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 (Δx̄ = –61.9 body weight (BW)/s or –57%), peak vertical ground reaction force (Δx̄ = –0.38 BW or –15%), and peak braking force (Δx̄ = –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 (Δx̄ = –9.16 watt/kg or –48%) and ankle generation (Δx̄ = –3.17 watt/kg or –30%). The bone mineral density increased to 1.245 g/cm² (+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.