Institution
Manchester Metropolitan University
Education•Manchester, Manchester, United Kingdom•
About: Manchester Metropolitan University is a education organization based out in Manchester, Manchester, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 5435 authors who have published 16202 publications receiving 442561 citations. The organization is also known as: Manchester Polytechnic & MMU.
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TL;DR: Loss of motor neurons and remodelling of surviving motor units constitutes the major change in ageing muscles and probably contributes to muscle loss and functional impairments.
Abstract: Voluntary control of skeletal muscle enables humans to interact with and manipulate the environment. Lower muscle mass, weakness and poor coordination are common complaints in older age and reduce physical capabilities. Attention has focused on ways of maintaining muscle size and strength by exercise, diet or hormone replacement. Without appropriate neural innervation, however, muscle cannot function. Emerging evidence points to a neural basis of muscle loss. Motor unit number estimates indicate that by age around 71 years, healthy older people have around 40 % fewer motor units. The surviving low- and moderate-threshold motor units recruited for moderate intensity contractions are enlarged by around 50 % and show increased fibre density, presumably due to collateral reinnervation of denervated fibres. Motor unit potentials show increased complexity and the stability of neuromuscular junction transmissions is decreased. The available evidence is limited by a lack of longitudinal studies, relatively small sample sizes, a tendency to examine the small peripheral muscles and relatively few investigations into the consequences of motor unit remodelling for muscle size and control of movements in older age. Loss of motor neurons and remodelling of surviving motor units constitutes the major change in ageing muscles and probably contributes to muscle loss and functional impairments. The deterioration and remodelling of motor units likely imposes constraints on the way in which the central nervous system controls movements.
112 citations
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TL;DR: The present study showed that muscle oxygen uptake and energy turnover are elevated during dynamic contractions at a frequency of 100 compared with 60 r.p.m. and that Muscle oxygen uptake increased as exercise progressed in a manner that was not solely related to the increase in muscle temperature and lactate accumulation.
Abstract: 1. It has been established that pulmonary oxygen uptake is greater during cycle exercise in humans at high compared to low contraction frequencies. However, it is unclear whether this is due to more work being performed at the high frequencies and whether the energy turnover of the working muscles is higher. The present study tested the hypothesis that human skeletal muscle oxygen uptake and energy turnover are elevated during exercise at high compared to low contraction frequency when the total power output is the same. 2. Seven subjects performed single-leg dynamic knee-extensor exercise for 10 min at contraction frequencies of 60 and 100 r.p.m. where the total power output (comprising the sum of external and internal power output) was matched between frequencies (54 +/- 5 vs. 56 +/- 5 W; mean +/- S.E.M.). Muscle oxygen uptake was determined from measurements of thigh blood flow and femoral arterial - venous differences for oxygen content (a-v O(2) diff). Anaerobic energy turnover was estimated from measurements of lactate release and muscle lactate accumulation as well as muscle ATP and phosphocreatine (PCr) utilisation based on analysis of muscle biopsies obtained before and after each exercise bout. 3. Whilst a-v O(2) diff was the same between contraction frequencies during exercise, thigh blood flow was higher (P < 0.05) at 100 compared to 60 r.p.m. Thus, muscle V(O2) was higher (P < 0.05) during exercise at 100 r.p.m. Muscle V(O2) increased (P < 0.05) by 0.06 +/- 0.03 (12 %) and 0.09 +/- 0.03 l min(-1) (14 %) from the third minute to the end of exercise at 60 and 100 r.p.m., respectively, but there was no difference between the two frequencies. 4. Muscle PCr decreased by 8.1 +/- 1.7 and 9.1 +/- 2.0 mmol (kg wet wt)(-1), and muscle lactate increased to 6.8 +/- 2.1 and 9.8 +/- 2.5 mmol (kg wet wt)(-1) during exercise at 60 and 100 r.p.m., respectively. The total release of lactate during exercise was 48.7 +/- 8.8 and 64.3 +/- 10.6 mmol at 60 and 100 r.p.m. (not significant, NS). The total anaerobic ATP production was 47 +/- 8 and 61 +/- 12 mmol kg(-1), respectively (NS). 5. Muscle temperature increased (P < 0.05) from 35.8 +/- 0.3 to 38.2 +/- 0.2 degrees C at 60 r.p.m. and from 35.9 +/- 0.3 to 38.4 +/- 0.3 degrees C at 100 r.p.m. Between 1 and 7 min muscle temperature was higher (P < 0.05) at 100 compared to 60 r.p.m. 6. The estimated mean rate of energy turnover during exercise was higher (P < 0.05) at 100 compared to 60 r.p.m. (238 +/- 16 vs. 194 +/- 11 J s(-1)). Thus, mechanical efficiency was lower (P < 0.05) at 100 r.p.m. (24 +/- 2 %) compared to 60 r.p.m. (28 +/- 3 %). Correspondingly, efficiency expressed as work per mol ATP was lower (P < 0.05) at 100 than at 60 r.p.m. (22.5 +/- 2.1 vs. 26.5 +/- 2.5 J (mmol ATP)(-1)). 7. The present study showed that muscle oxygen uptake and energy turnover are elevated during dynamic contractions at a frequency of 100 compared with 60 r.p.m. It was also observed that muscle oxygen uptake increased as exercise progressed in a manner that was not solely related to the increase in muscle temperature and lactate accumulation.
111 citations
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TL;DR: Four different filtering and differentiation sequences for the calculation of the higher derivatives from noisy displacement data when using a second-order Butterworth filter and first-order finite differences are investigated, indicating that the conventional strategy has to be reconsidered and modified.
111 citations
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TL;DR: The effect of combined action observation and MI on corticospinal excitability, in comparison to either observation or imagery alone, is investigated, with implications for stroke rehabilitation, where combined action observed and MI interventions may prove to be more effective than observation and imagery alone.
Abstract: Observation and imagery of movement both activate similar brain regions to those involved in movement execution. As such, both are recommended as techniques for aiding the recovery of motor function following stroke. Traditionally, action observation and movement imagery (MI) have been considered as independent intervention techniques. Researchers have however begun to consider the possibility of combining the two techniques into a single intervention strategy. This study investigated the effect of combined action observation and MI on corticospinal excitability, in comparison to either observation or imagery alone. Single-pulse transcranial magnetic stimulation (TMS) was delivered to the hand representation of the left motor cortex during combined action observation and MI, passive observation (PO), or MI of right index finger abduction-adduction movements or control conditions. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles of the right hand. The combined action observation and MI condition produced MEPs of larger amplitude than were obtained during PO and control conditions. This effect was only present in the FDI muscle, indicating the facilitation of corticospinal excitability during the combined condition was specific to the muscles involved in the observed/imagined task. These findings have implications for stroke rehabilitation, where combined action observation and MI interventions may prove to be more effective than observation or imagery alone.
111 citations
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TL;DR: The potential for conviviality and intimacy to be fostered in the dark, the aesthetics and atmospherics of darkness and shadow, the possibilities for apprehending the world through other senses and the dismissal of the star-saturated... as mentioned in this paper explores the various qualities of darkness that have contributed to the experience of the city.
Abstract: Given geography’s neglect of illuminated and dark space, this paper explores the various qualities of darkness that have contributed to the experience of the city. In recent history, darkness has been conceptualised negatively, for instance, with the ‘dark side’ and the ‘forces of darkness’ conceived as the opposite of that which enlightens and illuminates. Perhaps such metaphors testify to earlier urban conditions in which perils of all sorts lurked in the nocturnal city and doors were closed when darkness fell. Yet modern illumination has transformed nocturnal urban experience, producing cityscapes of regulation, hierarchical selectiveness, consumption, fantasy and imagination. However, this article suggests that the more positive qualities of darkness have been overlooked: the potential for conviviality and intimacy to be fostered in the dark, the aesthetics and atmospherics of darkness and shadow, the possibilities for apprehending the world through other senses and the dismissal of the star-saturated...
111 citations
Authors
Showing all 5608 results
Name | H-index | Papers | Citations |
---|---|---|---|
David T. Felson | 153 | 861 | 133514 |
João Carvalho | 126 | 1278 | 77017 |
Andrew M. Jones | 103 | 764 | 37253 |
Michael C. Carroll | 100 | 399 | 34818 |
Mark Conner | 98 | 379 | 47672 |
Richard P. Bentall | 94 | 431 | 30580 |
Michael Wooldridge | 87 | 543 | 50675 |
Lina Badimon | 86 | 682 | 35774 |
Ian Parker | 85 | 432 | 28166 |
Kamaruzzaman Sopian | 84 | 989 | 25293 |
Keith Davids | 84 | 604 | 25038 |
Richard Baker | 83 | 514 | 22970 |
Joan Montaner | 80 | 489 | 22413 |
Stuart Robert Batten | 78 | 325 | 24097 |
Craig E. Banks | 77 | 569 | 27520 |