Discussion
intradialytic exercise, intradialytic, HD
This study showed that intradialytic exercise for 6 months improved subsequent survival in adult patients receiving HD for 12 months. Furthermore, compared with controls, intradialytic exercise caused potentially beneficial improvements in selected laboratory parameters (serum albumin, hemoglobin, red blood cell count, serum calcium, serum PTH, serum phosphorus), physical function (6MWT) and nutritional status (GNRI) during the 6-month intervention period.The finding of a survival benefit from intradialytic exercise is in keeping that of with previous observational studies investigating the association between increased physical activity and survival in patients receiving dialysis [The mechanisms underpinning the improved survival of patients performing intradialytic exercise for 6 months may be explained by improvements in a number of factors associated with physical exercise including bone mineral metabolism [A major strength of the present study was the fact that all exercises were tailored according to each individual's functional status within a pre-specified structure. There was also a high participation rate, such that included HD patients exhibited considerable diversity with respect to demographic characteristics and associated comorbidities. The study also evaluated a range of biochemical and functional parameters. The intervention was designed so that it was broadly implementable in most HD centers, including in low resource settings.Balanced against these strengths, the study also had a number of limitations. The duration of the intradialytic exercise intervention was short (6 months), as was the subsequent follow-up (12 months), meaning that the long-term effects of exercise on patient survival remain uncertain. The small sample size led to an imprecise estimate of the effect of exercise on patient survival. Survival was timed from the end of the intervention, which introduced immortal time bias. Secondary outcome measures exploring the effects of intradialytic exercise and patient survival were only examined during the first 6 months of the study.