The Effect of Ground Reaction Forces on Gait

The estimation and evaluation of ground reaction forces can have significant implications in the biomechanical analysis procedure, especially while determining a pathological gait.

Dr Soutas-Little, Professor of Theoretical Mechanics and Director of the Biomechanics Evaluation Laboratory and Biodynamics Laboratory at Michigan State University, divides ground reaction forces into three components: vertical, anterior/posterior and medial/lateral.

Among these, the vertical component is the largest and is responsible for the acceleration of the body’s centre of mass in the vertical direction while walking.

A dynamic gait entails a greater vertical excursion of the centre of the mass followed by a greater deviation of the vertical ground reaction forces from body weight. 

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According to a study conducted by Winiarski and Kucharska from the University School of Physical Education in Poland, measuring the body centre of gravity as the centre of a multisegment human body is a more appropriate estimation of ground reaction force characteristics.

Kinematic studies have emphasised the motion of the centre of gravity, which undergoes periodic vertical displacement during walking; this is at its highest in the middle of the stance and swing phases, and lowest during double support.

With a forward motion of the body, the longitudinal speed of this centre of gravity fluctuates, being at its peak during the double stance phases and lowest in the middle of the stance and swing phases.

By collecting gait data for healthy individuals and patients after Anterior Cruciate Ligament (ACL) reconstruction, the authors compared the method of retrieving ground reaction force from kinematics of the centre of gravity to the Newtonian computation of double-differentiating the centre of gravity trajectory.

The authors concluded, “using kinematics to calculate the centre of gravity allows accurate calculation of its position, not just displacement, in both globally and subject-fixed frames of reference.”

Central to the concepts of balance and posture, gravity and antigravity muscles are the tools that provide us with the ability to maintain this centre of gravity within a stable base of support.

The antigravity muscles work against the opposing effect of gravity to help the individual maintain an upright, balanced posture.

In the event of any weakening of these muscles, MASS4D® customised foot orthotics act as an antigravity assistive force to facilitate the optimal functioning of the foot, correct postural malalignments and to prevent any deformities from shaping in the future.

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References: 

1. Winiarski S., Rutkowska-Kucharska A. (2009) Estimated ground reaction force in normal and pathological gait. Acta of bioengineering and biomechanics: February 2009, Vol. 11, No. 1, pp. 53-60
2. Soutas-Little W. R. (1998) Gait Analysis in the Science of Rehabilitation. Chapter 2: Motion Analysis and Biomechanics. DIANE Publishing. 

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