APAs Constraints to Voluntary Movements: The Case for Limb Movements Coupling

Fatigue may improve equally after balance and endurance training in multiple sclerosis: a randomised, crossover clinical trial

Introduction

Fatigue and poor balance are frequent and severe problems in multiple sclerosis (MS) that may interact. Endurance training is known to be effective on fatigue. This study aims to test if balance training is more effective against MS fatigue.

Methods

A randomised crossover trial was run, recruiting 31 MS people (21 women; median age: 46 years, range: 30-64; median EDSS: 4, range: 2.5-5). Participants received balance and endurance training alternately (15 one-to-one sessions, 5 days/week) and were assessed before (T0), after (T1), and 30 days after treatment ended (T2). The Modified Fatigue Impact Scale (MFIS) with scores linearised through Rasch analysis was the primary outcome (the lower the measure, the better the condition, i.e., the lower the fatigue symptoms). The Equiscale balance scale and posturography (EquiTest) were used to assess balance. Linear mixed-effects models with ANOVA were used for significance testing.

Results

Thirteen participants had no carryover effect and were included in the primary analysis. Fatigue significantly changed across the three time points (F2,58 = 16.0; p < 0.001), but no difference across treatments was found. Altogether, both treatments significantly improved the MFIS measure at T1 (95%CI: -1.24 logits; mean: -1.67 to -0.81 logits) and T2 (95%CI: -1.04; mean: -1.49 to -0.60) compared to T0 (95%CI: -0.51; mean: -0.95 to -0.08; p ≤ 0.001). Equiscale and posturography highlighted balance improvement after balance training but not after endurance training.

Conclusion

Balance and endurance training could similarly reduce fatigue in MS patients in the short term. However, only balance training also improved balance in MS.

Reversed Mirror Therapy (REMIT) after Stroke-A Proof-of-Concept Study

In mirror training (MIT), stroke patients strive to move their hands while looking at the reflected image of the unaffected one. The recruitment of the mirror neurons and visual-proprioceptive conflict are expected to facilitate the paretic voluntary movement. Here, a reversed MIT (REMIT) is presented, which requires moving hands while looking at the reflected image of the paretic one, giving the illusion of being unable to move the unimpaired hand. This study compares MIT and REMIT on post-stroke upper-limb recovery to gain clues on the mechanism of action of mirror therapies. Eight chronic stroke patients underwent two weeks of MIT and REMIT (five sessions each) in a crossover design. Upper-limb Fugl-Meyer, Box and Block and handgrip strength tests were administered at baseline and treatments end. The strength of the mirror illusion was evaluated after each session. MIT induced a larger illusory effect. The Fugl-Meyer score improved to the same extent after both treatments. No changes occurred in the Box and Block and the handgrip tests. REMIT and MIT were equally effective on upper-limb dexterity, challenging the exclusive role of mirror neurons. Contrasting learned nonuse through an intersensory conflict might provide the rationale for both forms of mirror-based rehabilitation after stroke.

Mechanisms of postural control in older adults based on surface electromyography data

OBJECTIVES

The present study aimed to clarify the mechanisms of postural control during standing in older adults and document the mechanisms of age-related motor control based on changes in muscle activities.

METHODS

A total of 26 healthy male adults (older adult group, ≥65-78 years: n = 16; younger adult group, 20-23 years: n = 10) participated in this study. Ground reaction force and kinematic data of the lower limbs (hip, knee, and ankle), and electromyographic data from 6 postural muscles on the right side were recorded and quantified for each motor phase during rapid voluntary center of pressure (COP) shift.

RESULTS

Although hip strategy was more frequently observed in older adults than in young adults (56.3% vs. 20.0%), no muscle activity of hip agonists was observed in some (31.3%) older adults. Furthermore, older adults had a statistically significant delay in the inhibition of postural muscles during anticipatory postural adjustments (p < 0.05). After the onset of COP motion, the co-contraction time between agonists and antagonists was significantly prolonged in the older adults than in the younger adults (p < 0.05), and the reciprocal muscle pattern was unclear in the older adults. Prior to the termination of movement, agonist activity continued longer in the older adult group than in the younger adult group; that is, inhibition was insufficient in the older adult group.

CONCLUSION

A series of postural strategies during the voluntary movement task were altered in older adults, and this was significantly related not only with the activation but also the inhibition of postural muscles.

Gait regularity assessed by wearable sensors: Comparison between accelerometer and gyroscope data for different sensor locations and walking speeds in healthy subjects

Inertial measurement units (IMU), including accelerometers and gyroscopes, can support the assessment of gait regularity, relevant for an effective walking. Gait regularity is typically quantified by an autocorrelation analysis of trunk/pelvis accelerations. A methodological upgrade fosters a multi-sensor approach including upper and lower limbs. Very few studies dealt with gait regularity using gyroscope data and no comparison between the two inertial sensors has been published. Therefore, this study compares gait regularity assessment by autocorrelation analyses performed on accelerometer and gyroscope data simultaneously acquired. Twenty-five adult healthy subjects walked steady-state on treadmill at three speeds (3.6, 5.0, 6.4 km/h), with rest between. Four IMUs were firmly attached on the trunk, pelvis, wrist and ankle. The autocorrelation method was applied to time-windows of the signal vector magnitude and resulted, on average for each trial, in its regularity index (RI) and periodicity index (PI), i.e. the stride time. Results showed that both sensors identified the same PI (Spearman correlation coefficient = 0.999), and evidenced that, for matched sensor locations and gait speeds, the accelerometer-based RI was larger/equal to the gyroscope-based RI on 86.3% of all conditions (overall median of gyroscope-to-accelerometer RI ratio was 91.1%). The two sensors gave always statistically different RI, with the exception of the ankle at the lowest speed and wrist at higher speeds. Such results help remove potential confounders from analyses performed with different sensors and support the use of accelerometers for gait regularity assessment, not excluding that gyroscopes may be more suitable for other human movements.

Disownership of body parts as revealed by a visual scale evaluation. An observational study

The disownership of body parts, that most frequently occurs on the left side of the body, contralateral to right-hemispheric lesions, is an infrequent disorder, as usually assessed by interviews asking for dichotomic "yes/no" responses. This observational study in right-brain-damaged stroke patients investigated the efficacy of a continuous Visual Analog Scale (VAS) to detect body disownership after right brain damage, compared to dichotomic questions. Thirty-two right-handed right-brain-damaged stroke patients were given a Standardized Interview (SI), asking "Whose hand/arm/leg is this?", followed by a VAS (asking patients to mark on a vertical line their agreement with the statement that a body part belonged to them). The neural correlates of this disorder and measures of extra-personal and personal spatial neglect were also assessed. Control data were recorded from 18 neurologically unimpaired right-handed participants. During the interview, no patient showed disownership of body parts. Conversely, on the VAS eight out of 32 (25%) patients' scores, but none of the controls' scores, indicated a judgement of disownership for left body parts, with a left-right difference larger than that of control participants. VAS-detected disownership was not systematically associated with extra-personal and personal unilateral spatial neglect. Lesion sites associated with disownership of left body parts included the caudate nucleus and the anterior part of the internal capsule. To conclude, the VAS task, compared to the interview, is a novel tool to detect disownership of left body parts in right brain-damaged patients. A revised classification of body-ownership disorders is proposed. The present variant, assessed and detected by the VAS task, is termed Covert disownership and distinguished from the Overt disownership assessed by a SI.

Three-dimensional path of the body centre of mass during walking in children: an index of neural maturation

Few studies have investigated the kinematic aspects of the body centre of mass motion, that is, its three-dimensional path during strides and their changes with child development. This study aimed to describe the three-dimensional path of the centre of mass in children while walking in order to disentangle the effect of age from that of absolute forward speed and body size and to define preliminary pediatric normative values. The three-dimensional path of the centre of mass during walking was compared across healthy children 5–6− years (n = 6), 7–8 years (n = 6), 9–10 years (n = 5), and 11–13 years of age (n = 5) and healthy adults (23–48 years, n = 6). Participants walked on a force-sensing treadmill at various speeds, and height normalization of speed was conducted with the dimensionless Froude number. The total length and maximal lateral, vertical, and forward displacements of the centre of mass path were calculated from the ground reaction forces during complete strides and were scaled to the participant’s height. The centre of mass path showed a curved figure-of-eight shape. Once adjusted for speed and participants’ height, as age increased, there was a decrease in the three-dimensional parameters and in the lateral displacement, with values approaching those of adults. At each step, lateral redirection of the centre of mass requires brisk transient muscle power output. The base of support becomes relatively narrower with increasing age. Skilled shortening of the lateral displacement of the centre of mass may therefore decrease the risk of falling sideways. The three-dimensional path of the centre of mass may represent maturation of neural control of gait during growth.

Down Syndrome: Gait Pattern Alterations in Posture Space Kinematics

Gait characteristics in Down syndrome (DS) are documented in terms of discrete kinematic variables. However, such features are strictly interrelated and reflect neurological and developmental delays. A phenotypical, quantitative assessment of how multi-joint walking patterns are activated and controlled during gait would enhance the understanding of locomotor mechanisms in such patients. We adopted an analysis framework based on principal component analysis: the gait kinematics of 221 patients aged 6-45 were expressed in terms of a reduced set of one-dimensional movement components. Their time course during the gait cycle was described by score vectors, here called principal positions; its second time derivative, called principal acceleration, characterized the activity of the neuromuscular controller on each component. Outcomes were compared to an age-matched group of 49 healthy individuals. After controlling for the effect of walking speed, we observed that the main alterations in gait patterns emerged in the fourth component which is mostly devoted to stability management (group differences, p < 0.001). Rather, the main sagittal-plane locomotor patterns showed only subtle differences from the control group. Using statistical parametrical mapping, we found when (step-to-step transitions) and how (interrelated joints motion) the fourth movement deviated from normal: in particular, an excessive hip adduction and trunk inclination during the transition between single and double support phases. These findings match the neurological and sensorimotor trait of DS and suggest the promotion of targeted rehabilitative interventions. Furthermore, this paper opens to the adoption of principal positions and principal accelerations to investigate the neuromuscular control of movement patterns during locomotion.

Hand-Foot Coupling: An Advantage for Crossed Legs

It is difficult to perform distinct, simultaneous motor actions with the ipsilateral hand and foot; for example, clockwise circles with the right hand and counter-clockwise circles with the right foot. By chance, we discovered that this hand-foot coupling task is easier when seated with legs crossed. We consider various explanations. First, that there are reduced demands on the contralateral hemisphere when the motor programme of the right foot is executed on the left side of the body. Second, that the legs-crossed scenario is easier because movements are symmetrical with respect to body midline. By considering related motor actions, we conclude that neither of these explanations provides a full account. Thus, we suggest a third explanation, which is that coupling effects are reduced by virtue of increased postural stability and reduced anticipatory postural adjustments.