Redistribution of Mechanical Work at the Knee and Ankle Joints During Fast Running in Minimalist Shoes.
CONTEXT Minimalist shoes have been suggested as a way to alter running biomechanics to improve running performance and reduce injuries. However, to date, researchers have only considered the effect of minimalist shoes at slow running speeds. OBJECTIVE To determine if runners change foot strike pattern and alter the distribution of mechanical work at the knee and ankle joints when running at a fast speed in minimalist shoes compared with conventional running shoes. DESIGN Crossover study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty six trained runners (age 30.0 7.9 years [age range, 18 40 years] height 1.79 0.06 m, mass 75.3 8.2 kg, weekly training distance 27 15 km) who ran with a habitual rearfoot foot strike pattern and had no experience running in minimalist shoes. INTERVENTION(S) Participants completed overground running trials at 18 km/h in minimalist and conventional shoes. MAIN OUTCOME MEASURE(S) Sagittal plane kinematics and joint work at the knee and ankle joints were computed using 3 dimensional kinematic and ground reaction force data. Foot strike pattern was classified as rearfoot, midfoot, or forefoot strike based on strike index and ankle angle at initial contact. RESULTS We observed no difference in foot strike classification between shoes (kh21 2.29, P .13) Ankle angle at initial contact was less (2.46deg versus 7.43deg; t25 3.34, P .003) and strike index was greater (35.97% versus 29.04% t25 2.38, P .03) when running in minimalist shoes compared with conventional shoes. We observed greater negative (52.87 J versus 42.46 J; t24 2.29, P .03) and positive work (68.91 J versus 59.08 J; t24 2.65, P .01) at the ankle but less negative (59.01 J versus 67.02 J; t24 2.25, P .03) and positive work (40.37 J versus 47.09 J; t24 2.11, P .046) at the knee with minimalist shoes compared with conventional shoes. CONCLUSIONS Running in minimalist shoes at a fast speed caused a redistribution of work from the knee to the ankle joint. This finding suggests that runners changing from conventional to minimalist shoes for short distance races could be at an increased risk of ankle and calf injuries but a reduced risk of knee injuries.
Journal of athletic training