance distributed across the heels, toes, balls and outside edge of both feet is adjusted when a single step is taken. The centre of gravity of the body’s mass is initially moved sideways over one supporting leg, then forward over the ball and toes of the supporting foot. It is then transferred sideways in the opposite direction if the other leg is then used for support in standing, or for another step.

Balance with a Double Support

When trying to find balance using two, or more, points of support, small movements by the muscles controlling the mass directly over each point can correct any tendency to tip over. These movements can compensate for each other, allowing a stable position to be reached. If any part of the body above the centre of gravity is repositioned, such as reaching out to open a door, then further movement to adjust balance will be needed. This is to compensate for the changed position of the centre of gravity.

Balance with a Single Support

When balance is over a single support then any movement or position over that support has to be counterbalanced, to ensure the centre of gravity remains directly above the supporting point. This is when flexibility becomes critical, for if a compensatory movement is not made at the same time as a movement is started, then the body will overbalance and fall.

Counterbalance and The Principle of Moments

When an object is balanced it is in equilibrium. The sum of the clockwise moments is equal to the sum of the anticlockwise moments. The moment is the turning effect of a force and is found by multiplying the force by its distance from the pivot. The effective pivot in a human body is the centre of gravity of the body. This means that a small force further away from the body can balance a larger force closer to the body.

Flexibility and Balance

The more rigid the position taken, the less likely a small correction can restore balance. The positions of the ends of the limbs, the hands and feet, often dictate if balance can be held, or not. This is especially relevant for a gymnast.

If an arm, wrist or fingers are locked in position then they cannot be flexed slightly to change position and correct balance before it has become critical.

If a foot is flopped or has scrunched toes then the early warning system of extended toes touching and giving neural feedback before a changed balance position is adopted is lost.

Citations

Balancing turning forces – the principle of moments.

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