Those with diabetes mellitus have an increased risk for falls. This is mostly due to the development of peripheral neuropathy which reduces the sensory input from the plantar surface of the foot. This neuropathy also puts them at increased risk for complication such a plantar ulcers, often referred to as the diabetic foot. A number of different strategies are often used to reduce the pressures under the ball of the foot to reduce the risk of these complications. One of these methods is a rocker bottom shoe. This has been shown to reduce plantar pressures, but there is a risk it may increase the risk for falls due to the instability the rocker may create.
A study in Gait and Posture from researchers at East Carolina University used 20 healthy controls to investigate what rocker sole shoes did to parameters associated with the center of mass and center of pressure which are measure of postural stability. They concluded:
In young healthy adults, shoes with rocker bottom soles had a destabilizing effect to perturbed stance, thereby increasing the potential for imbalance. These results raise concerns that footwear with rocker bottom sole modifications to accommodate an insensate foot may increase the risk of falls.
– the subjects were healthy adults and not people with diabetic neuropathy.
– its does point to a theoretical increase in instability in those who do have diabetic neuropathy.
– rocker sole shoes probably should be used with caution in those with diabetic foot complications, especially if they have other risk factors present for falls.
A recent news report talks about litigation against Skechers from a male who claims that his Achilles tendon was ruptured from the use of their Shape Up toning shoes. The case has not been heard yet and there is no statement from Skechers.
Is the claim valid?
Toning shoes do alter the way you walk. They do alter the loads on different tissues, and yes they do make the calf muscles work harder, so they do place a greater load on the Achilles tendon. Much more is needed to rupture it though (more on Achilles ruptures), so to claim it is the cause is, in my opinion, a bit of a stretch. There must be a number of other risk factors present first and an Achilles tendon rupture is usually accompanied with simultaneous ankle dorsiflexion and knee extension. That will possibly be increased somewhat in toning shoes that have a rocker bottom. Generally a number of risk factors need to be in place for the rupture to happen, so the toning shoes can only be one of them.
As by way of analogy, there was the controversy when the Cox-2 inhibitor, Vioxx which was used as an anti-inflammatory agent was withdrawn from the market due to the increased risk for cardiovascular events. A number of people who had heart attacks or strokes while on this drug sued. Most of the cases failed, as they already had the risk factors for the heart attack or stroke (see this Wikipedia discussion) and Vioxx was not found to be the causative factor.
It will be interesting to see which way this Skechers case goes, or if it is just settled (which would be shame, as I would like to know which way the courts would rule!). Would they rule in favor of the litigant that the shoes caused the Achilles rupture or will they rule like in the Vioxx cases that other risk factors were already present?