Handheld dynamometry: validity and reliability of measuring hip joint rate of torque development and peak torque

Introduction
Measuring rate of torque development (RTD) and peak torque (PT) for hip muscle performance presents challenges in clinical practice. This study investigated the construct validity of a handheld dynamometer (HHD) versus an isokinetic dynamometer (IKD), and intra-rater repeated reliability for RTD and PT and their relationship in hip joint movements.
Methods
Thirty healthy individuals (mean age = 30 ± 8 years, 13 males) underwent two test sessions in a single day. RTD (0-50, 0-100, 0-150, 0-200ms) and PT normalised to body mass in maximal voluntary isometric contractions were measured using a HHD and an IKD in hip flexion, extension, abduction, adduction, internal and external rotation.
Results
For validity between the devices, RTD0-50 exhibited the largest significant systematic bias in all hip movements (3.41-11.99 Nm·s-1 kg-1) and widest limits-of-agreement, while RTD0-200 had the lowest bias (-1.33-3.99 Nm·s-1 kg-1) and narrowest limits-of-agreement. For PT, agreement between dynamometers was observed for hip flexion (0.08 Nm·kg-1), abduction (-0.09 Nm·kg-1), internal (-0.01 Nm·kg-1), and external rotation (0.05 Nm·kg-1). For reliability, intra-rater intraclass correlation coefficient (ICC2,1) ranged from moderate to good in RTD0-50 and RTD0-100 (0.5-0.88), and good to excellent in RTD0-150 and RTD0-200 (0.87-0.95) in all movements.
The HHD displayed excellent intra-rater, relative reliability values (ICC2,1) in all movements (0.85-0.95). Pearson’s correlation revealed good linear correlation between PT and RTD0-150 and RTD0-200 in all movements (r = .7 to .87, p = <.001).
Conclusion
Validity analysis demonstrated significant systematic bias and lack of agreement in RTD measures between the HHD and IKD. However, the HHD displays excellent to moderate intra-rater, relative reliability for RTD and PT measures in hip movements. Clinicians may use the HHD for hip muscle PT assessment but note, late phase RTD measures are more reliable, valid, and relate to PT than early phase RTD. Additionally, the correlation between RTD and PT at various time epochs was examined to better understand the relationship between these measures.

引言
临床实践中，测量髋部肌肉性能的力矩发展速率（rate of torque development, RTD）与峰值力矩（peak torque, PT）存在诸多挑战。本研究旨在探究手持测力仪（handheld dynamometer, HHD）相较于等速测力仪（isokinetic dynamometer, IKD）的结构效度，以及髋部运动中RTD与PT的评定者内重复信度及其二者间的关联。

方法
本研究纳入30名健康受试者（平均年龄30±8岁，男性13名），于单日完成两次测试。采用HHD与IKD分别测量髋屈曲、伸展、外展、内收、内旋及外旋动作下，归一化至体质量的RTD（0~50ms、0~100ms、0~150ms、0~200ms）与PT，测试动作均为最大自主等长收缩（maximal voluntary isometric contractions）。

结果
针对两种设备的效度分析显示，RTD0-50在所有髋部运动中展现出最大的显著系统偏差（3.41~11.99 N·m·s⁻¹·kg⁻¹）与最宽的一致性界限（limits-of-agreement），而RTD0-200的偏差最小（-1.33~3.99 N·m·s⁻¹·kg⁻¹）且一致性界限最窄。
针对PT，两种测力仪在髋屈曲（0.08 N·m·kg⁻¹）、外展（-0.09 N·m·kg⁻¹）、内旋（-0.01 N·m·kg⁻¹）及外旋（0.05 N·m·kg⁻¹）中表现出一致性。
针对信度分析，所有运动模式下，RTD0-50与RTD0-100的评定者内组内相关系数（intraclass correlation coefficient, ICC2,1）处于中等至良好水平（0.5~0.88），RTD0-150与RTD0-200则处于良好至优秀水平（0.87~0.95）。
HHD在所有运动模式下均展现出优秀的评定者内相对信度值（ICC2,1：0.85~0.95）。皮尔逊相关分析（Pearson’s correlation）显示，所有运动模式下PT与RTD0-150、RTD0-200均存在良好的线性相关（r=0.7~0.87，p<0.001）。

结论
效度分析结果表明，HHD与IKD在RTD测量中存在显著系统偏差且一致性不足。但HHD用于髋部运动的RTD与PT测量时，其评定者内相对信度可达到中等至优秀水平。临床医师可采用HHD开展髋部肌肉PT评估，但需注意：晚期阶段的RTD测量相较于早期阶段，具备更优的信度与效度，且与PT的关联更强。此外，本研究还探究了不同时间窗下RTD与PT的相关性，以进一步明晰二者间的关联机制。