2000
DOI: 10.1002/(sici)1097-4598(200004)23:4<600::aid-mus20>3.0.co;2-d
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Steadiness is reduced and motor unit discharge is more variable in old adults

Abstract: The purpose of this study was to compare the steadiness and discharge rate of motor units during submaximal contractions performed by young and old adults. Subjects performed isometric and slow shortening and lengthening contractions with the first dorsal interosseous muscle. The steadiness of the isometric and slow anisometric contractions was less for the old subjects compared with young subjects, especially at the lower target forces and with the lightest loads. Furthermore, the steadiness of the lengthenin… Show more

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Cited by 341 publications
(165 citation statements)
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References 37 publications
(46 reference statements)
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“…Here, decreased accuracy was shown by higher NMAE and NPAE, and decreased steadiness was shown by increased NSAE (figure 2a) in force fluctuations with increased levels of force-matching tasks, at 15 per cent when compared with at 20 per cent MVICs. These results are in agreement with the previous studies which reported that higher levels of submaximal force output resulted in greater inaccuracy and unsteadiness, in particular at lower levels of effort (Enoka et al 1999;Slifkin & Newell 1999;Laidlaw et al 2000).…”
Section: Discussionsupporting
confidence: 93%
“…Here, decreased accuracy was shown by higher NMAE and NPAE, and decreased steadiness was shown by increased NSAE (figure 2a) in force fluctuations with increased levels of force-matching tasks, at 15 per cent when compared with at 20 per cent MVICs. These results are in agreement with the previous studies which reported that higher levels of submaximal force output resulted in greater inaccuracy and unsteadiness, in particular at lower levels of effort (Enoka et al 1999;Slifkin & Newell 1999;Laidlaw et al 2000).…”
Section: Discussionsupporting
confidence: 93%
“…In general, the lesser EMG during an eccentric contraction when lowering a given load (6,42) is attributed to a lower discharge rate and the recruitment of fewer motor units (6,23,34). The reduction in discharge rate likely includes an increased variability in discharge (12,23,29,30), which can decrease twitch fusion and increase the fluctuations in the forces exerted by individual motor units (12,14). Some evidence indicates that discharge rate variability of the motor units and fluctuations in motor output increase with movement speed for both concentric (40,41) and eccentric contractions (22).…”
Section: Discussionmentioning
confidence: 99%
“…One prediction of this theory is that the accuracy of goaldirected movements should decline as the amplitude of the force fluctuations increases. Therefore, the accuracy of goal-directed movements should vary with changes in movement velocity (41), the type of muscle contraction performed (2, 3, 5), and the age of the individual (1,12,15,23,38).The purpose of the study was to assess the effect of movement velocity on the fluctuations in acceleration and the ability to achieve a target velocity when young and old adults performed anisometric contractions with the first dorsal interosseus muscle. The results were consistent with the prediction of the minimum variance theory that movement accuracy declines with an increase in the fluctuations of acceleration; nonetheless, the relations differed for young and old adults.…”
mentioning
confidence: 99%
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“…In addition, lengthening contractions are also associated with reduced motor performance [12][13][14]. Interestingly, the magnitude of this deficit is thought to be increased by advancing age, with greater impairments in performance observed in old adults during lengthening movements [13,[15][16][17][18], which may contribute to the increased incidence of falls in the elderly [19].…”
Section: Introductionmentioning
confidence: 99%