title: Impaired K+ regulation contributes to exercise limitation in end-stage renal failure.
abstract: BACKGROUND
  Patients with end-stage renal failure (ESRF) exhibit grossly impaired maximal exercise performance. This study investigated whether K+ regulation during exercise is impaired in ESRF and whether this is related to reduced exercise performance.
  
  
  METHODS
  Nine stable hemodialysis patients and eight controls (CON) performed incremental cycling exercise to volitional fatigue, with measurement of peak oxygen consumption (VO2 peak). Arterial blood was sampled during and following exercise and analyzed for plasma [K+] (PK).
  
  
  RESULTS
  The VO2 peak was approximately 44% less in ESRF than in CON (P < 0.001), whereas peak exercise PK was greater (7.23 +/- 0.38 vs. 6.23 +/- 0.14 mmol x L-1, respectively, P < 0.001). In ESRF, the rate of rise in PK during exercise was twofold greater (0.43 +/- 0.05 vs. 0.23 +/- 0.03 mmol. L-1x min-1, P < 0.005) and the ratio of rise in PK relative to work performed was 3.7-fold higher (90.1 +/- 13.5 vs. 24.7 +/- 3.3 nmol. L-1. J-1, P < 0.001). A strong inverse relationship was found between VO2 peak and the DeltaPK. work-1 ratio (r = -0.80, N = 17, P < 0.001).
  
  
  CONCLUSIONS
  Patients with ESRF exhibit grossly impaired extrarenal K+ regulation during exercise, demonstrated by an excessive rise in PK relative to work performed. We further show that K+ regulation during exercise was correlated with aerobic exercise performance. These results suggest that disturbed K+ regulation in ESRF contributes to early muscle fatigue during exercise, thus causing reduced exercise performance.
authors.affiliation: School of Human Movement, Recreation and Performance, Centre for Rehabilitation, Exercise and Sports Science,Victoria University of Technology, Melbourne, Australia.
authors.forename: Termboon
authors.initials: T
authors.lastname: Sangkabutra
authors.forename: David P
authors.initials: DP
authors.lastname: Crankshaw
authors.forename: Claudia
authors.initials: C
authors.lastname: Schneider
authors.forename: Steve F
authors.initials: SF
authors.lastname: Fraser
authors.forename: Simon
authors.initials: S
authors.lastname: Sostaric
authors.forename: Kim
authors.initials: K
authors.lastname: Mason
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Burge
authors.forename: Sandford L
authors.initials: SL
authors.lastname: Skinner
authors.forename: Lawrence P
authors.initials: LP
authors.lastname: McMahon
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McKenna
mesh_terms: D000328:Adult; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000378:metabolism* / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D010101:Oxygen Consumption; D010953:Plasma Volume; D011188:Potassium / Q000097:blood*; D006435:Renal Dialysis
chemical_list: D011188:Potassium