Margaret K.Y. Mak

Joint torques during sit-to-stand in healthy subjects and people with Parkinson’s disease

OBJECTIVES To compare lower limb joint torques during sit-to-stand in normal elderly subjects and people with Parkinsons disease, using a developed biomechanical model simulating all phases of sit-to-stand.Design. A cross-sectional study utilizing a Parkinsonian and a control group. BACKGROUND Subjects with Parkinsons disease were observed to experience difficulty in performing sit-to-stand. The developed model was used to calculate the lower limb joint torques in normal elderly subjects and subjects with Parkinsons disease, to delineate possible causes underlying difficulties in initiating sit-to-stand task. METHODS Six normal elderly subjects and seven age-matched subjects with Parkinsons disease performed five sit-to-stand trials at their self-selected speed. Anthropometric data, two-dimensional kinematic and foot-ground and thigh-chair reactive forces were used to calculate, via inverse dynamics, the joint torques during sit-to-stand in both before and after seat-off phases. The difference between the control and Parkinsons disease group was analysed using independent t-tests. RESULTS Both control and Parkinsons disease groups had a similar joint kinematic pattern, although the Parkinsons disease group demonstrated a slower angular displacement. The latter subjects produced significantly smaller normalized hip flexion torque and presented a slower torque build-up rate than the able-bodied subjects (P<0.05). CONCLUSION Slowness of sit-to-stand in people with Parkinsons disease could be due to a reduced hip flexion joint torque and a prolonged rate of torque production.

Cued task-specific training is better than exercise in improving sit-to-stand in patients with Parkinson's disease: A randomized controlled trial

We examined whether 4 weeks of audio‐visual (AV) cued task‐specific training could enhance sit‐to‐stand (STS) and whether the treatment effects could outlast the treatment period by 2 weeks. Fifty‐two subjects with PD completed the study. They were randomly allocated to receive 4 weeks of AV cued task‐specific training, conventional exercise (Ex), or no treatment (control). Each subject was assessed before, at the end of 2 and 4 weeks of treatment, and 2 weeks after treatment ended. After 2 weeks of training, the AV group significantly increased the peak horizontal velocity (by 13%, P<0.01) when compared with the Ex group. After 4 weeks of training, AV group increased both peak horizontal and vertical velocities, respectively by 18% and 51%, and reduced the time taken to complete STS by 25%. These improvements were greater than those of the Ex group, who showed 8% (nonsignificant between‐group) and 20% (P<0.05 between‐group) increases respectively for peak horizontal and vertical velocities, and 10% decrease in movement time (P<0.05). Worth‐noting is the improvements in AV group could be carried over to 2 weeks after treatment ended. These findings provided concrete evidence for the use of AV cued task‐specific training to reeducate STS in patients with PD.

Mediolateral sway in single-leg stance is the best discriminator of balance performance for Tai-Chi practitioners.

OBJECTIVES To identify a balance measure that can best distinguish Tai-Chi from non-Tai-Chi practitioners and to examine whether longer Tai-Chi practice results in better balance control. DESIGN Cross-sectional comparative study. SETTING Community. PARTICIPANTS Nineteen Tai-Chi practitioners (who practiced Tai Chi for 30-45min at least 3/wk for >1y) and 19 healthy subjects with regular exercise habits (who practiced Tai Chi for 30-45min at least 3/wk for >1y). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Scores on 2 clinical tests (functional reach, gait) and 1 laboratory test (postural sway). RESULTS Tai-Chi practitioners had better clinical test scores for functional reach, gait speed, stride length, and sway parameters during single-leg stance (P<.05). Sway in mediolateral direction during single-leg stance was the balance performance variable that best discriminated the Tai-Chi group from non-Tai-Chi group. More experience practicing Tai Chi was associated with better balance performance. CONCLUSIONS Tai-Chi practitioners performed better both in clinical and laboratory tests when compared with subjects who did not practice Tai Chi. More Tai-Chi experience was associated with better postural control.

Speed-dependent treadmill training is effective to improve gait and balance performance in patients with sub-acute stroke.

OBJECTIVE To compare the effects of speed-dependent treadmill training on gait and balance performance in patients with sub-acute stroke. DESIGN Single-blinded randomized controlled trial. SUBJECTS A total of 26 patients with sub-acute stroke were randomly assigned to experimental (n = 13) and control (n = 13) groups. METHODS Subjects in the experimental group underwent short interval walking trials with stepwise increases in treadmill speed (speed-dependent treadmill training), following the principles of sprint training. Control subjects received gait training on the treadmill at a steady speed. Gait speed, stride length, cadence, and Bergs Balance Score were recorded and analysed before and after the 10 training sessions. RESULTS Results of 2-way repeated measures analysis of variance showed significant group×time interactions for gait speed and stride length (p < 0.05). Within each subject group there were improvements in all gait parameters and Berg’s Balance Score after the training programme. In addition, the experimental group showed significantly larger increases in gait speed (mean 0.15 m/s, 95% confidence interval 0.04–0.26) and stride length (mean 0.16 m, 95% confidence interval 0.02–0.30) than the control subjects. CONCLUSION Speed-dependent treadmill training in patients with sub-acute stroke resulted in larger gains in gait speed and stride length compared with steady speed. The positive findings provide evidence for clinical practice of speed-dependent treadmill training in enhancing gait function after stroke.

Quantitative measurement of trunk rigidity in parkinsonian patients

We aimed to develop an objective measurement to quantify trunk rigidity in patients with Parkinson’s disease (PD), and to examine its reliability, validity and sensitivity in differentiating PD patients from control subjects. In Study 1, an isokinetic dynamometer was employed to assess trunk rigidity in 6 PD patients and 6 healthy controls. Passive trunk flexion and extension at 4 angular velocities were applied and resistive torques were recorded. Both work done and resistive peak torques to passive trunk flexion (TorquePF) and extension (TorquePE) were found to be highly reliable within a 2-day interval in PD patients and control subjects. In Study 2, trunk muscle tone was compared between 15 PD and 15 control subjects. Significantly higher muscle tone, as shown by increases in work done, and in TorquePF and TorquePE at higher movement speeds, was found in PD patients. Within each subject group, resistive trunk muscle tone was found to increase with increasing velocity of passive movement, but the extent of increase was greater in PD patients. Our results thus suggest that the objective method developed by us was reliable and could differentiate trunk rigidity in PD patients from that of healthy subjects.

Gait Difficulty, Postural Instability, and Muscle Weakness Are Associated with Fear of Falling in People with Parkinson's Disease

The present study aimed to examine the contribution of gait impairment, postural stability and muscle weakness to the level of fear of falling in people with Parkinsons disease (PD). Fifty-seven community-dwelling individuals with PD completed the study. Fear of falling was assessed by the Activities-specific Balance Confidence (ABC) scale. Postural stability and gait difficulty were determined by the posture and gait subscores of the Unified Parkinsons Disease Rating Scale (UPDRS-PG). A Cybex dynamometer was used to measure isokinetic knee muscle strength. Individuals with PD achieved a mean ABC score of 73.6 ± 19.3. In the multiple regression analysis, after accounting for basic demographics, fall history and disease severity, the UPDRS-PG score remained independently associated with the ABC score, accounting for 13.4% of the variance (P < 0.001). The addition of knee muscle strength significantly improved the prediction model and accounted for an additional 7.3% of the variance in the ABC score (P < 0.05). This is the first study to demonstrate that the UPDRS-PG score and knee muscle strength are important and independent determinants of the level of fear of falling in individuals with PD. Improving balance, gait stability and knee muscle strength could be crucial in promoting balance confidence in the appropriately targeted PD population.

The speed of sit-to-stand can be modulated in Parkinson's disease.

OBJECTIVE To evaluate whether Parkinsonian patients could modify the speed of a sit-to-stand (STS) task to the same extent as that of healthy subjects. METHODS Twenty Parkinsonian patients and 20 control subjects were instructed to stand up at a natural and fast speed. Kinematic data and kinetic data were recorded. RESULTS Parkinsonian patients were significantly slower than healthy individuals during STS at a natural speed. When required to perform STS task at a fast speed, these patients could increase both peak horizontal and vertical velocities of the task, by significantly increasing hip and ankle dorsiflexion torques and the rate of torque production, just as the control subjects did. In fact, no difference was found for the percentage changes in both peak velocities and movement time between the two groups, though similar between-group differences during STS at a natural speed still existed at a fast speed. CONCLUSIONS Parkinsonian patients had problems in generating adequate lower limb joint torques and in the rate of torque production when performing STS at a natural speed. However, these patients were capable of increasing the speed of their STS with the same percentage changes as those of healthy subjects. SIGNIFICANCE The capability of Parkinsonian patients for increasing movement speed gives new insights to rehabilitation strategy.

tHE MInI-BEStESt cAn PREdIct PARkInSonIAn REcuRREnt FAllERS: A 6-MontH PRoSPEctIvE Study

OBJECTIVES To examine whether the Mini-Balance Evaluation Systems Test (Mini-BESTest) independently predicts recurrent falls in people with Parkinsons disease. DESIGN The study used a longitudinal cohort design. SUBJECTS A total of 110 patients with Parkinsons disease completed the study and were included in the final analysis. Most of the patients had moderate disease severity. METHODS All subjects were measured to establish a baseline. The tests used were Unified Parkinsons Disease Rating Scale (MDS-UPDRS III), Freezing of Gait Questionnaire, Five-Time-Sit-To-Stand Test, and Mini-BESTest. All patients were followed by telephone interview for 6 months to register the incidence of monthly falls. RESULTS Twenty-four patients (21.2%) reported more than one fall and were classified as recurrent fallers. Results of the multivariate logistic regression showed that, after adjusting for fall history and MDS-UPDRS III score, the Mini-BESTest score remained a significant predictor of recurrent falls. We further established that a cut-off Mini-BESTest score of 19 had the best sensitivity (79%) for predicting future falls in patients with Parkinsons disease. CONCLUSION The results indicate that those with a Mini-BESTest score < 19 at baseline had a significantly higher risk of sustaining recurrent falls in the next 6 months. These findings highlight the importance of evaluating dynamic balance ability during fall risk assessment in patients with Parkinsons disease.

Effects of Exercise on Falls, Balance, and Gait Ability in Parkinson’s Disease A Meta-analysis

Postural instability and falls are complex and disabling features of Parkinson’s disease (PD) and respond poorly to anti-Parkinsonian medication. There is an imperative need to evaluate the effectiveness of exercise interventions in enhancing postural stability and decreasing falls in the PD population. The objectives of our study were to determine the effects of exercise training on the enhancement of balance and gait ability and reduction in falls for people with PD and to investigate potential factors contributing to the training effects on balance and gait ability of people with PD. We included 25 randomized control trials of a moderate methodological quality in our meta-analysis. The trials examined the effects of exercise training on balance and gait ability and falls against no intervention and placebo intervention. The results showed positive effects of exercise intervention on enhancing balance and gait performance (Hedges’ g = 0.303 over the short-term in 24 studies and 0.419 over the long-term in 12 studies; P < .05) and reducing the fall rate (rate ratio = 0.485 over the short-term in 4 studies and 0.413 over the long-term in 5 studies; P < .05). The longest follow-up duration was 12 months. There was no evidence that training decreased the number of fallers over the short- or long-term (P > .05). The results of our metaregression and subgroup analysis showed that facility-based training produced greater training effects on improving PD participants’ balance and gait ability (P < .05). The findings support the application of exercise training to improve balance and gait ability and prevent falls in people with PD.

Technology-assisted balance and gait training reduces falls in patients with Parkinson's disease: a randomized controlled trial with 12-month follow-up.

Objective. To examine the effects of technology-assisted balance and gait training on reducing falls in patients with Parkinson’s disease (PD). Methods. Eligible subjects were randomly allocated to an experimental group given technology-assisted balance and gait training (BAL, n = 26) and an active control group undertaking strengthening exercises (CON, n = 25). The training in each group lasted for 3 months. The number of fallers and fall rate were used as primary outcomes, and single-leg-stance-time, latency of postural response to perturbation, self-selected gait velocity, and stride length as secondary outcomes. Fall incidence was recorded over 15 months after the baseline assessment (Pre). Other tests were performed at Pre, after 3-month intervention (Post3m), at 3 months (Post6m), and 12 months (Post15m) after treatment completion. Results. Forty-five subjects who completed the 3-month training were included in the data analysis. There were fewer fallers in the BAL than in the CON group at Post3m, Post6m, and Post15m (P < .05). In addition, the BAL group had lower fall rate than the CON group at Post3m and Post6m (incidence rate ratio: 0.111-0.188, P < .05), and marginally so at Post15m (incidence rate ratio: 0.407, P = .057). Compared with the CON subjects, the BAL subjects demonstrated greater reduction in the postural response latency and increase in the stride length against baseline at each assessment interval (P < .05), and marginally more increases of single-leg-stance-time at Post3m (P = .064), Post6m (P = .041) and Post15m (P = .087). Conclusions. Our positive findings provide evidence for the clinical use of technology-assisted balance and gait training in reducing falls in people with PD.