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

Abstract

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.

Keywords: Bone; Gait analysis; Ground reaction force; Load; Running.

Graphical abstract

Fig. 1

Diagram showing the flow of participants included for the comparative and regression analyses of distance runners.

Fig. 2

Stick figure of marathoner (blue) and control group of typical rearfoot strikers (black) at initial contact. Ensemble curves of the running ground reaction forces, and instantaneous joint angles, joint moments, and powers for the ankle and knee during stance. The grey area represents ± 1 SD bound around the mean of the control group. The vertical ground reaction force is scaled to the average foot–ground contact times to illustrate the difference in stance time between case and controls. The area under the curve in the left corner panel gives the eccentric work of muscles crossing the ankle joint during the initial plantarflexion movement. BW = body weight; D. = dorsi; P. = plantar; W = Watt.

Fig. 3

(A) The non-linear relationship between foot strike angle and peak vertical loading rate during over-ground and level running at multiple running speeds. The dots represent the 52 runners previously included in the study by Breine and colleagues, with the open dots showing the typical rearfoot strikers. (B) The relationship between the rearfoot and shank angles at touchdown for the controls at ∼3.3 m/s. The marathoner's data point (square) was added in blue for illustrative purposes. BW = body weight.

Fig. 4

Relationship between duty factor and force-related characteristics (B), (C), (D) in the control group. The marathoner's data point (square) was added in blue for illustrative purposes. Duty factor = contact time/(2(contact time + flight time)); r = Pearson correlation coefficient. BW = body weight; GRF = ground reaction force. ∥ denotes absolute values of negative numbers.