NDT Advance Access published online on April 23, 2009
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfp157
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Effects of endurance training on extrarenal potassium regulation and exercise performance in patients on haemodialysis
1 Muscle, Ions and Exercise Group, School of Sport and Exercise Science, Centre for Ageing, Rehabilitation, Exercise and Sport (CARES), Victoria University, Melbourne 2 Department of Nephrology, Royal Melbourne Hospital and Western Hospital, Australia
Correspondence and offprint requests to: Michael J. McKenna; E-mail: michael.mckenna{at}vu.edu.au
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Abstract |
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Background. Haemodialysis patients (HDP) with anaemia display impaired plasma K+ regulation during exercise and poor exercise performance. Epoetin treatment and exercise training improve exercise performance in HDP, but whether this is associated with improved K+ regulation is unknown.
Methods. Six HDP with near-normal [Hb] were tested for aerobic power (
) and plasma [K+] during incremental exercise; quadriceps muscle strength (peak torque, PT) from 0 to 360° s–1 and fatiguability (decline in strength during thirty contractions). Tests were conducted at baseline, after 6 weeks of normal activity (pre-train) and following 6 weeks cycle training (post-train). Six healthy untrained controls (CON) matched for age, sex, mass and height were tested at baseline.
Results. In HDP at baseline, 
and PT from 0 to 360° s–1 were respectively reduced by 37% and 27–42%, compared to CON (P < 0.05). Plasma [K+], the rise in [K+] (
[K+]) and the [K+] relative to total work done ([K+] work–1 ratio) during incremental exercise were all higher in HDP at baseline compared to CON (P < 0.05). Exercise training increased time to fatigue by 12% (P < 0.05) but did not improve K+ regulation or 
. An inverse correlation was found between the [K+] work–1 ratio and 
for pooled CON and HDP data.
Conclusions. In HDP treated with epoetin, poor exercise performance was related to impaired extrarenal K+ regulation, whilst training improved exercise performance but not K+ regulation. Thus, although impaired extrarenal K+ regulation may contribute to poor exercise performance in HDP, exercise performance can still improve with training despite unchanged K+ regulation.
Keywords: exercise training; haemodialysis; muscle strength; potassium regulation; VO2peak
Received for publication: 11. 2.08
Accepted in revised form: 16. 3.09