title: Intense interval training in healthy older adults increases skeletal muscle [3H]ouabain-binding site content and elevates Na+,K+-ATPase α2isoform abundance in Type II fibers.
abstract: Young adults typically adapt to intense exercise training with an increased skeletal muscle Na+,K+-ATPase (NKA) content, concomitant with reduced extracellular potassium concentration [K+] during exercise and enhanced exercise performance. Whether these changes with longitudinal training occur in older adults is unknown and was investigated here. Fifteen older adults (69.4 ± 3.5 years, mean ± SD) were randomized to either 12 weeks of intense interval training (4 × 4 min at 90-95% peak heart rate), 3 days/week (IIT,n= 8); or no exercise controls (n= 7). Before and after training, participants completed an incremental cycle ergometer exercise test until a rating of perceived exertion of 17 (very hard) on a 20-point scale was attained, with measures of antecubital venous [K+]vParticipants underwent a resting muscle biopsy prior to and at 48-72 h following the final training session. After IIT, the peak exercise work rate (25%), oxygen uptake (16%) and heart rate (6%) were increased (P< 0.05). After IIT, the peak exercise plasma [K+]vtended to rise (P= 0.07), while the rise in plasma [K+]vrelative to work performed (nmol.L-1J-1) was unchanged. Muscle NKA content increased by 11% after IIT (P< 0.05). Single fiber measurements, increased in NKA α2isoform in Type II fibers after IIT (30%,P< 0.05), with no changes to the other isoforms in single fibers or homogenate. Thus, intense exercise training in older adults induced an upregulation of muscle NKA, with a fiber-specific increase in NKA α2abundance in Type II fibers, coincident with increased muscle NKA content and enhanced exercise performance.
authors.affiliation: Clinical Exercise Science Research Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria, Australia.
authors.forename: Victoria L
authors.identifier: http://orcid.org/0000-0001-6921-4638
authors.initials: VL
authors.lastname: Wyckelsma
authors.affiliation: Clinical Exercise Science Research Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria, Australia.
authors.forename: Itamar
authors.initials: I
authors.lastname: Levinger
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Victoria, Australia.
authors.forename: Robyn M
authors.initials: RM
authors.lastname: Murphy
authors.affiliation: Clinical Exercise Science Research Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria, Australia.
authors.forename: Aaron C
authors.initials: AC
authors.lastname: Petersen
authors.affiliation: Clinical Exercise Science Research Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria, Australia.|Renal Division, Department of Medicine, Emory University, Atlanta, Georgia.
authors.forename: Ben D
authors.initials: BD
authors.lastname: Perry
authors.affiliation: Clinical Exercise Science Research Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria, Australia.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Hedges
authors.affiliation: Clinical Exercise Science Research Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria, Australia.|Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Anderson
authors.affiliation: Clinical Exercise Science Research Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria, Australia michael.mckenna@vu.edu.au.
authors.forename: Michael J
authors.identifier: http://orcid.org/0000-0001-9998-0093
authors.initials: MJ
authors.lastname: McKenna
mesh_terms: D000368:Aged; D001665:Binding Sites; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D064797:Physical Conditioning, Human / Q000502:physiology*; D020033:Protein Isoforms / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Aging; Na+,K+‐pump; exercise; potassium; single fiber