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Effects of sprint training on extrarenal potassium regulation with intense exercise in Type 1 diabetes

¹School of Exercise and Sport Science, and ²School of Physiotherapy, The University of Sydney, Lidcombe; ³School of Human Movement, Recreation, and Performance, Centre for Aging Rehabilitation, Exercise, and Sport, Victoria University of Technology, Melbourne; ⁴The Garvan Institute of Medical Research, Darlinghurst; and ⁵Diabetes Centre, Bankstown-Lidcombe Hospital, Bankstown, Australia

Submitted 1 March 2005 ; accepted in final form 20 September 2005

Effects of sprint training on plasma K⁺ concentration ([K⁺]) regulation during intense exercise and on muscle Na⁺-K⁺-ATPase were investigated in subjects with Type 1 diabetes mellitus (T1D) under real-life conditions and in nondiabetic subjects (CON). Eight subjects with T1D and seven CON undertook 7 wk of sprint cycling training. Before training, subjects cycled to exhaustion at 130% peak O₂ uptake. After training, identical work was performed. Arterialized venous blood was drawn at rest, during exercise, and at recovery and analyzed for plasma glucose, [K⁺], Na⁺ concentration ([Na⁺]), catecholamines, insulin, and glucagon. A vastus lateralis biopsy was obtained before and after training and assayed for Na⁺-K⁺-ATPase content ([³H]ouabain binding). Pretraining, Na⁺-K⁺-ATPase content and the rise in plasma [K⁺] ([K⁺]) during maximal exercise were similar in T1D and CON. However, after 60 min of recovery in T1D, plasma [K⁺], glucose, and glucagon/insulin were higher and plasma [Na⁺] was lower than in CON. Training increased Na⁺-K⁺-ATPase content and reduced [K⁺] in both groups (P < 0.05). These variables were correlated in CON (r = –0.65, P < 0.05) but not in T1D. This study showed first that mildly hypoinsulinemic subjects with T1D can safely undertake intense exercise with respect to K⁺ regulation; however, elevated [K⁺] will ensue in recovery unless insulin is administered. Second, sprint training improved K⁺ regulation during intense exercise in both T1D and CON groups; however, the lack of correlation between plasma [K⁺] and Na⁺-K⁺-ATPase content in T1D may indicate different relative contributions of K⁺-regulatory mechanisms.

glycemia; potassium regulation; Na⁺-K⁺-ATPase; high-intensity exercise; insulin

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