Physical exercise in haemodialysis patients: time to start

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Abstract
Many phrases and epigrams of Juvenal, an ancient Roman poet, have entered common parlance, and his ‘Mens sana in corpore sano,’ literally meaning that physical health goes together with mental health, is one of most well known. Despite this ancient, common belief, scientific evidence that physical exercise is beneficial for human health has just been documented at the end of the last century [1, 2]. In a study involving a large cohort of alumni enrolled between 1916 and 1950 at Harvard University, a stepwise risk reduction for coronary artery disease was shown to be associated with increased physical activity and, notably, physical activity was very accurately assessed [3]. Moreover, exercise training was shown to produce beneficial effects on cardiovascular (CV) mortality and hospitalization when in-protocol specified supplementary analyses were performed by adjusting for prognostic factors [4] in a high risk population such as heart failure patients. These findings were consistent with previous trials and meta-analyses that showed improved outcomes in heart failure patients. In addition to that, Flynn et al. [5] showed, in the same cohort of heart failure patients, an increase in health-related quality of life. There is therefore no question that physical activity is a well-established predictor of adverse outcomes even in pathological conditions such as diabetes [6] and in end-stage kidney disease (ESKD) as well [7–9]. ESKD patients present an extremely elevated risk of CV events and mortality [10], and they are characterized by low levels of physical activity and a continuous decline in physical function. Physical inactivity among adults with chronic kidney disease (CKD), particularly among patients undergoing haemodialysis (HD), is a long-standing clinical problem. Avesani et al. [11], although in a descriptive manner, assessed the number of footsteps per day, the activity-related energy expenditure and the physical activity level in HD patients using a device that objectively monitored the activity actually performed. This study provided evidence that the daily number of footsteps and the calculated parameters were in line with a sedentary condition of HD patients and performance was even worse during the dialysis day. These findings confirmed the low degree of physical activity previously reported by other investigators using pedometers or patient self-reports [12, 13] and highlighted the notion that a low degree of physical activity is a common and persistent burden in HD patients, worldwide. The enrolment of CKD patients in exercise programmes is a challenging undertaking at all CKD stages, from the early stages to ESKD, and knowledge about physical activity and outcomes in ESKD patients mainly originates from observational studies, registry data or small-sized clinical trials [14–17]. However, as properly quoted in the study by Bennett et al. [18] that appears in this issue of Nephrology Dialysis Transplantation, a Cochrane meta-analysis of 32 studies including only parallel group randomized controlled trials (RCTs) [19] indicated that exercising for more than 30 min three times per week for people with ESKD improved physical fitness, physical function, blood pressure, health-related quality of life and some nutritional parameters. Regrettably, other outcomes such as survival or hospitalization had insufficient evidence due to the lack of data from RCTs. On the other hand, much difference of opinion and debate still linger around the best type of exercise intervention in dialysis patients, i.e. at home or during the dialysis session, and aerobic exercise. The majority of studies in the current literature deal with exercise during the dialysis session, but in order to reach the greatest number of subjects in a programme of physical activity, other modalities should be contemplated.

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