Dataset Information

Functional impact of sarcopenia in respiratory muscles.

ABSTRACT: The risk for respiratory complications and infections is substantially increased in old age, which may be due, in part, to sarcopenia (aging-related weakness and atrophy) of the diaphragm muscle (DIAm), reducing its force generating capacity and impairing the ability to perform expulsive non-ventilatory motor behaviors critical for airway clearance. The aging-related reduction in DIAm force generating capacity is due to selective atrophy of higher force generating type IIx and/or IIb muscle fibers, whereas lower force generating type I and IIa muscle fiber sizes are preserved. Fiber type specific DIAm atrophy is also seen following unilateral phrenic nerve denervation and in other neurodegenerative disorders. Accordingly, the effect of aging on DIAm function resembles that of neurodegeneration and suggests possible common mechanisms, such as the involvement of several neurotrophic factors in mediating DIAm sarcopenia. This review will focus on changes in two neurotrophic signaling pathways that represent potential mechanisms underlying the aging-related fiber type specific DIAm atrophy.

SUBMITTER: Elliott JE

PROVIDER: S-EPMC4838572 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Functional impact of sarcopenia in respiratory muscles.

Elliott Jonathan E JE Greising Sarah M SM Mantilla Carlos B CB Sieck Gary C GC

Respiratory physiology & neurobiology 20151020

The risk for respiratory complications and infections is substantially increased in old age, which may be due, in part, to sarcopenia (aging-related weakness and atrophy) of the diaphragm muscle (DIAm), reducing its force generating capacity and impairing the ability to perform expulsive non-ventilatory motor behaviors critical for airway clearance. The aging-related reduction in DIAm force generating capacity is due to selective atrophy of higher force generating type IIx and/or IIb muscle fibe ...[more]

PMID: 26467183

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Project description:BackgroundLittle is known about the response of the equine respiratory muscles to training.ObjectivesTo measure an index of inspiratory muscle strength (IMSi) before and after a period of conventional exercise training (phase 1) and inspiratory muscle training (IMT), comparing high-load (treatment) and low-load (control) groups (phase 2).Study designProspective randomised controlled trial.MethodsPhase 1: Twenty National Hunt Thoroughbred racehorses performed an inspiratory muscle strength test (IMST) twice on two occasions; when unfit at timepoint A (July), and when race fit at timepoint B (October). Phase 2: Thirty-five Thoroughbred racehorses at race fitness were randomly assigned into a high-load (treatment, n = 20) or low-load (control, n = 15) IMT group. The high-load group followed an IMT protocol that gradually increased the inspiratory pressure applied every 4 days. The low-load group underwent sham IMT with a low training load. The IMT was performed 5 days/week for 10 weeks. The IMST was performed twice on two occasions, timepoint B (October) and timepoint C (January). Conventional exercise training and racing continued during the study period. The peak IMSi values obtained from the different groups at timepoints A, B and C were compared using a Wilcoxon Signed Rank Test.ResultsPhase 1: There was a significant increase in IMSi from timepoint A: 22.5 cmH2 O (21-25) to timepoint B: 26 cmH2 O (24-30) (p = 0.015). Phase 2: From timepoint B to C there was a significant increase in IMSi for the high-load group 34 cmH2 O (28-36) (p = 0.001) but not the low-load group 26 cmH2 O (24-30) (p = 0.929). The peak IMSi at timepoint C was significantly higher for the high-load than low-load group (p = 0.019).Main limitationsSingle centre study with only National Hunt horses undergoing race-training included.ConclusionsIn horses undergoing race training there is a significant increase in IMSi in response to conventional exercise training and high-load IMT.

Project description:BackgroundHigher gait variability after stroke increases risk of falls and compromises safe community ambulation. Corticomotor connectivity plays an important role in walking after stroke, however, its relation to gait variability remains unknown.Research questionDo corticomotor characteristics of the proximal and distal lower limb muscles predict gait variability in individuals with chronic stroke?MethodsRetrospective analysis of data from 30 individuals with chronic stroke was conducted. Corticomotor characteristics were measured in the paretic and non-paretic tibialis anterior (TA, distal muscle) and rectus femoris (RF, proximal muscle) using transcranial magnetic stimulation. We calculated corticomotor excitability ratio of paretic TA and RF (CMETA/RF), corticomotor excitability symmetry (CMEsym) between hemispheres for the TA and RF, and ipsilateral corticomotor excitability (ICE) of the paretic TA. Gait variability was quantified as the coefficient of variation of the paretic step length (spatial) and step time (temporal) during comfortable walking. Relations between corticomotor characteristics and gait variability were tested with multiple linear regression.ResultsCMETA/RF and CMEsym of RF were significant predictors of spatial gait variability. Greater corticomotor input to the paretic RF compared to the paretic TA and greater symmetry of RF were related to higher spatial gait variability. There were no significant predictors of temporal gait variability.SignificanceCorticomotor inputs to the proximal RF may be important for spatial gait variability, reflecting a compensatory role of RF in walking after stroke. Stroke survivors with relatively greater corticomotor input to the paretic RF may adopt compensatory strategy to enhance propulsion and achieve foot clearance, but it may also increase spatial gait variability, particularly when combined with impaired motor control of the paretic TA. These findings may provide novel rehabilitative targets to decrease gait variability and promote safe ambulation in individuals with stroke.

Project description:BackgroundLimited information exists regarding changes in the size of respiratory and locomotor muscles in response to exercise training in the Thoroughbred racehorse.ObjectivesTo describe and compare the responses of the respiratory and locomotor muscles to conventional exercise training and inspiratory muscle training (IMT).Study designProspective randomised controlled trial.MethodsThoroughbred racehorses, in training for competition in National Hunt races, were recruited from two training establishments. Ultrasonographic images were obtained for selected muscles of the upper airway, diaphragm, accessory respiratory, and locomotor systems and their sizes measured. Examinations were performed at three timepoints: (A) when unfit, (B) following 12 weeks of conventional exercise training and (C) following 10-12 weeks continued training at race fitness. In addition, horses at yard 1 performed IMT, between timepoint B and C, and were randomly assigned into high-load (treatment) or low-load (control) group. Repeated measures models were constructed to compare the change in muscle measurements over time, and to investigate the effects of yard, previous airway surgery and IMT on the change in ultrasonographic size measurements obtained.ResultsUpper airway muscle size increased in response to conventional race training between timepoints A-C, and B-C. Diaphragm size increased in response to conventional exercise training between timepoints A and B. The diaphragm size of horses that undertook high-load IMT was either maintained or increased, whereas diaphragm size decreased in horses that undertook low-load IMT or no IMT between timepoints B and C. A significant interaction between gluteal muscle size and airway surgery status was observed, with greater gluteal muscle thicknesses measured in horses that had not previously undergone airway surgery (left gluteal 3.9%, p < 0.001; right 4.5%, p = 0.04).Main limitationsLow number of horses underwent IMT.ConclusionsRespiratory and locomotor muscles increase in size in response to conventional exercise training, with a further change in diaphragm size in response to inspiratory muscle training.

Dataset Information

Functional impact of sarcopenia in respiratory muscles.

Publications

Functional impact of sarcopenia in respiratory muscles.

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