Objectives Patients with chronic kidney disease (CKD) have aberrant changes in body composition, including low skeletal muscle mass, a feature of “sarcopenia.” The measurement of the (quadriceps) rectus femoris (RF) cross‐sectional area (CSA) is widely used as a marker of muscle size. Cutoff values are needed to help discriminate the condition of an individual's muscle (eg, presence of sarcopenia) quickly and accurately. This could help distinguish those at greater risk and aid in targeted treatment programs. Methods Transverse images of the RF were obtained by B‐mode 2‐dimensional ultrasound imaging. Sarcopenic levels of muscle mass were defined by established criteria (1, appendicular skeletal muscle mass [ASM]; 2, ASM/height2; and 3, ASM/body mass index) based on the ASM and total muscle mass measured by a bioelectrical impedance analysis. The discriminative power of RF‐CSA was assessed by receiver operating characteristic curves, and optimal cutoffs were determined by the maximum Youden index (J). Results One hundred thirteen patients with CKD (mean age [SD], 62.0 [14.1] years; 48% male; estimated glomerular filtration rate, 38.0 [21.5] mL/min/1.73m2) were included. The RF‐CSA was a moderate predictor of ASM (R2 = 0.426; P < .001) and total muscle mass (R2 = 0.438; P < .001). With a maximum J of 0.47, in male patients, an RF‐CSA cutoff of less than 8.9 cm2 was deemed an appropriate cutoff for detecting sarcopenic muscle mass. In female patients, an RF‐CSA cutoff of less than 5.7 cm2 was calculated on the basis of ASM/height2 (J = 0.71). Conclusions Ultrasound may provide a low‐cost and simple means to diagnose sarcopenia in patients with CKD. This would allow for early management and timely intervention to help mitigate the effects in this group.

Measuring physical activity in CKD4 Background The majority of patients with chronic kidney disease (CKD) are physically inactive. Simple yet accurate assessment of physical activity is important in identifying those in need of intervention. The 'General Practice Physical Activity Questionnaire' (GPPAQ) is a well-used clinical and research tool, but has not been validated.Methods Forty individuals with CKD (age 62.5 (SD: 11.1) years, eGFR 33.2 (SD:19.1) ml/min/1.73m 2 ) completed the GPPAQ and objective physical activity was measured using a GENEActiv accelerometer for 7 days. Physical activity status was grouped as 'Active' (i.e. meeting current physical activity UK guidelines) or 'Inactive'. Sensitivity and specificity were calculated. Accuracy was defined as the probability the GPPAQ could correctly classify a patient as either 'Active' or 'Inactive' (based on accelerometery). ResultsUsing accelerometery, 18% of participants met the current UK guidelines, whereas 27% were classed as 'Active' according to GPPAQ. Sensitivity of the GPPAQ was 54.6% and specificity was 96.6%. The 'accuracy' of the GPPAQ was 85.0%. The accuracy of the GPPAQ was marginally greater in males and those not in employment/retired, although these differences were not statistically significant. ConclusionsThe GPPAQ may be a useful tool to identify CKD patients who would benefit most from a physical activity intervention. In particular, the GPPAQ can accurately identify those not sufficiently active.

Introduction: Chronic kidney disease (CKD) is characterized by adverse physical function. Mechanical muscle power describes the product of muscular force and velocity of contraction. In CKD, the role of mechanical muscle power is poorly understood and often overlooked as a target in rehabilitation. The aims of this study were to investigate the association of mechanical power with the ability to complete activities of daily living and physical performance. Method: Mechanical muscle power was estimated using the sit-to-stand-5 test. Legs lean mass was derived using bioelectrical impedance analysis. Physical performance was assessed using gait speed and 'timed-up-and-go' (TUAG) tests. Self-reported activities of daily living (ADLs) were assessed via the Duke Activity Status Index. Balance and postural stability (postural sway and velocity) was assessed using a FysioMeter. Sex-specific tertiles were used to determine low levels of power.Results: One hundred and two non-dialysis CKD participants were included (age: 62.0 (±14.1) years, n = 49 males (48%), eGFR: 38.0 (±21.5) ml/min/1.73m 2 ). The mean relative power was 3.1 (±1.5) W/kg in females and 3.3 (±1.3) W/kg in males. Low relative power was found in 34% of patients. Relative power was an independent predictor of ADLs (β = .413, p = .004), and TUAG (β = À.719, p < .001) and gait speed (β = .404, p = .003) performance. Skeletal muscle mass was not associated with any outcomes. Conclusion:Knowledge of the factors that mediate physical function impairment is crucial for developing effective interventions. Incorporation of power-based training focusing primarily on movement velocity may present the best strategy for improving physical function in CKD, above those that focus on increasing muscle mass.

Background and Aims Individuals living with CKD are characterised by adverse changes in physical function. Knowledge of the factors that mediate impairments in physical functioning is crucial for developing effective interventions that preserve mobility and future independence. Mechanical muscle power describes the rate of performing work and is the product of muscular force and velocity of contraction. Muscle power has been shown to have stronger associations with functional limitations and mortality than sarcopenia in older adults. In CKD, the role of mechanical muscle power is poorly understood and is overlooked as a target in many rehabilitation programmes, often at the expense of muscle mass or strength. The aims of this study were to 1) explore the prevalence of low absolute mechanical power, low relative mechanical power, and low specific mechanical power in CKD; and 2) investigate the association of mechanical power with the ability to complete activities of daily living and physical performance. Method Mechanical muscle power (relative, allometric, specific) was calculated using the sit-to-stand-5 (STS5) test as per previously validated equations. Legs lean mass was derived from regional analyses conducted using bioelectrical impedance analysis (BIA). Physical performance was assessed using two objective tests: usual gait speed and the ‘time-up-and-go’ (TUAG) test. Self-reported activities of daily living (ADLs) were assessed via the Duke Activity Status Index (DASI). Balance and postural stability (postural sway and velocity) was assessed using a FysioMeter. Sex-specific tertiles were used to determine low, medium and high levels of relative STS power and its main components. Results 102 participants with non-dialysis CKD were included (mean age: 62.0 (±14.1) years, n=49 males (48%), mean eGFR: 38.0 (±21.5) ml.min.1.73m2). The mean estimated relative power was 3.1 (±1.5) W.kg in females and 3.3 (±1.3) W.kg in males. Low relative power was found in 35/102 (34%) patients. Relative power was a significant independent predictor of self-reported ADLs (via the DASI) (B=.413, P=.004), and performance on the TUAG (B=-.719, P&lt;.001) and gait speed (B=.404, P=.003) tests. Skeletal muscle mass was not associated with the DASI or any of the objective function tests Conclusion Patients presenting with low muscle power would benefit from participation in appropriate interventions designed to improve the physiological components accounting for low relative muscle power. Assessment of power can be used to tailor renal rehabilitation programmes as shown in Figure 1. Incorporation of power-based training, a novel type of strength training, designed by manipulating traditional strength training variables and primarily movement velocity and training intensity may present the best strategy for improving physical function in CKD.