Foot strike patterns while running can have implications in the development of a host of conditions of the lower limbs such as plantar fasciitis and patellar tendinopathy; the magnitude and rate of change of the vertical impact forces vary according to the foot strike type.
These impact forces are considered as important kinetic variables in determining risk factors for a number of pathologies of the lower extremity because of their use in the measurement of the loading rate of the musculoskeletal system during running.
The three primary foot strike patterns present among runners are described as – rearfoot, midfoot and forefoot.
Rearfoot striking involves initial heel contact with the ground, with the foot and ankle in a dorsiflexed position. Vertical impact peak tends to be at its highest in this form of running, when compared to other foot strike styles.
The rapid change in velocity and direction of the centre of mass from posterior to anterior leads to an absence of posterior and medial impact forces in rearfoot strikers, as observed by Boyer et al. in their study on rearfoot, midfoot and forefoot impacts in habitually shod runners.
Upon studying 40 highly trained runners on a motorised treadmill, Ahn et al. noted that the plantar flexion which follows heel contact in rearfoot strikers is possibly passive because of the lag in plantar flexors to generate force.
The ankle is more plantar flexed in a midfoot strike, with simultaneous contact between the heel and forefoot. The contact time with the ground tends to be shorter with a longer flight time in this foot strike style.
A study conducted by Ana Ogueta-Alday, of the Department of Physical Education and Sports at the University of León, divided 20 sub-elite long-distance runners into two groups – rearfoot and midfoot strikers.
By measuring the anthropometric and biomechanical characteristics of both groups, the authors concluded that while no significant differences were found, the increase of contact time and decrease of flight time made rearfoot strikers more economical than midfoot strikers at submaximal running speeds.
This could be attributed to the greater oscillation of the centre of mass in a midfoot strike, which has been associated with poor running economy.
In a forefoot strike, the lateral edge of the forefoot makes initial contact with the ground while the ankle dorsiflexes as the midfoot and heel touch the ground.
Impact peaks are present in the posterior and medial directions for forefoot strikers, with a better stretching of the foot arch and a better storage and release of elastic energy from tendons, ligaments, and muscles of the lower limbs during the first part of ground contact.
Forefoot strikers are observed to run with shorter stride lengths, higher stride frequencies, and shorter contact times with the ground; this pattern of running involves flexion of the knee at strike, resulting in shortening of both stride length and frequency.
While there is considerable debate on which foot strike pattern enhances running form and efficiency, an understanding of the biomechanical differences between foot strike techniques can be useful in the modification of these patterns as part of early intervention and preventative strategies.
The additional stress of an abnormal foot posture on the kinetic chain can facilitate the onset of overuse injuries because of the unhealthy movement of the body in conjunction with the repetitive movements of the lower limbs required while running.
A customised orthotic intervention should be incorporated as part of a preventative programme to reduce excessive pronation in runners in order to improve their performance and protect them from musculoskeletal disorders in the long-term.
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