Skeletal Muscle Fatigue and Decreased Efficiency

Grassi, Bruno; Rossiter, Harry B.; Zoladz, Jerzy A.

doi:10.1249/jes.0000000000000043

Cited by 191 publications

(221 citation statements)

References 36 publications

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“…Back weakness is one known risk factor for low back pain 45,48 and our laboratory is analyzing BieringSorensen back extension endurance data to help characterize a structure-function relationship among the crewmembers. Even so, muscle endurance and strength depend not only on cross-sectional area, but also on many other factors such as muscle contractility, metabolism, and fiber type atrophy 49,50 , as well as neuromuscular recruitment, coordination, and fatigue mechanisms 51,52 , pain and psychosocial factors 53 .…”

Section: Discussionmentioning

confidence: 99%

Lumbar Spine Paraspinal Muscle and Intervertebral Disc Height Changes in Astronauts After Long-Duration Spaceflight on the International Space Station

Chang

Healey

Snyder

et al. 2016

Spine

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Study Design-Prospective case seriesObjective-Evaluate lumbar paraspinal muscle (PSM) cross-sectional area and intervertebral disc (IVD) height changes induced by a 6-month space mission on the International Space Station (ISS). The long-term objective of this project is to promote spine health and prevent spinal injury during space missions as well as here on Earth.Summary of Background-NASA crewmembers have a 4.3 times higher risk of herniated IVDs, compared to the general and military aviator populations. The highest risk occurs during the first year after a mission. Microgravity exposure during long-duration spaceflights results in ~5cm lengthening of body height, spinal pain, and skeletal deconditioning. How the PSMs and IVDs respond during spaceflight is not well described.Methods-Six NASA crewmembers were imaged supine with a 3T MRI. Imaging was conducted pre-flight, immediately post-flight and then 33 to 67 days after landing. Functional cross-sectional area (FCSA) measurements of the PSMs were performed at the L3-4 level. FCSA was measured by grayscale thresholding within the posterior lumbar extensors to isolate lean muscle on T2-weighted scans. IVD heights were measured at the anterior, middle and posterior sections of all lumbar levels. Repeated measures ANOVA was used to determine significance at p<0.05, followed by post-hoc testing.Results-Paraspinal lean muscle mass, as indicated by the FCSA, decreased from 86% of the total PSM cross-sectional area down to 72%, immediately after the mission. Recovery of 68% of HHS Public AccessAuthor manuscript Spine (Phila Pa 1976 Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript the post-flight loss occurred over the next 6 weeks, still leaving a significantly lower lean muscle fractional content compared to pre-flight values. In contrast, lumbar IVD heights were not appreciably different at any time point.Conclusions-The data reveal lumbar spine PSM atrophy after long-duration spaceflight. Some FCSA recovery was seen with 46 days post-flight in a terrestrial environment, but it remained incomplete compared to pre-flight levels.

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Section: Discussionmentioning

confidence: 99%

Lumbar Spine Paraspinal Muscle and Intervertebral Disc Height Changes in Astronauts After Long-Duration Spaceflight on the International Space Station

Chang

Healey

Snyder

et al. 2016

Spine

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“…While is it also tempting to assume the energy expended is simply the oxygen consumption measured over the event, like the numerator there is clearly more chemical energy being used by the body than is being accounted for in the denominator. Even so, misuse of "efficiency" persists (11).…”

Section: (External Mechanical Work Done/energy Expended) X 100mentioning

confidence: 99%

Misuse of “Power” and Other Mechanical Terms in Sport and Exercise Science Research

Winter

Abt

Brookes

et al. 2016

Journal of Strength and Conditioning Research

122

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“…[2][3][4][5][6][7][8][9] Generally, an experimental finding that a given OXPHOS complex deficiency/inhibition significantly decreases V O 2 in isolated mitochondria in state 3 does not mean that the same effect will be seen in intact skeletal muscle during moderate and heavy work for the same degree of complex deficiency.…”

Section: Theoretical Resultsmentioning

confidence: 99%

Effects of OXPHOS complex deficiencies and ESA dysfunction in working intact skeletal muscle: implications for mitochondrial myopathies

Korzeniewski

2015

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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The effects of inborn oxidative phosphorylation (OXPHOS) complex deficiencies or possible each-step activation (ESA) dysfunction on the bioenergetic system in working intact skeletal muscle are studied using a computer model of OXPHOS published previously. The curves representing the dependencies of V˙O2 and metabolite concentrations on single complex activity, entire OXPHOS activity or ESA intensity exhibit a characteristic threshold at some OXPHOS complex activity/ESA intensity. This threshold for V˙O2 of single complex activities is significantly lower in intact muscle during moderate and heavy work, than in isolated mitochondria in state 3. Metabolite concentrations and pH in working muscle start to change significantly at much higher OXPHOS complex activities/ESA intensities than V˙O2. The effect of entire OXPHOS deficiency or ESA dysfunction is potentially much stronger than the effect of a single complex deficiency. Implications of these findings for the genesis of mitochondrial myopathies are discussed. It is concluded that V˙O2 in state 3 and its dependence on complex activity in isolated mitochondria is not a universal quantitative determinant of the effect of mitochondrial dysfunctions in vivo. Moderate and severe mitochondria dysfunctions are defined: the former affect significantly only metabolite concentrations and pH, while the latter also decrease significantly V˙O2 in intact skeletal muscle during work. The dysfunction-caused decrease in V˙O2/oxidative ATP synthesis flux, disturbance of metabolite homeostasis, elevated ROS production and anaerobic glycolysis recruitment can account for such mitochondrial myopathy symptoms as muscle weakness, exercise intolerance (exertional fatigue) and lactic acidosis.

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Skeletal Muscle Fatigue and Decreased Efficiency

Cited by 191 publications

References 36 publications

Lumbar Spine Paraspinal Muscle and Intervertebral Disc Height Changes in Astronauts After Long-Duration Spaceflight on the International Space Station

Lumbar Spine Paraspinal Muscle and Intervertebral Disc Height Changes in Astronauts After Long-Duration Spaceflight on the International Space Station

Misuse of “Power” and Other Mechanical Terms in Sport and Exercise Science Research

Effects of OXPHOS complex deficiencies and ESA dysfunction in working intact skeletal muscle: implications for mitochondrial myopathies

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