INFLUENCE OF DIFFERENT RUNNING SHOES ON REARFOOT PRONATION
AbstractINTRODUCTION Acute and overuse injuries of runners are still a central topic in the field of sports traumatology. The major part of these overuse injuries, for example shin splint or achillodynia, depended on repetitive forced pronation movements during the phase of landing: Especially the interaction of the foot with the surface is regarded to be the main cause for developing injuries (Stacoff 1985,1987; Nigg 1986,1987; Stussi 1987; Reuter 1987, Geyer et al. 1991, Komi et al. 1993). Using different sports footwear it is possible to reduce these negative effects. The normal pronation has a significant importance with regard to the correct function of the foot (Hennig 1994, James et al. 1978) but the excessive pronation, caused by unfit running shoes considered to be a frequent cause for complaints on one's foot, lower leg and knee (Segesser & Nigg 1980; Clement et al. 1981; Luethi et al. 1986, Nigg et al. 1986; Stacof et al. 1988; Cavanagh 1990; Robins & Gout 1990,1991). One important parameter is the angle of the Achilles tendon which is measured as the angle between the lower leg and the heel-bone. The purpose of our study was the evaluation of efficiency using different running shoes regarding the pronation angle. MATERIALS AND METHODS Twenty-seven volunteers (mean age 25, from 15-45 years; weight: 75.0± 5.5 kg; height: 180.2±4.7 cm) were tested 4 times with 6 different types of running shoes (3 normal running shoes and 3 running shoes which inhibited the pronation) using a high-frequency motion analyzing system with a total sampling frequency of 7.5 kHz and a force plate. This total frequency had to be divided by the number of measuring dots - in this case four - this meant that the motion could be registered by means of a frequency of 1875 Hz. The fixation of the reflective markers was always done at the left leg on the skin (therefore we punched the heel cap of the shoes with a diameter of 2 cm) and was performed according to the test design of Stacoff & Kalin & Stussi (1991). RESULTS Our results revealed that special running shoes could significantly reduce the maximum pronation angle as well as total angle deviation comparing to inormali running shoes. For the parameters contact time and pronation angle at impact peak we could not demonstrate significant differences between the tested types of running shoes. We also revealed higher pronation angles running barefoot comparing to those by using running shoes. CONCLUSION With regard to the influence of footwear it seems to be necessary to use pronation limiting running shoes, especially for those runners who showed a excessive pronation, preventing overuse injuries in lower extremities.