Effects of endurance training on extrarenal potassium regulation and exercise performance in patients on haemodialysis.
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 degrees 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 degrees s(-1) were respectively reduced by 37% and 27-42%, compared to CON (P < 0.05). Plasma [K(+)], the rise in [K(+)] (Delta[K(+)]) and the Delta[K(+)] relative to total work done (Delta[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 Delta[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.
Petersen
Aaron C
AC
Centre for Ageing, Rehabilitation, Exercise and Sport, Victoria University, Melbourne, Australia.
Leikis
Murray J
MJ
McMahon
Lawrence P
LP
Kent
Annette B
AB
McKenna
Michael J
MJ
D000328:Adult; D000740:Anemia / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology; D016022:Case-Control Studies; D004921:Erythropoietin / Q000627:therapeutic use; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000503:physiopathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D011188:Potassium / Q000097:blood*; D011994:Recombinant Proteins; D006435:Renal Dialysis / Q000009:adverse effects
D011994:Recombinant Proteins; D004921:Erythropoietin; D011188:Potassium