Measurement of Knee Extensor Torque During Repetitive Peripheral Magnetic Stimulation: Comparison of the Forces Induced by Different Stimulators.

Objective: To investigate the factors that induce strong contractions during repetitive peripheral magnetic stimulation (rPMS) and compare the muscle torque induced by two stimulators (Stim A and Stim B) with different coil properties. Methods: rPMS was applied to the right vastus lateralis of 30 healthy young adults. Stim A contained a 10.1 cm2 rectangular iron core coil, while Stim B contained a 191 cm2 round coil. The knee extensor torque (KET) induced by rPMS at 30 Hz was measured isometrically and divided by the maximum voluntary contraction (MVC) to obtain a relative value of MVC (%MVC). KET at 100% intensity of Stim A (A100%, 1.08 T) was compared to those at 100% or 70% intensity of Stim B (B100%, 1.47 T vs. B70%, 1.07 T). Additionally, we conducted a comprehensive literature search for studies that measured the KET during rPMS. Results: Both the mean values of %MVC using B100% and B70% were significantly greater than that using A100%. Furthermore, the KET induced by Stim B was found to be larger than that described in previous reports, unless booster units were used to directly stimulate the main trunk of the femoral nerve. Conclusion: Stim B induced a stronger muscle contraction force than Stim A did. This may be because the larger the coil area, the wider the area that can be stimulated. Additionally, a circular coil allows for deeper stimulation.

Factors Involved in Higher Knee Extension Torque Induced by Repetitive Peripheral Magnetic Stimulation.

OBJECTIVE: The study aimed to determine the relationship between knee extension torque induced by repetitive peripheral magnetic stimulation and the characteristics of the participants. DESIGN: This was a basic study with noninvasive intervention. Knee extension torque induced by repetitive peripheral magnetic stimulation (repetitive peripheral magnetic stimulation-induced torque) and maximum voluntary contraction were measured. Stepwise method of multiple regression was performed to determine the factors affecting repetitive peripheral magnetic stimulation-induced torque at 100% intensity and repetitive peripheral magnetic stimulation-induced torque divided by maximum voluntary contraction (percent maximum voluntary contraction). Subcutaneous fat thickness, vastus lateralis muscle thickness measured by ultrasound, maximum voluntary contraction, and mean power frequency of electromyography during maximum voluntary contraction were selected as independent variables. RESULTS: Repetitive peripheral magnetic stimulation was applied to the right vastus lateralis of 30 young healthy adults (average age, 21.1 ± 0.3 yrs). In the multiple regression analysis, repetitive peripheral magnetic stimulation-induced torque ( P < 0.001) was shown to be independently and significantly associated with maximum voluntary contraction (ß = 0.510), subcutaneous fat thickness (ß = -0.358), and vastus lateralis muscle thickness (ß = 0.208), while percent maximum voluntary contraction value ( P < 0.05) was independently and significantly associated with vastus lateralis muscle thickness (ß = 1.059). CONCLUSIONS: Repetitive peripheral magnetic stimulation-induced torque decreases with thicker subcutaneous fat and increases with stronger maximum voluntary contraction or with thicker muscle.

Individual differences in processing ability to transform visual stimuli during the mental rotation task are closely related to individual motor adaptation ability.

Mental rotation (MR) is a well-established experimental paradigm for exploring human spatial ability. Although MR tasks are assumed to be involved in several cognitive processes, it remains unclear which cognitive processes are related to the individual ability of motor adaptation. Therefore, we aimed to elucidate the relationship between the response time (RT) of MR using body parts and the adaptive motor learning capability of gait. In the MR task, dorsal hand, palmar plane, dorsal foot, and plantar plane images rotated in 45° increments were utilized to measure the RTs required for judging hand/foot laterality. A split-belt treadmill paradigm was applied, and the number of strides until the value of the asymmetrical ground reaction force reached a steady state was calculated to evaluate the individual motor adaptation ability. No significant relationship was found between the mean RT of the egocentric perspectives (0°, 45°, and 315°) or allocentric perspectives (135°, 180°, and 225°) and adaptive learning ability of gait, irrespective of body parts or image planes. Contrarily, the change rate of RTs obtained by subtracting the RT of the egocentric perspective from that of the allocentric perspective in dorsal hand/foot images that reflect the time to mentally transform a rotated visual stimulus correlated only with adaptive learning ability. Interestingly, the change rate of RTs calculated using the palmar and plantar images, assumed to reflect the three-dimensional transformation process, was not correlated. These findings suggest that individual differences in the processing capability of visual stimuli during the transformation process involved in the pure motor simulation of MR tasks are precisely related to individual motor adaptation ability.

Clinical reasoning of ultrasound imaging-guided manual passive manipulation for adhesion prevention in a patient with total knee arthroplasty: a case report.

INTRODUCTION: Patients with total knee arthroplasty occasionally develop postoperative abnormalities such as posttraumatic knee stiffness and arthrofibrosis, which may affect activities of daily living. However, there are no clear assessment methods or interventions for knee stiffness. Musculoskeletal ultrasound imaging enables real-time evaluation of mobility and flexibility of tissues. The purpose of this case report was to describe the use of musculoskeletal ultrasound imaging for evaluating the optimal location and methods of passive manipulation. CASE DESCRIPTION: The patient was an 82-year-old woman who had undergone total knee arthroplasty. She was unable to climb stairs due to limited knee flexion. Based on the results of musculoskeletal ultrasound imaging assessment, we hypothesized that the knee flexion limitation was caused by decreased sliding movement of the suprapatellar pouch. Hence, we performed passive manipulation on the tissue with decreased sliding under musculoskeletal ultrasound guidance. OUTCOMES: The patient's knee flexion angle increased from 90° to 110° within 1 week of intervention, and her gait speed improved from 16.48 to 13.2 s per 10 m. Furthermore, after the intervention, she was able to climb 10 steps using a handrail. DISCUSSION: Ultrasound imaging is important because it allows the examination of tissues with mobility changes such as in arthrofibrosis. Our work highlights the use of musculoskeletal ultrasound imaging for identifying the target region for therapy and for providing guidance during passive manipulation.

Quercetin improves lacrimal gland function through its anti-oxidant actions: Evidence from animal studies, and a pilot study in healthy human volunteers.

Anti-oxidant properties of polyphenols have been gaining medical attention as a preventive factor against aging and/or lifestyle diseases. In this study, we examined the anti-oxidant activity of quercetin improved tear function through its effects on the lacrimal gland in mice and humans. Six week-old diabetic mice, a model for decreased tear production, were fed for 12 weeks ad libitum with an experimental diet containing 0.5% quercetin. As a result, the tear volume was significantly improved compared to the control, despite no changes in body weight, food intake, lacrimal gland morphology or biochemical serum parameters. Moreover, significantly higher SOD-1 and SOD-2 protein levels were detected in the lacrimal glands of quercetin-treated mice by western blot. In addition, quercetin treatment of mouse corneal cell lines exposed to oxidative stress resulted in dose-dependent inhibition of ROS production and enhanced cell survival. Finally, we examined quercetin pharmacokinetics, specifically its presence in serum and tears subsequent to onion consumption in healthy volunteers, and found that the distribution of quercetin and its metabolite shifted from serum to tear following onion intake. An improvement in tear film stability also resulted following the intake by these healthy volunteers of a new, quercetin-rich onion cultivar ("Quergold") in powder form. These results suggested that quercetin improved tear function through its effects on the lacrimal gland in mice and humans.

Effects of different exercise intensities on prefrontal activity during a dual task.

The effects of physical exercise on cognitive tasks have been investigated. However, it is unclear how different exercise intensities affect the neural activity. In this study, we investigated the neural activity in the prefrontal cortex (PFC) by varying the exercise intensity while participants performed a dual task (DT). Twenty healthy young adults performed serial subtraction while driving a cycle ergometer. Exercise intensity was set to one of three levels: low, moderate, or high intensity. We did not find any significant change in PFC activity during DT under either the control (no exercise) or low-intensity conditions. In contrast, we observed a significant increase in PFC activity during DT under moderate- and high-intensity conditions. In addition, we observed complex hemodynamics after DT. PFC activity decreased from baseline after DT under the control condition, while it increased under the low-intensity condition. PFC activity remained higher than the baseline level after DT under the moderate-intensity condition but returned to baseline under the high-intensity condition. The results suggest that moderate-intensity exercise with a cognitive load effectively increases PFC activity, and low-intensity exercise may increase PFC activity when combined with a cognitive load.

Effect of Increased Flexor Hallucis Longus Muscle Activity on Ground Reaction Force during Landing.

Repeated high-impact ground forces can lead to injury and decreased performance. While increasing flexor hallucis longus (FHL) muscle activity is known to increase stiffness and elasticity, it is unknown if this also decreases ground reaction forces by shock absorption during landing. This study aimed to determine whether increasing FHL muscle activity affects ground reaction force during landing in healthy subjects. Eight subjects performed single-leg steps onto a force platform for five trials, with and without flexion of the metatarsophalangeal (MTP) joint at the moment of landing. Integrated surface electromyography (sEMG) of the FHL and medial gastrocnemius (MG) and ground reaction forces (GRFs) were measured. sEMG and GRF during the 50 ms before and 100 ms following initial ground contact were analyzed and compared. Flexion of the MTP joint condition significantly decreased the vertical and mediolateral force peaks of GRF, and FHL muscle activity increased. Flexion of the MTP joint at the moment of landing reduces GRF in healthy subjects through force dissipation in the foot, by increased FHL muscle activity. The results suggest that this may contribute to injury prevention by reducing the impact force through flexing the MTP joint at the moment of landing.

Visual Attention and Motion Visibility Modulate Motor Resonance during Observation of Human Walking in Different Manners.

To advance our knowledge on the motor system during cyclic gait observation, we aimed to explore the effects of gaze fixation on corticospinal excitability evaluated by single-pulse transcranial magnetic stimulation (TMS). Fourteen healthy adult volunteers watched a video of a demonstrator walking on a treadmill under three different conditions: (1) observing the right lower limb, (2) observing the right ankle joint, and (3) observing the right lower limb on a video focused on the area below the knee. In each condition, motor-evoked potentials elicited by TMS in the tibialis anterior (TA) muscle were measured synchronously with the demonstrator's initial contact and toe-off points. Directing visual attention to the ankle joint and focusing on its movements caused corticospinal facilitation in the TA muscle compared with watching the video without any visual fixation. In addition, phase-dependent differences in corticospinal excitability between the initial contact and toe-off points were only detected when the visibility range was restricted to below the knee. Our findings indicated that motor resonance during cyclic gait observation is modulated by visual attention and motion visibility in different activation manners.

Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site.

Tsubahara A, Kamiue M, Ito T, Kishimoto T, Kurozumi C. Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site. Jpn J Compr Rehabil Sci 2021; 12: 27-31. Purpose: To identify the optimal stimulation site and technique for inducing strong muscle contraction using a high-frequency magnetic stimulator. Methods: High-frequency magnetic stimulation was administered to the right vastus lateralis (VL) of eight healthy adults at maximal intensity within the range of tolerable pain. The stimulation sites were as follows: section A, the area between the lateral edge of the base of the patella (LEBP) and the distal one-third of the thigh (point D); section B, the area between point D and the proximal one-third of the thigh (point P). Isometric maximal muscle contraction forces induced by magnetic stimulation (Stim-MCF) were compared between the two sections. Results: The Stim-MCF was significantly higher in section B than in section A. Additionally, the sites susceptible to stimulation were confined to a narrow area near point D in section A and the central part between points D and P in section B. The degree of pain was very low in both sections. Conclusion: The optimal site for magnetic stimulation of the VL was limited to the central part of the thigh. In addition to the superficial proximal sub-branch, the deep proximal sub-branch and/or deeply clustered motor nerve endings may have been stimulated. Our results suggested that moving the probe was a useful way to identify the site that elicited the strongest muscle contraction force.

Preventive Effects of Repetitive Peripheral Magnetic Stimulation on Muscle Atrophy in the Paretic Lower Limb of Acute Stroke Patients: A Pilot Study.

OBJECTIVE: The aim of this study was to investigate the effect of repetitive peripheral magnetic stimulation (rPMS) on muscle atrophy prevention in the rectus femoris muscle (RF) of the paretic limb in acute stroke patients. METHODS: Twelve acute stroke patients with a National Institute of Health Stroke Scale score >5 and a motor score of the paretic lower limb >2 at admission were divided into an intervention group (rPMS: mean age, 75±6.4 years) and a conventional care group (non-rPMS: mean age, 62±11.8 years). Baseline measurements were performed within 4 days of stroke onset. In the rPMS group, treatment was applied to the paretic thigh only for 2 weeks, 5 days a week, in addition to conventional care. The cross-sectional area (CSA) of the RF was assessed in both limbs using ultrasound at baseline and 2 weeks later. Data on patient characteristics were collected from the clinical records to assess correlations with the CSA rate of change. RESULTS: Patients in the rPMS group were significantly older. Although the CSA of the RF did not change significantly on either side in the rPMS group, there was a significant decrease in the CSA on the paretic side in the non-rPMS group. However, no significant difference was observed in the CSA rate of change in the rPMS and non-rPMS groups. The CSA rate of change on the paretic side correlated negatively with age in the rPMS group. CONCLUSIONS: Our results suggest that rPMS prevents muscle atrophy more effectively in patients in their 60s than in patients more than 70 years old.

Motor activation is modulated by visual experience during cyclic gait observation: A transcranial magnetic stimulation study.

Transcranial magnetic stimulation (TMS) has been widely utilized to noninvasively explore the motor system during the observation of human movement. However, few studies have characterized motor cortex activity during periodic gait observation. Thus, this study examined the effects of an observer's visual experience and/or intention to imitate on corticospinal excitability during the observation of another's gait. Twenty-six healthy volunteers were included in this study and allocated to two different groups. Participants in the visual experience group had formal experience with gait observation (physical therapist training), while those in the control group did not. Motor-evoked potentials induced by TMS in the tibialis anterior and soleus muscles were measured as surrogates of corticospinal excitability. Participants were seated and, while resting, they observed a demonstrator's gait or observed it with the intention to subsequently reproduce it. Compared with the resting state, cyclic gait observation led to significant corticospinal facilitation in the tibialis anterior and soleus muscles. However, this pattern of corticospinal facilitation in the measured muscles was not coupled to the pattern of crural muscle activity during actual gait and was independent of the step cycle. This motor cortex facilitation effect during gait observation was enhanced by the observer's visual experience in a manner that was not step cycle-dependent, while the observer's intent to imitate did not affect corticospinal excitatory input to either muscle. In addition, visual experience did not modulate corticospinal excitability in gait-related crural muscles. Our findings indicate that motor cortex activity during gait observation is not in line with the timing of muscle activity during gait execution and is modulated by an individual's gait observation experience. These results suggest that visual experience acquired from repetitive gait observation may facilitate the motor system's control on bipedal walking, but may not promote the learning of muscle activity patterns.

Compensatory increases in tear volume and mucin levels associated with meibomian gland dysfunction caused by stearoyl-CoA desaturase-1 deficiency.

The stearoyl-CoA desaturase (SCD) family of enzymes catalyzes monounsaturated fatty acid synthesis by inserting a cis double bond at the Δ9 position of saturated fatty acids. Disruption of these enzymes has been reported to induce a severe dry skin phenotype. Since lipid abnormalities in the meibomian glands have been associated with dry eye, we analyzed selected eye tissues contributing to tear volume and composition in genetically SCD-1-deficient mice (SCD-1 KO), including the lacrimal glands and conjunctiva. Previous histopathological analysis had revealed atrophy and loss of meibomian glands; taken together with the increased goblet cell and MUC5AC expression in the conjunctiva reported here, these findings suggest that the tear volume and mucin levels secreted are enhanced in the absence of lipid secretion as a compensatory mechanism. The expression of lipid metabolism genes in lacrimal glands was decreased in SCD1 KO mice. Thus, these results provide new pathophysiological mechanisms to pursue with regard to meibomian gland dysfunction. In addition, lack of SCD-1 causes a compensatory increase in the tear volume and mucin levels associated with changes in expression of lipid metabolism genes. These results may be useful as a new concept for dry eye treatment strategies.

Association between trunk acceleration during walking and clinically assessed balance in patients with stroke.

BACKGROUND: Accelerometers provide information regarding balance and gait, but they are rarely used in clinical settings for stroke patients. Clinically, balance is assessed with simple tests, but their relationships with accelerometry results after stroke are unknown. OBJECTIVE: We examined the relationship between accelerometry-assessed gait indices calculated from trunk acceleration and results of the Timed Up and Go (TUG) and Berg Balance Scale (BBS) tests in stroke patients. METHODS: Twenty-nine stroke patients completed assessments with the TUG, BBS, and trunk acceleration during walking using a tri-axial accelerometer. The root mean square (RMS), stride regularity (SR), and step symmetry (SS), which indicate gait fluctuations, regularity, and symmetry, respectively, were calculated based on trunk acceleration. These were calculated in the vertical (VT), anteroposterior, and mediolateral directions. A multiple linear regression analysis was performed to determine whether these gait indices contributed independently to TUG and BBS results. RESULTS: VT-RMS and VT-SS were significant determinants of TUG, and VT-SS, VT-RMS, and VT-SR were significant determinants of BBS. CONCLUSIONS: This study suggested that the gait indices calculated from trunk acceleration that were relevant to balance were those in the VT direction. These may be useful for evaluating dynamic gait balance in patients with stroke.

Intra-rater and inter-rater reliabilities of real-time acceleration gait analysis system.

PURPOSE: The purposes of this study were to construct a real-time acceleration gait analysis system equipped with software to analyse real-time trunk acceleration during walking and to examine the intra-rater and inter-rater reliabilities of the this system. METHODS: This system has been comprised of an accelerometer, an acceleration amplifier, a transmitter, two foot switches, a receiver and a personal computer installed with the real-time acceleration analysis software. The acceleration signals received were analysed using the real-time acceleration analysis software, and gait parameters were calculated. The subjects were 20 healthy individuals and two raters. The intra-rater and inter-rater reliabilities of the measurement results obtained from this system were examined by performing intraclass correlation coefficients (ICC) and Bland-Altman analysis. RESULTS: The intra-rater and inter-rater ICCs ranged from 0.61 to 0.92 in any gait parameters. In the Bland-Altman analysis, neither fixed nor proportional bias was found in any of the gait parameters. CONCLUSIONS: From the ICC and Bland-Altman analysis results, the gait measurement using this system clearly demonstrates that the intra-rater and inter-rater measurements had good reproducibility. Owing to this system, we can improve the clinical efficiency of gait analysis and gait training for physiotherapy. Implication for Rehabilitation This study focused on the advantage of a gait analysis method using an accelerometer and constructed a gait analysis system that calculates real-time gait parameters from trunk acceleration measurements during walking. The gait analysis using this system has good intra-rater and inter-rater reliabilities, and using this system can improve the clinical efficiency of gait analysis and gait training.

Investigation of effect of leg support elevation timing on the horizontal force acting on the buttocks in a reclining wheelchair.

[Purpose] The purpose of this study was to investigate the effect of the timing of leg support elevation on the horizontal force acting on the buttocks in a reclining wheelchair. [Subjects and Methods] The participants were 17 healthy men. Two experimental conditions were tested: the leg-down and leg-up conditions. The back support was reclined at increasing angles, from the initial upright position (IUP), proceeding to the fully reclined position (FRP), and returned to the upright position (RUP). The posterior inclination phase was from IUP to FRP, and the returning inclination phase was from FRP to RUP. [Results] The horizontal force under the leg-up condition was significantly higher than that under the leg-down condition in all positions of back support. [Conclusion] The leg supports should be positioned downward before reclining the back support of a wheelchair.

Excitability changes in intracortical neural circuits induced by differentially controlled walking patterns.

Our previous single-pulse transcranial magnetic stimulation (TMS) study revealed that excitability in the motor cortex can be altered by conscious control of walking relative to less conscious normal walking. However, substantial elements and underlying mechanisms for inducing walking-related cortical plasticity are still unknown. Hence, in this study we aimed to examine the characteristics of electromyographic (EMG) recordings obtained during different walking conditions, namely, symmetrical walking (SW), asymmetrical walking 1 (AW1), and asymmetrical walking 2 (AW2), with left to right stance duration ratios of 1:1, 1:2, and 2:1, respectively. Furthermore, we investigated the influence of three types of walking control on subsequent changes in the intracortical neural circuits. Prior to each type of 7-min walking task, EMG analyses of the left tibialis anterior (TA) and soleus (SOL) muscles during walking were performed following approximately 3 min of preparative walking. Paired-pulse TMS was used to measure short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the left TA and SOL at baseline, immediately after the 7-min walking task, and 30 min post-task. EMG activity in the TA was significantly increased during AW1 and AW2 compared to during SW, whereas a significant difference in EMG activity of the SOL was observed only between AW1 and AW2. As for intracortical excitability, there was a significant alteration in SICI in the TA between SW and AW1, but not between SW and AW2. For the same amount of walking exercise, we found that the different methods used to control walking patterns induced different excitability changes in SICI. Our research shows that activation patterns associated with controlled leg muscles can alter post-exercise excitability in intracortical circuits. Therefore, how leg muscles are activated in a clinical setting could influence the outcome of walking in patients with stroke.

Influence of rotational axis height of back support on horizontal force applied to buttocks in a reclining wheelchair.

BACKGROUND: Studies have not been conducted to investigate the influence of the height of the rotational axis of a wheelchair's back support on the shear force applied to the buttocks during the reclining motion. OBJECTIVES: The purpose of this study was to investigate the influence of the difference in the rotational axis position of back support in the vertical direction on the horizontal force applied to buttocks for preventing decubitus ulcers. STUDY DESIGN: Repeated measures design. METHODS: The subjects were 13 healthy adult men without leg and/or trunk diseases. The shear force was measured using a force plate. A comfortable sitting posture in the experimental chair was selected for measurement. The rotational axis was positioned 13 cm forward on the horizontal plane from the intersection between the seat and the back support. The axis positions on the vertical plane as two experimental conditions were the seat height and the 7.5-cm upward from the seat height which was nearer to the hip joint. RESULTS: In returning the back support to an upright position, the horizontal force was 12.4 ± 1.6 (percent body weight) under the seat height-axis condition and 10.1 ± 1.8 (percent body weight) under the upward-axis condition (p < 0.01). CONCLUSION: This result suggested that the wheelchair might have to be capable of adjusting the height of the rotational axis of the back support to reduce the horizontal force applied to buttocks. CLINICAL RELEVANCE: This study shows one of the suggestions regarding seating approach for the prevention of decubitus ulcers. There is a possibility of reducing horizontal force applied to buttocks after reclined back support, by adjusting the height of the rotational axis position of wheelchair back support.

Correlation between Peak Expiratory Flow and Abdominal Muscle Thickness.

[Purpose] The purpose of this study was to determine whether forced expiration is correlated with abdominal muscle thickness. [Subjects] Twenty-three healthy male volunteers participated in this study. [Methods] The peak expiratory flow (PEF) was obtained using a peak flow meter with subjects in the sitting position. The thicknesses of the right rectus abdominis, external oblique, internal oblique, and transverse abdominis muscles were measured using B-mode ultrasonography at the end of a relaxed expiration in the supine position. [Results] Among the abdominal muscles, only the thickness of the external oblique muscle displayed a significant correlation with PEF. [Conclusion] It appears that the thickness of the external oblique muscle might be associated with PEF during forced expiration.

Effect of rotational axis position of wheelchair back support on shear force when reclining.

[Purpose] The purpose of this study was to investigate the influence of the rotational axis position of a reclining wheelchair's back support on fluctuations in the shear force applied to the buttocks while the back support is reclined. [Subjects] The subjects were 12 healthy adult men. [Methods] The shear force applied to the buttocks was measured using a force plate. This study used two different experimental conditions. The rotational axis of the back support was positioned at the joint between the seat and the back support for the rear-axis condition, and was moved 13 cm forward for the front-axis condition. [Results] With the back support fully reclined, the shear forces were 11.2 ± 0.8%BW and 14.1 ± 2.5%BW under the rear-axis and front-axis conditions, respectively. When returned to an upright position, the shear forces were 17.1 ± 3.1%BW and 13.8 ± 1.7%BW under the rear-axis and front-axis conditions, respectively. Significant differences appeared between the two experimental conditions (p < 0.01). [Conclusion] These results suggest that the shear force value could be changed by altering the position of the back support's rotational axis during reclining.