The influence of age on the assessment of motor unit activation in a human hand muscle

Spiegel, KM; Stratton, James; Burke,; Glendinning, DS; Rm, Enoka

doi:10.1113/expphysiol.1996.sp003978

Cited by 72 publications

(52 citation statements)

References 20 publications

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“…Appearance of a decline in tension from 21/22 to 27 mo of age for type FF and FR units might indicate that the capture of extra-muscle fibers and the subsequent recovery of the contractile function of reinnervated muscle fibers take time to overwhelm the effects of atrophy and a decrease in specific tension. This remodeling of the motor units may be related to findings of Masakado et al (1994), who reported that the variance in the relationship between the motor-unit tension and recruitment threshold was greater in the elderly subject compared with younger ones (but see also Spiegel et al 1996). Erim et al (1999) also observed a disturbance of the onionskin phenomenon in the relationship between firing rate and recruitment threshold in a human muscle.…”

Section: Discussionmentioning

confidence: 68%

Progress of Age-Related Changes in Properties of Motor Units in the Gastrocnemius Muscle of Rats

Sugiura¹,

Kanda²

2004

Journal of Neurophysiology

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Sugiura, Miho and Kenro Kanada. Progress of age-related changes in properties of motor units in the gastrocnemius muscle of rats. J Neurophysiol 92: 1357-1365, 2004. First published April 14, 2004 10.1152/jn.00947.2003. The mechanical properties of individual motor units in the medial gastrocnemius muscle, as well as the whole muscle properties and innervating motor nucleus, were investigated in dietary-restricted, male Fischer 344/DuCrj rats at ages of 4, 7, 12, 21/22, 27, 31, and 36 mo. The tetanic tension of the type S units continuously increased until the age of 36 mo. Those of type FF and FR units declined from 21/22 to 27 mo of age but did not change further while the whole muscle tension decreased greatly. The atrophy of muscle fibers, the decline in motoneuron number and axonal conduction velocity, and the decrease in the posttetanic potentiation of twitch contraction of motor units seemed to start after 21/22 mo of age and were accelerated with advancing age. Prolongation of twitch contraction time was evident for only type S and FR units in 36-moold rats. The fatigue index was greatly increased for type FF units in 36-mo-old rats. These findings indicated that the progress of changes in various properties occurring in the senescent muscle was different in terms of their time course and degree and also dependent on the types of motor unit. The atrophy and decrease in specific tension of muscle fibers affected the decline in tension output of motor units. This was effectively compensated for by the capture of denervated muscle fibers over time.

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Section: Discussionmentioning

confidence: 68%

Progress of Age-Related Changes in Properties of Motor Units in the Gastrocnemius Muscle of Rats

Sugiura¹,

Kanda²

2004

Journal of Neurophysiology

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“…For example, in-phase modulation of percent power in the interference EMG of the agonist and antagonist muscles would increase coactivation, thereby stiffening the joint and reducing the fluctuations in acceleration (19,31). There is evidence that old adults exhibit increased coactivation during slow abduction-adduction movements of the index finger (1,24,35). Furthermore, the broader peak in the power spectrum for the old adults (50-125 Hz vs. 25-50 Hz) likely reduced phase differences between the frequency components of the signal (28) and resulted in less alternating activation between the agonist and antagonist muscles.…”

Section: Discussionmentioning

confidence: 99%

Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults

Christou

Shinohara

Enoka

2003

Journal of Applied Physiology

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Christou, Evangelos A., Minoru Shinohara, and Roger M. Enoka. Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults. J Appl Physiol 95: 373-384, 2003. First published March 21, 2003 10.1152/japplphysiol.00060. 2003.-The purpose of the study was to assess the effect of movement velocity on the relation between fluctuations in acceleration and the ability to achieve a target velocity during voluntary contractions performed by young (29.5 Ϯ 4.3 yr) and old (74.9 Ϯ 6.2 yr) adults. Subjects performed concentric and eccentric contractions with the first dorsal interosseus muscle while lifting a submaximal load (15% of maximum) at six movement velocities (0.03-1.16 rad/s). Fluctuations in acceleration, the accuracy of matching the target velocity, and electromyographic (EMG) activity were determined from three trials for each contraction type and movement velocity. The fluctuations in acceleration increased with movement velocity for both concentric and eccentric contractions, but they were greatest during fast eccentric contractions (ϳ135%) when there was stronger modulation of acceleration in the 5-to 10-Hz bandwidth. Nonetheless, EMG amplitude for first dorsal interosseus increased with movement velocity only for concentric and not eccentric contractions. Consistent with the minimum variance theory, movement accuracy was related to the fluctuations in acceleration for both types of contractions in all subjects. For a given level of fluctuations in acceleration, however, old subjects were three times less accurate than young subjects. Although the EMG amplitude at each speed was similar for young and old adults, only the young adults modulated the power in the EMG spectrum with speed. Thus the fluctuations in acceleration during voluntary contractions had a more pronounced effect on movement accuracy for old adults compared with young adults, probably due to factors that influenced the frequency-domain characteristics of the EMG. concentric contraction; eccentric contraction; electromyogram; first dorsal interosseus; frequency spectrum THE FORCE EXERTED BY A MUSCLE during a voluntary contraction is not constant, but rather it fluctuates about an average value (2,15,25,33,36). The neural mechanisms most responsible for the fluctuations in the force exerted by hand muscles appear to be the regularity with which motoneurons discharge action potentials and the common modulation of motor unit discharge in the agonist and antagonist muscles (7,10,13,16,41). Fluctuations in muscle force impose a significant constraint on the ability of the nervous system to control movement by influencing the capacity to exert a desired force and to achieve an intended trajectory (17,18,43).The minimum variance theory postulates that the central nervous system attenuates this constraint during the performance of goal-directed movements by selecting activation strategies that minimize the variance in the trajectory of the movement (18,43). One prediction of this theory is t...

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“…We did this because there is evidence that force variability increases with contraction speed (Christou and Carlton 2002;Poston et al 2010). In addition, previous work suggests that older adults exhibit a faster rate of force release than young adults and compared with force increase (Spiegel et al 1996). Thus, constraining the rate of force provided a more fair comparison of the capacity of young and older adults to control force for the two phases.…”

Section: )mentioning

confidence: 99%

“…This finding seemed to be independent of the participant's age or rate of force generation. Another study involving isometric contractions of the first dorsal interosseous muscle demonstrated that older adults exhibited more difficulty during the release force phase of the task (Spiegel et al 1996). In both studies, the rate of force increase and release was not controlled.…”

mentioning

confidence: 98%

Motor control differs for increasing and releasing force

Park

Kwon

Solis

et al. 2016

Journal of Neurophysiology

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The influence of age on the assessment of motor unit activation in a human hand muscle

Cited by 72 publications

References 20 publications

Progress of Age-Related Changes in Properties of Motor Units in the Gastrocnemius Muscle of Rats

Progress of Age-Related Changes in Properties of Motor Units in the Gastrocnemius Muscle of Rats

Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults

Motor control differs for increasing and releasing force

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