Second Metatarsal Stress During Prolonged Load Carriage
Ankur Anand Padhye, John D. Willson, Kiavash Sharifi, Moritz Dannhauer, Stacey A. MeardonBackground:
High volume and intensity of physical activity by military service members during training contributes to high incidences of lower extremity overuse injuries, especially in women. The second metatarsal is prone to injury, accounting for most metatarsal stress fractures. However, the effects of exertion and load carriage on second metatarsal bone stress during military-relevant training tasks remain underexplored. This study aimed to compare second metatarsal bone stress in response to exertion and added load in active females.
Methods:
22 active females (22.4 years, 1.65 m, 58.2 kg) walked 5 km at 1.5 m/s on a force treadmill with and without a 22.7-kg load on separate days in standardized footwear. Following left foot computed tomography (CT), 3D kinematics, in-shoe plantar pressure, and ground reaction forces were collected at the start and end. Data from 5 left leg stance phases were input to a CT-informed scaled model of the second metatarsal to calculate mid-shaft dorsal and plantar peak stress. Load and exertion effects were assessed with 2-factor repeated measures analyses of variance (α = .05).
Results:
Dorsal second metatarsal stress was compressive and plantar was tensile with baseline walking stress averaging −86 (22) and 73 (21) MPa. Added load increased peak dorsal compression by 28% (
Conclusion:
Walking with load consistently increases metatarsal stress throughout a 5-km training task. Exertion effects illustrate the complex interaction of biomechanical and neuromuscular factors relevant to bone stress injuries in females during military-specific tasks.