Yusuke Sekiguchi

The contribution of quasi-joint stiffness of the ankle joint to gait in patients with hemiparesis

BACKGROUND The role of ankle joint stiffness during gait in patients with hemiparesis has not been clarified. The purpose of this study was to determine the contribution of quasi-joint stiffness of the ankle joint to spatiotemporal and kinetic parameters regarding gait in patients with hemiparesis due to brain tumor or stroke and healthy individuals. METHODS Spatiotemporal and kinetic parameters regarding gait in twelve patients with hemiparesis due to brain tumor or stroke and nine healthy individuals were measured with a 3-dimensional motion analysis system. Quasi-joint stiffness was calculated from the slope of the linear regression of the moment-angle curve of the ankle joint during the second rocker. FINDINGS There was no significant difference in quasi-joint stiffness among both sides of patients and the right side of controls. Quasi-joint stiffness on the paretic side of patients with hemiparesis positively correlated with maximal ankle power (r=0.73, P<0.01) and gait speed (r=0.66, P<0.05). In contrast, quasi-joint stiffness in controls negatively correlated with maximal ankle power (r=-0.73, P<0.05) and gait speed (r=-0.76, P<0.05). INTERPRETATION Our findings suggested that ankle power during gait might be generated by increasing quasi-joint stiffness in patients with hemiparesis. In contrast, healthy individuals might decrease quasi-joint stiffness to avoid deceleration of forward tilt of the tibia. Our findings might be useful for selecting treatment for increased ankle stiffness due to contracture and spasticity in patients with hemiparesis.

Influence of constrained visual and somatic senses on controlling centre of mass during sit-to-stand

This study aimed to investigate the manner in which healthy individuals execute robust whole body movements despite unstable body structure from the perspective of perception-action coupling. Twelve healthy adults performed sit-to-stand (STS) movements under conditions of constrained visual and somatic senses. During this movement, centre of mass (COM) of the body in the anterior-posterior, upward-downward and right-left directions was computed. The conditions of perceptual constraint were set as vision-restricted, somatosensory-restricted, vision- and somatosensory-restricted, and normal conditions. To evaluate COM control under these perceptual constraints, the variability in position and velocity of COM were assessed. The variabilities in COM velocity in the anterior-posterior and upward-downward directions decreased around the lift-off period only when both vision and somatic senses were constrained, whereas the variability of the COM position in the right-left direction increased under the somatosensory-restricted condition. Our findings suggested that control of COM velocity was enhanced in the major moving directions (anterior and upward directions) around the lift-off period during STS when both modalities of perception with regard to postural orientation were constrained. These motor regulations with perceptual constraints facilitate better adaptation to changes in body and environmental situations in daily life.

Noninvasive assessment of the activity of the shoulder girdle muscles using ultrasound real-time tissue elastography.

The purpose of this study was to clarify whether the activity of the shoulder girdle muscles could be estimated by measuring the elasticity of these muscles under several levels of muscle contraction through ultrasound real-time tissue elastography (RTE). Ten healthy men performed submaximal voluntary contractions (MVC) in each manual muscle testing position for the middle deltoid, upper trapezius, supraspinatus, levator scapulae, and rhomboid major. The elasticity of these muscles was measured using ultrasound RTE during the task. The strain ratio of the muscle to an acoustic coupler was calculated as an assessment index of the muscle elasticity. Higher strain ratio values imply lower elasticity. In addition, the electromyographic activity was recorded from surface electrodes attached only to the middle deltoid and upper trapezius. The strain ratios were negatively correlated with the normalized root mean square values for the middle deltoid (r=-0.659, p<0.001) and upper trapezius (r=-0.554, p<0.001). The strain ratios of all the muscles decreased with an increase from 10% MVC force to 30% MVC force. Ultrasound RTE may be useful for noninvasively assessing the activity of the shoulder girdle muscles at certain shoulder positions with low levels of muscle contraction.

Relationship between activation of ankle muscles and quasi-joint stiffness in early and middle stances during gait in patients with hemiparesis

It is unclear whether muscle contraction is necessary to increase quasi-joint stiffness (QJS) of the ankle joint during gait in patients with hemiparesis. The purpose of the present study was to investigate the relationship between QJS and muscle activation at the ankle joint in the stance phase during gait in patients with hemiparesis. Spatiotemporal and kinetic gait parameters and activation of the medial head of the gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) muscles were measured using a 3-dimensional motion analysis system and surface electromyography, in 21 patients with hemiparesis due to stroke and 10 healthy individuals. In the early stance, the QJS on the paretic side (PS) of patients was greater than that on the non-PS (p<0.05) and not significantly correlated with activation of the three muscles. In the middle stance, the QJS on the PS was lower than that on the non-PS (p<0.05) and that on the right side of controls (p<0.001), which was positively correlated with activation of the MG (r=0.51, p<0.05) and SOL (r=0.49, p<0.05). In the patients with hemiparesis, plantarflexor activation may not contribute to QJS in the early stance. On the other hand, QJS in the middle stance may be attributed to activation of the MG and SOL. Our findings suggest that activation of the MG and SOL in the middle stance on the PS may require to be enhanced to increase QJS during gait in patients with hemiparesis.

Auditory foot: A novel auditory feedback system regarding kinesthesia

In this study, we proposed a novel biofeedback system for rehabilitation that transforms weak or deficient kinesthetic feedback into an alternative sensor modality using “model-based rehabilitation.” As the first example, we focused on an auditory feedback system for walking rehabilitation, whereby plantar sensation is transformed into auditory signals. We developed an auditory feedback device for multipoint cutaneous plantar sensations, and plan to apply the device in rehabilitation, e.g., stroke patients with hemiplegia.

Short-Term Effect of Prosthesis Transforming Sensory Modalities on Walking in Stroke Patients with Hemiparesis

Sensory impairments caused by neurological or physical disorders hamper kinesthesia, making rehabilitation difficult. In order to overcome this problem, we proposed and developed a novel biofeedback prosthesis called Auditory Foot for transforming sensory modalities, in which the sensor prosthesis transforms plantar sensations to auditory feedback signals. This study investigated the short-term effect of the auditory feedback prosthesis on walking in stroke patients with hemiparesis. To evaluate the effect, we compared four conditions of auditory feedback from plantar sensors at the heel and fifth metatarsal. We found significant differences in the maximum hip extension angle and ankle plantar flexor moment on the affected side during the stance phase, between conditions with and without auditory feedback signals. These results indicate that our sensory prosthesis could enhance walking performance in stroke patients with hemiparesis, resulting in effective short-term rehabilitation.

Influence of thoracic posture on scapulothoracic and glenohumeral motions during eccentric shoulder external rotation

BACKGROUND Throwing injuries to the shoulder joint often occur during shoulder external rotation. An appropriate combination of thoracic, scapular, and humeral motion during throwing is important to prevent such injuries, but it is unclear how thoracic posture contributes to shoulder motion during throwing. RESEARCH QUESTION The purpose of this study, therefore, was to clarify the influence of thoracic posture on scapulothoracic and glenohumeral motion during shoulder external rotation. METHODS Eccentric external rotation at 90° of shoulder abduction in thoracic flexion and extension postures was performed by 15 asymptomatic participants. Three-dimensional scapulothoracic and glenohumeral movements were measured with an electromagnetic tracking device at 75°, 80°, 85°, and maximum shoulder external rotation. The thoracic angle and maximum shoulder external rotation in absolute coordination were measured with a three-dimensional motion capture system. RESULTS The results showed that scapular posterior tilting and external rotation in the thoracic extension posture were significantly greater than those in the flexion posture (p < 0.05). Glenohumeral horizontal extension was significantly less in the thoracic extension posture than in the flexion posture (p < 0.05), whereas maximum shoulder external rotation was significantly greater (p < 0.01). Thus, thoracic extension increased scapulothoracic posterior tilting and external rotation and reduced glenohumeral horizontal extension during shoulder external rotation, as well as increasing maximum shoulder external rotation. SIGNIFICANCE These findings suggest that thoracic extension may contribute to reduction of mechanical demand in the glenohumeral joint during throwing, potentially reducing shoulder injuries.

Regulation of quasi-joint stiffness by combination of activation of ankle muscles in midstances during gait in patients with hemiparesis

BACKGROUND The regulation of ankle joint stiffness by combination of activation of plantarflexor and dorsiflexor during gait has not been investigated in patients with hemiparesis. The objective of the present study was to examine the relationship between combination of activation of ankle muscles and quasi-joint stiffness (QJS) during the stance phase of gait. METHODS The activation of the medial head of the gastrocnemius (MG), soleus, and tibialis anterior, gait parameters were collected from 19 patients with hemiparesis due to stroke and from 12 healthy controls using a three-dimensional motion analysis system. The indexes of reciprocal activation and coactivation were calculated from the ratio of plantarflexor to dorsiflexor activation and magnitude of coactivation (MC), which is computed by multiplying an index of simultaneous activation of ankle muscles by plantarflexor activation. RESULTS QJS was significantly correlated with MC of MG on the paretic side, whereas it correlated with the ratio of MG (r = 0.63, p < 0.05) in healthy controls and the ratio of MG (r = 0.67, p < 0.05) and soleus (r = 0.61, p < 0.05) on the non-paretic side in midstance. Furthermore, QJS on the paretic side was lower than that on the non-paretic side and in healthy controls (p < 0.05). SIGNIFICANCE Our findings support that the regulation of QJS in midstance by reciprocal activation is altered on the paretic side, whereas it may be regulated by reciprocal activation and enhanced by relatively high activity of plantarflexor on the non-paretic side and in healthy controls.

Hip flexor muscle dysfunction during walking at self-selected and fast speed in patients with aortoiliac peripheral arterial disease

Objective: Intermittent claudication aggravates physical function and is associated with an increased risk of death in patients with peripheral arterial disease (PAD). Previous studies on kinetic parameters (joint moment and power) of lower limbs in these patients have largely focused on the decline in the ankle plantar flexor moment and power at self‐selected (SS) walking speed, which may not be an optimal condition to induce claudication pain. In the present study, we investigated the abnormalities in joint kinetic parameters in patients with PAD at both SS and at fast walking speeds. Methods: We recruited 16 patients with aortoiliac PAD (4 unilateral and 12 bilateral) and 10 healthy controls. The participants were instructed to walk at SS and fast speeds along a 7‐meter walkway embedded with a force plate. Spatiotemporal parameters and joint kinetic parameters of the lower limbs during the stance phase were recorded using a three‐dimensional motion analysis device. Results: Compared with the controls, patients with PAD showed a significant reduction in their walking speed, step length, stride length, and cadence. Further, a reduction in peak hip flexor moment at fast walking speed and in peak hip flexor generation power was observed in both modes of walking. However, no significant between‐group differences were observed for the peak ankle plantar flexor moment or power at either walking speed. Multiple regression analysis showed peak hip flexor generation power was a strong contributor to reduction at both SS and fast walking speeds in patients with PAD. Conclusions: Patients with aortoiliac PAD walk slowly and show reduced kinetic parameters of the hip joint at both SS and fast walking speeds. Our results suggest that hip flexor muscles may be a useful target for exercise training in patients with aortoiliac PAD.

Effects of grab bar on utilized friction and dynamic stability when elderly people enter the bathtub

Background The effect of the grab bar on dynamic stability when elderly people enter the bathtub remains unclear. The purpose of the present study is to examine the age‐related effect of the grab bar on dynamic stability during lateral stepping over an obstacle when entering bathtub. Methods Sixteen young, healthy adults and sixteen elderly adults participated. The subjects performed lateral stepping over an obstacle with and without vertical and horizontal bars. Displacement and velocity of the center of mass and utilized friction, which is the required coefficient of friction to avoid slipping, were simultaneously measured by a three‐dimensional motion analysis system and two force plates. Findings A post hoc test for two‐way ANOVA revealed that velocity of the center of mass in the vertical direction (p < 0.05) and peak‐to‐peak values of the center of mass in the lateral (p < 0.05) and vertical directions (p < 0.05) with each grab bar were significantly slower and smaller than those without the grab bar in young and elderly people. Moreover, the utilized friction at push off of the trailing leg with the vertical bar in elderly people was lower (p < 0.05) than that in participants without the grab bar. Interpretation The use of each grab bar while performing a lateral step over an obstacle may help maintaining balance in lateral and vertical directions. However, use of the vertical bar while lateral stepping over an object in elderly people may need low utilized friction to prevent slipping. HighlightsThe use of a vertical bar in elderly participants reduced utilized friction.The use of a horizontal bar led to the smallest sway in a vertical direction.The use of each grab bar reduced sway in lateral and vertical directions.