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July 2019

Reliability of a portable device for quantifying tone and stiffness of quadriceps femoris and patellar tendon at different knee flexion angles

Guoqian Chen, Jiatao Wu, Guocai Chen, Yanyan Lu, Wei Ren, Wu Xu, Xuemeng Xu, Zugui Wu, Yingxin Guan, Yi Zheng, Bofan Qiu
Fifth Clinical Medical School, Guangzhou University of Chinese Medicine; Guangdong Second Traditional Chinese Medicine Hospital; Orthopedics Department, Guangdong Second Traditional Chinese Medicine Hospital - Guangzhou, Guangdong, China
PLOS ONE - July 31, 2019, 14/7 (DOI: 10.1371/journal.pone.0220521)

The reliability of MyotonPRO that can monitor the mechanical properties of tissues is still unclear. This study aimed to analyze the within-day inter-operator and between-day intraoperator reliability of MyotonPRO for assessing tone and stiffness of quadriceps femoris and patellar tendon at different knee angles. The tone and stiffness of healthy participants (15 males and 15 females, aged 24.7±1.6 years) in the supine and resting position were measured using the MyotonPRO device.

The measurements were quantified at 0˚, 30˚, 60˚, and 90˚ of knee flexion. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable change (MDC) were calculated and a Bland–Altman analysis was conducted to estimate reliability.

The results indicated excellent interoperator reliability (ICC > 0.78) and good to excellent intra-operator reliability (ICC > 0.41). The inter-operator SEM measurements ranged between 0.1–0.9 Hz and 3.8–37.9 N/m, and intra-operator SEM ranged between 0.5–1.3 Hz and 7.9–52.0 N/m. The inter-operator MDC ranged between 0.3–2.5 Hz and 10.5–105.1 N/m, and intra-operator SEM ranged between 1.1–3.3 Hz and 21.9–144.1 N/m. The agreement of inter-operator was better than that of intra-operator. The study concluded that MyotonPRO is a reliable device to detect the tone and stiffness of quadriceps femoris and patellar tendon.

In conclusion, our study established the tone and stiffness values of quadriceps femoris (RF, VM, VL) and PT in healthy humans at different knee angles using MyotonPRO. The present study also suggested that the MyotonPRO is an acceptable device for the detection of tone and stiffness of quadriceps femoris and PT. The device will be useful for studying the mechanical properties of muscles and tendons, such as training, disease, growth, and aging.

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