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Muscle Work (muscle + work)
Selected AbstractsPhysiological costs of the hearing due to noise exposure, additional physical stress, and combined exposure to alcohol and cigarette smokeHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 3 2002H. Strasser In 2 studies, each with 5 test series, physiological costs of the hearing due to legally tolerable noise exposures of 94 dB (A) for 1 hr have been measured audiometrically. The temporary threshold shifts (TTS) and their restitution time, as well as cardiovascular responses in work-related heart rate increases, of 10 and 8 subjects (Ss), respectively, could be shown to be modulated by additional physical stress and combined exposure to alcohol (Study 1) and cigarette smoke (Study 2). Moderate dynamic muscle work (50 W) administered via a bicycle ergometer either immediately after noise, or simultaneous to the noise exposure, significantly reduced restitution time as well as the integrated restitution temporary threshold shift (IRTTS). A physical stress to 100 W,which exceeded the endurance level when demanded simultaneously to the noise exposure,did not show any favorable effects. However, if the same physical stress succeeded the noise exposure, and when it was interrupted several times for the audiometric measurements, it also brought about significant accelerations of the restitution processes. Some reductions in physiological costs of the hearing were found due to an intervening alcohol consumption (blood alcohol concentration , 0.08%) prior to the noise exposure and a simultaneous physical load of 50 W. Smoking 10 cigarettes instead of the consumption of alcohol was associated with a reduced TTS, but a prolonged restitution time. IRTTS as total physiological costs of the most unfavorable combination of noise, simultaneous high physical workload, and preceding smoke exposure was increased. The results of the test series with cigarette smoke,probably due to the small group of just 8 Ss and the counteracting effects of the agents carbon monoxide (CO) and nicotine,were not statistically significant, but these exposures were associated with a substantial activation of the cardiovascular system. Significant heart rate increases are evidence that CO and nicotine must not be neglected as influential factors in the context of physiological costs that the organism, and especially the hearing, has to pay for noise exposures. © 2002 Wiley Periodicals, Inc. [source] Muscle Endurance in Elderly Nursing Home Residents Is Related to Fatigue Perception, Mobility, and Circulating Tumor Necrosis Factor-Alpha, Interleukin-6, and Heat Shock Protein 70JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 3 2008(See editorial comments by Drs. Hermes Florez, Bruce R. Troen, pp 55 OBJECTIVES: To explore the relationships between muscle endurance and circulating interleukin (IL)-6, tumor necrosis factor alpha (TNF-,), and heat shock protein (Hsp)70 in nursing home residents and to assess how muscle endurance relates to self-perceived fatigue and mobility. DESIGN: Exploratory study. SETTING: Three nursing homes of the Foundation for Psychogeriatrics (Brussels, Belgium). PARTICIPANTS: Seventy-seven residents (53 female and 24 male, mean age 81 ± 8). MEASUREMENTS: Participants were assessed for muscle endurance (fatigue resistance and grip work); perceived fatigue (visual analogue scale for fatigue); fatigue during daily activities (Mobility-Tiredness Scale); effect of fatigue on quality of life (World Health Organization Quality Of Life questionnaire); mobility (Tinetti Test & Elderly Mobility Scale (EMS)); and circulating IL-6, TNF-,, and Hsp70. RESULTS: Residents with better fatigue resistance reported less self-perceived tiredness (P<.05). Similar trends were observed for fatigue during daily activities and for the extent to which fatigue bothered subjects. Higher grip work was associated with less self-perceived fatigue on all fatigue scales (P<.01). Fatigue resistance and grip work were positively related to balance and basic mobility (all P<.01; trend for relationship between fatigue resistance and EMS). Subjects with high IL-6 and Hsp70 showed significantly worse fatigue resistance (P=.007) and muscle work (P=.045) than those with high IL-6 and low Hsp70. In male residents, higher TNF-, was related to worse fatigue resistance and grip work (P<.05). CONCLUSION: Elderly nursing home residents complaining of fatigue need to be taken seriously, because they show worse muscle endurance, which is related to poorer mobility. Inflammatory processes involving TNF-, and the interaction between IL-6 and Hsp70 are related to poorer muscle endurance in these patients. [source] Characterisation of human soft palate muscles with respect to fibre types, myosins and capillary supplyJOURNAL OF ANATOMY, Issue 2 2000PER S. STÅL Four human soft palate muscles, and palatopharyngeus, the uvula, the levator and tensor veli palatini were examined using enzyme-histochemical, immunohistochemical and biochemical methods and compared with human limb and facial muscles. Our results showed that each palate muscle had a distinct morphological identity and that they generally shared more similarities with facial than limb muscles. The palatopharyngeus and uvula muscles contained 2 of the highest proportions of type II fibres ever reported for human muscles. In contrast, the levator and tensor veli palatini muscles contained predominantly type I fibres. A fetal myosin heavy chain isoform (MyHC), not usually found in normal adult limb muscles, was present in a small number of fibres in all palate muscles. The mean muscle fibre diameter was smaller than in limb muscles and the individual and intramuscular variability in diameter and shape was considerable. All palate muscles had a high capillary density and an unusually high mitochondrial enzyme activity in the type II fibres, in comparison with limb muscles. No ordinary muscle spindles were observed. The fibre type and MyHC composition indicate that the palatopharyngeus and uvula muscles are functionally involved in quick movements whereas the levator and tensor veli palatini muscles perform slower and more continuous contractions. The high aerobic capacity and the rich capillarisation suggest that the palate muscles are relatively fatigue resistant. Absence of ordinary muscle spindles indicates a special proprioceptive control system. The special morphology of the palate muscles may be partly related to the unique anatomy with only one skeletal insertion, a feature consistent with muscle work at low load and tension and which may influence the cytoarchitecture of these muscles. Other important factors determining the special morphological characteristics might be specific functional requirements, distinct embryological origin and phylogenetic factors. [source] MRP1/GS-X pump ATPase expression: is this the explanation for the cytoprotection of the heart against oxidative stress-induced redox imbalance in comparison to skeletal muscle cells?CELL BIOCHEMISTRY AND FUNCTION, Issue 1 2007Maurício S. Krause Abstract Striated muscle activity is always accompanied by oxidative stress (OxStress): the more intense muscle work and/or its duration, the more a redox imbalance may be attained. In spite of cardiac muscle functioning continuously, it is well known that the heart does not suffer from OxStress-induced damage over a broad physiological range. Although the expression of antioxidant enzymes may be of importance in defending heart muscle against OxStress, a series of combined antioxidant therapeutic approaches have proved to be mostly ineffective in avoiding cellular injury. Hence, additional mechanisms may be involved in heart cytoprotection other than antioxidant enzyme activities. The strong cardiotoxic effect of doxorubicin-induced cancer chemotherapy shed light on the possible role for multidrug resistance-associated proteins (MRP) in this context. Muscle activity-induced ,physiological' OxStress enhances the production of glutathione disulfide (GSSG) thus increasing the ratio of GSSG to glutathione (GSH) content inside the cells, which, in turn, leads to redox imbalance. Since MRP1 gene product (a GS-X pump ATPase) is a physiological GSSG transporter, adult Wistar rats were tested for MRP1 expression and activity in the heart and skeletal muscle (gastrocnemius), in as much as the latter is known to be extremely sensitive to muscle activity-induced OxS. MRP1 expression was completely absent in skeletal muscle. In contrast, the heart showed an exercise training-dependent induction of MRP1 protein expression which was further augmented (2.4-fold) as trained rats were challenged with a session of acute exercise. On the other hand, inducible expression of the 70-kDa heat shock protein (HSP70), a universal marker of cellular stress, was completely absent in the heart of sedentary and acutely exercised rats, whereas skeletal muscle showed a conspicuous exercise-dependent HSP70 expression, which decreased by 45% with exercise training. This effect was paralleled by a 58% decrease in GSH content in skeletal muscle which was even higher (an 80%-fall) after training thus leading to a marked redox imbalance ([GSSG]/[GSH] raised up to 38-fold). In the heart, GSH contents and [GSSG]/[GSH] ratio remained virtually unchanged even after exercise challenges, while GS-X pump activity was found to be 20% higher in the heart related to skeletal muscle. These findings suggest that an intrinsic higher capacity to express the MRP1/GS-X pump may dictate the redox status in the heart muscle thus protecting myocardium by preventing GSSG accumulation in cardiomyocytes as compared to skeletal muscle fibres. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||