title: Insights into central and peripheral factors affecting the "oxidative performance" of skeletal muscle in aging.
abstract: During exercises with relatively small muscle masses, limitations to exercise performance by the cardiovascular system should be significantly reduced, allowing one to fully-test the "oxidative potential" of the investigated muscles. Ten elderly males (E, 77.8 +/- 2.9 years [x +/- SD]) and eight young controls (Y, 26.6 +/- 3.0) underwent incremental exercises to voluntary exhaustion on a dynamic leg-extension (dominant limb) machine (knee-extension, KE) and on a cycloergometer (CYCLO). During KE the load was increased every 3 min to loads corresponding to 20, 40 and 60% of the force of one-repetition maximum (1RM). The following variables were determined (vastus lateralis muscle): concentration changes of deoxygenated haemoglobin and myoglobin (Delta[deoxy(Hb + Mb)]) by near-infrared spectroscopy (NIRS), expressed as percentage of the maximal value obtained during transient limb ischemia, and taken as an index of O2 extraction; root mean square (RMS) and median power frequency (MDF) by electromyography. The total lifted load during KE and peak workload during CYCLO were lower in E versus Y (620.4 +/- 321.9 kg vs. 1347.4 +/- 458.7; 113.5 +/- 23.9 W vs. 224.3 +/- 41.0, respectively). During CYCLO Delta[deoxy(Hb + Mb)] peak (i.e. the value determined at exhaustion) was lower in E (44.5 +/- 17.7%) versus Y (67.1 +/- 22.9), whereas during KE Delta[deoxy(Hb + Mb)] peak was higher in E (56.8 +/- 20.9%) versus Y (38.6 +/- 15.8). "Thresholds", that is abrupt increases in RMS slopes, were detected in Y but not in E, suggesting less recruitment or a preferential atrophy of type 2 fibers in the elderly. These findings, associated with the preserved capacity of O2 extraction, suggest a shift towards oxidative metabolism in skeletal muscles of 78 year-old subjects, which could preserve, at least in part, their capacity to carry out exercise.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biomediche, Università degli Studi di Milano, LITA, Via Fratelli Cervi 93, 20090, Segrate, MI, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Ferri
authors.forename: Saverio
authors.initials: S
authors.lastname: Adamo
authors.forename: Miriam
authors.initials: M
authors.lastname: Longaretti
authors.forename: Mauro
authors.initials: M
authors.lastname: Marzorati
authors.forename: Francesca
authors.initials: F
authors.lastname: Lanfranconi
authors.forename: Antonietta
authors.initials: A
authors.lastname: Marchi
authors.forename: Bruno
authors.initials: B
authors.lastname: Grassi
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D004576:Electromyography; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D009211:Myoglobin / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D052097:Quadriceps Muscle / Q000502:physiology; D011999:Recruitment, Neurophysiological / Q000502:physiology; D019265:Spectroscopy, Near-Infrared
chemical_list: D006454:Hemoglobins; D009211:Myoglobin; D010100:Oxygen