Plantar fasciitis – an overuse injury in which the connective tissues on the bottom of the foot become inflamed – is the most common cause of heel pain in athletes (‘The Impact of Custom Semirigid Foot Orthotics on Pain and Disability for Individuals with Plantar Fasciitis,’ Journal of Orthopaedic and Sports Physical Therapy, Vol. 32, pp. 149-157, 2002) and may account for about 15% of all foot-related problems (‘Plantar Fasciitis and Other Causes of Heel Pain,’ American Family Physician, Vol. 59, pp. 2200-2206, 1999). Athletes with plantar fasciitis usually experience pain upon initial weight-bearing in the morning, after periods of inactivity, when standing on hard surfaces, while standing on tiptoe, or while climbing stairs. Often, the pain of plantar fasciitis may subside after a few minutes of exercise, but discomfort tends to increase over the course of the day. Without appropriate interventions, plantar fasciitis can ultimately prevent athletes from training and competing in their normal ways.
There are various theories about how plantar fasciitis develops, but one popular idea is that a decrease in the height of the longitudinal arch of the foot (i.e., a collapsed arch) may overly stretch the underlying plantar fascia and increase tensile stress on the heel bone. That’s of course why orthotics are often recommended for plantar-fasciitis sufferers, the idea being that an orthotic device could actually lift the arch and take strain off the fascia and heel. Indeed, one study carried out with cadavers (‘Biomechanics of Longitudinal Arch Support Mechanisms in Foot Orthoses and Their Effect on Plantar Aponeurosis Strain,’ Clinical Biomechanics, Vol. 11, pp. 243-252, 1996) showed that plantar-fascia strain was lowest in situations in which the medial longitudinal arch received the highest amount of lift (sceptics criticised this study, however, suggesting that the subjects were too stiff).
The orthotics story is a reasonable one, but surprisingly little research has actually taken a close look at the effects of orthotics on plantar fasciitis. To try to correct that situation, researchers at the University of North Carolina recently studied eight men and seven women who had experienced plantar-fasciitis symptoms for an average of 21 months (see first reference above). At the beginning of the research, all subjects walked 100 metres while recording the pain experienced during the walk on a ten-point scale, with ten representing ‘worst-possible pain’. Bilateral, custom, semirigid foot orthotics were then created for each individual, with each orthotic consisting of four layers: a vinyl top, a 2.4-millimetre, low-density material designed to absorb shock, a 2.5-millimetre thermoplastic core, and a leather covering. Each orthotic was heated in a convection oven at 250-degrees Fahrenheit for approximately five minutes and then moulded to the plantar surface of a subject’s foot. An investigator applied a superior force of about 22 Newtons (five pounds) to the underside of the foam cushion to push the orthotic against the bottom surface of the foot, in effect creating an arch. Cork material was shaped and inserted under the medial longitudinal arch of the orthotic to provide support and limit foot-flattening during exercise.
The subjects then wore their orthotics as frequently as possible for the next 12 to 17 days. When the orthotic wearers reported back to the laboratory, their levels of general foot pain – measured with the use of a ‘Foot Function Index’ – had dropped by about 66%. Average plantar pain during exercise was also appreciably lower, plummeting by around 75% from pre- to post-orthotic use. Only one of the 15 subjects had more pain during exercise after the 12 to 17 days of orthotic wearing, compared with before the orthotic fittings.
This new study suggests that mechanical factors causing a decrease in the arch height of the foot may well increase the risk of plantar fasciitis, and that if one can restore the loftiness of the arch with orthotics, strain and pain may decrease as a result. A couple of caveats are in order, however. First, it may be possible to return some lift to one’s arches by carrying out arch-strengthening exercises (provided there is no underlying anatomical abnormality), and these exercises might also have a positive impact on athletic performance by making the foot more springy and energy-efficient. Second, you should bear in mind that there was no control group in this North-Carolina study (and subjects were fully aware that the purpose of the research was to investigate the effectiveness of custom foot orthotics for foot pain), and thus it is possible that factors other than orthotic use (for example, the well-known placebo effect) might have produced the positive results. However, it is remarkable that individuals who had been suffering from plantar fasciitis for an average of 21 months (and in some cases as long as 96 months) were helped so dramatically over the 12- to 17-day period. Overall, the research is a valuable contribution to this area of study and should lead to further investigations which will help athletes stay away from troubles on the bottom of their feet.