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

2003 ◽  
Vol 95 (1) ◽  
pp. 373-384 ◽  
Author(s):  
Evangelos A. Christou ◽  
Minoru Shinohara ◽  
Roger M. Enoka
Keyword(s):  
Young Adults ◽  
Eccentric Contractions ◽  
Emg Activity ◽  
Target Velocity ◽  
Movement Velocity ◽  
Movement Accuracy ◽  
Old Adults ◽  
Emg Amplitude ◽  
First Dorsal Interosseus ◽  
Voluntary Contractions

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 ± 4.3 yr) and old (74.9 ± 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 (∼135%) 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.

Modification in Movement Accuracy in the Triphasic Pattern during a Rapid Forearm-Flexion Task

1988 ◽  
Vol 67 (2) ◽  
pp. 455-460 ◽  
Author(s):  
Michel André Roy ◽  
Betsy A. Keller ◽  
Pierre P. Lagassé
Keyword(s):  
Movement Time ◽  
Limb Movement ◽  
Emg Activity ◽  
Maximum Speed ◽  
Propulsive Force ◽  
Antagonist Activity ◽  
Movement Velocity ◽  
Movement Accuracy ◽  
Triphasic Pattern

The present study was designed to investigate modifications in the triphasic EMG pattern during a forearm-flexion task at maximum speed which required three levels of movement accuracy. 36 subjects participated in 4 training sessions, performing a total of 200 repetitions of each movement. The fastest movement time was associated with the least accurate movement task. Likewise, the slowest movement time was found for the movement requiring the greatest accuracy. Differences in the duration and amplitude of agonist 1 activity, the start of agonist 2 activity, and the start and amplitude of antagonist activity were observed for the three movements. The results indicate that agonist 1 provides a propulsive force to initiate limb movement. The antagonist EMG activity was thought responsible for braking and correcting limb movement. Modifications in agonist 2 activity suggest this burst is related to movement velocity.

scholarly journals Age and load compliance alter time to task failure for a submaximal fatiguing contraction with the lower leg

2010 ◽  
Vol 108 (6) ◽  
pp. 1510-1519 ◽  
Author(s):  
Erin E. Griffith ◽  
Tejin Yoon ◽  
Sandra K. Hunter
Keyword(s):  
Young Adults ◽  
Force Control ◽  
Position Control ◽  
Lower Leg ◽  
Emg Activity ◽  
Time To Failure ◽  
Control Task ◽  
Task Failure ◽  
Old Adults ◽  
Rate Of Increase

The purpose of this study was to compare the time to failure and muscle activation of young and old adults for a sustained isometric submaximal contraction with the dorsiflexor muscles when the foot was restrained to a force transducer (force-control task) compared with supporting an equivalent inertial load unrestrained in the sagittal plane (position-control task). Seventeen young (23.6 ± 6.5 yr) and 12 old (70.0 ± 5.0 yr) adults performed the force-control and position-control tasks at 30% maximal voluntary contraction (MVC) until task failure on separate days. Despite the similar load torque for each task, time to failure was longer for the force-control than position-control task (10.4 ± 4.5 vs. 8.6 ± 3.4 min, P = 0.03) for the young and old adults. The old adults, however, had a longer time to task failure than the young adults for both tasks (11.4 ± 4.4 vs. 8.1 ± 2.1 min, P = 0.01), with no interaction of age and task ( P = 0.83). The rate of increase in agonist and antagonist root-mean-square EMG, agonist EMG bursting activity, mean arterial pressure, and heart rate during the fatiguing contraction was greater for the position-control than force-control task for the young and old adults. The old adults had a less rapid rate of increase in EMG activity, fluctuations in motor output, and cardiovascular measures than the young adults for both tasks. Development of fatigue can be manipulated in young and old adults by providing greater support to the foot and less ankle compliance during daily and ergonomic tasks that require prolonged activation of the lower leg. Minimizing load compliance to one degree of freedom during a position-control task maintained the greater fatigue resistance with age for an isometric contraction.

scholarly journals Recovery from supraspinal fatigue is slowed in old adults after fatiguing maximal isometric contractions

2008 ◽  
Vol 105 (4) ◽  
pp. 1199-1209 ◽  
Author(s):  
Sandra K. Hunter ◽  
Gabrielle Todd ◽  
Jane E. Butler ◽  
Simon C. Gandevia ◽  
Janet L. Taylor
Keyword(s):  
Young Adults ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Voluntary Activation ◽  
Old Adults ◽  
Flexor Muscles ◽  
Fatiguing Exercise ◽  
Voluntary Contractions ◽  
Potential Area ◽  
Period Duration

This study compared the contribution of supraspinal fatigue to muscle fatigue in old and young adults. Transcranial magnetic stimulation (TMS) of motor cortex was used to assess voluntary activation during maximal voluntary contractions (MVCs) of elbow flexor muscles in 17 young adults (25.5 ± 3.6 yr; mean ± SD) and 7 old adults (73.0 ± 3.3 yr). Subjects performed a fatigue task involving six sustained MVCs (22-s duration, separated by 10 s). Young adults exhibited greater reductions in maximal voluntary torque (67 ± 15% of baseline) than the old (37 ± 6%; P < 0.001). Increments in torque (superimposed twitch) generated by TMS during sustained MVCs increased for the young and old ( P < 0.001) but were larger for the old adults at the start of the sustained contractions and during recovery ( P < 0.05). Voluntary activation was less for the old adults at the start of some sustained contractions and during recovery ( P = 0.02). Motor-evoked potential area increased similarly with age during the fatiguing task but was greater for the old adults than young during recovery. Silent period duration lengthened less for the old adults during the fatigue task. At the end of the fatiguing task, peak relaxation rate of muscle fibers had declined more in the young than the old adults. The greater endurance with age is largely due to a difference in mechanisms located within the muscle. However, recovery from the fatiguing exercise is impaired for old adults because of greater supraspinal fatigue than in the young.

The 1- to 2-Hz oscillations in muscle force are exacerbated by stress, especially in older adults

2004 ◽  
Vol 97 (1) ◽  
pp. 225-235 ◽  
Author(s):  
Evangelos A. Christou ◽  
Jennifer M. Jakobi ◽  
Ashley Critchlow ◽  
Monika Fleshner ◽  
Roger M. Enoka
Keyword(s):  
Young Adults ◽  
Grip Force ◽  
Stress Hormones ◽  
Plasma Concentrations ◽  
Precision Grip ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Old Adults ◽  
Force Fluctuations ◽  
Pinch Grip

Although force fluctuations during a steady contraction are often heightened in old adults compared with young adults and are enhanced in young adults during the stress response, the mechanisms underlying the augmentation are uncertain. The purpose of the study was to compare the effect of a stressor on the plasma concentrations of selected stress hormones and on the force fluctuations experienced by young and old adults during the performance of a precision grip. Thirty-six men and women (19–86 yr) participated in a protocol that comprised anticipatory (30 min), stressor (15 min), and recovery periods (25 min). The stressor was a series of noxious electrical stimuli applied to the dorsal surface of the left hand. Subjects sustained a pinch-grip force with the right hand at 2% of the maximal voluntary contraction force. The fluctuations in pinch-grip force, the interference electromyogram (EMG) of six muscles, and the spectra for the force and EMG were quantified across the 70-min protocol. The stressor increased the force fluctuations, largely due to an enhancement of the power at 1–2 Hz in the force spectrum ( r2 = 0.46). The effect was greatest for the old adults compared with young and middle-aged adults. The plasma concentrations of the stress hormones (adrenocorticotropin, epinephrine, and norepinephrine) were elevated to similar levels for all three age groups, and the changes were not associated with modulation of the force fluctuations. Furthermore, the heightened EMG activity exhibited by the old adults during all periods was not related to the changes in the force fluctuations or the 1- to 2-Hz force oscillations. The absence of a change in the mean pinch-grip force during the protocol and the lack of an association between elevation of the plasma concentrations for the stress hormones and modulation of the force fluctuations suggest that the enhanced force fluctuations caused by the stressor was due to an increase in the low-frequency output of the spinal motor neurons.

scholarly journals Supraspinal fatigue impedes recovery from a low-intensity sustained contraction in old adults

2012 ◽  
Vol 112 (5) ◽  
pp. 849-858 ◽  
Author(s):  
Tejin Yoon ◽  
Bonnie Schlinder-Delap ◽  
Manda L. Keller ◽  
Sandra K. Hunter
Keyword(s):  
Young Adults ◽  
Pressor Response ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Voluntary Activation ◽  
Age Difference ◽  
Task Failure ◽  
Old Adults ◽  
Sustained Contraction ◽  
Low Intensity

This study determined the contribution of supraspinal fatigue and contractile properties to the age difference in neuromuscular fatigue during and recovery from a low-intensity sustained contraction. Cortical stimulation was used to evoke measures of voluntary activation and muscle relaxation during and after a contraction sustained at 20% of maximal voluntary contraction (MVC) until task failure with elbow flexor muscles in 14 young adults (20.9 ± 3.6 yr, 7 men) and 14 old adults (71.6 ± 5.4 yr, 7 men). Old adults exhibited a longer time to task failure than the young adults (23.8 ± 9.0 vs. 11.5 ± 3.9 min, respectively, P < 0.001). The time to failure was associated with initial peak rates of relaxation of muscle fibers and pressor response ( P < 0.05). Increments in torque (superimposed twitch; SIT) generated by transcranial magnetic stimulation (TMS) during brief MVCs, increased during the fatiguing contraction ( P < 0.001) and then decreased during recovery ( P = 0.02). The increase in the SIT was greater for the old adults than the young adults during the fatiguing contraction and recovery ( P < 0.05). Recovery of MVC torque was less for old than young adults at 10 min post-fatiguing contraction (75.1 ± 8.7 vs. 83.6 ± 7.8% of control MVC, respectively, P = 0.01) and was associated with the recovery of the SIT ( r = −0.59, r2 = 0.35, P < 0.001). Motor evoked potential (MEP) amplitude and the silent period elicited during the fatiguing contraction increased less for old adults than young adults ( P < 0.05). The greater fatigue resistance with age during a low-intensity sustained contraction was attributable to mechanisms located within the muscle. Recovery of maximal strength after the low-intensity fatiguing contraction however, was impeded more for old adults than young because of greater supraspinal fatigue. Recovery of strength could be an important variable to consider in exercise prescription of old populations.

scholarly journals Specific modulation of corticomuscular coherence during submaximal voluntary isometric, shortening and lengthening contractions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dorian Glories ◽  
Mathias Soulhol ◽  
David Amarantini ◽  
Julien Duclay
Keyword(s):  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Beta Band ◽  
Lengthening Contractions ◽  
Time Frequency ◽  
Corticomuscular Coherence ◽  
Emg Signal ◽  
Voluntary Contractions ◽  
Spinal Excitability

AbstractDuring voluntary contractions, corticomuscular coherence (CMC) is thought to reflect a mutual interaction between cortical and muscle oscillatory activities, respectively measured by electroencephalography (EEG) and electromyography (EMG). However, it remains unclear whether CMC modulation would depend on the contribution of neural mechanisms acting at the spinal level. To this purpose, modulations of CMC were compared during submaximal isometric, shortening and lengthening contractions of the soleus (SOL) and the medial gastrocnemius (MG) with a concurrent analysis of changes in spinal excitability that may be reduced during lengthening contractions. Submaximal contractions intensity was set at 50% of the maximal SOL EMG activity. CMC was computed in the time–frequency domain between the Cz EEG electrode signal and the unrectified SOL or MG EMG signal. Spinal excitability was quantified through normalized Hoffmann (H) reflex amplitude. The results indicate that beta-band CMC and normalized H-reflex were significantly lower in SOL during lengthening compared with isometric contractions, but were similar in MG for all three muscle contraction types. Collectively, these results highlight an effect of contraction type on beta-band CMC, although it may differ between agonist synergist muscles. These novel findings also provide new evidence that beta-band CMC modulation may involve spinal regulatory mechanisms.

Older Adults Use a Unique Strategy to Lift Inertial Loads With the Elbow Flexor Muscles

2000 ◽  
Vol 83 (4) ◽  
pp. 2030-2039 ◽  
Author(s):  
Andrew E. Graves ◽  
Kurt W. Kornatz ◽  
Roger M. Enoka
Keyword(s):  
Young Adults ◽  
Elbow Joint ◽  
Muscle Activation ◽  
Angular Displacement ◽  
Elbow Flexor ◽  
Lengthening Contractions ◽  
Old Adults ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
Target Force

The purpose of this study was to determine the effect of age on the ability to exert steady forces and to perform steady flexion movements with the muscles that cross the elbow joint. An isometric task required subjects to exert a steady force to match a target force that was displayed on a monitor. An anisometric task required subjects to raise and lower inertial loads so that the angular displacement around the elbow joint matched a template displayed on a monitor. Steadiness was measured as the coefficient of variation of force and as the normalized standard deviation of wrist acceleration. For the isometric task, steadiness as a function of target force decreased similarly for old adults and young adults. For the anisometric task, steadiness increased as a function of the inertial load and there were significant differences caused by age. Old adults were less steady than young adults during both shortening and lengthening contractions with the lightest loads. Furthermore, old adults were least steady when performing lengthening contractions. These behaviors appear to be associated with the patterns of muscle activation. These results suggest that different neural strategies are used to control isometric and anisometric contractions performed with the elbow flexor muscles and that these strategies do not change in parallel with advancing age.

scholarly journals Differences between young and old users when interacting with a humanoid robot: a qualitative usability study

2018 ◽  
Vol 9 (1) ◽  
pp. 183-192 ◽  
Author(s):  
Ronit Feingold-Polak ◽  
Avital Elishay ◽  
Yonat Shahar ◽  
Maayan Stein ◽  
Yael Edan ◽  
...  
Keyword(s):  
Young Adults ◽  
Humanoid Robot ◽  
Motor Task ◽  
Humanoid Robots ◽  
Limited Information ◽  
Old Adults ◽  
Body Of Knowledge ◽  
People With Dementia ◽  
Touch Interaction ◽  
The Difference

Abstract With the aging of the population worldwide, humanoid robots are being used with an older population, e.g., stroke patients and people with dementia. There is a growing body of knowledge on how people interact with robots, but limited information on the difference between young and old adults in their preferences when interacting with humanoid robots and what factors influence these preferences.We developed a gamified robotic platform of a cognitive-motor task.We conducted two experiments with the following aims: to test how age, location of touch interaction (touching the robot’s tablet or hand), and embodied presence of a humanoid robot affect the motivation of different age-group users to continue performing a cognitive-motor task. A total of 60 participants (30 old adults and 30 young adults) took part in two experiments with the humanoid Pepper robot (Softbank robotics). Both old and young adults reported they enjoyed the interaction with the robot as they found it engaging and fun, and preferred the embodied robot over the non-embodied computer screen. This study highlights that in order for the experience of the user to be positive a personalization of the interaction according to the age, the needs of the user, the characteristics, and the pace of the task is needed.

Contact-Evoked Changes in EMG Activity During Human Grasp

1999 ◽  
Vol 81 (5) ◽  
pp. 2215-2225 ◽  
Author(s):  
D. F. Collins ◽  
B. Knight ◽  
A. Prochazka
Keyword(s):  
Local Anesthesia ◽  
Index Finger ◽  
Emg Activity ◽  
Evoked Responses ◽  
Emg Amplitude ◽  
Sensory Activity

Contact-evoked changes in EMG activity during human grasp. 2215 Cutaneous receptors in the digits discharge bursts of activity on contact with an object during human grasp. In this study, we investigated the contribution of this sensory activity to the responses of muscles involved in the task. Twelve subjects performed a standardized precision grasp task without the aid of vision. Electromyographic (EMG) responses in trials when the object was present were compared with those in which the object, and hence the associated afferent responses, were unexpectedly absent. Significant differences in EMG amplitude occurred in the interval 50–100 ms after contact in all subjects and in 33/46 of the muscles sampled. The differences emerged as early as 34 ms after contact and comprised as much as a fourfold change in EMG from 50 to 100 ms after contact with the object. Typically, EMG responses were larger when the object was present (OP), though there were cases, particularly in the thenar muscles, in which the responses increased when the object was absent (OA). Local anesthesia of the thumb and index finger attenuated contact-evoked EMG activity in at least one muscle in all four subjects tested. In one subject, contact-evoked responses were abolished completely during the anesthesia in all four muscles sampled. The results indicate that the sensory activity signaling contact plays a key role in regulating EMG activity during human grasp. Much of this feedback action is attributable to cutaneous receptors in the digits and probably involves both spinal and supraspinal pathways.

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