Shun-Hwa Wei

Effects of local muscle fatigue on three-dimensional scapulohumeral rhythm

The relationship of scapulothoracic motion to glenohumeral motion, commonly referred to as the scapulohumeral rhythm, has been the subject of numerous investigations. The purpose of this study was to assess the effects of localized muscular fatigue on three-dimensional scapulothoracic motion and the resulting scapulohumeral rhythm during elevation of the humerus in the plane of the scapula. A six-degree-of-freedom digitizing system (Metrecom(TM)) was used to define scapular and trunk reference frames, and three-dimensional Eulerian angles were determined for scapular motion for 0-135 degrees of humeral elevation before and after fatigue of the upper and lower trapezius muscles. Local muscle fatigue was determined using spectral analysis of electromyographic signals for the upper and lower trapezius muscles. The results demonstrated an average of 22% decrease in the median frequencies of the muscles sampled following resistive exercise, suggesting a state of local muscle fatigue. Concomitant with the fatigue was a selective decrease in scapulothoracic motion about two of the three scapular axes. RELEVANCE: Occupational and recreational conditions often require repetitive overhead elevations of the arms, resulting in muscular fatigue and various pathologies. During repetitive arm elevations the scapulohumeral rhythm or synchronization between the humerus and the scapula is balanced to allow the most efficient elevation of the arm. A better understanding of this much-discussed scapulohumeral rhythm and the changes induced by muscular fatigue may provide insight into the pathomechanics associated with shoulder dysfunction.

Wrist kinematic characterization of wheelchair propulsion in various seating positions: implication to wrist pain

OBJECTIVEnTo investigate wrist kinematic characterization at various wheelchair seat positions.nnnDESIGNnA comparative study using a repetitive measures design.nnnBACKGROUNDnPeople who use wheelchairs often sit on pressure-relief cushions, increasing the seat height. Wrist kinematic properties during manual propulsion could be altered. Wrist kinematics from a clinical perspective has not been previously investigated. This study characterizes wrist kinematic performance of subjects during manual wheelchair propulsion at various seat positions.nnnMETHODSnSubjects for this investigation were 11 people with disabilities who use wheelchairs. Combinations of horizontal positions of the rear wheel and vertical seat height were evaluated. Consecutive EMG, wrist joint angle, and trigger signals were collected.nnnRESULTSnAltered seat height resulted in significant changes to temporal phases and wrist kinematic parameters; however, altered horizontal seat position did not cause significant variations. For all seat positions investigated, wrist extensor and flexor EMG signals maintained a similar level of contraction.nnnCONCLUSIONnDuring wheelchair propulsion, seat height was found to be a critical factor affecting the temporal parameters of movement and wrist kinematic properties of the subjects. Wrist joint angles and wrist flexion-extension range of motion all varied according to seat height. Observations and statistical analysis of the results provided useful information; however, an ideal seat position was not indicated.nnnRELEVANCEnStudy results have enhanced our understanding of wheelchair design, and should aid in development of future designs. In addition, the results may provide a strategy for dealing with the onset of arm/wrist pain and the prevention of carpal tunnel syndrome and other soft tissue injuries in people who use wheelchairs.

Using an Optimization Approach to Design an Insole for Lowering Plantar Fascia Stress—A Finite Element Study

Plantar heel pain is a commonly encountered orthopedic problem and is most often caused by plantar fasciitis. In recent years, different shapes of insole have been used to treat plantar fasciitis. However, little research has been focused on the junction stress between the plantar fascia and the calcaneus when wearing different shapes of insole. Therefore, this study aimed to employ a finite element (FE) method to investigate the relationship between different shapes of insole and the junction stress, and accordingly design an optimal insole to lower fascia stress.A detailed 3D foot FE model was created using ANSYS 9.0 software. The FE model calculation was compared to the Pedar device measurements to validate the FE model. After the FE model validation, this study conducted parametric analysis of six different insoles and used optimization analysis to determine the optimal insole which minimized the junction stress between plantar fascia and calcaneus.This FE analysis found that the plantar fascia stress and peak pressure when using the optimal insole were lower by 14% and 38.9%, respectively, than those when using the flat insole. In addition, the stress variation in plantar fascia was associated with the different shapes of insole.

Lower limb power rehabilitation (LLPR) using interactive video game for improvement of balance function in older people

Declined balance functions have adverse effects on elderly population. Lower limbs muscle power training is currently an emerging concept in rehabilitation on individuals with decreased balance and mobility. In this prospective, controlled study, we used a human-computer interactive video-game-based rehabilitation device (LLPR) for training of lower limb muscle power in the elderly. Forty (aged >65 years) individuals were recruited from the community. Twenty participants in the exercise group received 30-min training, twice a week, using the LLPR system. The LLPR system allows participants to perform fast speed sit-to-stand (STS) movements. Twenty age-matched participants in the control group performed slow speed STS movements, as well as strengthening and balance exercises, with the same frequency and duration. The results were compared after 12 sessions (6 weeks) of training. The mechanical and time parameters during STS movement were measured using the LLPR system. Modified falls efficacy scale (MFES), Tinetti Performance-Oriented Mobility Assessment (POMA), function reach test, five times sit to stand (FTSS) and Timed Up and Go (TUG) were administered to participants as clinical assessments. Results showed that in the exercise group, all the mechanical and time parameters showed significant improvement. In control group, only the maximal vertical ground reaction force (MVGRF) improved significantly. For clinical assessments (balance, mobility, and self-confidence), exercise group showed significantly better scores. The STS movements in video-game-based training mimic real life situations which may help to transfer the training effects into daily activities. The effectiveness of lower limb muscle training is worthy of further investigation.

Comparison of shock transmission and forearm electromyography between experienced and recreational tennis players during backhand strokes.

ObjectiveTo test the hypothesis that recreational tennis players transmit more shock impact from the racket to the elbow joint than experienced tennis players during the backhand stroke. Also, to test whether recreational tennis players used higher electromyographic (EMG) activities in common wrist extensor and flexor around epicondylar region at follow-through phase. DesignA repeated-measure, cross-sectional study. SettingNational College of Physical Education and Sports at Taipei, Taiwan. ParticipantsTwenty-four male tennis players with no abnormal forearm musculoskeletal injury participated in the study. According to performance level, subjects were categorized into 2 groups: experienced and recreational. Main Outcome MeasurementsImpact transmission and wrist extensor-flexor EMG for backhand acceleration, impact, and follow-through phases were recorded for each player. An independent t test with a significance level of 0.05 was used to examine mean differences of shock impact and EMG between the 2 test groups. One-way ANOVA associated with Tukey multiple comparisons was used to identify differences among different impact locations and EMG phases. ResultsExperienced athletes reduced the racket impact to the elbow joint by 89.2%, but recreational players reduced it by only 61.8%. The largest EMG differences were found in the follow-through phase (P<0.05). Experienced athletes showed that their extensor and flexor EMGs were at submaximal level for follow-through phase, whereas recreational players maintained their flexor and extensor EMGs at either supramaximal or maximal level. ConclusionsOur results support the hypothesis that recreational players transmit more shock impact from the racket to the elbow joint and use larger wrist flexor and extensor EMG activities at follow-through phase of the backhand stroke. Follow-through control is proposed as a critical factor for reduction of shock transmission. Clinicians or trainers should instruct beginners to quickly release their grip tightness after ball-to-racket impact to reduce shock impact transmission to the wrist and elbow.

Can sit-to-stand lower limb muscle power predict fall status?

Sit-to-stand (STS) movements are essential for daily activities. Failure to perform STS movements efficiently and smoothly may lead to falls. In this study, we developed a forceplate to analyze vertical ground reaction force (VGRF), STS duration and generated muscle power to investigate which parameters were fall status predictors. A total of 105 participants were included in this study and were grouped into those (1) aged between 20 and 30 years (Young), (2) aged above 65 years without a history of falling (Non-fallers) and (3) aged above 65 with a history of falling in the past 12 months (Fallers). The results indicated a significantly higher maximal lower limb muscle power (MP) for the Young (9.05 ± 3.66 W/kg), followed by Non-fallers (5.50 ± 2.02W/kg) and Fallers (3.66 ± 1.45 W/kg) as well as higher modified falls efficacy scale (MFES) scores for the Young (Young: 9.88 ± 0.10; Non-fallers: 6.27 ± 1.40; Fallers: 4.83 ± 0.89) and shorter times for the five times sit-to-stand test (FSTST) for the young (Young: 6.09 ± 2.20 s; Non-fallers: 15.65 ± 3.30s; Fallers: 19.82 ± 4.46 s). There was a significant difference between the Young group and the Non-fallers in the maximal vertical ground reaction force (VGRF) (138.79 ± 24.20 N/BW in Young, 117.51 ± 8.57 N/BW in old Non-fallers, p < 0.01), and there was a significant difference between the Non-fallers and the Fallers in the duration of the STS movement (2.74 ± 0.87 s for the Non-fallers, 4.27 ± 2.56 s for the Fallers, p < 0.01). The regression analysis results further indicated that only MP and the STS stabilization phase could differentiate individuals who had past fall events. Therefore, the equipment we developed could potentially be useful in the assessment and monitoring of balance and the risk of falling in older people.

Leg stiffness and electromyography of knee extensors/flexors: comparison between older and younger adults during stair descent.

This study investigated differences in knee extensor/flexor electromyography (EMG), leg loading rate, and leg stiffness in older and younger men during stair descent. Sixteen older men (mean +/- standard deviation [SD] = 72 +/- 4.5 years) and sixteen younger men (mean +/- SD = 21.2 +/- 0.5 years) were recruited. The EMG signals were recorded from the rectus femoris and the biceps femoris, while an electrogoniometer measured knee joint angle changes, and a force platform recorded the ground reaction forces (GRFs). We calculated leg stiffness by dividing the first peak GRF by the corresponding leg displacement. We used the Students t-test to examine group differences. Results showed that the older subjects had 78.6% higher preactivated EMG values in the knee extensor and 128% greater coactivity in the knee extensors/ flexors in the prelanding phase. At the impact phase, we observed leg stiffness to be 26.6% greater in the older than the younger subjects. The older subjects needed 94.6% more support time in performing push-off and also developed a compensatory strategy in stair descent, which altered the scaling of muscle preactivity and increased leg stiffness.

Impaired microvascular flow motion in subclinical diabetic feet with sudomotor dysfunction

Impaired cutaneous blood flow and sweating dysfunction might be among the earliest manifestations of diabetic autonomic neuropathy. This study assessed the pathophysiological basis underlying skin vasomotion changes and their relation with progressive sudomotor dysfunction and other autonomic and somatic measures in subclinical diabetic feet. Laser Doppler skin perfusion was assessed on 68 diabetic and 25 control subjects. The low-frequency vasomotion was transformed into three frequency intervals 0.0095-0.021, 0.021-0.052 and 0.052-0.145 Hz, respectively, for the investigation of endothelial, neurogenic and myogenic effects on microcirculatory alterations. The diabetic patients were categorized into three groups by increasing severity of sudomotor dysfunction: SSR+ (sympathetic skin response present; 27 patients), SSR- (SSR absent; 23 patients) and at-risk (SSR absent and of preulcerative cracked skin; 18 patients). All diabetic patients underwent nerve conduction and cardiovascular autonomic studies. The total spectral and endothelial activity was significantly decreased only in the at-risk group. The SSR- group had lower neurogenic vasomotion than the SSR+ group (p<0.05). Although no statistical difference was noted between any group in absolute myogenic spectrum, the SSR- group had higher normalized myogenic activity than the SSR+ group (p<0.01). The larger drop in orthostatic pressure was paralleled by a reduction in the myogenic amplitude (r=-0.33, p<0.01). These results suggested that early impairment of low-frequency flow motion correlated closely with the presence of sudomotor dysfunction of subclinical feet mainly in neurogenic and endothelial components. Impaired systemic vascular tone as manifested by orthostatic hypotension was proportional to the degree of myogenic dysregulation in diabetic patients.

Interactive wiimote gaze stabilization exercise training system for patients with vestibular hypofunction

BackgroundPeripheral vestibular hypofunction is a major cause of dizziness. When complicated with postural imbalance, this condition can lead to an increased incidence of falls. In traditional clinical practice, gaze stabilization exercise is commonly used to rehabilitate patients. In this study, we established a computer-aided vestibular rehabilitation system by coupling infrared LEDs to an infrared receiver. This system enabled the subjects’ head-turning actions to be quantified, and the training was performed using vestibular exercise combined with computer games and interactive video games that simulate daily life activities.MethodsThree unilateral and one bilateral vestibular hypofunction patients volunteered to participate in this study. The participants received 30 minutes of computer-aided vestibular rehabilitation training 2 days per week for 6 weeks. Pre-training and post-training assessments were completed, and a follow-up assessment was completed 1 month after the end of the training period.ResultsAfter 6 weeks of training, significant improvements in balance and dynamic visual acuity (DVA) were observed in the four participants. Self-reports of dizziness, anxiety and depressed mood all decreased significantly. Significant improvements in self-confidence and physical performance were also observed. The effectiveness of this training was maintained for at least 1 month after the end of the training period.ConclusionReal-time monitoring of training performance can be achieved using this rehabilitation platform. Patients demonstrated a reduction in dizziness symptoms after 6 weeks of training with this short-term interactive game approach. This treatment paradigm also improved the patients’ balance function. This system could provide a convenient, safe and affordable treatment option for clinical practitioners.

Microcirculatory vasomotor changes are associated with severity of peripheral neuropathy in patients with type 2 diabetes

Systemic microvascular complications are related to the presence of diabetic neuropathy. This study investigated the associations of blood flow oscillations with peripheral neuropathy in 25 controls and 3 diabetic groups including clinical (24), subclinical (27) and without neuropathy (26). Laser Doppler skin perfusion was transformed into three low-frequency subintervals corresponding to endothelial, neurogenic and myogenic vasomotor controls. The average vasomotion was significantly reduced in clinical neuropathy group and characterized by endothelial and neural but not smooth muscle–related changes. The normalized spectrums revealed a relative increase of myogenic and decrease of neurogenic activity in subclinical neuropathy group. The myogenic component showed a statistically inverse correlation with postural fall in systolic blood pressure (r = −0.32, p < 0.01). The diabetic patients with decreased low-frequency vasomotor responses were associated with increased odds ratio of peripheral neuropathy [odds ratio = 3.51 (95% confidence interval = 1.19–10.31), p = 0.02]. This study elucidated possible interaction between impaired microvascular flow motion and diabetic peripheral neuropathy. The vasomotor changes of skin microcirculation could be detected even in the absence of overt cardiovascular dysfunction.