Effects of running-induced fatigue on plantar pressure distribution in runners with different strike types

Background: Running induced-fatigue is an important factor in running related injuries. Runners with different strike types have different running mechanics and suffer from different injury patterns. Underlying mechanism of this difference is not well understood. Research question: The aim of this study was to examine the effects of running-induced fatigue on plantar pressure distribution in runners with different strike types. Methods: 30 rearfoot (age = 21.56 +/- 2.28 years; height = 1.67 +/- 0.08 m; mass = 61.43 +/- 11.57 kg; BMI = 21.77 +/- 2.9 kg.m(-2)) and 30 forefoot (age = 19.73 +/- 1.68 years; height = 1.71 +/- 0.08 m; mass = 65.7 +/- 13.45; BMI = 22.53 +/- 3.39 kg.m(-2)) strike male and female recreational runners were recruited to this study. Participants ran in 3.3 m/s barefoot along the plantar pressure measuring device (Footscan (R), Rsscan International) before and after running-induced fatigue. Fatigue protocol was performed on a treadmill. Peak plantar pressure and peak plantar force (% body weight), contact time and medio-lateral force ratio were calculated while running. Repeated measures ANOVA test was used to investigate the effect of running-induced fatigue on plantar pressure variables (p = 0.05). Results: After running-induced fatigue, in the rearfoot strike group, increases in loading of medial and lateral portions of the heel, first metatarsal and big toe was observed, and in lesser toes and in the forefoot push off phase, the medio-lateral force ratio decreased. While, in the forefoot strike group first to third metatarsals loading increased and fifth metatarsal loading decreased after fatigue, and medio-lateral force ratio in the foot flat and forefoot push off phase increased. In both groups contact time increased after fatigue. Significance: Our data indicate that running-induced fatigue has different effects on plantar pressure distribution pattern in runners with different strike type. These different effects reflect different adaptation strategies in runners with different strike types, and could explain existence of different injury patterns in runners with different strike types.