Timing of Intradialytic Exercise and Its Impact on Intradialytic Hypotension

The objective of this study is to compare the rate of low blood pressure events (Intradialytic Hypotension: IDH) when intradialytic exercise is performed in the first half of the hemodialysis (HD) session as compared to that when intradialytic exercise is performed in the second half of the HD session. The investigators expect that there will be little to no difference in occurrence of IDH episodes between the two time periods based on the experience of the 3 centres and imaging studies of the heart with exercise in HD.

Intradialytic hypotension (IDH) is a common complication during hemodialysis, occurring in 20-30% of HD treatments. IDH can cause unpleasant symptoms and lead to decline in residual kidney function, vascular access thrombosis, ischemic damage to white matter of the brain, volume overload, increased risk of cardiovascular events and increased mortality risk.

Intradialytic exercise has been shown to improve physical function, health-related quality of life and cardiac function. Initial concerns regarding the potential for intradialytic exercise to increase the rate of IDH have been mitigated by multiple interventional studies in which intradialytic exercise has been shown to be safe with minimal adverse effects. However, concerns regarding the potential of intradialytic exercise to increase frequency of IDH if exercise is performed in second half of HD remain.

No study has specifically compared the frequency IDH episodes when exercise is performed during second half of HD as compared to that when exercise is performed during the first half of a HD session to fully characterize the effect of timing of intradialytic exercise and its effect on IDH.

The investigators aim to address this knowledge gap with a crossover study examining the rate of IDH when individuals in a clinical intradialytic cycling program exercise during the first half of their hemodialysis session as compared with the IDH rate when exercise is performed during the second half of hemodialysis.

To facilitate study implementation and optimize use of exercise resources and equipment, participants at each site will be randomly split into 2 groups. Group 1 will perform 2 weeks of their usual intradialytic cycling (6 sessions) during the first half of their usual HD and then perform 2 weeks of intradialytic cycling (6 sessions) during the second half of their usual HD. Group 2 will perform the intervention in reverse order to Group 1. No washout period is required as there is no biological plausibility for carry over effect. However, as participation in the cycling program is voluntary, some participants choose not to exercise during some of their HD sessions. The investigators will monitor these non-cycling sessions for IDH as well and will compare IDH rate in these non-exercise sessions with IDH rate during sessions when intradialytic exercise was performed, if numbers allow.

Participants will perform their usual duration and intensity of intradialytic cycling at each HD session as per standard clinical intradialytic cycling protocol procedures in each unit. Prescribed exercise time and intensity will remain unchanged over the course of the study.

The investigators will attempt to keep dialysate composition, dialyzer, dialysate temperature, HD access, dialysis duration and medications unchanged over the course of the study, but will not intervene/interfere with usual clinical care. The research assistant will record any changes to dialysis prescription related to routine clinical care on a weekly basis.

Baseline demographic and clinical data will be collected from the hemodialysis chart. This will include age, sex, race, time on hemodialysis, hemodialysis access, dialysis vintage, comorbidities (including hypertension, diabetes, congestive heart failure and ischemic heart disease), amount of fluid removed at each HD, hemoglobin, Kt/V (dialysis efficacy), medications and blood work results as measured on last monthly bloodwork.

The investigators will use the initial BP measurement obtained once the patient has commenced HD (i.e. patient "hooked up" and blood present in both venous and arterial lines) for the baseline BP. Blood pressure (BP) will be measured as per routine procedures used in the participants' HD units (usual arm/leg, usual BP cuff). Pre and post HD BP will be collected as per usual HD Unit practice. During HD, BP will be collected more frequently than the usual routine (q30 min) at q15min intervals or more frequently when clinically indicated based on patient symptoms or status. This timing will be pre-programmed into HD machines to minimize work for bedside HD nurses. However, bedside HD nurses will need to record each measurement on the HD run sheet.

Eligibility Criteria:
Inclusion Criteria:

* adult (\>= 18 years old), receiving three times per week chronic in-centre hemodialysis, current active participant in clinical intradialytic cycling program offered at each study site, able to communicate in English, able to provide written consent

Exclusion Criteria:

* dialysis frequency not three times per week