Short communicationLong distance running increases plantar pressures beneath the metatarsal heads: A barefoot walking investigation of 200 marathon runners
Introduction
The beneficial effects of aerobic exercise and endurance-type activities for the improvement of physical fitness and the prevention of cardiovascular disease are well established [1], [2]. Health-motivated activities as well as competitively oriented events, such as road races with distances between 5 km and the classical marathon distance of 42.2 km became popular in recent years [3]. It is not surprising, however, that along with these developments the incidence of running related and overload injuries has also risen. The yearly incidence of injury among runners has been estimated between 37% and 56% [4]. More than 90% of running related injuries are localized in the lower extremity, equally affecting the knee, shank or foot [5]. Various studies have investigated potential causes of overuse injuries in runners but to-date no single factor has been shown to be related to the incidence or frequency of sports injuries [6], [7].
Stress fractures of the metatarsals are frequently reported overload injuries of long distance runners and are considered as a result of a multi-factorial process [4]. Potential causes include mechanical loading with excessive intensity or frequency, anthropometric factors like step length or foot type, muscle fatigue, bone health and exercise properties, such as duration or frequency of training [8], [9], [10], [11]. Other studies investigated the incidence of stress fractures of the metatarsals and the tibia in male and female military recruits and reported low aerobic fitness level as a predictor of fatigue fractures [12], [13]. Korpelainen et al. reported increased incidence of metatarsal stress fractures in runners with high-arched feet (40%) [14]. Burnfield et al. reported that higher running speed leads to increased peak plantar pressure [15]. Furthermore, fatigue of the foot and shank muscles – especially of the dorsiflexor muscles – apparently leads to higher impact forces during landing [16]. Weist et al. reported increased peak pressures in the forefoot region with increasing fatigue after running on a treadmill at speeds near the anaerobic threshold [17]. Therefore, the question arises on whether or not long distance running affects foot loading characteristics, such as the ground reaction force and peak pressure in specific areas. Common strategies to prevent abnormal foot loading in running include cushioning running shoes [18] or using orthopedic insoles [1].
In the present study, the plantar peak pressure before and after long distance running in a formal marathon race was analyzed to compare the foot loading in the rested and fatigued conditions. The aim of this study was to measure functional changes of foot loading due to an exhausting marathon race.
Section snippets
Material and methods
Two hundred participants of the third Muenster marathon, which took place on September 5, 2004, were measured before and after the race. All subjects – 33 women and 167 men – were registered participants and official race results were electronically available. The average age was 39.5 (±8.8) years with a range between 21 and 64 years (Table 1). Subjects were invited to participate via the homepage of the event (www.volksbank-muenster-marathon.de) and information flyers in the mailing of the
Results
For the total group no significant difference in the contact time of the whole foot was found between the pre- and post-race measurements indicating repeatable gait dynamics. However, the contact time of the heel, midfoot and metatarsals was significantly increased (Table 2). The contact area of the whole foot was significantly reduced by 2 cm2 due to a reduced contact area in all toe regions. The peak pressure was significantly increased under the second and the third to fifth metatarsal heads
Discussion
The aim of the present study was to investigate the effects of exhausting long distance running on foot loading characteristics during barefoot walking. Although walking is less demanding compared to running, the differences in foot loading characteristics between pre- and post-race measurements would indicate the general effects of the fatiguing condition. The whole group of athletes demonstrated major differences that were reflected in reduced peak pressures and impulses under the toes at the
Conclusion
In summary, the present results show that an exhausting long distance run, such as a marathon race, leads to changes in foot loading characteristics demonstrated in the peak pressure and impulse values under the forefoot and toe regions. Due to the exhausting effort and the decreased involvement of the toes in the push-off phase, the loads are transferred from the toe region to the forefoot, thus causing a higher bending load on the metatarsal heads. This mechanism could explain the risk for
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