A model based study of a quantitative relation between joint strengthening and the highest achievable speed of human walking

There is a common belief that muscle strengthening would enhance the capability of fast walking, but the specific impact of different joint's strength on walking speed and the quantitative relation between them is not well explored. While the majority of the previous works in this area are based on experimental methods, it would be very expensive and time consuming to conduct as much experiment as necessary to establish such a quantitative relation. In the current research, instead of experimental methods, a mathematical framework is utilized to solve this problem. The objective of this paper is to briefly introduce this framework and present the obtained results based on that, for the mentioned relation. To achieve the objective of this paper, the highest achievable speed in sagittal plane with normal joint strength was first determined in the mathematical framework for three age groups. Afterward, the highest achievable speed was calculated for different levels of ankle, knee, and hip strength by changing the strength level in the mathematical model in all the studied groups. The results supported the crucial role of plantar flexors in all ages. It was shown that ankle strengthening up to certain critical value affected the speed significantly; whereas increasing the knee and hip strength may only facilitate fast walking without considerable effect on the speed value. Moreover, the critical level of ankle strengthening decreased with age increment. The attained results could be utilized in planning comprehensive joint strengthening exercises in sports and rehabilitation of subjects with lower limb disabilities.