School of Kinesiology, Western University, London, ON, CANADA.
Med Sci Sports Exerc. 2023 Sep 1;55(9):1706-1716. doi: 10.1249/MSS.0000000000003201.
Individuals with anterior cruciate ligament reconstruction (ACLR) generally exhibit limb underloading behaviors during walking, but most research focuses on per-step comparisons. Cumulative loading metrics offer unique insight into joint loading as magnitude, duration, and total steps are considered, but few studies have evaluated if cumulative loads are altered post-ACLR. Here, we evaluated if underloading behaviors are apparent in ACLR limbs when using cumulative load metrics and how load metrics change in response to walking speed modifications.
Treadmill walking biomechanics were evaluated in 21 participants with ACLR at three speeds (self-selected (SS); 120% SS and 80% SS). Cumulative loads per step and per kilometer were calculated using knee flexion and adduction moment (KFM and KAM) and vertical ground reaction force (GRF) impulses. Traditional magnitude metrics for KFM, KAM, and GRF were also calculated.
The ACLR limb displayed smaller KFM and GRF in early and late stances, but larger KFM and GRF during midstance compared with the contralateral limb ( P < 0.01). Only GRF cumulative loads (per step and per kilometer) were reduced in the ACLR limb ( P < 0.01). In response to speed modifications, load magnitudes generally increased with speed. Conversely, cumulative load metrics (per step and per kilometer) decreased at faster speeds and increased at slow speeds ( P < 0.01).
Patients with ACLR underload their knee in the sagittal plane per step, but cumulatively over the course of many steps/distance, this underloading phenomenon was not apparent. Furthermore, cumulative load increased at slower speeds, opposite to what is identified with traditional single-step metrics. Assessing cumulative load metrics may offer additional insight into how load outcomes may be impacted in injured populations or in response to gait modifications.
前交叉韧带重建（ACLR）患者在行走过程中通常会出现下肢负重不足的行为，但大多数研究都集中在每一步的比较上。累积负荷指标可以提供关节负荷的独特见解，因为它考虑了幅度、持续时间和总步数，但很少有研究评估 ACLR 后累积负荷是否发生改变。在这里，我们评估了在使用累积负荷指标时 ACLR 肢体是否存在明显的负重不足行为，以及负荷指标如何响应行走速度的改变而发生变化。
在三个速度（自主选择（SS）；120%SS 和 80%SS）下，对 21 名 ACLR 患者在跑步机上行走的生物力学进行了评估。使用膝关节屈曲和内收力矩（KFM 和 KAM）和垂直地面反作用力（GRF）冲量计算每步和每公里的累积负荷。还计算了 KFM、KAM 和 GRF 的传统幅度指标。
与对侧肢体相比，ACLR 肢体在早期和晚期站立时的 KFM 和 GRF 较小，但在中期站立时的 KFM 和 GRF 较大（P<0.01）。只有 GRF 累积负荷（每步和每公里）在 ACLR 肢体中减少（P<0.01）。为了响应速度的改变，负荷幅度通常随速度的增加而增加。相反，累积负荷指标（每步和每公里）在较快速度下减小，在较慢速度下增加（P<0.01）。
ACL 患者在矢状面上每步都会使膝关节负重不足，但在许多步/距离的过程中，这种负重不足的现象并不明显。此外，在较慢的速度下，累积负荷增加，与传统的单步指标所确定的情况相反。评估累积负荷指标可能会提供额外的见解，了解负荷结果如何在受伤人群中或响应步态改变时受到影响。
