Table 3.

Assessments of physical function.

Assessments	Description	Thresholds	Limitations
Muscle strength
Knee Extension Strength (Isometric or Isokinetic)	Quadriceps strength measured by isometric or isokinetic methods. Using hand-held or isokinetic dynamometer.	· Predictor of slow gait speed81 Isometric: Men < 154.6N-m  Women < 89.8N-m Isokinetic: Men < 94.5N-m  Women < 62.3N-m · Higher risk of mortality in HD patients66) Isometric: < 0.4kgf/kg	Requires equipment (isokinetic dynamometer) that is expensive
Handgrip strength	Upper limb muscle strength Measure the grip strength using hand dynamometer	· Sarcopenia definition Europe8): men < 27kg, women < 16kg Asia82): men < 28kg, women < 18kg	Required hand dynamometer
5-chair stand	Lower limb strength test. Patients seated the chair with arms folded cross their chest, then sit to stand five times as fast as possible.	· Sarcopenia definition Europe8): >15sec Asia82): ≥12sec · Predictor of multiple falls: ≥ 12sec83)	Difficult to measure the objective value among patients with very low physical function
Gait ability
Gait speed	The time one tasks to walk specified distance (3–10m) on level surface at usual or maximum pace. Gait speed = distance/time (m/s)	· Sarcopenia definition Usual gait speed Europe8): ≤ 0.8m/sec Asia82): ≤ 1.0m/sec · Higher risk of cardio-cerebrovascular events in HD patients62. Maximum gait speed: men: < 1.48 m/sec women: < 1.42 m/sec	Unable to measure among gait dependent patients
Balance function
One-leg stand	Static balance test. Maintain single-leg standing balance with eye opened as long as possible.	· Predictor of injurious falls: < 5 sec84)	Difficult to measure the objective value among patients with very low physical function. Risk of fall during the examination
Timed Up and Go test	Dynamic balance test. Starts in a seated position, stands up and walks 3-meters, turn around, walks back to the chair and sit down.	· Sarcopenia definition Europe8): ≥ 20sec · Predictor of falls85: > 13.5sec	Unable to measure among patients with difficulty with gait Risk of fall during the examination
Berg Balance Scale	14-items balance scale (e.g. sitting to standing, standing balance, etc.) Score 0–54 points Higher score indicates better balance function	· Predictor of falls86: ≤ 49 points	More complicated than other test (time required approximately 20min)
Muscle mass
Bioelectrical impedance analysis (BIA)	Method for predicting body composition based on whole-body electrical conductivity.	· Sarcopenia definition ASM predicted by BIA Europe8): men < 27kg  women <15kg ASM/height2 Europe8): men < 7.0kg/m2  women < 5.5kg/m2 Asia82): men < 7.0kg/m2  women < 5.7kg/m2	Required equipment (Although it is more affordable and portable than DXA) Influenced by the hydration status of the patients
Dual-energy X-ray absorptiometry (DXA)	Method for measuring body composition such as fat tissue, muscle mass and bone density using the X-ray.	· Sarcopenia definition ASM measured by DXA Europe8: men < 27kg  women <15kg ASM/height2 Europe8: men < 7.0kg/m2  women < 5.5kg/m2 Asia82: men < 7.0kg/m2  women < 5.4kg/m2	Required equipment (expensive and not portable) Influenced by the hydration status of the patients Radiation exposure (extremely small)
Mid-arm muscle circumference (MAMC)	The method measured surrogate of lean body mass. MAMC (cm) = mid-arm circumference (cm) − 3.142 × triceps skinfold (cm)	· Indicator of low muscle mass87 MAMC: men < 21.1cm women < 19.9cm	Requires sophisticated techniques for measuring Influenced by the patients’ volume status and edema
Calf circumstances (CC)	The method measured surrogate of lean body mass. Measured at the point of greatest circumference of calf.	· Sarcopenia definition CC Asia82: men < 34cm  women < 33 cm · Predictor of low physical performance88 < 31cm	Requires sophisticated techniques for measuring Influenced by the patients’ volume status and edema
Creatinine index (CI)	CI is a surrogate of lean body mass derived from pre-dialysis serum creatinine and Kt/v for urea in HD patients. Original CI calculated complex mathematical formula. Therefore, modified CI that simplified formula89) as below is used in recent years. Modified CI (mg/kg/day) = 16.21+1.12×[1 if men; 0 if women]−0.06×age (years)−0.08×single pool Kt/Vurea+0.009×serum creatinine before dialysis(μmol/L)	· Higher risk of mortality in HD patients90 Modified CI : men < 22.13 mg/kg/day women < 19.43 mg/kg/day · Higher risk for bone fracture in HD patients91 Modified CI : men < 21.01 mg/kg/day women < 19.43 mg/kg/day	Standard value of CI indicates low muscle mass is not clear
Exercise capacity
Cardiopulmonary Exercise testing (CPX, CPET or CPEX)	Measure the exercise capacity, cardiac reaction and endurance using the ventilatory gas analysis The cardiorespiratory indicator such as peak VO2, anaerobic threshold, and metabolic equivalents [MET(s)] are used for detailed exercise prescription. 1MET = VO2 of 3.5ml/kg/min	· Higher risk of mortality92 Peak exercise capacity < 5 METs	Requires expensive equipment and well-trained physician
6-minute walk distabce/test (6MWD/6MWT)	Measure the distance that patients can walk in a period of 6 minutes. Longer distance indicates better aerobic capacity and endurance.	· Higher risk of mortality in pre-dialysis patients51 6MWT < 350m	Requires the gait course Unable to measure the objective time among patients with difficulty to gait
400-meter walk test	Measures the walk time to complete 400m Less time indicates better aerobic capacity and endurance.	· Sarcopenia definition Europe8: 400m walk ≥ 6min or Non-completion	Requires the gait course Unable to measure the objective time among patients with difficulty with gait
General physical performance
Short Physical Performance Battery (SPPB)	3-items performance test (Balance, Gait, and 5-times chair stand test) Score 0–12 points Higher score indicates high physical performance	· Sarcopenia definition SPPB score Europe8: ≤ 8 Asia82: ≤ 9 · Higher risk of mortality93) SPPB <10	Ceiling effect in community-dwelling adults
SARC-F	5-items questionnaire (Strength, Assistance in walking, Rise from a chair, Climb stairs, Falls) Score 0–10 points Higher score indicates low physical performance	· Probable Sarcopenia SARC-F score ≥ 482,94	Subjective data Poor sensitivity for confirming sarcopenia
SARC-CalF	5-items questionnaire (SARC-F) + Calf circumference (Add 10 points if it is below the circumference cut-off) Score 0–20 points Higher score indicates low physical performance	· Probable Sarcopenia SARC-Calf score ≥ 118	Influenced by the patients volume overload and edema