Resistance Training Reduces Force Tremor and Improves Manual Dexterity in Older Individuals With Essential Tremor

Resist-as-Needed ADL Training With SPINDLE for Patients With Tremor

Individuals with neurological disorders often exhibit altered manual dexterity and muscle weakness in their upper limbs. These motor impairments with tremor lead to severe difficulties in performing Activities of Daily Living (ADL). There is a critical need for ADL-focused robotic training that improves individual's strength when engaging with dexterous ADL tasks. This research introduces a new approach to training ADLs by employing a novel robotic rehabilitation system, Spherical Parallel INstrument for Daily Living Emulation (SPINDLE), which incorporates Virtual Reality (VR) to simulate ADL tasks. The study results present the feasibility of training individuals with movements similar to ADLs while interacting with the SPINDLE. A new game-based robotic training paradigm is suggested to perform ADL tasks at various intensity levels of resistance as needed. The proposed system can facilitate the training of various ADLs requiring 3-dimensional rotational movements by providing optimal resistance and visual feedback. We envision this system can be utilized as a table-top home device by restoring the impaired motor function of individuals with tremor and muscle weakness, guiding to improved ADL performance and quality of life.

Supporting Tremor Rehabilitation Using Optical See-Through Augmented Reality Technology

Tremor is a movement disorder that significantly impacts an individual's physical stability and quality of life, and conventional medication or surgery often falls short in providing a cure. Rehabilitation training is, therefore, used as an auxiliary method to mitigate the exacerbation of individual tremors. Video-based rehabilitation training is a form of therapy that allows patients to exercise at home, reducing pressure on rehabilitation institutions' resources. However, it has limitations in directly guiding and monitoring patients' rehabilitation, leading to an ineffective training effect. This study proposes a low-cost rehabilitation training system that utilizes optical see-through augmented reality (AR) technology to enable tremor patients to conduct rehabilitation training at home. The system provides one-on-one demonstration, posture guidance, and training progress monitoring to achieve an optimal training effect. To assess the system's effectiveness, we conducted experiments comparing the movement magnitudes of individuals with tremors in the proposed AR environment and video environment, while also comparing them with standard demonstrators. Participants wore a tremor simulation device during uncontrollable limb tremors, with tremor frequency and amplitude calibrated to typical tremor standards. The results showed that participants' limb movement magnitudes in the AR environment were significantly higher than those in the video environment, approaching the movement magnitudes of the standard demonstrators. Hence, it can be inferred that individuals receiving tremor rehabilitation in the AR environment experience better movement quality than those in the video environment. Furthermore, participant experience surveys revealed that the AR environment not only provided a sense of comfort, relaxation, and enjoyment but also effectively guided them throughout the rehabilitation process.

The relationship of tremor severity with proximal and distal muscle strength and upper extremity functional skills in older adults with essential tremor

BACKGROUND

Although it is known that muscle strength training is effective in Essential Tremor (ET), it is not known which muscle groups are more affected.

AIM

The study was conducted to examine the relationship between tremor severity and proximal and distal muscle strength and upper extremity functional skills in older adults with ET.

METHODS

A total of 40 older adults who were diagnosed with ET (mean age of 74.07 ± 4.83 years) and 40 older adults without tremor (mean age of 70.10 ± 4.05 years) were included in the study. Tremor severity was evaluated with the Fahn-Tolosa-Marin Tremor Rating Scale (FTMTRS), the proximal muscular strength with digital muscle dynamometer, handgrip strength with hand dynamometer, and pinch grip strength with pinchmeter. The Arm and Shoulder Problems Questionnaire (DASH) was used to determine the functional status of the upper extremities. Fine Manual Dexterity was measured with the Nine-Hole Peg Test (NHPT).

RESULTS

All proximal and distal muscle strengths were significantly lower, DASH and NHPT were significantly higher in the group with ET (p < 0.05). A significant negative correlation was detected between tremor severity and all proximal and distal muscular strength and a significant positive correlation between tremor severity and DASH in group with ET (p < 0.05). However, no significant correlations were found between tremor severity and NHPT in the group with ET.

CONCLUSIONS

It was found that older adults who had tremors had low proximal and distal muscular strength, upper extremity functionality was affected and hand skills was impaired. Furthermore tremor severity is affected by both proximal and distal muscle strength.

Training induced improvements in knee extensor force accuracy are associated with reduced vastus lateralis motor unit firing variability

NEW FINDINGS

What is the central question of this study? We aimed to determine levels of bilateral knee extensor force accuracy and any subsequent alterations to central and/or peripheral motor unit features, following 4 weeks of unilateral force accuracy training. What is the main finding and its importance? In the trained limb only, knee extensor force tracking accuracy improved with reduced motor unit firing rate variability in the vastus lateralis, and no change to neuromuscular junction transmission instability. Interventional strategies to improve force accuracy may be directed to older/clinical populations where such improvements may aid performance of daily living activities.

ABSTRACT

Background Muscle force output during sustained submaximal isometric contractions fluctuates around an average value and is partly influenced by variation in motor unit (MU) firing rates. MU firing rate (FR) variability seemingly reduces following exercise training interventions, however, much less is known with respect to peripheral MU properties. We therefore investigated whether targeted force accuracy training could lead to improved muscle functional capacity and control, in addition to determining any alterations of individual MU features. Methods Ten healthy participants (7 females, 3 males, 27±6 years, 170±8 cm, 69±16kg) underwent a 4-week supervised, unilateral knee extensor force accuracy training intervention. The coefficient of variation for force (FORCE^CoV ) and sinusoidal wave force tracking accuracy (FORCE^Sinu ) were determined at 25% maximal voluntary contraction (MVC) pre- and post-training. Intramuscular electromyography was utilised to record individual MU potentials from the vastus lateralis (VL) muscles at 25% MVC during sustained contractions, pre- and post-training. Results Knee extensor muscle strength remained unchanged following training, with no improvements in unilateral leg-balance. FORCE^CoV and FORCE^Sinu significantly improved in only the trained knee extensors by ∼13% (p = 0.01) and ∼30% (p<0.0001) respectively. MU FR variability significantly reduced in the trained VL by ∼16% (n = 8; p = 0.001), with no further alterations to MU FR or neuromuscular junction transmission instability. Conclusion Our results suggest muscle force control and tracking accuracy is a trainable characteristic in the knee extensors, which is likely explained by the reduction in MU FR variability which was apparent in the trained limb only. This article is protected by copyright. All rights reserved.

Overcoming the impact of physiologic tremors in ophthalmology

PURPOSE

Ophthalmic surgery involves the manipulation of micron-level sized structures such as the internal limiting membrane where tactile sensation is practically absent. All humans have physiologic tremors that are of low amplitude and not discernible to the naked eye; they do not adversely affect the majority of the population's daily functioning. However, during microsurgery, such tremors can be problematic. In this review, we focus on the impact of physiological tremors on ophthalmic microsurgery and offer a comparative discussion on the impact of such tremors on other surgical specialties.

METHODS

A single investigator used the MEDLINE database (via PubMed) to search for and identify articles for inclusion in this systematic review. Ten key factors were identified as potentially having an impact on tremor amplitude: beta-blockers, muscle fatigue, robotic systems, handheld tools/micromanipulators, armrests/wrist supports, caffeine, diet, sleep deprivation, consuming alcohol, and workouts (exercise). These key terms were then searched using the advanced Boolean search tool and operators (i.e., AND, OR) available on PubMed: (*keyword*) AND (surgeon tremor OR microsurgery tremor OR hand steadiness OR simulator score).

RESULTS

Ten studies attempted to quantify the baseline severity of operator physiologic tremor. Approximately 89% of studies accessing the impact of tremors on performance in regards to surgical metrics reported an improvement in performance compared to 57% of studies concluding that tremor elimination was of benefit when considering procedural outcomes.

CONCLUSIONS

Robotic technology, new instruments, exoskeletons, technique modifications, and lifestyle factors have all demonstrated the potential to assist in overcoming tremors in ophthalmology.

Integrated jerk as an indicator of affinity for artificial agent kinematics: laptop and virtual reality experiments involving index finger motion during two-digit grasping

Uncanny valley research has shown that human likeness is an important consideration when designing artificial agents. It has separately been shown that artificial agents exhibiting human-like kinematics can elicit positive perceptual responses. However the kinematic characteristics underlying that perception have not been elucidated. This paper proposes kinematic jerk amplitude as a candidate metric for kinematic human likeness, and aims to determine whether a perceptual optimum exists over a range of jerk values. We created minimum-jerk two-digit grasp kinematics in a prosthetic hand model, then added different amplitudes of temporally smooth noise to yield a variety of animations involving different total jerk levels, ranging from maximally smooth to highly jerky. Subjects indicated their perceptual affinity for these animations by simultaneously viewing two different animations side-by-side, first using a laptop, then separately within a virtual reality (VR) environment. Results suggest that (a) subjects generally preferred smoother kinematics, (b) subjects exhibited a small preference for rougher-than minimum jerk kinematics in the laptop experiment, and that (c) the preference for rougher-than minimum-jerk kinematics was amplified in the VR experiment. These results suggest that non-maximally smooth kinematics may be perceptually optimal in robots and other artificial agents.

Correlation of proximal and distal muscle strength with upper limb functional ability in patients with essential tremor

Despite being considered as a benign, genetic and monosymptomatic disorder, ET is a poorly understood entity with etiological and pathological heterogeneity. The aim of the present study was to examine the relation between proximal and distal muscle strength and upper limb functionality and tremor severity in patients with essential tremor (ET). The study enrolled 25 tremor patients followed at the neurology clinic of a university hospital and 19 healthy controls. Demographic data, risk factors, disease duration and dominant hand of the participants were recorded. Back and leg strength was assessed using a back and leg dynamometer and hand dynamometer and pinchmeter were used to determine hand strength. Functional ability of the participants was evaluated using the Minnesota Manual Dexterity Test (MMDT), Perdue Pegboard (PPBT) and Nine Hole Peg Test (NHPT). Tremor severity was assessed using the Fahn-Tolosa-Marin Tremor Rating Scale (FTMTRS) and the Lower Extremity Clinical Tremor Assessment Scale (LECTAS). A significant difference was found in the average back and leg muscle strength between ET patients and healthy controls (p < 0.05). The mean values for right/left hand muscle strength were not significantly different between the two groups (p > 0.05). Among the upper limb functional ability tests, significant differences were found between the two groups in the mean time to complete NHPT, Minnesota placing subtest and PPBT test (p < 0.05). While gender and risk factors were not significantly different between the two groups (p > 0.05), there was a significant difference with respect to the educational level (p < 0.01). No significant difference was found between back and leg muscle strength and FTMTRS and LECTAS (p > 0.05). A negative correlation and a significant association were found between average strength measurements obtained with the left hand dynamometer and FTMTRS in the ET group (p = 0.030, r = - 0.434). A positive correlation and a significant association were found between left hand strength and mean turning time in the MMDT in the control group (p = 0.041, r = 0.473). ET patients experience loss of proximal muscle strength and functional disability. Further studies are planned to investigate the effects of physical therapy modalities targeting increased proximal muscle strength on tremor severity and functional ability in ET patients.

Can Resistance Training Improve Upper Limb Postural Tremor, Force Steadiness and Dexterity in Older Adults? A Systematic Review

BACKGROUND

The ageing process and several health conditions may increase tremor and reduce force steadiness and dexterity, which can severely impact on function and quality of life. Resistance training can evoke a range of neuromuscular adaptions that may significantly reduce tremor and/or increase force steadiness and/or dexterity in older adults, irrespective of their health condition.

OBJECTIVES

The objective of this study was to systematically review the literature to determine if a minimum of 4 weeks' resistance training can reduce postural tremor and improve force steadiness and/or dexterity in older adults, defined as aged 65 years and over.

METHODS

An electronic search using Ovid, CINAHL, SPORTDiscus and EMBASE was performed. Risk of bias was assessed using the Cochrane Risk of Bias Tool.

RESULTS

Fourteen studies met the eligibility criteria, including six randomised controlled trials and two quasi-randomised controlled trials. All eight studies that recruited healthy older adults reported significant reductions in postural tremor and/or improvements in force steadiness and dexterity. Five out of seven studies that examined older adults with a particular health condition reported some improvements in force steadiness and/or dexterity. Specifically, significant benefits were observed for older adults with chronic obstructive pulmonary disease and essential tremor; however, small or no changes were observed for individuals with osteoarthritis or stroke.

CONCLUSIONS

Resistance training is a non-pharmacological treatment that can reduce tremor and improve force steadiness and dexterity in a variety of older adult populations. Future research should employ randomised controlled trials with larger sample sizes, better describe training programme methods, and align exercise prescription to current recommendations for older adults.

Sex differences in muscle activity emerge during sustained low-intensity contractions but not during intermittent low-intensity contractions

Sex differences in motor performance may arise depending on the mode of contraction being performed. In particular, contractions that are held for long durations, rather than contractions that are interspersed with rest periods, may induce greater levels of fatigue in men compared to women. The purpose of this study was to examine fatigue responses in a cohort of healthy men (n = 7, age [mean] = 21.6 ± [SD] 1.1 year) and women (n = 7, age: 22.0 ± 2.0 year) during sustained isometric and intermittent isometric contractions. Two contraction protocols were matched for intensity (20% MVC) and total contraction time (600-s). Biceps brachii EMG and elbow flexion torque steadiness were examined throughout each protocol, and motor nerve stimulation was used to quantify central and peripheral fatigue. Overall, there were few sex-related differences in the fatigue responses during intermittent contractions. However, men exhibited progressively lower maximal torque generation (39% versus 27% decrease), progressively greater muscle activity (220% versus 144% increase), progressively greater declines in elbow flexion steadiness (354% versus 285% decrease), and progressively greater self-perception of fatigue (Borg scale: 8.8 ± 1.2 versus 6.3 ± 1.1) throughout the sustained contractions. The mechanism underlying fatigue responses had a muscle component, as voluntary activation of the biceps brachii did not differ between sexes, but the amplitude of resting twitches decreased throughout the sustained contractions (m: 32%, w: 10% decrease). As generating large sustained forces causes a progressive increase in intramuscular pressure and mechanical occlusion-which has the effect of enhancing metabolite accumulation and peripheral fatigue-it is likely that the greater maximal strength of men contributed to their exacerbated levels of fatigue.

Ataxic Gait in Essential Tremor: A Disease-Associated Feature?

Background

While accumulating evidence suggests that balance and gait impairments are commonly seen in patients with essential tremor (ET), questions remain regarding their prevalence, their relationship with normal aging, whether they are similar to the impairments seen in spinocerebellar ataxias, their functional consequences, and whether some ET patients carry greater susceptibility.

Methods

We conducted a literature search (until December 2018) on this topic.

Results

We identified 23 articles on gait or balance impairments in ET. The prevalence of balance impairment (missteps on tandem walk test) was seven times higher in ET patients than controls. Gait impairments in ET included reduced speed, increased asymmetry, and impaired dynamic balance. While balance and gait problems worsened with age, ET patients were more impaired than controls, independent of age. The pattern of impairments seen in ET was qualitatively similar to that seen in spinocerebellar ataxias. Balance and gait impairments resulted in greater number of near falls in ET patients. Factors associated with balance and gait impairments in ET included age, presence of tremor in midline structures, and cognitive dysfunction.

Discussion

Accumulating evidence suggests that balance and gait impairments are common in ET patients and occur to a greater extent in controls. Thus, they represent a disease-associated feature. These impairments, which are qualitatively similar to those seen in spinocerebellar ataxias, are not merely subclinical but result in difficulty performing functional tasks and increase falls risk. A subset of patients is more susceptible to balance and gait impairments. The full spectrum of impairments remains to be characterized.

Yoga led by a physical therapist for individuals with Essential Tremor: An explorative pilot study

PURPOSE

The purpose of this pilot study is to evaluate the outcomes for individuals with Essential Tremor (ET) who participate in a community-based yoga class, led by a neurologic physical therapist.

METHODS

Six subjects with ET completed an 8-week intervention consisting of weekly 1-h yoga classes (in the Vinyasa style) guided by an instructor (200-h registered yoga teacher, physical therapist, and neurological resident).

RESULTS

Five subjects demonstrated improvements on the Tremor Research Group Essential Tremor Rating Scale (mean 15.3%, range 8.3-34.7%). The mean improvement on the Fullerton Advanced Balance Scale was 10.8% (range 2.5-20%). Five subjects maintained pre-intervention anxiety levels ("very low") while one reported increased anxiety secondary to a non-study related factor. Minimal improvements were noted in the McGill Quality of Life Questionnaire.

CONCLUSION

This pilot study offers support for further examining the benefits of integration of yoga into an exercise program for individuals with ET and specific suggestions for future research are offered. There were no adverse events with participation in yoga.