Publications

Introduction: Patients with chronic kidney disease (CKD) have reduced physical functioning partially caused by reductions in muscle mass but also quality (Wilkinson et al. 2018). Considered an important criterion of muscle function (Gervasi et al. 2017), viscoelastic characteristics (tone, elasticity, and stiffness) describe the mechanical properties of skeletal muscles at rest (Aird et al. 2012). For the first time, we present preliminary data on these characteristics in skeletal muscle of patients with non-dialysis CKD.

Methods: The viscoelastic characteristics (tone, elasticity, and stiffness) of 9 patients with non-dialysis dependent CKD [mean age: 66.0 (±13.1) years, 44% females, eGFR: 23.0 (±12.3) ml/min/1.73m2] were assessed using a MyotonPRO device (Figure 1). The measurements were made in the non-dominant rectus femoris muscle at rest by positioning the device’s 3mm probe perpendicular to the skin over the muscle (0.18 N preloading). The device applied ten brief (15 m/s) low force (0.4 N) mechanical impulses, inducing damped natural oscillations of the underlying tissues which are recorded by an accelerometer connected to a friction measurement mechanism. The device then calculated the resting tone parameters [frequency of oscillation (Hz)], elasticity of weak oscillations [logarithmic decrement (arbitrary units, AU)], and stiffness (N/m). To assess the relationship with muscle function, patients completed a 4m gait speed test (m/s) and the ‘Timed-Up-and-Go’ (secs).

Results: The mean frequency (tone) was 13.1 (±2.5) Hz, decrement (elasticity) 2.0 (±0.3) AU, and stiffness 258.22 (±43.2) N/m. Viscoelastic characteristics were not associated with age, sex, or renal function. Greater decrement (poor elasticity) was significantly associated with slower gait speed (r = -.725, P = .027) and TUG (r = -.701, P = .036) (Figure 2).

Whilst frequency and stiffness values appear consistent with norm reported data, elasticity was greater than that reported in older individuals (~72 years) (Aird et al. 2012). Decreased muscle elasticity brings on easier fatigability and limited speed of movement (Chaung et al. 2012). In support, we found only greater decrement (and thus poorer muscle elasticity) was associated with poor physical function. The MyotonPRO provides a novel simple means to collect in-vivo assessment of muscular viscoelastic characteristics in CKD patients.