Two-week cumulative tendon load estimated from insole sensor contact forces is associated with plantar flexor function in Achilles tendinopathy

Tendon loading dictates rehabilitation outcomes in Achilles tendinopathy but is difficult to track in the real world. In this study, we used instrumented insole sensors to monitor Achilles tendon load for two weeks in fifteen individuals with Achilles tendinopathy, who also completed assessments of their plantar flexor strength, dynamic function, and survey-based outcomes. We used insole data to estimate two types of cumulative Achilles tendon load: overall (≥0.3×body weight) and high-level load (≥3×body weight). We determined Pearson correlations between (1) overall and high-level tendon loads, (2) plantar flexor moment, power, work, (3) heel raise height, repetitions, countermovement jump height, and (4) self-reported symptoms and activity. Overall cumulative tendon load moderately correlated to isometric plantar flexor moment (r = 0.543) and weakly to isokinetic and dynamic functions (0.128–0.413). Cumulative high-level tendon load strongly correlated to heel raise height (0.687) and fast isokinetic moment (0.625), and moderately to other functional measures (0.470–0.592). Symptoms weakly correlated to overall (0.392) and moderately to high-level load (0.436). Self-reported activity weakly correlated to overall (0.297) and strongly to high-level load (0.617). Stronger associations with the high-level Achilles tendon load than the overall load suggest that clinical function assessments provide insight into the real-world performance of high-loading activities. In contrast, the disconnect between overall tendon loading and plantar flexor function may explain the variability in recovery outcomes. Self-reported activity and standard heel raises represent high-level tendon load well, yet they do not always suggest functional deficit. Sensor-monitored tendon load shows promise as a new biomarker for real-world plantar flexor function in Achilles tendinopathy.跟腱病变（Achilles tendinopathy）患者的康复结局取决于跟腱负荷，但在真实临床场景中难以对其进行实时追踪。本研究纳入15名跟腱病变患者，采用传感鞋垫（instrumented insole sensors）连续两周监测其跟腱负荷；同时受试者需完成跖屈肌力量、动态功能评估以及基于问卷的结局指标调查。本研究基于传感鞋垫数据估算两种类型的跟腱累积负荷：总体负荷（≥0.3倍体重）与高强度负荷（≥3倍体重），并计算了四组指标间的皮尔逊（Pearson）相关系数：(1) 总体跟腱负荷与高强度跟腱负荷；(2) 跖屈肌力矩、功率及做功量；(3) 提踵高度、重复次数与反向跳高度；(4) 自我报告的症状与活动水平。结果显示，总体累积跟腱负荷与等长跖屈肌力矩呈中度相关（r=0.543），与等速收缩及动态功能则呈弱相关（相关系数范围0.128~0.413）；累积高强度跟腱负荷与提踵高度（r=0.687）以及快速等速力矩（r=0.625）呈强相关，与其余功能指标则呈中度相关（相关系数范围0.470~0.592）；自我报告的症状与总体负荷呈弱相关（r=0.392），与高强度负荷则呈中度相关（r=0.436）；自我报告的活动水平与总体负荷呈弱相关（r=0.297），与高强度负荷则呈强相关（r=0.617）。相较于总体跟腱负荷，各项指标与高强度跟腱负荷的关联更强，这提示临床功能评估可反映受试者在真实场景中进行高负荷活动的表现；与之相反，总体跟腱负荷与跖屈肌功能之间的脱节，或可解释康复结局的异质性。自我报告的活动水平与标准提踵测试可较好地反映高强度跟腱负荷，但二者并不总能提示功能缺损。经传感器监测的跟腱负荷有望成为跟腱病变患者真实场景下跖屈肌功能的新型生物标志物。