Effect of Pre- and Post-Dialysis Exercise on Functional Capacity Using Portable Ergometer in Chronic Kidney Disease Patients
Article information
Abstract
Objective
To assess whether performing exercises during hemodialysis reduces the risk of developing intradialytic hypotension and enhances exercise capacity in patients with chronic kidney disease.
Methods
This study included patients aged ≥18 years undergoing hemodialysis. Participants performed exercises using a portable lower extremity ergometer during hemodialysis sessions for 3 weeks. Data regarding walking distance, knee strength, quality of life, fat-free mass, arterial pressure, blood pressure, heart rate, frequency of intradialytic hypotension, fatigue, and duration of hemodialysis were collected and analyzed.
Results
Significant improvements in walking distance and knee strength were observed following the implementation of exercise training during hemodialysis. Although there was no significant reduction in the frequency of intradialytic hypotension, a decreasing trend was noted. Other parameters such as quality of life and fatigue did not show significant changes.
Conclusion
Using a portable ergometer during hemodialysis improved exercise capacity and knee strength in patients with chronic kidney disease. There was a trend toward reduced intradialytic hypotension, suggesting potential cardiovascular benefits. Further research with larger sample sizes is needed to confirm these findings.
INTRODUCTION
A reduction in functional ability and quality of life has been observed in patients with chronic kidney disease (CKD) [1,2]. Symptoms associated with CKD, such as nausea, dizziness, and cramps, can adversely affect the quality of life and the ability to tolerate hemodialysis (HD) [3]. Intradialytic hypotension (IDH), which occurs owing to the elimination of plasma fluid via ultrafiltration (UF) exceeding the rate of fluid replenishment, has often been observed in patients undergoing HD [4].
Various strategies, such as accurate dry weight assessment, minimizing excessive weight gain between HD sessions, fasting during HD sessions, appropriate adjustment of antihypertensive agents, sodium and UF profiling, cooling the dialysate, using dialysate with bicarbonate buffering or higher calcium concentration, administration of α1-adrenergic agonists, and convective treatments (hemofiltration and hemodiafiltration) have been implemented for the prevention and management of IDH [5-8]. Karmiel [9] reported that cycling exercises performed during HD led to an improvement in energy levels; supported cardiovascular health, muscle strength, and endurance; and a reduction in fatigue after HD sessions. Gołębiowski et al. [10] evaluated the stability of a bicycle-type lower extremity rehabilitation device, and used it to enhance the lower limb function of patients undergoing HD. Anding et al. [11] reported that exercise training during HD could enhance physical function and muscle mass, and improve cardiovascular risk factors, such as blood pressure (BP) and lipid profiles. Previous studies [2,12] have also reported an improvement in mood and overall quality of life following exercise training, in addition to a reduction in feelings of hostility and anxiety.
Many patients continue to face difficulties during treatment owing to the side effects associated with HD treatment, which often persist post-treatment and impact their daily lives, despite the advancements in HD technology. Prevention of these side effects plays a crucial role in ensuring patient compliance, avoiding early treatment termination, and maintaining the efficiency and effectiveness of HD. Frequent incidence of hypotension has been reported in previous studies involving exercise with an ergometer in a seated position, which makes receiving treatment for IDH challenging.
Considering these challenges and the potential for improvement, the primary aim of this study was to assess whether a 3-week exercise program for patients with CKD undergoing regular HD sessions could enhance walking ability as measured using the 6-minute walk distance (6-MWD), improve physical function, and reduce the frequency of IDH during dialysis.
METHODS
Participants
Patients with CKD aged 20–85 years who were undergoing HD at least twice a week between October 2017 to February 2022 were eligible for inclusion in this study. The eligibility criteria were as follows: age ≥18 years, having undergone HD for ≥3 consecutive months, having been undergoing ≥3 HD sessions per week, having at least one non-prosthetic lower limb, ability to walk (with the use of walking aids if necessary), and ability to provide informed consent. Only patients who had not received ergometer treatment previously were included in this study to maintain the integrity of blinding. By including only ergometer-naive patients, the study could better assess the true effects of the exercise intervention without the influence of previous exposure. All participants were evaluated for eligibility based on these criteria.
The exclusion criteria were as follows: having severe untreated cardiovascular diseases, being deemed medically unfit for participation in the clinical trial (e.g., unstable angina, recent myocardial infarction within the past 3 months, uncontrolled hypertension, or any condition that poses a high-risk during exercise), having significant cognitive impairments that hindered adherence to the examiner’s instructions, and undergoing lower limb amputations. Furthermore, patients admitted to the hospital for reasons unrelated to the study (e.g., treatment for other acute medical conditions, elective surgeries, or complications from unrelated chronic diseases), as well as those presenting with hypertensive crisis (characterized by systolic BP [SBP] of >180 mmHg or diastolic BP [DBP] of >120 mmHg) [13] or other unfavorable events during the treatment phase, were excluded from the study. This study was approved by the Institutional Review Board of Jeonbuk National University Hospital (CUH 2017-03-021); CRIS number (KCT0002537). Informed consent was obtained from all participants prior to commencing the study.
Sample-size calculation
The hypothesis used to determine the sample size for this study is based on results from previous studies and is defined as follows: The null hypothesis H₀ states that the pre-exercise 6-minute walk test score (μpre) is equal to the post-exercise score (μpost), versus the alternative hypothesis H1 which states that μpre is not equal to μpost. To achieve a 5% significance level and 90% power, the sample size calculation is based on a formula that incorporates a dropout rate of 20%. In previous studies involving similar exercise interventions in kidney dialysis patients, the baseline pre-exercise 6-minute walk test score was 360±132 [11]. If a 10% improvement is clinically significant, the difference score was set at 36, and the standard deviation of the mean change was set at 133. The calculated sample size is 15 participants; considering a 20% dropout rate, the total required sample size is 19 participants (as indicated in the RESULTS section).
Study design
Overview
This study used a pre-post-test crossover single-group design and included 20 participants in the experimental group. It was divided into three phases: Periods (P) 1, 2, and 3 (Fig. 1). HD was conducted for 3 weeks without any additional interventions other than the routine medications administered during each period. The study periods were defined as follows. HD P1, P2, and P3 each included a total of 9 sessions, making a total of 27 HD sessions, conducted consecutively within each participant’s dialysis cycle, excluding Saturdays and Sundays (HD1–9 for P1, HD10–18 for P2, and HD19–27 for P3). The study was conducted from October 2017 to February 2022.
Flow chart of the study protocol. HD, hemodialysis.
Screening
During the screening period of the study, participants visited the clinical research facility, where they were provided with detailed explanations of the study. After understanding the study, the participants voluntarily signed written consent forms to participate. The information of age, sex, duration of dialysis, cause of CKD, and laboratory findings related to kidney function was gathered. Participants could withdraw from the clinical study at any time at their own discretion or upon the investigator's decision. Conditions for withdrawal or dropout included the participant no longer wishing to participate, developing a condition or meeting an exclusion criterion that necessitated withdrawal, experiencing adverse effects deemed detrimental to their health, or failing to adhere to scheduled visits and becoming lost to follow-up. Adverse events were defined as any undesirable experience associated with the use of the ergometer, including but not limited to mild dizziness, fatigue, and back pain during dialysis. The withdrawal was managed according to the established criteria, ensuring the integrity and safety of the study.
Study device and intervention
A portable lower extremity exercise device (Q Health PUL; Cybermedic) (Fig. 2) designed to enhance muscle strength and facilitate joint movement recovery was used in this study. A key advantage of this device is that it can be used while the patient is in the supine position on the bed during HD. The device has two modes, passive and active, which can be selected using the mode button. The default mode is the passive mode, which is especially beneficial for patients with difficulty operating the device independently. The main power switch activates the device and initializes the system. The motor does not run automatically upon pressing the start button. However, resistance is generated when a load is applied to the motor, enabling the patient to perform strength exercises based on controlled resistance. The device’s resistance can be adjusted from levels 1 to 20 during strength training.
Image of the study device in action.
Intervention protocol
Detailed information on the criteria and extent of the intervention is provided. The passive mode was administered to patients unable to actively participate in the exercises. While the degree of assistance provided by the device in this mode was standardized, specific details on the revolutions per minute (rpm) and the level of assistance were customized based on the patient’s initial assessment. The active mode was for patients able to participate actively, resistance levels were individually determined, ranging from level 1 to 20, depending on the patient’s capabilities and progress. Exercise intensity was individualized based on target heart rate (HR) and target rate of perceived exertion (RPE). Exercise intensity was included setting specific target HR and RPE for each patient to ensure exercises were tailored to their fitness levels. Exercise duration, frequency, and progression were also individualized to optimize outcomes. Regular assessments were conducted to modify resistance levels as needed, ensuring a gradual increase in exercise intensity. The rpm in both passive and active modes was monitored and adjusted to ensure safety and effectiveness. Exact rpm values were recorded and modified based on patient tolerance and feedback. By providing these detailed criteria and individualization methods, this study ensures that the exercise intervention can be effectively replicated and tailored for dialysis patients.
Intervention and evaluation
During the initial 3-week phase (P1), participants received standard HD without adjunctive exercise modalities. Hemodynamic indicators, including mean arterial pressure (MAP), SBP, HR, and the presence of IDH-related symptoms and fatigue, were systematically monitored at 30-minute intervals during three weekly HD treatments. IDH was defined as an intradialytic decrease of >20 mmHg in SBP to a level <90 mmHg compared to the baseline BP [14]. When IDH episodes occurred, patients were asked about symptoms like abdominal discomfort, nausea, vomiting, muscle cramps, fatigue, dizziness, and anxiety. The frequency of these symptoms was documented.
During the subsequent 3-week phase (P2), patients exercised in the supine position using a portable ergometer while undergoing HD. The exercise regimen involved 60 minutes of activity during each HD session, split into two segments: 30 minutes at the beginning and another 30 minutes towards the end of the HD session. The exercise intensity for each patient was conducted in passive mode, with speeds ranging from 20 to 25 rpm. For patients unable to perform the exercise actively, the passive mode was utilized, ensuring the exercise was maintained at speeds between 20 and 25 rpm. Most patients performed the exercise at 25 rpm. However, if a patient had low compliance with the intervention, the intervention dose was reduced to 20 rpm. The same parameters, such as MAP, HR, presence of IDH-related symptoms, and fatigue, were measured every 30 minutes during HD.
Throughout the final 3-week phase (P3), patients reverted to standard HD without exercise. The same parameters, such as MAP, HR, the presence of IDH-related symptoms, and fatigue, were measured every 30 minutes during HD, as in P1. Evaluations (E) were conducted two weeks prior to the start of each phase. By comparing these periods, the study assessed the impact of the exercise intervention on hemodynamic stability and the presence of IDH-related symptoms and fatigue. For detailed evaluation timing and processes, refer to Fig. 1.
Assessments
Outcome assessments, including measurement of exercise capacity, such as the 6-MWD, knee extensor strength, fat-free mass (FFM), and the Kidney Disease Quality of Life (KDQOL) questionnaires, were conducted once before each of P1, P2, and P3 (E1, E2, and E3). BP measurements were consistently taken from the brachial artery using either a mercury or aneroid sphygmomanometer to ensure consistency [15].
Primary outcome: 6-MWD
The primary outcome was the 6-MWD [16], which measures a patient’s ability to walk within a 6-minute timeframe and assess their exercise capacity. Participants were instructed to walk from one end of a 30-m hallway to the other, covering the maximum distance possible at their own pace within the allotted 6 minutes. The total distance walked during this time was recorded to assess their functional exercise capacity. They were also instructed to report whether they experienced dyspnea, chest pain, or leg pain while walking. This measurement was taken before and after the HD sessions to evaluate the participants’ walking endurance at E1, E2, and E3.
Secondary outcomes: cardiovascular parameters (MAP, BP, HR), frequency of IDH, fatigue, KDQOL, knee extensor strength, FFM
The secondary outcomes focused on cardiovascular parameters, all of which were recorded during the HD sessions. MAP was determined using the following equation:
Both SBP and DBP were measured, along with HR during the HD sessions. In this study, we documented each occurrence of IDH during the same HD session and measured the frequency of IDH events in each participant. Additionally, we monitored the frequency of IDH and assessed patient fatigue using a visual analogue scale (VAS) [18], along with recording the duration of each HD session. Additional demographic and clinical data were collected separately, including patient age, sex, underlying medical conditions, and mean dialysis duration. The KDQOL-Short Form [19,20], an essential tool used to evaluate the quality of life of patients with kidney disease, comprises two components: the physical component summary (PCS) and mental component summary (MCS). The PCS and MCS assess the impact of kidney disease on the physical and mental health of a patient, respectively. The handheld dynamometer (Newton, N) was used to assess the thigh muscle strength. The evaluation method for knee extensor strength (N) involved using a dynamometer to measure the maximum voluntary isometric contraction of the quadriceps muscle group. Participants were seated with their hips and knees at a 90-degree angle. They were instructed to exert maximal force against the dynamometer pad positioned just above the ankle. The peak force generated was recorded from three trials, and the highest value was used for analysis. FFM is the total bodyweight measured in kilograms that includes water, muscle protein, carbohydrates, and bone but excludes fat. FFM was measured using the InBody device in the present study.
Statistical analysis
Continuous variables, such as age, height, and weight of the participants, were analyzed using descriptive statistics (mean and standard deviation). Categorical variables, such as sex, were represented as percentages based on frequency. The values for P1, P2, and P3, including all assessments, were determined by averaging the data measured during HD over three weeks. The total number of HD sessions and exercise interventions varied among participants; this variation was accounted for in the descriptive analysis. Comparisons between P1 and P2 and between P2 and P3 were performed using the paired t-test for continuous variables and the Wilcoxon signed-rank test for non-continuous variables. The choice between the paired t-test and the Wilcoxon signed-rank test was made according to the results of a normality test. Potential confounders, such as baseline characteristics, were controlled for by including them as covariates in the analyses where appropriate. Subgroup analyses were conducted based on baseline characteristics such as age, sex, and duration of HD. Interaction terms were included in the regression models to examine potential interactions between the intervention and these baseline characteristics. Missing data were handled using multiple imputation techniques to ensure that the analysis remained robust and unbiased. Sensitivity analyses were conducted to test the robustness of the study findings. These analyses included comparing results from different statistical models, such as using alternative imputation methods for missing data and excluding participants with incomplete data. Loss to follow-up was addressed by analyzing only the data from participants who completed all three periods of the study.
RESULTS
Patient demographics
A total of 20 patients were examined for eligibility, and all 20 were confirmed eligible and included in the study. During the follow-up period, 19 patients completed the study, as one patient dropped out due to personal scheduling conflicts. Ultimately, data from 19 patients were analyzed. The mean age of the participants was 62.1±12.6 years, with an age range of 22 to 78 years. The group consisted of 11 males and 8 females. The following demographic information was gathered (Table 1). The mean dialysis duration was 2,016.0±46.6 days, ranging from 3.5 to 4.2 years. The mean estimated glomerular filtration rate (eGFR) (mL/min/1.73 m2) at the start of dialysis was 5.1±2.2, with a range of 2.5 to 9.5. The causes of CKD among the participants included Type II diabetes mellitus (12 participants), Hypertension (6 participants), and Immunoglobulin A nephropathy (1 participant). Most participants were patients with stage 5 CKD and had underlying conditions of diabetes mellitus.
Participant’s demographic information
Effects of exercise during HD on exercise capacity and knee extensor strength
The 6-MWD was measured in 16 of the 19 participants. Data for the 6-MWD in 3 participants were unobtainable due to muscle fatigue, headache, and dizziness. The baseline 6-MWD was 327 m in E1. The 6-MWD increased slightly to 333 m after 3 weeks without exercise in E2. The 6-MWD further increased to 371 m in E3. The p-value for the comparison of values obtained before and after the exercise (E2 and E3) was 0.006, indicating statistical significance (Table 2). Additionally, the analysis of bilateral knee extensor strength using mean values before and after the exercise intervention revealed a statistically significant p-value (Table 3). This demonstrates that the average muscle strength of the patients increased post-exercise, further supporting the effectiveness of the intervention. Knee extensor strength significantly increased by 11.93 N on left knee extension between pre-exercise E2 and post-exercise E3 (p=0.004). However, no significant difference was observed in the KDQOL score or FFM measured before HD. Thus, exercise training for 30 minutes at the start and end of HD sessions improved exercise capacity and muscle strength (Table 3).
Analysis of 6-MWD as the primary outcome
Comparative analysis of knee extensor strength, KDQOL, and FFM pre- and post-dialysis sessions
Effects of exercise during HD on hemodynamic parameters
No significant differences were observed between P2 and P3 in terms of fatigue scores, MAP, BP, VAS scores, or duration of HD; however, a trend indicated a reduction in the frequency of IDH following exercise intervention (Table 4). Notably, although the exercise regimen implemented did not result in a significant reduction in the frequency of IDH, an encouraging observation was the decrease in HR post-exercise. For a more meaningful assessment of “resting HR decrease,” HR measured during E1–E3 (Table 4, below DBP) should be compared. It is important to note that the HR values in Table 4 are “during dialysis,” not exactly the same as resting HR, and P2 shows an even higher value than P1 (as well as P3). Although this study observed a trend toward a reduction in the frequency of IDH, this was not significant (p=0.05 for comparison between P1 and P2). While analyzing MAP instead of DBP in Table 4 may offer a broader understanding of hemodynamic stability, DBP was used as a representative value for BP due to its relevance in assessing peripheral resistance and cardiovascular risk during dialysis.
Assessment of MAP, BP, heart rate, frequency of IDH, and fatigue evaluated using a VAS during dialysis sessions
Safety events
One patient reported experiencing back, chest, and shoulder pain during exercise training. Another patient reported experiencing dizziness and fatigue. No significant life-threatening adverse events were observed during study.
DISCUSSION
The primary objective of this study was to evaluate the effects of exercise training during HD on exercise capacity, muscle strength, and the prevention of IDH. The key findings of the study include a significant improvement in the 6-MWD and knee extensor strength following the exercise intervention. Despite a non-significant reduction in the frequency of IDH, a notable trend towards improvement was observed. Additionally, a significant decrease in HR post-exercise indicates potential cardiovascular benefits of the exercise regimen. These results align with the study objectives, highlighting the positive impact of exercise during HD on physical function and potential cardiovascular health.
The primary outcome of this study, the 6-MWD, was significantly different before and after exercise. This finding suggests that exercising with an ergometer during HD can enhance muscle strength and functional abilities. The present study also aimed to determine whether exercise training during HD could aid in evaluating lower extremity strength and function and whether it could prevent IDH, the most common side effect of HD. A comparison of the frequency of IDH before and after exercise exhibited no significant difference; however, the decreasing trend remained significant. Gołębiowski et al. [10] and Anding et al. [11] reported that exercise training during HD enhances physical function. However, only a few studies have provided objective statistics to determine whether exercise training during HD can prevent hypotension or evaluate physical function before and during HD.
The 6-MWD exhibited a significant difference before and after exercise training, suggesting that exercising with an ergometer during HD can enhance muscle strength and functional abilities. However, no significant correlation was observed between the fatigue scores assessed using VAS, MAP, BP, and HD duration before and after exercise. Previous studies have demonstrated decreased exercise capacity and quality of life in patients undergoing HD [2,21-23]. This decline can be attributed to factors such as anemia, diminished heart function, weakened musculoskeletal function, and reduced lung capacity resulting from HD [24,25]. Furthermore, the physiological changes and time constraints associated with HD contribute to a reduction in the ability of patients to engage in physical activities [26]. A reduction in physical activity and muscle strength, which can be attributed to exercise-induced fatigue, decreased pulmonary function, chronic pain, other comorbidities, and depression, has been observed in most patients undergoing HD [27,28].
Based on the findings of previous studies, exercise training during HD was hypothesized to be beneficial [29-31]. IDH occurring during HD was managed by adopting the Trendelenburg position to restore the circulating blood volume and administering saline solution while preventing airway aspiration. In addition, bicarbonate can be administered to increase the sodium or ionized calcium concentration in the dialysate and correct anemia and hypoalbuminemia to prevent IDH. We hypothesized that exercise training could help reduce the incidence of IDH-related symptoms. Regarding knee extensor strength, an improvement was observed only in the left side. This may be attributed to the fact that the average muscle strength in the left leg was lower before the exercise intervention. Post-exercise, the muscle strength between the left and right legs equalized, indicating that the initially weaker side had more potential for improvement and that the exercise regimen effectively corrected the muscle imbalance. Alternatively, variations in individual muscle imbalances and usage patterns could have contributed to this discrepancy. Additionally, the analysis of bilateral knee extensor strength using mean values before and after the exercise intervention revealed a statistically significant p-value. This demonstrates that the average muscle strength of the patients increased post-exercise, further supporting the effectiveness of the intervention.
In Anding-Rost et al.’s study [32] involving 917 participants, the group that participated in physical activities exhibited notable improvements compared with the group receiving usual care over 12 months. Specifically, the exercise group demonstrated a decrease in the Timed-Up-and-Go test by -1.1 seconds (95% confidence interval [CI], -1.9 to -0.3) and an increase in the 6-MWD by 37.5 m (95% CI, 14.7 to 60.4). However, there was no significant difference between the groups in the vitality subscale of the 36-item Short Form Health Survey (SF-36). In parallel, our study also indicated a similar enhancement in the 6-MWD following the exercise intervention. When evaluated using the KDQOL questionnaire, which provides more intricate details than the SF-36, we found no significant differences compared with the previous study.
However, the present study adopted a different approach from that of previous research. We asked patients to use an ergometer to exercise while lying down for 30 minutes at the start and end of their HD sessions. This protocol was established to maximize the benefits of exercise while accommodating the time constraints and physical condition of the patients. Exercising at the start of the HD session aims to improve circulation and prepare the body for the stress of dialysis, while exercising at the end helps in recovery and enhances muscle retention post-dialysis. Additionally, due to the difficulty some patients have in exercising for more than 30 minutes continuously, the exercise was split into two sessions. This approach contrasts with previous studies that often did not specify the timing or structure of exercise sessions during HD, providing a unique insight into the potential benefits of structured exercise regimens during dialysis. The American College of Sports Medicine (ACSM) recommends 150–300 minutes of moderate-intensity exercise per week for individuals with chronic medical conditions [33]. By incorporating exercise within the dialysis sessions, our protocol ensures that patients can achieve these recommended exercise amounts, thereby maximizing potential health benefits while minimizing additional time burdens. References to ACSM guidelines and previous studies were considered to ensure that the protocol not only meets recommended exercise amounts but also optimally fits the patients' dialysis schedules and physical capacities. We also ensured a clear definition of the criteria used to measure the results of the study.
Additionally, a key innovative aspect of our study was the detailed comparison of functional abilities using various assessment tools before and after dialysis, specifically during dialysis. The exercise was conducted during dialysis sessions, ensuring that dialysis times were consistent. To minimize potential confounding variables influenced by time, participants were evaluated within one week of the conclusion of HD P2. We confirmed that variables such as renal function (eGFR) and lab indicators during dialysis remained stable, and a review of patients’ medical records indicated that there were no significant changes in dialysis conditions. There were also no vital issues during the study period.
This study provides substantial evidence for the benefits of using an ergometer in improving the 6-MWD and strengthening the lower extremity muscles in patients with CKD undergoing HD. Notably, although the exercise regimen implemented did not significantly reduce the frequency of IDH, an encouraging observation was the decrease in HR post-exercise. This finding suggests a potential cardiovascular benefit of exercise, which may be of clinical significance, particularly in this patient population where cardiovascular concerns are prevalent.
Moreover, the results emphasize the potential of appropriate exercise therapy to enhance muscle strength and cardiovascular health in patients undergoing HD. The observed HR reduction could indicate improved cardiovascular efficiency, which is a crucial factor for patients with CKD, who often experience cardiovascular comorbidities. However, the implications of these findings on long-term cardiovascular health and their translation into clinical practice require further exploration.
Despite the positive outcomes, this study had some limitations. The small sample size and the study’s design limit the generalizability of the results. As this study is a clinical trial that is neither controlled nor randomized, there are inherent limitations in establishing causality and ruling out potential confounding factors. Therefore, the results should be interpreted with caution. Future studies should incorporate controlled and randomized designs to strengthen the validity of the findings. Moreover, the lack of significant improvement in the frequency of IDH precludes definitive conclusions about the efficacy of exercise training in preventing this common complication of HD. Also, the inability to correlate changes in functional ability with exercise intensity highlights a gap in our understanding of the dose-response relationship between exercise and its benefits in this patient population. Potential sources of bias include the selection bias due to the non-randomized nature of the study and measurement bias from self-reported data. The magnitude of these biases could potentially overestimate the benefits of exercise interventions.
The generalizability (external validity) of the study results is limited by the small sample size and the specific characteristics of the study population. The findings may not be applicable to all patients undergoing HD, particularly those with different comorbidities or in different healthcare settings. Further research with larger, more diverse populations is needed to confirm the applicability of these results to the broader CKD patient population.
Recommend a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies, and other relevant evidence. Overall, while the study provides promising evidence for the benefits of exercise during HD, the findings should be interpreted cautiously due to the noted limitations. The observed improvements in exercise capacity and muscle strength are encouraging, but further research is needed to confirm these benefits and to explore their long-term impacts on cardiovascular health and quality of life in patients with CKD. The consistency of these results with findings from similar studies adds credibility, but the lack of significant changes in IDH frequency and other hemodynamic parameters suggests that exercise alone may not be sufficient to address all complications associated with HD. Future studies should aim to clarify these relationships and determine optimal exercise protocols.
Ultimately, this study makes a significant contribution to the field of nephrology and rehabilitation medicine by highlighting the potential of exercise therapy to enhance the quality of life in patients undergoing HD. The positive effects on exercise capacity and lower limb strength observed in this study underscore the benefits of integrating an exercise regimen during HD sessions. Patients demonstrated significant improvements in the 6-MWD and knee extensor strength, which are indicative of enhanced physical function and muscle strength.
Future research should focus on addressing these limitations. Larger randomized controlled trials with diverse patient populations are essential to validate our findings. Additionally, exploring different exercise intensities and durations could provide insights into the optimal exercise prescription for this patient group. Understanding how exercise impacts various aspects of health in patients with CKD undergoing HD, including cardiovascular function, muscle strength, and quality of life, is vital for developing comprehensive, patient-centered rehabilitation protocols. This paves the way for further research to lead to more effective and personalized rehabilitation strategies for this vulnerable patient population.
Notes
CONFLICTS OF INTEREST
Myoung-Hwan Ko is an Editorial Board member of Annals of Rehabilitation Medicine. The author did not engage in any part of the review and decision-making process for this manuscript. Otherwise, no potential conflict of interest relevant to this article was reported.
FUNDING INFORMATION
None.
AUTHOR CONTRIBUTION
Conceptualization: Won YH. Data curation: Won YH. Investigation: Won YH. Methodology: Won YH. Formal analysis: Chae TS, Won YH. Project administration: Kim DS, Ko MH. Resources: Won YH. Visualization: Chae TS. Supervision: Kim DS, Ko MH, Won YH. Writing – original draft: Chae TS. Writing – review and editing: Chae TS, Won YH. Approval of final manuscript: all authors.
Acknowledgements
The authors extend their appreciation to all members of the Department of Physical Medicine and Rehabilitation.