Training-related enhancement in the control of motor output in elderly humans

1994 ◽  
Vol 77 (6) ◽  
pp. 2648-2658 ◽  
Author(s):  
D. A. Keen ◽  
G. H. Yue ◽  
R. M. Enoka
Keyword(s):  
Training Program ◽  
Motor Unit ◽  
Maximum Voluntary Contraction ◽  
The Elderly ◽  
Voluntary Contraction ◽  
Elderly Subjects ◽  
Contraction Force ◽  
Unit Force ◽  
Young And Elderly Subjects ◽  
Elderly Humans

The increase in motor unit force that occurs with aging has been hypothesized to cause a decline in the ability to maintain a constant submaximal force. To test this hypothesis, young and elderly subjects performed a 12-wk strength-training program that was intended to increase motor unit force. The training program caused similar increases (%initial) in the training load (137.4 +/- 17.2%), twitch force (23.1 +/- 7.4%), and maximum voluntary contraction force (39.2 +/- 6.8%) of the first dorsal interosseus muscle for the young and elderly subjects. The increase in strength was associated with a modest increase in muscle volume (7% of initial value) and a nonmonotonic increase in the surface-recorded electromyogram that was significant at week 8 but not at week 12. The elderly subjects reduced the variability in force at the lower target forces (2.5, 5.0, and 20.0% maximum voluntary contraction force). This improvement, however, was unrelated to changes in the distribution of motor unit forces, which was not consistent with the hypothesis that the greater coefficient of variation for the force fluctuations is due to increased motor unit forces.

Older adults can maximally activate the biceps brachii muscle by voluntary command

1998 ◽  
Vol 84 (1) ◽  
pp. 284-291 ◽  
Author(s):  
Sophie J. De Serres ◽  
Roger M. Enoka
Keyword(s):  
Older Adults ◽  
Muscle Activation ◽  
Biceps Brachii ◽  
Maximum Voluntary Contraction ◽  
The Elderly ◽  
Voluntary Contraction ◽  
Elderly Subjects ◽  
Biceps Brachii Muscle ◽  
Activation Level ◽  
Voluntary Command

De Serres, Sophie J., and Roger M. Enoka. Older adults can maximally activate the biceps brachii muscle by voluntary command. J. Appl. Physiol. 84(1): 284–291, 1998.—Because some of the decline in strength with age may be explained by an impairment of muscle activation, the purpose of this study was to determine the activation level achieved in biceps brachii by older adults during a maximum voluntary contraction (MVC). This capability was assessed with two superimposition techniques: one calculated the activation level that was achieved during an MVC, and the other provided an estimate of the expected MVC force based on extrapolation with submaximal forces. The activation level in biceps brachii was incomplete (<100%) for the young ( n = 16) and elderly ( n = 16) subjects, with the elderly subjects exhibiting the greater deficit. In contrast, there was no difference between the measured and expected MVC forces for either group of subjects, whether the extrapolation involved a third-order polynomial or linearization of the data. Because of the lower signal-to-noise ratio associated with the measurement of activation level and the greater number of measurements that contributed to the estimate of the expected MVC force, we conclude that the older adults were able to achieve complete activation of the biceps brachii muscle during an MVC.

scholarly journals Age and Sex Effects on the Active Stiffness of Vastus Intermedius under Isometric Contraction

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Cong-Zhi Wang ◽  
Jing-Yi Guo ◽  
Tian-Jie Li ◽  
Yongjin Zhou ◽  
Wenxiu Shi ◽  
...  
Keyword(s):  
Knee Joint ◽  
Isometric Contraction ◽  
Maximum Voluntary Contraction ◽  
The Elderly ◽  
Voluntary Contraction ◽  
Muscle Stiffness ◽  
Elderly Subjects ◽  
Vastus Intermedius ◽  
Significant Difference ◽  
Age And Sex

Previously, a novel technique was proposed to quantify the relationship between the muscle stiffness and its nonfatigue contraction intensity. The method extended the measured range of isometric contraction to 100% maximum voluntary contraction (MVC) using an ultrasonic shear wave measurement setup. Yet, it has not been revealed how this relationship could be affected by factors like age or sex. To clarify these questions, vastus intermedius (VI) stiffness of 40 healthy subjects was assessed under 11 step levels of isometric contraction. The subjects were divided into four groups: young males, young females, elderly males, and elderly females (n=10for each). In a relaxed state, no significant difference was observed between the male and female subjects (p=0.156) nor between the young and elderly subjects (p=0.221). However, when performing isometric contraction, the VI stiffness of males was found to be significantly higher than that of females at the same level (p<0.001), and that of the young was higher than the elderly (p<0.001). Meanwhile, for two knee joint angles used, the stiffness measured at a 90° knee joint angle was always significantly larger than that measured at 60° (p<0.001). Recognizing the active muscle stiffness of VI contributes to body stability, and these results may provide insight into the age and sex bias in musculoskeletal studies, such as those on fall risks.

scholarly journals The Effects of Spinal Manipulation on Motor Unit Behavior

2021 ◽  
Vol 11 (1) ◽  
pp. 105
Author(s):  
Lucien Robinault ◽  
Aleš Holobar ◽  
Sylvain Crémoux ◽  
Usman Rashid ◽  
Imran Khan Niazi ◽  
...  
Keyword(s):  
Motor Unit ◽  
Conduction Velocity ◽  
Spinal Manipulation ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Movement Control ◽  
Position Sense ◽  
Joint Position Sense ◽  
Voluntary Contraction ◽  
Passive Movement

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

Age Effects on Measures of Auditory Duration Discrimination

1994 ◽  
Vol 37 (3) ◽  
pp. 662-670 ◽  
Author(s):  
Peter J. Fitzgibbons ◽  
Sandra Gordon-Salant
Keyword(s):  
Hearing Loss ◽  
Stimulus Frequency ◽  
The Elderly ◽  
Duration Discrimination ◽  
Elderly Subjects ◽  
Hearing Sensitivity ◽  
Choice Procedure ◽  
Forced Choice Procedure ◽  
Tonal Stimuli ◽  
Young And Elderly Subjects

This study examined auditory temporal sensitivity in young adult and elderly listeners using psychophysical tasks that measured duration discrimination. Listeners in the experiments were divided into groups of young and elderly subjects with normal hearing sensitivity and with mild-to-moderate sloping sensorineural hearing loss. Temporal thresholds in all tasks were measured with an adaptive forced-choice procedure using tonal stimuli centered at 500 Hz and 4000 Hz. Difference limens for duration were measured for tone bursts (250 msec reference duration) and for silent intervals between tone bursts (250 msec and 6.4 msec reference durations). Results showed that the elderly listeners exhibited diminished duration discrimination for both tones and silent intervals when the reference duration was 250 msec. Hearing loss did not affect these results. Discrimination of the brief temporal gap (6.4 msec) was influenced by age and hearing loss, but these effects were not consistent across all listeners. Effects of stimulus frequency were not evident for most of the duration discrimination conditions.

Atrial natriuretic peptide suppresses osmostimulated vasopressin release in young and elderly humans

1991 ◽  
Vol 261 (2) ◽  
pp. E252-E256 ◽  
Author(s):  
B. A. Clark ◽  
D. Elahi ◽  
L. Fish ◽  
M. McAloon-Dyke ◽  
K. Davis ◽  
...  
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Hypertonic Saline ◽  
Natriuretic Peptide ◽  
Serum Sodium ◽  
The Elderly ◽  
Sodium Concentration ◽  
Elderly Subjects ◽  
Vasopressin Release ◽  
Young And Elderly Subjects ◽  
Atrial Natriuretic

Atrial natriuretic peptide (ANP) may suppress vasopressin release, but the dynamics of this interaction as well as the influence of age have not been defined. We studied six or seven young (19-40 yr old) and seven elderly volunteers (65-83 yr old) under two circumstances: 1) after infusion of 5% saline (0.04 ml.kg-1.min-1) for 2 h and 2) after the same infusion given with simultaneous synthetic human ANP (0.05 micrograms.kg-1.min-1). Hypertonic saline alone produced a progressive rise in plasma vasopressin with increasing serum sodium. During hypertonic saline alone, vasopressin levels began to rise at an increment in serum sodium of 1.67 +/- 0.35 mM in the young and 1.43 +/- 0.32 mM in the elderly and rose linearly with increasing serum sodium. When ANP was infused with hypertonic saline (with peak ANP levels of approximately 1,000 pM), vasopressin levels began to rise at an increment in serum sodium of 4.43 +/- 0.67 mM in the young and 4.57 +/- 0.43 mM in the elderly (P less than 0.01 vs. saline alone). Furthermore, the vasopressin response for any given serum sodium was significantly reduced in both young and elderly subjects, resulting in a rightward displacement of the curve relating vasopressin response to sodium concentration (P less than 0.001). In conclusion, ANP not only suppresses vasopressin but raises the threshold for release of vasopressin in response to osmotic stimulation in both young and elderly individuals. High circulating ANP levels may be responsible in part for the suppression of vasopressin levels and water diuresis seen during states of volume expansion.

scholarly journals Evaluating the effectiveness of dichotic training in the elderly adults: a single subject study

2021 ◽  
Author(s):  
Zahra Shahidipour ◽  
Saeid Farahani ◽  
Ghassem Mohammadkhani ◽  
Elham Tavanai ◽  
Nariman Rahbar ◽  
...  
Keyword(s):  
Training Program ◽  
Elderly People ◽  
Dichotic Listening ◽  
Poor Performance ◽  
The Elderly ◽  
Elderly Subjects ◽  
Intensity Difference ◽  
Single Subject ◽  
Elderly Adults ◽  
Dichotic Training

Background and Aim: Elderly people usually show poor performance in dichotic listening tasks. In this condition, the left ear being often the weaker one shows a performance below the normal limits. Studies have shown the effectiveness of dichotic listening training in auditory and language processing for adults and children with neurological disorders. This study aimed to develop a home-version of dichotic training and investigate its effectiveness in elderly adults. Methods: Participants in this single-subject interventional study (AB design) were four elderly subjects (two males and two females) aged 65−75 years. The main inclusion criteria were dichotic listening deficit demonstrated by the dichotic digit test (DDT), no neurological or cognitive disorders, and normal hearing threshold. Dichotic listening training was performed with an informal home-version of dichotic interaural intensity difference (DIID) training program for seven weeks. DDT was performed seven consecutive weeks before (phase A) and after the intervention (phase B) at the end of each week. Results: Data were analyzed by single-subject study statistics. Findings demonstrated an improvement in DDT scores for the left ear and decrease in right ear advantage scores in all the elderly adults after DIID training program. It seems that this training program could remediate poor performance in dichotic listening tasks in elderly people. Conclusion: The advantage of this method is that it can be easily done at home and is costeffective. However, further studies are needed to approve the neuroplasticity and structural changes in the brain after the DIID training program in this population. Keywords: Auditory rehabilitation; dichotic training; dichotic listening; elderly; singlesubject study

scholarly journals Maximum Voluntary Activation in Nonfatigued and Fatigued Muscle of Young and Elderly Individuals

2001 ◽  
Vol 81 (5) ◽  
pp. 1102-1109 ◽  
Author(s):  
Scott K Stackhouse ◽  
Jennifer E Stevens ◽  
Samuel CK Lee ◽  
Karen M Pearce ◽  
Lynn Snyder-Mackler ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Quadriceps Femoris ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Elderly Subjects ◽  
Central Activation ◽  
Quadriceps Femoris Muscle ◽  
Age Related ◽  
Young Subjects ◽  
Femoris Muscle

Abstract Background and Purpose. Researchers studying central activation of muscles in elderly subjects (≥65 years of age) have investigated activation in only the nonfatigued state. This study examined the ability of young and elderly people to activate their quadriceps femoris muscles voluntarily under both fatigued and nonfatigued conditions to determine the effect of central activation failure on age-related loss of force. Subjects and Methods. Twenty young subjects (11 men, 9 women; mean age=22.67 years, SD=4.14, range=18–32 years) and 17 elderly subjects (8 men, 9 women; mean age=71.5 years, SD=5.85, range=65–84 years) participated in this study. Subjects were seated on a dynamometer and stabilized. Central activation was quantified, based on the change in force produced by a 100-Hz, 12-pulse electrical train that was delivered during a 3- to 5-second isometric maximum voluntary contraction (MVC) of the quadriceps femoris muscle. Next, subjects performed 25 MVCs (a 5-second contraction with 2 seconds of rest) to fatigue the muscle. During the last MVC, central activation was measured again. Results. In the nonfatigued state, elderly subjects had lower central activation than younger subjects. In the fatigued state, this difference became larger. Discussion and Conclusion. Central activation of the quadriceps femoris muscle in elderly subjects was reduced in both the fatigued and nonfatigued states when compared with young subjects. Some part of age-related weakness, therefore, may be attributed to failure of central activation in both the fatigued and nonfatigued states.

Ageing and the α2-adrenergic system of the platelet

1987 ◽  
Vol 73 (5) ◽  
pp. 507-513 ◽  
Author(s):  
Pamela B. Davis ◽  
Catherine Silski
Keyword(s):  
Cyclic Amp ◽  
The Elderly ◽  
Elderly Subjects ◽  
Adrenergic System ◽  
Scatchard Analysis ◽  
Adrenergic Agents ◽  
Α2 Adrenoceptor ◽  
Effector System ◽  
Potent Agonist ◽  
Young And Elderly Subjects

1. Platelets taken from healthy unmedicated subjects over 65 years of age display less inhibition of prostaglandin E1 (PGE1)-stimulated adenosine 3′:5′-cyclic monophosphate (cyclic AMP) synthesis by noradrenaline than do platelets taken from young adults aged 18–25 years (P < 0.03). The inhibition of cyclic AMP production by noradrenaline (10−5 mol/l) correlates negatively with age over the range 18–92 years (r = −0.338, n = 108, P < 0.005). The reduced cyclic AMP inhibition by noradrenaline in the elderly is not explained by basal cyclic AMP levels or degree of stimulation of platelets by PGE1, which do not differ between young and elderly subjects. The reduction itself is small, though, and cannot be demonstrated for a more potent agonist, adrenaline. 2. Despite the reduced noradrenaline response in the cyclic AMP system in the aged, platelet aggregation in response to α2-adrenergic agents is normal or even slightly increased. Aggregation responses to adrenergic agents correlate well with aggregation responses to adenosine 5′-diphosphate, suggesting that the effector system is a major determinant of the aggregation response. 3. α2-Adrenoceptor number measured by Scatchard analysis of equilibrium binding of [3H]yohimbine to platelet membranes is comparable in young and old subjects, and does not correlate with age. The KD for [3H]yohimbine does not correlate with age. The IC50 for noradrenaline displacing [3H]yohimbine is comparable in young and elderly subjects. Therefore the reduced inhibition of cyclic AMP production by noradrenaline in platelets from elderly subjects is not explained by changes in α2-adrenoceptor number, or agonist- or antagonist-binding properties, but may reside in the coupling of receptor to cyclase.

Development of a Walking-Assistance Apparatus for Neuro-Rehabilitation

2012 ◽  
Vol 162 ◽  
pp. 258-265 ◽  
Author(s):  
Eiichirou Tanaka ◽  
Tadaaki Ikehara ◽  
Tomohiro Sakurai ◽  
Takahiro Suzuki ◽  
Shota Roppongi ◽  
...  
Keyword(s):  
Weight Bearing ◽  
Maximum Voluntary Contraction ◽  
Pressure Sensors ◽  
The Elderly ◽  
Thenar Eminence ◽  
Voluntary Contraction ◽  
Hip Joints ◽  
Walking Behavior ◽  
Leg Alignment ◽  
Soles Of The Feet

We have developed a prototype for a walking-assistance apparatus that serves as a next-generation vehicle or a movable neuro-rehabilitation training appliance for the elderly or motor palsy patients. Our prototype uses a novel spatial parallel link mechanism with a weight-bearing lift. Flat steps of the apparatus move in parallel with the ground; the apparatus supports the entire leg alignment (including soles of the feet) and assists walking behavior at the ankle, knee, and hip joints simultaneously. To estimate the walking phase of each leg of the equipped person, pressure sensors were attached under the thenar eminence and the heel of the sole and the pressure variation at each sensing point was measured. To determine the direction in which the equipped person is walking, a pressure sensor was attached to the flexible crural link. Motor palsy patients and those with muscle weakness can walk with the assistance of the apparatus. Patients who have ambulation difficulty can also use the apparatus with a weight-bearing lift that we developed. Using the apparatus with the weight-bearing lift prevents stumbling and enables input of walking movement to the brain motor area. The validity of the weight-bearing lift can be confirmed from the results of the measured %maximum voluntary contraction (MVC).

Effects of contraction force and frequency on postexercise hyperemia in human calf muscles

1980 ◽  
Vol 49 (4) ◽  
pp. 649-654 ◽  
Author(s):  
D. Richardson ◽  
R. Shewchuk
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Calf Muscle ◽  
Contraction Force ◽  
A Value ◽  
True Blood ◽  
The Right ◽  
Human Calf

The purpose of this study was to examine the separate effects of contraction force and frequency on postexercise hyperemia in the human calf muscle. Nine male subjects were used. Each was seated in a chair with the right foot on a pedal coupled to a load cell and the knee secured. Calf muscle blood flow, measured by a Whitney gauge, was determined before and periodically after 3-pmin bouts of rhythmic isometric plantar-flexor exercise. The contraction frequency was graded from 20 to 50 to 80 contractions/min. The force per contraction was graded from 7.5 to 15 to 30% of maximum voluntary contraction (MVC) of the calf muscle. The average MCV was 502 lb. Peak postexercise blood flow (PBF) increased with either increasing frequency at a given force or increasing force at a given frequency. However, at the higher levels of exercise, PBF tended to plateau at a value of about 50 ml.min-1.100 ml-1. The plateau phase of PBF was associated with a substantial increase in the total volume of postexercise hyperemia. This appeared to be well above any repayment of a blood flow deficit. However, it is not certain that the extra volume represented the repayment of a true blood flow debt.

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