Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada; McCaig Institute for Bone and Joint Health, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, MD, USA; The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, MD, USA.
Gait Posture. 2020 Mar;77:190-194. doi: 10.1016/j.gaitpost.2020.01.009. Epub 2020 Jan 28.
Military personnel are required to run while carrying heavy body-borne loads, which is suggested to increase their risk of tibial stress fracture. Research has retrospectively identified biomechanical variables associated with a history of tibial stress fracture in runners, however, the effect that load carriage has on these variables remains unknown.
What are the effects of load carriage on running biomechanical variables associated with a history of tibial stress fracture?
Twenty-one women ran at 3.0 m/s on an instrumented treadmill in four load carriage conditions: 0, 4.5, 11.3, and 22.7 kg. Motion capture and ground reaction force data were collected. Dependent variables included average loading rate, peak absolute free moment, peak hip adduction, peak rearfoot eversion, and stride frequency. Linear mixed models were used to asses the effect of load carriage and body mass on dependent variables.
A load x body mass interaction was observed for stride frequency only (p = 0.017). Stride frequency increased with load carriage of 22.7-kg, but lighter participants illustrated a greater change than heavier participants. Average loading rate (p < 0.001) and peak free moment (p = 0.015) were greater in the 22.7-kg condition, while peak rearfoot eversion (p ≤ 0.023) was greater in the 11.3- and 22.7-kg conditions, compared to the unloaded condition. Load carriage did not affect peak hip adduction (p = 0.67).
Participants adapted to heavy load carriage by increasing stride frequency. This was especially evident in lighter participants who increased stride frequency to a greater extent than heavier participants. Despite this adaptation, running with load carriage of ≥11.3-kg increased variables associated with a history of tibial stress fracture, which may be indicative of elevated stress fracture risk. However, the lack of concomitant change amongst variables as a function of load carriage may highlight the difficulty in assessing injury risk from a single measure of running biomechanics.
军人需要背负重物跑步，这可能会增加胫骨应力性骨折的风险。研究人员回顾性地确定了与跑步者胫骨应力性骨折史相关的生物力学变量，但负重对这些变量的影响尚不清楚。
负重对与胫骨应力性骨折史相关的跑步生物力学变量有什么影响？
21 名女性以 3.0m/s 的速度在装有仪器的跑步机上跑步，分为 4 种负重条件：0、4.5、11.3 和 22.7kg。采集运动捕捉和地面反力数据。依赖变量包括平均加载率、峰值绝对自由力矩、峰值髋关节内收、峰值足跟外翻和步频。线性混合模型用于评估负重和体重对依赖变量的影响。
仅在步频上观察到负重与体重的交互作用（p=0.017）。当负重为 22.7kg 时，步频增加，但较轻的参与者比较重的参与者变化更大。在 22.7kg 条件下，平均加载率（p<0.001）和峰值自由力矩（p=0.015）更大，而在 11.3kg 和 22.7kg 条件下，峰值足跟外翻（p≤0.023）更大，与未负重条件相比。负重对峰值髋关节内收没有影响（p=0.67）。
参与者通过增加步频来适应重负荷。这在较轻的参与者中尤为明显，他们比较重的参与者增加步频的幅度更大。尽管有这种适应，但负重≥11.3kg 会增加与胫骨应力性骨折史相关的变量，这可能表明骨折风险增加。然而，负重对跑步生物力学变量的影响缺乏一致性，这可能突出了从单一跑步生物力学测量评估受伤风险的困难。
