title: Greater loss in muscle mass and function but smaller metabolic alterations in older compared with younger men following 2 wk of bed rest and recovery.
abstract: This investigation aimed to compare the response of young and older adult men to bed rest (BR) and subsequent rehabilitation (R). Sixteen older (OM, age 55-65 yr) and seven young (YM, age 18-30 yr) men were exposed to a 14-day period of BR followed by 14 days of R. Quadriceps muscle volume (QVOL), force (QF), and explosive power (QP) of leg extensors; single-fiber isometric force (Fo); peak aerobic power (V̇o2peak); gait stride length; and three metabolic parameters, Matsuda index of insulin sensitivity, postprandial lipid curve, and homocysteine plasma level, were measured before and after BR and after R. Following BR, QVOL was smaller in OM (-8.3%) than in YM (-5.7%,P= 0.031); QF (-13.2%,P= 0.001), QP (-12.3%,P= 0.001), and gait stride length (-9.9%,P= 0.002) were smaller only in OM. Fo was significantly smaller in both YM (-32.0%) and OM (-16.4%) without significant differences between groups. V̇o2peakdecreased more in OM (-15.3%) than in YM (-7.6%,P< 0.001). Instead, the Matsuda index fell to a greater extent in YM than in OM (-46.0% vs. -19.8%, respectively,P= 0.003), whereas increases in postprandial lipid curve (+47.2%,P= 0.013) and homocysteine concentration (+26.3%,P= 0.027) were observed only in YM. Importantly, after R, the recovery of several parameters, among them QVOL, QP, and V̇o2peak, was not complete in OM, whereas Fo did not recover in either age group. The results show that the effect of inactivity on muscle mass and function is greater in OM, whereas metabolic alterations are greater in YM. Furthermore, these findings show that the recovery of preinactivity conditions is slower in OM.
authors.affiliation: Institute for Kinesiology Research, Science and Research Centre, University of Primorska, Koper, Slovenia;
authors.forename: Rado
authors.initials: R
authors.lastname: Pišot
authors.affiliation: Institute for Kinesiology Research, Science and Research Centre, University of Primorska, Koper, Slovenia;
authors.forename: Uros
authors.initials: U
authors.lastname: Marusic
authors.affiliation: Department of Medical, Surgical and Health Sciences, Division of Internal Medicine, University of Trieste, Trieste, Italy;
authors.forename: Gianni
authors.initials: G
authors.lastname: Biolo
authors.affiliation: Department of Medical, Surgical and Health Sciences, Division of Internal Medicine, University of Trieste, Trieste, Italy;
authors.forename: Sara
authors.initials: S
authors.lastname: Mazzucco
authors.affiliation: Department of Medical and Biological Sciences, University of Udine, Udine, Italy;
authors.forename: Stefano
authors.initials: S
authors.lastname: Lazzer
authors.affiliation: Department of Medical and Biological Sciences, University of Udine, Udine, Italy; bruno.grassi@uniud.it.
authors.forename: Bruno
authors.initials: B
authors.lastname: Grassi
authors.affiliation: Department of Biomedical Sciences, University of Padua, Padua, Italy;
authors.forename: Carlo
authors.identifier: http://orcid.org/0000-0001-8080-361X
authors.initials: C
authors.lastname: Reggiani
authors.affiliation: Department of Biomedical Sciences, University of Padua, Padua, Italy;
authors.forename: Luana
authors.initials: L
authors.lastname: Toniolo
authors.affiliation: Department of Medical and Biological Sciences, University of Udine, Udine, Italy;
authors.forename: Pietro Enrico
authors.initials: PE
authors.lastname: di Prampero
authors.affiliation: Department of Medical Sciences, Section of Internal and Cardiorespiratory Medicine, University of Ferrara, Ferrara, Italy;
authors.forename: Angelina
authors.initials: A
authors.lastname: Passaro
authors.affiliation: MRC/ARUK Centre for Musculoskeletal Ageing Research, University of Nottingham, Derby Royal Hospital, Derby, United Kingdom;
authors.forename: Marco
authors.initials: M
authors.lastname: Narici
authors.affiliation: MRC/ARUK Centre for Musculoskeletal Ageing Research, University of Nottingham, Derby Royal Hospital, Derby, United Kingdom;
authors.forename: Shahid
authors.initials: S
authors.lastname: Mohammed
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany;
authors.forename: Joern
authors.initials: J
authors.lastname: Rittweger
authors.affiliation: Department of Vascular Surgery, General Hospital Izola, Izola, Slovenia; and.
authors.forename: Mladen
authors.initials: M
authors.lastname: Gasparini
authors.affiliation: National Institute of Public Health of the Republic of Slovenia, Ljubljana, Slovenia.
authors.forename: Mojca
authors.initials: M
authors.lastname: Gabrijelčič Blenkuš
authors.affiliation: Institute for Kinesiology Research, Science and Research Centre, University of Primorska, Koper, Slovenia;
authors.forename: Boštjan
authors.initials: B
authors.lastname: Šimunič
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D001510:Bed Rest; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D008055:Lipids / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D055815:Young Adult
chemical_list: D008055:Lipids; D006710:Homocysteine
keywords: aging; functional decline; prolonged physical inactivity; reconditioning