Step-to-step transitions are mechanically different during walking.

Step-to-step transitions are mechanically different during walking.
Darren James
Sport & Exercise Research Centre, London South Bank University.

Ever wondered how we walk? The answer for the majority of us is probably not. But it was the asking of this question that led to the development of FitFlopTM, which was designed as a training aid to increase the metabolic cost of walking.

Generally, it is not until the ability to walk is taken away such as during injury and in disease do we realise what we have lost. Our gait pattern is as unique and individual as our DNA, yet while each step appears on the surface to be repeatable this cannot be said for the internal mechanics that govern this motion.

Take for example the below illustration, which clearly shows how quadriceps (m. vasti medialis) muscle activity alters with each step during undisturbed barefoot walking. The top half of the diagram consists of the power from each step resulting from accelerations recorded at the lower leg of a 59kg female subject aged 19. Dr. Joseph Hamill and colleagues at the University of Massachusetts, USA, have previously used this method of analysis in a 1995 study. Each graph produces two distinct peaks which relate to the power resulting from active movement and a higher frequency peak associated with energy due to ground impact.

The first graph (from left to right) is the initiation step which shows low power in both peaks due to a lack of momentum. In the next step, the power of active movement is twice that of impact, and shows greater muscle activity than the initiation step. Is this too much central control? Obviously so, as the next step shows reduced active movement power but greater power of the ground impact peak suggesting a greater reliance on an eccentric contraction of the knee extensor muscle to effectively damp the resulting shock transmission. Consequently, because of this, the system is tuned for the next step (last graph – far right) with the greatest recorded active movement power and muscle activity, and reduced impact power.



So what? Well this clearly describes the energetics of walking by highlighting that the magnitude of low frequency power from ground impact is a result of alterations in muscle activity. This understanding is beneficial in the design of footwear for healthy people, clinical interventions or as training tools.

If we can show that manipulations in footwear increase lower extremity muscle activity, such as FitFlopTM; then the exercise ratio of return (ROR) may well exceed that of other fitness activities in providing an effective workout by simply wearing a form shoe.
So by safely perturbing your gait pattern it is possible to increase the metabolic cost of walking and increase the training benefits of low impact activities such as walking.

The FitFlopTM Innovation

The FitFlopTM Innovation

Summer 2007 saw the introduction of the FitFlopTM on to the health and fitness market. This product was soon causing a stir in both the UK and US with demand outstripping supply and stockists such as Harvey Nichols being forced to open waiting lists pending fresh deliveries.

This innovation was developed by a team from the Sport and Exercise Science department at London South Bank University. Biomechanists, Dr David Cook and Darren James were approached with the idea of developing a flip-flop that increased the output of the muscles of the lower extremity. Cook and James believed the answer lay in the sole of the footwear.

Constructed out of differing mid-sole densities, the FitFlopTM creates an unstable base utilising a patent-pending ‘micro-wobbleboard’ approach developed by Cook and James that serves to change the ‘stimulus’ provided to the plantar surface of the foot. During the early phases of the gait cycle, the lower extremity muscles that control pronation are required to increase their activation patterns in an attempt to regain stability.

Tests revealed a greater intensity of muscle activation (≤12%) in the muscles of the lower extremity in the FitFlopTM when compared to a control shoe, particularly in those muscles associated to control of pronation. The positive results reported by the research team of Cook, James and Mileva from the Sport and Exercise Science Research centre were substantiated by independent experimental tests performed by Salford University Biomechanics department.


As this concept is designed to place a greater demand on lower extremity muscles, consumers should be advised that fatigue will be a consequence with use of the FitFlopTM, and therefore requires adequate regulation.