MO395: Physical Function, Muscle Force Production and Physical Activity Levels In Peritoneal Dialysis Patients
Authors: Vaz Leal Diogo , Pereira Luciano , Inácio Mário , Cardoso Daniela , Viana João 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Chronic kidney disease (CKD) is a highly predominant worldwide disease, representing an enormous economic burden with profound social implications. In addition to frequent infections and mineral and bone disorders, CKD patients also experience exacerbated mobility deficits and severe skeletal muscle wasting, which further contributes to the development of co-morbidities and increased mortality. CKD patients suffering from end-stage renal disease often undergo dialysis treatment, such as peritoneal dialysis (PD), whose treatment-associated symptoms and physical fatigue have been reported to be less noticeable than in haemodialysis patients. In healthy individuals, there is substantial evidence to support the associations between reduced physical activity (PA) levels with a sedentary lifestyle and aggravated bone disorders and muscle wasting. It is conceivable that these associations become exacerbated in CKD patients. Hence, the present preliminary study aims to characterize PD patients in terms of their physical function, muscle force production and daily PA levels.

METHOD
A total of 18 CKD patients undergoing PD have volunteered to partake in this study (10 males, mean ± SD: age = 55 ± 11 years). Of these 15 have completed physical function testing (Timed Up and Go (TUG), Sit-to-Stand (STS) 5 and, STS 60s) and isometric handgrip strength assessment through handheld dynamometry. Isometric peak force (surrogate of maximum strength), rate of force development (RFD, surrogate of explosive muscle strength) and force-time root mean square (RMS, surrogate of muscle endurance) of the knee extensors, elbow flexors and hip flexors, were also assessed in 12 of these patients using a portable load cell. All participants used tri-axial accelerometers continuously for a week, that were used to estimate PA levels and the number of impacts (movements that expose an individual to accelerations of a certain magnitude). In total, 8 patients have completed all measurements.

RESULTS
PD patients were able to complete the TUG test in 6.6 ± 0.3s, the STS 5 in 10.8 ± 0.6s and stood 26.8 ± 1.8 times in the STS 60. Participants showed isometric peak forces of 272.9 ± 28.5N (handgrip), 92.6 ± 10.7N (elbow flexion), 93.0 ± 14.3N (hip flexion) and 137.0 ± 33.4N (knee extension). The RFD observed during elbow flexion, hip flexion and knee extension was 92.3 ± 15.3N/s, 104.3 ± 29.7N/s and 144.4 ± 43.4N/s, respectively. RMS of the elbow flexors, hip flexors and knee extensors was 68.8 ± 9.1, 64.7 ± 11.8 and 92.3 ± 21.7, respectively. The accelerometers were used for 7.2 ± 0.2 days (15.7 ± 0.7 h/day) and showed that 94.3 ± 2.8% of impacts experienced by participants were under 0.5 g (over 640 000 impact loadings/day), 0.8 ± 0.3% of observed impacts were between 0.5–1g (&gt;5800 daily impacts), the impact loadings between 1–1.5g accounted for 0.11 ± 0.01% of impact loadings (731 ± 349 impacts/day) and 0.03 ± 0.01% of impact loadings (155 ± 62 impacts/day) were ˃ 1.5g. Participants spent 646.2 ± 59.2 min/day in sedentary behaviour (73.2 ± 3.7% of time), 210.2 ± 30.2 min/day in light PA (25.6 ± 3.5% of time), 7.9 ± 1.9 min/day in moderate PA (1.0 ± 0.2% of time) and just 1.8 ± 1.8 min/day in vigorous PA (0.2 ± 0.2% of time). Lastly, hip flexion peak force and force-time curve RMS were significantly associated with the number of repetitions completed during the STS 60 (r = 0.85 and r = 0.91 respectively, P &lt; 0.05).

CONCLUSION
Although CKD patients undergoing PD showed apparently healthy physical function, the muscle force production values tend to be on the lower end compared to existing literature. Nonetheless, those with stronger hip flexors had better results in the STS 60 test. It is possible that the disproportionate amount of time spent in sedentary behaviour and low-intensity PA and the very limited exposure to moderate and vigorous impact loadings may be responsible, at least in part, for these exacerbated deficits.
FUNDING: Portuguese Foundation of Science and Technology (UID/04045/2020).