Active vs. Passive – Intradialytic Pedaling Exercises Study

Although changes in serum electrolytes were not statistically significant in both exercises; however, these changes might be clinically important.

In the present study, performing the eight weeks of passive exercise resulted in an increase in URR and dialysis efficacy up to 1.36% and 11%, respectively. Although these changes were not significant, they can be important from clinical viewpoint. According to the Disease Outcomes Quality Initiative (DOQI) clinical guideline recommendations, the minimum acceptable dialysis efficacy should be 1.2 for patients undergoing hemodialysis (2).

The exercise programs in this study increased the dialysis efficacy to 1.43 and this is obviously higher than the minimum acceptable efficacy. Consistent with our results, Parsons et al. have reported that a 5-month intradialytic exercise program could increase the dialysis efficacy up to 11% at the end of the first month, which then increased to 19% at the end of the fifth month (1).

In another study, Mohseni et al. have reported that an eight-week intradialytic exercise program could increase the URR and dialysis efficacy about 11% and 38%, respectively (7). Fallahi et al. have also conducted an eight-week intradialytic exercise program on 14 patients and reported that although the URR and dialysis efficacy were increased, changes were not statistically significant (2).

It appears that intradialytic exercise increases the muscle-blood flow and opens the capillary surface area that consequently would increase the leak of urea from the tissue to the vascular compartment and finally enhances the serum urea clearance and improves the dialysis efficacy (1).

The present study showed that the passive exercise had better effects on dialysis efficacy than active exercise, especially at the end of the study. This finding may be attributed to the weakness of musculoskeletal system in these patients. Such weakness may resulted in intolerance of active exercise while passive exercise can be tolerated and resulted in better consequences in patients with ESRD undergoing chronic hemodialysis. The current study showed that passive intradialytic exercise had better effects on systolic and diastolic blood pressures than active exercise. This finding is consistent with results reported by Henrique et al. (11). McMurray et al. (9) and Fallahi et al. (2) who studied the effects of intradialytic exercise in patients under chronic hemodialysis. However, several studies could not confirm the positive effects of intradialytic exercise on blood pressure (9, 13).

In the present study, phosphorus levels were significantly lower than the baseline both at the end of the fourth and eighth weeks of active exercise.

The effect of active exercise on phosphorus level was in line with findings of the several previous studies (16, 17). Borzou et al. also reported that increasing the blood flow to 250 mL/min and then to 300 mL/min can be effective in clearance of phosphorus from the blood (5). It is suggested that more time or the severity of exercise is required to see a noticeable change in phosphorus levels (2).

The present study showed that passive exercise did not affect serum potassium level. However, serum potassium levels were decreased at the end of the fourth and eighth weeks of active exercise. Few studies have confirmed the effectiveness of exercise in the reduction of potassium level (16). However, some studies have shown that serum potassium levels did not significantly change after 12 weeks of intradialytic exercise (1). Although the dose of Eprex (erythropoietin) did not change during the study, the level of hemoglobin was increased after active and passive intradialytic exercise programs. This increase was up to 0.6 of µmol/L. In passive exercise.

Although this increase was not statistically significant, it is clinically valuable. Similar results were reported by Fallahi et al. (2). However, Parsons et al. have reported that hemoglobin level was decreased after exercise during dialysis (1).

It seems that intradialytic exercise can strengthen the effects of erythropoietin in patients with lower hemoglobin levels. Results of the present study indicated significant changes in patients’ QOL after intradialytic exercise. Although another studies have reported no significant difference between the QOL before and after intradialytic exercise (1, 15) a recent study reported that an intradialytic exercise program could significantly improve the QOL of dialysis patients in the areas of physical functioning, physical limitations, bodily pain and mental health (18). The present study showed that the active intradialytic exercise had positive effects on blood pressure.

The exercise program could also decrease the serum phosphorus and potassium levels and increase the hemoglobin, especially in active exercise. Also, the passive exercise had positive effects on blood pressure, dialysis efficacy and hemoglobin.

This study was conducted in one center and in a small sample size and the small sample size may affect not only on the statistical power of the results but also on the generalizability of the findings. Moreover, the exercise programs used in this study conducted in short duration and only in the first two hours of the dialysis. Then, replication of the same studies with larger sample size and longer periods are suggested.