DEPENDENCY OF REARFOOT PRONATION ON PHYSICAL STRAIN DURING RUNNING
AbstractlNTRODUCTlON Acute and chronic injuries of runners are still a central topic in the field of Sports Medicine. The cause for acute running injuries is relatively easy to determine but the search for reasons regarding running-related chronic sports injuries as runner's knee, shin splint or achillodynia are by far more difficult. Training parameters, as extent and ground, and anatomical conditions as foot mafformations as well are functional criteria which should be taken into consideration when determing the reason for running injuries. Especially the interaction of the foot with the surface is regarded to be the main cause for developing injuries (REUTER 1987). The normal pronation has a significant importance with regard to the correct function of the foot (HENNIG 1994, JAMESIBATESIOSTERNIG 1978) but the excessive pronation, the so-called overpronation- is considered to be a frequent cause for complaints on one's foot. lower leg and knee (KliLIN et al. 1988, REUTER 1987). In order to quantify the degree of the pronation different methods are employed to record different parameters. One important parameter is the angle of the Achilles tendon which is measured as the angle between the lower leg and the heel-bone. Results from gait analyses and examinations with different running speeds exist in order to describe the effect on the angle of the Achilles tendon (MANNIHAGY 1980, NlGG 1986). MATERIALS AND METHODS In 20 volunteers the correlation between rearfoot pronation and increasing physical strain during treadmill ergometry was examined. In order to assess the influence of regularly performed running training a group of 10 endurance trained middle- and long-distance runners (age: 7.4 + 4.9 years; weight: 71.0 + 8.8 kg; height: 184.2 + 8.3 cm) was compared to another group of 10 untrained persons (age: 24.7 t 2.1 years; weight: 73.3 + 9.8 kg; height: 179.1 f 8.3 cm). The examinations were carried out on a treadmill using a high-frequency motion analyzing system. Heart rate, blood lactate as well as rearfoot pronation were measured. RESULTS Regarding heart rate and lactate concentration there were significant differences between trained and untrained volunteers. The pronation angle increased with raising speed up to a maximum of 6.54 + 4.22" for the trained group and 6.84 + 4.59" for the untrained group. With reference to maximal as well as to submaximal stages the pronation angles showed no significant differences between both groups. After the maximal step the runners performed an additional 3-min run with a velocity reduced by 8 kmlh compared to the maximal speed. On this stage the total group as well as the untrained group showed significantly greater pronation angles compared to those of the corresponding velocity at the beginning of the test. The extent of the differences, however, was not significantly correlated with the lactate levels. CONCLUSION Our results demonstrate that the increase of the pronation angle is a function of the running speed. But there is also an influence of fatigue, which depends neither on the running velocity nor on the lactate levels during exercise. Therefore, further investigations should lay emphasis upon the question which factors are responsible for this effect.
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