Discussion
CKD, chronic kidney disease, CKD-MBD, bone loss, HD, fracture, bone mineral disorders, bone disorder, intradialytic, renal insufficiency, intradialytic exercise
HIGH TURNOVER BONE DISEASE, BONE LOSS, METABOLIC BONE DISEASE, LIVER DISEASE, COMPLICATION, BONE DISORDER, SECONDARY, RENAL HYPERPARATHYROIDISM, RENAL INSUFFICIENCY
The purpose of this study was to examine the effects of intradialytic exercise on calcium, phosphorous and parathyroid hormone. Our primary findings showed that the 6-month intradialytic concurrent exercise program was effective in improving PTH levels, reducing serum phosphorous and improving serum calcium and calcium-phosphorous product as well. However, contradictory results have been reported by some other studies.Previous work showed that exercise decreased plasma PTH levels in CKD patients [In the present study, phosphorus levels in the intervention group were significantly reduced to lower than the baseline. The effect of exercise on phosphorus level was in line with findings of the several previous studies [Reviewing the limited available research on the effects of exercise in reducing phosphorus levels showed that although exercise often decreases the level of phosphorus, longer-term exercise and perhaps more intense exercise might be required to see reductions in some studies [This study revealed that serum calcium levels showed significant change in the intervention group, but some other researchers failed to show any influence of exercise on serum calcium [Renal hyperparathyroidism is a common complication of chronic kidney disease characterized by elevated PTH levels secondary to derangements in the homeostasis of calcium, phosphate, and vitamin D [Abnormalities in calcium, phosphorous, and PTH, hallmarks of the condition known as chronic kidney disease – mineral and bone disorder (CKD-MBD) [Cardoso et al. in their systemic review found evidence supporting a positive relation between physical activity and bone outcomes in patients with CKD [The present study demonstrated that ALP levels significantly decreased in exercise group, but controls showed no similar change.Previous observational studies on dialysis patients revealed a relationship between physical activity and serum levels of ALP due to the fact that energy expenditure has a strong relationship to the total BMD [The study by Gomes et al. and the other one by Elshinnawy et al. showed there was significant increase in ALP levels following exercise in patients with CKD [One of the reasons for the contradiction in ALP changes with the previous studies is that in those studies, the ALP level of the patients was within the normal range before the intervention, and the intervention has somehow improved the condition. However, in the current study, the ALP level of the patients was much higher than normal, and exercise has been able to have a significant positive effect on improving the patients' condition by reducing the ALP level.ALP is an enzyme measurable in most body fluids and usually originates from the liver or bone. In CKD patients without liver disease, ALP is a surrogate of high turnover bone disease and is used to monitor the metabolic bone disease associated with renal insufficiency [Bones are subjected to two sources of loading, including ground reaction force and muscular force [High proinflammatory cytokine levels may contribute to bone loss and fracture in patients with CKD [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, despite including HD patients that exhibit considerable diversity with respect to demographic characteristics and associated comorbidities. It is also important to recognize that by the end of the study, levels of calcium, phosphorus and parathyroid hormone in the intervention group reached the level recommended by KDOQI guidelines [This discrepancy between the results of the present study and the findings of the above-mentioned studies may be attributed to differences in participants’ age and sex or duration, intensity, and type of exercise program. In particular, the duration of our intervention was longer than much of what is in the intradialytic exercise literature. Moreover, the intradialytic intervention included both endurance and resistance training components, as opposed to most other studies was performed as concurrent exercise which was different from other studies that include only resistance or aerobic exercise.Balanced against these strengths, the study also had a number of limitations. Not measuring the effect of exercise on bone mass and cardiovascular indexes are limitations of this study. Indeed, not measuring bone mineral density in this work is a limitation as bone strength depends on bone quality and quantity. Future work should focus on observing and comparing the effect of different types of exercise on bone mineral disorders and all-cause mortality in HD patients.