One hundred marathons in 100 days:Unique biomechanical signature and the evolution of force characteristics and bone density

Background:An extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance.An extraordinary runner(age=55 years,height=1.81 m,mass=92 kg) scheduled a marathon a day for 100 consecutive days.His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.Methods:Overground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion.The case’s running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.Results:The case’s peak vertical loading rate(Δx=-61.9 body weight(BW)/s or-57%),peak vertical ground reaction force(Δx=-0.38 BW or-15%),and peak braking force(Δx=-0.118 BW or-31%) were remarkably lower(p<0.05) than the control group at~3.3 m/s.The relatively low loading-related magnitudes were attributed to a remarkably high duty factor(0.41) at the evaluated speed.The foot strike angle of the marathoner(29.5°) was greater than that of the control group,affecting the peak vertical loading rate.Muscle powers in the lower extremity were also remarkably low in the case vs.controls:peak power of knee absorption(Δx=-9.16 watt/kg or-48%) and ankle generation(Δx=-3.17 watt/kg or-30%).The bone mineral density increased to 1.245 g/cm;(+2.98%) near completion of the challenge,whereas the force characteristics showed no statistically significant change.Conclusion:The remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.