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Original articles: R Clinghan, G P Arnold, T S Drew, L A Cochrane, and R J Abboud Do you get value for money when you buy an expensive pair of running shoes? Br J Sports Med 2008; 42: 189-193 [Abstract] [Full text] [PDF]

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Comment on Clinghan et al.

Colin A Walker   (2 November 2007)

Comment on Clinghan et al. 2 November 2007
Colin A Walker, Reader (retd.) University of Strathclyde, Department of Mechanical Engineering Send letter to journal: Re: Comment on Clinghan et al. colin.walker{at}strath.ac.uk Colin A Walker	Dear editor Re:Do you get value for money when you buy an expensive pair of running shoes? [1] When the ground-force-reaction is measured as a function of time during running or walking, the result is a function of speed and underfoot conditions [2]. At any speed, however, the area under the force-time plot represents the total momentum change during the stance phase of gait. This cannot be altered by any shoe design, since the consequence would be that the runner would either rise up into the air or sink lower and lower with bent knees. At the start of the contact phase, the centre of mass of the runner is moving downwards. At the end of the contact phase, the centre of mass is moving upwards – the motion must be exactly reversed. Attempts to find a design of running shoe that will alter the ground-force-reaction are doomed to failure for this reason. It was shown, however, by McMahon & Greene [3]that if the underfoot compliance were to be chosen in the range 100-200kN/m, then the spike seen in the GRF-time plot, as a result of heel impact, will not be observed. The basic premise of Clinghan et al, that changes should be detectable in the GRF as a result of differences in shoe design between expensive and inexpensive shoes, may be seen to be one that would not survive experimental inquiry. In fact, their results were defined before any tests were carried out, since no differences can be found. The fact that differences were seen between different areas of the foot may be put down to experimental variation, and the fact that while the GRF cannot be changed radically, it is possible to redistribute the force across the foot. References 1. Clinghan R T, Arnold G P,Drew T S, Cochrane L, and Abboud R J Do you get value for money when you buy an expensive pair of running shoes? Br J Sports Med 2007.038844v1 2.Walker CA & Blair R Leg stiffness and damping factors as a function of running speed, Sports Engineering 2002, 5, 129-139. 3. McMahon TA & Greene PR The influence of track compliance on running, J. Biomech. 1979, 12, 893-904.