Effects of Force Requirements on Pinch Force Production in Healthy Adults

Motor Control ◽  
2016 ◽  
Vol 20 (3) ◽  
pp. 299-315 ◽  
Author(s):  
Aisha Khan ◽  
Stacey L. Gorniak
Keyword(s):  
Motor Unit ◽  
Visual Feedback ◽  
Grip Force ◽  
Force Production ◽  
Error Rates ◽  
Visual Signal ◽  
Signal Frequency ◽  
Fine Motor ◽  
Pinch Force ◽  
Motor Unit Firing

Previous studies of fine motor control have focused on the ability of participants to match their grip force production to a visually provided template. We investigated differences exhibited in pinch force control during variable force production templates, including sine-, sawtooth-, and square-wave templates. Our results indicate that increased force requirements are associated with increased error rates and a noisier frequency spectrum, consistent with previous studies. Our results also indicate that visual feedback, in the form of template shape, directly affect pinch force production features and motor unit firing patterns, despite the use of consistent baseline force requirements, amplitude changes, and visual signal frequency. This suggests that CNS modulation of motor unit responses can be triggered by basic changes in visual feedback unrelated to force requirements. The potential implications of error compensation based on this study due to aging are also discussed.

Neuromuscular drive and force production are not altered during bilateral contractions

1998 ◽  
Vol 84 (1) ◽  
pp. 200-206 ◽  
Author(s):  
J. M. Jakobi ◽  
E. Cafarelli
Keyword(s):  
Motor Unit ◽  
Force Production ◽  
Young Male ◽  
Neuromuscular Control ◽  
Force Generation ◽  
Isometric Contractions ◽  
Firing Rates ◽  
Significant Limitation ◽  
Motor Unit Firing ◽  
Male Subjects

Jakobi, J. M., and E. Cafarelli. Neuromuscular drive and force production are not altered during bilateral contractions. J. Appl. Physiol. 84(1): 200–206, 1998.—Several investigators have studied the deficit in maximal voluntary force that is said to occur when bilateral muscle groups contract simultaneously. A true bilateral deficit (BLD) would suggest a significant limitation of neuromuscular control; however, some of the data from studies in the literature are equivocal. Our purpose was to determine whether there is a BLD in the knee extensors of untrained young male subjects during isometric contractions and whether this deficit is associated with a decreased activation of the quadriceps, increased activation of the antagonist muscle, or an alteration in motor unit firing rates. Twenty subjects performed unilateral (UL) and bilateral (BL) isometric knee extensions at 25, 50, 75, and 100% maximal voluntary contraction. Total UL and BL force (Δ3%) and maximal rate of force generation (Δ2.5%) were not significantly different. Total UL and BL maximal vastus lateralis electromyographic activity (EMG; 2.7 ± 0.28 vs. 2.6 ± 0.24 mV) and coactivation (0.17 ± 0.02 vs. 0.20 ± 0.02 mV) were also not different. Similarly, the ratio of force to EMG during submaximal UL and BL contractions was not different. Analysis of force production by each leg in UL and BL conditions showed no differences in force, rate of force generation, EMG, motor unit firing rates, and coactivation. Finally, assessment of quadriceps activity with the twitch interpolation technique indicated no differences in the degree of voluntary muscle activation (UL: 93.6 ± 2.51 Hz, BL: 90.1 ± 2.43 Hz). These results provide no evidence of a significant limitation in neuromuscular control between BL and UL isometric contractions of the knee extensor muscles in young male subjects.

Neural correlates of task-related changes in physiological tremor

2013 ◽  
Vol 110 (1) ◽  
pp. 170-176 ◽  
Author(s):  
Christopher M. Laine ◽  
Francesco Negro ◽  
Dario Farina
Keyword(s):  
Motor Unit ◽  
Visual Feedback ◽  
Muscle Force ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
The Self ◽  
Frequency Content ◽  
Neural Drive ◽  
Force Tremor ◽  
Command Signals

Appropriate control of muscle contraction requires integration of command signals with sensory feedback. Sensorimotor integration is often studied under conditions in which muscle force is controlled with visual feedback. While it is known that alteration of visual feedback can influence task performance, the underlying changes in neural drive to the muscles are not well understood. In this study, we characterize the frequency content of force fluctuations and neural drive when production of muscle force is target guided versus self guided. In the self-guided condition, subjects performed isometric contractions of the first dorsal interosseous (FDI) muscle while slowly and randomly varying their force level. Subjects received visual feedback of their own force in order to keep contractions between 6% and 10% of maximum voluntary contraction (MVC). In the target-guided condition, subjects used a display of their previously generated force as a target to track over time. During target tracking, force tremor increased significantly in the 3–5 and 7–9 Hz ranges, compared with self-guided contractions. The underlying changes in neural drive were assessed by coherence analysis of FDI motor unit activity. During target-guided force production, pairs of simultaneously recorded motor units showed less coherent activity in the 3–5 Hz frequency range but greater coherence in the 7–9 Hz range than in the self-guided contractions. These results show that the frequency content of common synaptic input to motoneurons is altered when force production is visually guided. We propose that a change in stretch-reflex gain could provide a potential mechanism for the observed changes in force tremor and motor unit coherence.

Doublet Discharges in Motoneurons of Young and Older Adults

2006 ◽  
Vol 95 (5) ◽  
pp. 2787-2795 ◽  
Author(s):  
Anita Christie ◽  
Gary Kamen
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Force Production ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Older Individuals ◽  
Motor Unit Firing ◽  
Older Subjects ◽  
Young Subjects ◽  
Ramp Contractions

The purpose of this study was to investigate the occurrence of motor unit doublet discharges in young and older individuals at different rates of increasing force. Participants included eight young (21.9 ± 3.56 yr) and eight older (74.1 ± 8.79 yr) individuals, with equal numbers of males and females in each group. Motor unit activity was recorded from the tibialis anterior during isometric dorsiflexion using a four-wire needle electrode. Subjects performed three ramp contractions from zero to 50% maximal voluntary contraction (MVC) force at each of three rates: 10, 30, and 50% MVC/s. Overall, the occurrence of doublets was significantly higher in the young than in the older individuals. However, neither group showed differences in the occurrence of doublets across the three rates of force production. Doublet firings were observed in 45.6 (young) and 35.1% (old) of motor units at 10% MVC/s; 48.6 (young) and 22.5% (old) of motor units at 30% MVC/s; and 48.4 (young) and 31.4% (old) at 50% MVC/s. The maximal firing rate was significantly higher and the force at which the motor units were recruited was significantly lower for those units that fired doublets than those that did not. The force at which doublets occurred ranged from 3.42 to 50% MVC in the young subjects and from 0 (force onset) to 50% MVC in the older subjects. The results of this study suggest that the occurrence of doublets is dependent on both motor unit firing rate and force level. The lower incidence of doublets in older individuals may be attributable to changes in the intrinsic properties of the motoneurons with aging, which appear to play a role in doublet discharges.

scholarly journals Impaired Object Handling during Bimanual Task Performance in Multiple Sclerosis

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Stacey L. Gorniak ◽  
Matthew Plow ◽  
Corey McDaniel ◽  
Jay L. Alberts
Keyword(s):  
Multiple Sclerosis ◽  
Grip Force ◽  
Force Production ◽  
Fine Motor ◽  
Bimanual Task ◽  
Relapsing Remitting ◽  
Task Time ◽  
Opening And Closing ◽  
Relapsing Remitting Multiple Sclerosis ◽  
Healthy Participants

We investigated the kinetic features of manual dexterity and fine motor control during a task that resembles an activity of daily living in 30 persons with relapsing-remitting multiple sclerosis (PwMS). Specifically, a novel two-transducer system was used to measure time and grip-load forces during a bimanual task that is similar to opening and closing a jar. We hypothesized that PwMS would have increased grip force production, deteriorations in kinetic timing, and preserved grip-load coupling indices compared to healthy controls (i.e., young and older adults). Increased grip force production and deterioration in timing indices were confirmed in PwMS. Abnormal grip-load coupling was exhibited by PwMS, in contrast to healthy participants. The correlation between task time and self-reported disability scores suggests that objective measurement of impaired upper-extremity movements relates to perception of overall function.

Estimates of persistent inward currents in tibialis anterior motor units during standing ramped contraction tasks in humans

2021 ◽  
Author(s):  
Obaid U Khurram ◽  
Francesco Negro ◽  
CJ Heckman ◽  
Christopher K. Thompson
Keyword(s):  
Motor Unit ◽  
Visual Feedback ◽  
Discharge Rate ◽  
Motor Units ◽  
Firing Patterns ◽  
Persistent Inward Currents ◽  
Analysis Technique ◽  
Motor Unit Firing ◽  
Inward Currents ◽  
Unit Analysis

Persistent inward currents (PICs) play an essential role in setting motor neuron gain and shaping motor unit firing patterns. Estimates of PICs in humans can be made using the paired motor unit analysis technique, which quantifies the difference in discharge rate of a lower-threshold motor unit at the recruitment onset and offset of a higher-threshold motor unit (∆F). Because PICs are highly dependent on the level of neuromodulatory drive, ∆F represents an estimate of level of neuromodulation at the level of the spinal cord. Most of the estimates of ∆F are performed under constrained, isometric, seated conditions. In the present study, we used high-density surface EMG arrays to discriminate motor unit firing patterns during isometric seated conditions with torque or EMG visual feedback and during unconstrained standing anterior-to-posterior movements with RMS EMG visual feedback. We were able to apply the paired motor unit analysis technique to the decomposed motor units in each of the three conditions. We hypothesized that ∆F would be higher during unconstrained standing anterior-to-posterior movements compared to the seated conditions, reflecting an increase in the synaptic input to MNs drive while standing. In agreement with previous work, we found that there was no evidence of a difference in ∆F between the seated and standing postures, although slight differences in the initial and peak discharge rates were observed. Taken together, our results suggest that both the standing and seated postures are likely not sufficiently different--both being "upright" postures--to result in large changes in neuromodulatory drive.

scholarly journals A Musculoskeletal Model of the Hand and Wrist Capable of Simulating Functional Tasks

2021 ◽  
Author(s):  
Daniel Clinton McFarland ◽  
Benjamin I Binder-Markey ◽  
Jennifer A Nichols ◽  
Sarah J Wohlman ◽  
Marije de Bruin ◽  
...  
Keyword(s):  
Open Source ◽  
Grip Force ◽  
Force Production ◽  
Musculoskeletal Model ◽  
Pinch Strength ◽  
Wrist Flexion ◽  
Pinch Force ◽  
Maximum Grip ◽  
Hand Opening

Objective: The purpose of this work was to develop an open-source musculoskeletal model of the hand and wrist and to evaluate its performance during simulations of functional tasks. Methods: The musculoskeletal model was developed by adapting and expanding upon existing musculoskeletal models. An optimal control theory framework that combines forward-dynamics simulations with a simulated-annealing optimization was used to simulate maximum grip and pinch force. Active and passive hand opening were simulated to evaluate coordinated kinematic hand movements. Results: The model's maximum grip force production matched experimental measures of grip force, force distribution amongst the digits, and displayed sensitivity to wrist flexion. Simulated lateral pinch strength fell within variability of in vivo palmar pinch strength data. Additionally, predicted activation for 7 of 8 muscles fell within variability of EMG data during palmar pinch. The active and passive hand opening simulations predicted reasonable activations and demonstrated passive motion mimicking tenodesis, respectively. Conclusion: This work advances simulation capabilities of hand and wrist models and provides a foundation for future work to build upon. Significance: This is the first open-source musculoskeletal model of the hand and wrist to be implemented during both functional kinetic and kinematic tasks. We provide a novel simulation framework to predict maximal grip and pinch force which can be used to evaluate how potential surgical and rehabilitation interventions influence these functional outcomes while requiring minimal experimental data.

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.

scholarly journals Effects Of Resistance Training On Maximal Motor Unit Firing Rates In Young And Older Males

2018 ◽  
Vol 50 (5S) ◽  
pp. 429-430
Author(s):  
Phuong L. Ha ◽  
Garrett M. Hester ◽  
Ryan J. Colquhoun ◽  
Mitchel A. Magrini ◽  
Zachary K. Pope ◽  
...  
Keyword(s):  
Resistance Training ◽  
Motor Unit ◽  
Firing Rates ◽  
Motor Unit Firing ◽  
Older Males

Intermittency in the Control of Continuous Force Production

2000 ◽  
Vol 84 (4) ◽  
pp. 1708-1718 ◽  
Author(s):  
Andrew B. Slifkin ◽  
David E. Vaillancourt ◽  
Karl M. Newell
Keyword(s):  
Visual Feedback ◽  
Visual Information ◽  
Spectral Power ◽  
Force Production ◽  
Motor Output ◽  
Force Variability ◽  
Force Output ◽  
Feedback Information ◽  
Information Processes ◽  
Feedback Frequency

The purpose of the current investigation was to examine the influence of intermittency in visual information processes on intermittency in the control continuous force production. Adult human participants were required to maintain force at, and minimize variability around, a force target over an extended duration (15 s), while the intermittency of on-line visual feedback presentation was varied across conditions. This was accomplished by varying the frequency of successive force-feedback deliveries presented on a video display. As a function of a 128-fold increase in feedback frequency (0.2 to 25.6 Hz), performance quality improved according to hyperbolic functions (e.g., force variability decayed), reaching asymptotic values near the 6.4-Hz feedback frequency level. Thus, the briefest interval over which visual information could be integrated and used to correct errors in motor output was approximately 150 ms. The observed reductions in force variability were correlated with parallel declines in spectral power at about 1 Hz in the frequency profile of force output. In contrast, power at higher frequencies in the force output spectrum were uncorrelated with increases in feedback frequency. Thus, there was a considerable lag between the generation of motor output corrections (1 Hz) and the processing of visual feedback information (6.4 Hz). To reconcile these differences in visual and motor processing times, we proposed a model where error information is accumulated by visual information processes at a maximum frequency of 6.4 per second, and the motor system generates a correction on the basis of the accumulated information at the end of each 1-s interval.

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