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Skeletal Muscle Mass & Function in Older Women: Health-Enhancing Influences of Combined Resistance Exercise & Diet
Örebro University, School of Health Sciences.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ageing is accompanied by a progressive decline in skeletal muscle mass and strength which may lead to impaired ability to perform activities of daily living in older adults. Although the exact cause of the gradual decline in muscle mass is unknown, identifying efficient strategies aiming to prevent age-related loss of muscle mass and strength is important in order to promote healthy ageing. The overall aim of this thesis was to explore the effects of resistance training alone or combined with a healthy diet on skeletal muscle mass and function of healthy recreationally active older women and to determine mechanisms by which elevated systemic inflammation may contribute to the age-related decline of muscle mass in older adults. The combination of resistance training and a healthy diet induced gains in leg lean mass as well as greater gains in dynamic explosive force than resistance training alone in healthy recreationally active older women. The observed gains in leg lean mass were accompanied by increases in the size of type IIA muscle fibres together with down-regulation in gene expression of a pro-inflammatory factor (IL-1β) and upregulation in gene expression of a regulator of cellular growth (mTOR) in skeletal muscle of older women. Additionally, reduced muscle protein synthesis and size of muscle cells may mediate the detrimental effects of elevated circulating markers of inflammation on muscle mass in older adults. In conclusion, the present thesis depicts mechanistic links between elevated systemic marker of inflammation and muscle mass and provides new information on the effects of combined resistance training and healthy diet on muscle mass and strength in a group of healthy recreationally active older women. This knowledge is instrumental for development of strategies aiming to prevent age-related loss of muscle mass and function.

Place, publisher, year, edition, pages
Örebro: Örebro University , 2017. , p. 79
Series
Örebro Studies in Sport Sciences, ISSN 1654-7535 ; 26
Keywords [en]
Healthy ageing, Chronic inflammation, C-reactive protein, Omega-3 fatty acids, Resistance training, Physical function
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:oru:diva-61234ISBN: 978-91-7529-218-2 (print)OAI: oai:DiVA.org:oru-61234DiVA, id: diva2:1146669
Public defence
2017-12-12, Örebro universitet, Hörsal G, Gymnastikhuset, Fakultetsgatan 1, Örebro, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2017-10-03 Created: 2017-10-03 Last updated: 2017-11-23Bibliographically approved
List of papers
1. Influence of combined resistance training and healthy diet on muscle mass in healthy elderly women: a randomized controlled trial
Open this publication in new window or tab >>Influence of combined resistance training and healthy diet on muscle mass in healthy elderly women: a randomized controlled trial
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2015 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 119, no 8, p. 918-925Article in journal (Refereed) Published
Abstract [en]

The delivery of efficient nonpharmacological treatment to prevent the loss of muscle mass in older adults is a major challenge, and information on the combined effects of training and diet is particularly important. Here we aimed to evaluate the effects of 24 wk of resistance training combined with a healthy dietary approach (n-6/n-3 ratio < 2) in a population of healthy and physically active older women (65-70 years). The three-armed randomized controlled trial included a resistance training + healthy diet group (RT-HD), a resistance training group (RT), and controls (CON). All subjects included in the study were physically active and had low levels of serum inflammatory markers. In accordance with the dietary goals, the n-6/n-3 ratio dietary intake significantly decreased only in RT-HD by 42%. An increase in 1 repetition maximum in leg extension occurred in RT (+20.4%) and RT-HD (+20.8%), but not in CON. Interestingly, leg lean mass significantly increased only in RT-HD (+1.8%). While there were no changes in serum C-reactive protein and IL-6 levels, a significant decrease in serum level of the pro-inflammatory precursor arachidonic acid (-5.3 +/- 9.4%) together with an increase in serum n-3 docosahexaenoic acid (+8.3%) occurred only in RT-HD. Altogether, this study demonstrates that the effects of resistance training on muscle mass in healthy older adults can be optimized by the adoption of a healthy diet.

Place, publisher, year, edition, pages
American Physiological Society, 2015
Keywords
aging, C-reactive protein, exercise, fatty acids, inflammation, skeletal muscle
National Category
Sport and Fitness Sciences Physiology
Research subject
Physiology
Identifiers
urn:nbn:se:oru:diva-46442 (URN)10.1152/japplphysiol.00066.2015 (DOI)000362959800009 ()26338453 (PubMedID)2-s2.0-84946046698 (Scopus ID)
Note

Funding Agency:

Swedish National Center for Research in Sports P2012/0102 P2014-0117

Available from: 2015-11-10 Created: 2015-11-10 Last updated: 2018-01-10Bibliographically approved
2. Lower limb explosive strength capacity in elderly women: effects of resistance training and healthy diet
Open this publication in new window or tab >>Lower limb explosive strength capacity in elderly women: effects of resistance training and healthy diet
2017 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 123, no 1, p. 190-196Article in journal (Refereed) Published
Abstract [en]

The effects of 24 wk of resistance training combined with a healthy diet on lower limb explosive strength capacity were investigated in a population of healthy elderly women. Participants (n = 63; 67.5 ± 0.4 yr) were randomized into three groups; resistance training (RT), resistance training and healthy diet (RT-HD), and control (CON). Progressive resistance training was performed at a load of 75-85% one-repetition maximum. A major adjustment in the healthy dietary approach was an n-6/n-3 polyunsaturated fatty acid (PUFA) ratio below 2. Lower limb maximal strength, explosive force capacity during dynamic and isometric movements, whole body lean mass, and physical function were assessed. Whole body lean mass significantly increased by 1.5 ± 0.5% in RT-HD only. Isometric strength performance during knee extension as well as the performance in the five sit-to-stand and single-leg-stance tests increased similarly in RT and RT-HD. Improvements in dynamic peak power and time to reach peak power (i.e shorter time) during knee extension occurred in both RT (+15.7 ± 2.6 and -11.0 ± 3.8%, respectively) and RT-HD (+24.6 ± 2.6 and -20.3 ± 2.7%, respectively); however, changes were significantly larger in RT-HD. Similarly, changes in peak force and rate of force development during squat jump were higher in RT-HD (+58.5 ± 8.4 and +185.4 ± 32.9%, respectively) compared with RT (+35.7 ± 6.9 and +105.4 ± 22.4%, respectively). In conclusion, a healthy diet rich in n-3 PUFA can optimize the effects of resistance training on dynamic explosive strength capacity during isolated lower limb movements and multijoint exercises in healthy elderly women.

NEW & NOTEWORTHY Age-related decline in lower limb explosive strength leads to impaired ability to perform daily living tasks. The present randomized controlled trial demonstrates that a healthy diet rich in n-3 polyunsaturated fatty acid (n-3 PUFA) enhances resistance training-induced gains in dynamic explosive strength capacity during isolated lower limb movements and multijoint exercises in healthy elderly women. This supports the use of strategies combining resistance training and dietary changes to mitigate the decline in explosive strength capacity in older adults.

Place, publisher, year, edition, pages
American Physiological Society, 2017
Keywords
aging, muscle mass, omega-3 fatty acids, physical function, rate of force development
National Category
Sport and Fitness Sciences Physiotherapy
Identifiers
urn:nbn:se:oru:diva-60897 (URN)10.1152/japplphysiol.00924.2016 (DOI)28473614 (PubMedID)
Available from: 2017-09-19 Created: 2017-09-19 Last updated: 2017-11-23Bibliographically approved
3. Mechanisms mediating skeletal muscle hypertrophy in older women following resistanceexercise combined to healthy diet
Open this publication in new window or tab >>Mechanisms mediating skeletal muscle hypertrophy in older women following resistanceexercise combined to healthy diet
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(English)Manuscript (preprint) (Other academic)
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:oru:diva-62773 (URN)
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2017-11-23Bibliographically approved
4. Mechanistic Links Underlying the Impact of C-Reactive Protein on Muscle Mass in Elderly
Open this publication in new window or tab >>Mechanistic Links Underlying the Impact of C-Reactive Protein on Muscle Mass in Elderly
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2017 (English)In: Cellular Physiology and Biochemistry, ISSN 1015-8987, E-ISSN 1421-9778, Vol. 44, no 1, p. 267-278Article in journal (Refereed) Published
Abstract [en]

BACKGROUND/AIMS: Mechanisms underlying the relationship between systemic inflammation and age-related decline in muscle mass are poorly defined. The purpose of this work was to investigate the relationship between the systemic inflammatory marker CRP and muscle mass in elderly and to identify mechanisms by which CRP mediates its effects on skeletal muscle, in-vitro.

METHODS: Muscle mass and serum CRP level were determined in a cohort of 118 older women (67±1.7 years). Human muscle cells were differentiated into myotubes and were exposed to CRP. The size of myotubes was determined after immunofluorescent staining using troponin. Muscle protein synthesis was assessed using stable isotope tracers and key signalling pathways controlling protein synthesis were determined using western-blotting.

RESULTS: We observed an inverse relationship between circulating CRP level and muscle mass (β= -0.646 (95% CI: -0.888, -0.405) p<0.05) and demonstrated a reduction (p < 0.05) in the size of human myotubes exposed to CRP for 72 h. We next showed that this morphological change was accompanied by a CRP-mediated reduction (p < 0.05) in muscle protein fractional synthetic rate of human myotubes exposed to CRP for 24 h. We also identified a CRP-mediated increased phosphorylation (p<0.05) of regulators of cellular energy stress including AMPK and downstream targets, raptor and ACC-β, together with decreased phosphorylation of Akt and rpS6, which are important factors controlling protein synthesis.

CONCLUSION: This work established for the first time mechanistic links by which chronic elevation of CRP can contribute to age-related decline in muscle function.

Place, publisher, year, edition, pages
Karger, 2017
Keywords
Ageing; AMPK; Akt/mTOR; Chronic Inflammation; CRP; Myoblast; Protein Synthesis; Skeletal Muscle Cell; Old women
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy) Physiology
Identifiers
urn:nbn:se:oru:diva-62772 (URN)10.1159/000484679 (DOI)000423087200020 ()29130969 (PubMedID)2-s2.0-85033489852 (Scopus ID)
Note

Funding Agency:

Swedish National Center for Research in Sports  P2012/0102  P2014-0117

Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2018-02-06Bibliographically approved

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Strandberg, Emelie

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