Investigating the efficacy of a tactile feedback system to increase the gait speed of older adults.

The objective of this study was to determine (1) if a novel haptic feedback system could increase the walking speed of older adults while it is being employed during overground walking and (2) whether the frequency at which this feedback was presented would have a differential impact on the ability of users to change walking speed while it was present. Given that peak thigh extension has been found to be a biomechanical surrogate for stride length, and consequently gait speed, vibrotactile haptic feedback was provided to the participants' thighs as a cue to increase peak thigh extension while the effect on gait speed was monitored. Ten healthy community-dwelling older adults (68.4 ± 4.1 years) participated. Participants' peak thigh extension, cadence, normalized stride length and velocity, along with their coefficients of variation (COV) were compared across baseline normal and fast walking (with no feedback) and three different frequency of feedback conditions. The findings indicated that, compared to self-selected normal and fast walking speeds, peak thigh extension was significantly increased when feedback was present and after it was withdrawn in a post-test. An increase in thigh extension led to an increase in stride length and, consequently, an increase in stride velocity compared to normal speed. There were no significant differences in the gait parameters as a function of feedback frequency during its application. In conclusion, while present, the haptic feedback system increased thigh extension and walking speed in older adults regardless of the feedback frequency and when the feedback was withdrawn, participants could maintain an increase in those parameters.

The identification of fall risk through tests of mediolateral stability during gait.

INTRODUCTION: Many falls in older adults are due to a loss of mediolateral stability during gait. This investigation examines if a simple beam-walking task can assess fall risk in older adults by taxing mediolateral control during gait. MATERIAL AND METHODS: 50 older adults (65-96 yrs.) and 20 younger adults (20-35 yrs.) walked along three 6 m long beams (12, 9 and 6 cm wide). Distance walked, number of steps and velocity were recorded. Participants also completed the Narrow Path Walking Test on a computerized gait mat and walked unrestricted across the mat. The number of falls in the 6 months pre- and post-testing were recorded. RESULTS: The beam data revealed significant differences between fallers and non-fallers in distance walked and number of steps taken on the 9 cm beam but not on the other beam widths. The coefficient of variation (CV) for step time and step length for unrestricted walking and for the NPWT were also significantly different between fallers and non-fallers. Falls in the 6 months before testing was not correlated with gait velocity but was significantly correlated with the number of steps and the distance walked on the 9 cm beam and with step length and step time CV. Falls in the 6 months following testing were strongly correlated with distance walked on the 9 cm beam. CONCLUSION: This research suggests that examining an older adult's ability to walk on a 9 cm wide beam might contribute significantly to the assessment of that person's fall risk.

Visual detection of affordances for aperture negotiation in people with Parkinson disease.

BACKGROUND: An essential requirement for the guidance of action in cluttered environments is that people can accurately perceive what actions are afforded by particular surroundings given the person's action capabilities. Research has shown that healthy young individuals turn their shoulders when walking through a doorway when the aperture is less than a certain percentage of their shoulder width and that they are able to detect this critical width with visual inspection. These findings imply that movements are constrained by perception of the environment in body-scaled unit. OBJECTIVES: The present work examined whether the visual affordance of doorway passability is altered in people with Parkinson disease (PD). METHODS: People with PD, healthy age-matched controls, and young adults (16 participants per group) walked through a series of apertures scaled to shoulder width. Participants also had to visually judge a series of apertures to determine if they could walk through the gap with their normal gait pattern. Finally, participants had to estimate their eye height. RESULTS: Statistical analysis revealed that people with PD initiated shoulder turning to go through the doorway at larger apertures (A) relative to their shoulder (S) width (A/S = 1.61) in comparison to healthy age-matched participants (A/S = 1.41) and young adults (A/S = 1.26). In comparison to healthy participants, People with PD also judged wider apertures as impassable. Individuals with PD were less accurate in their estimation of eye height (Error = 10.1%) than the healthy older (Error = 6.29%) and younger adults (Error = 4.79%). CONCLUSIONS: PD significantly impacted the affordances for aperture negotiation. Such altered perceptual affordances may contribute to gait pattern changes in people with PD when walking through doorways. These findings suggest that some of the motor symptoms in PD might have a perceptual underpinning.

The Role of Postural Support in Young Adults' Control of Stationary Kicking.

PURPOSE: The requirement for postural stability during the performance of motor skills has been clearly demonstrated in infants, but the necessity for such a postural substrate is not well documented in adults. The present study investigated the role of postural stability during a ballistic ball-kicking task in adults by providing varying degrees of external postural support. METHOD: In the 1st experiment, 30 participants performed 20 maximal-velocity kicks under each of 3 conditions: grasping a rigid stable handle, light fingertip touch, and grasping a suspended elastic tube. A 2nd experiment with 16 participants varied the position of the stable handle to examine if the handle position in Experiment 1 might simply act as a fulcrum to enhance torque generation. RESULTS: In Experiment 1, ball velocity was significantly higher in the stable-grasp condition in both men and women with the men showing greater improvement relative to the other conditions. Experiment 2 showed that the position of the stable handle did not significantly affect kicking velocity, indicating that the handle was not simply acting as a fulcrum during the kick. CONCLUSION: Together, the findings suggest that postural stability may be a rate limiter in the performance of dynamic motor tasks in adults.

Contextual Interference Can Facilitate Motor Learning in Older Adults and in Individuals With Parkinson's Disease.

In healthy young adults motor learning is typically improved by practice under conditions of high contextual interference such as that created when a series of skills are practiced in a random sequence. The authors examined whether individuals with Parkinson's disease and age-matched older adults might also benefit from such a learning environment. Participants learned 3 peg placement movements under both random practice and blocked practice schedules. Participants completed free-recall, cued-recall, and transfer tests 1 day and 1 week following practice. During acquisition all learners had shorter movement times (MTs) during blocked than random practice but during retention testing, MTs were shorter if the patterns had been learned with random practice. Fewer errors during free recall following random practice were evident in both groups of learners and MTs to complete a novel transfer task were shorter following random practice. These findings suggest employing a cognitively challenging practice environment might improve motor skill learning in elderly learners and in people with Parkinson's disease.

The role of head position and prior contraction in manual aiming.

We sought to determine if the asymmetrical tonic neck reflex influences the accuracy of self-selected arm positioning without vision and to ascertain if such accuracy is influenced by a pre-contraction of the prime movers. Participants reproduced an arm position using their abductors with the head in midline, rotated towards and away from the arm. Arm movements were made with and without a pre-contraction of the abductors. Twenty participants performed eight trials in each of the six different conditions. Compared to the midline position, participants undershot the reference position with the head turned away and overshot the position with the head rotated towards the arm. A pre-contraction caused undershooting regardless of head position. Results suggest that head position and pre-contraction may have significant and independent effects on arm positioning.

Kicking performance in relation to balance ability over the support leg.

Balance control is presumed to be a fundamental constraint on the organization of skilled movement. The current experiment explored whether single-leg balance ability predicted kicking performance on the other leg. Thirty-eight participants ranging widely in skill kicked a soccer ball with the right and left legs for maximum accuracy and velocity and performed single-leg balance on a force plate for 30 s with the right and left legs. Significant correlations between single-leg balance and kicking accuracy, but not velocity, were found. Left leg balance was more highly correlated than right leg balance with right (dominant) leg kicking accuracy. However, the same pattern of relations was not seen between single-leg balance and left (non-dominant) leg kicking accuracy. These findings provide preliminary support for the importance of balance ability in kicking performance. The importance of balance in the production of athletic skills is discussed and additional experimental paradigms are suggested that might further our knowledge in this area.

Comparing the reliability of a trigonometric technique to goniometry and inclinometry in measuring ankle dorsiflexion.

OBJECTIVES: The purpose of this study was to compare the reliability of three previously used techniques for the measurement of ankle dorsiflexion ROM, open-chained goniometry, closed-chained goniometry, and inclinometry, to a novel trigonometric technique. METHODS: Twenty-one physiotherapy students used four techniques (open-chained goniometry, closed-chained goniometry, inclinometry, and trigonometry) to assess dorsiflexion range of motion in 24 healthy volunteers. All student raters underwent training to establish competence in the four techniques. Raters then measured dorsiflexion with a randomly assigned measuring technique four times over two sessions, one week apart. Data were analyzed using a technique by session analysis of variance, technique measurement variability being the primary index of reliability. Comparisons were also made between the measurements derived from the four techniques and those obtained from a computerized video analysis system. RESULTS: Analysis of the rater measurement variability around the technique means revealed significant differences between techniques with the least variation being found in the trigonometric technique. Significant differences were also found between the technique means but no differences between sessions were evident. The trigonometric technique produced mean ROMs closest in value to those derived from computer analysis. CONCLUSIONS: Application of the trigonometric technique resulted in the least variability in measurement across raters and consequently should be considered for use when changes in dorsiflexion ROM need to be reliably assessed.

Interaction of feedback frequency and task difficulty in children's motor skill learning.

BACKGROUND: Providing adults with knowledge of results (KR) after each practice trial (100% KR) usually is found to be detrimental to motor skill learning compared with conditions in which feedback is less frequently provided. The effect of 100% KR on children's learning is less clear, with research showing that children with cerebral palsy benefit from less frequent KR, whereas children with typical development do not. OBJECTIVE: This study was designed to examine the interaction of KR frequency and task complexity on the acquisition, retention, and transfer of a novel throwing skill in fourth- and fifth-grade children with typical development. DESIGN: This was an observational study. METHODS: Children threw beanbags for accuracy at an unseen target while walking or while standing still. These 2 levels of task complexity were crossed with 2 frequencies (33% and 100%) of KR provision. Following practice, retention tests without feedback were performed 5 minutes later and then 1 week later along with transfer tests to assess the generalizability of learning. RESULTS: Analyses revealed that learning was improved on the easy version of the task when a 33% KR frequency was provided during practice. In contrast, in the difficult version, learning was facilitated by provision of a 100% KR frequency during practice. CONCLUSIONS: Structuring practice conditions for children should take into account task complexity and feedback frequency in determining the cognitive challenge necessary for optimal skill learning. More generally, the findings suggest that practitioners teaching motor skills should design practice conditions in accordance with the cognitive processing capacity of the learner.

A comparison of manual guidance and knowledge of results in the learning of a weight-bearing skill.

BACKGROUND AND PURPOSE: Patients with certain neurological or orthopedic conditions often present with asymmetrical weight-bearing in stance. In the treatment of such patients, physical therapists often use manual guidance to promote symmetrical weight-bearing. Research investigating the efficacy of manual guidance to effect a change in weight-bearing status however, is lacking. As a first step in assessing the utility of such guidance, the present study compared the effect of providing two frequencies of manual guidance and of knowledge of results (KR) in the learning of a weight-bearing skill in healthy subjects. SUBJECTS AND METHODS: Forty healthy subjects (20 males and 20 females) with a mean age of 21.8 years (SD = 4.9 years) were randomly assigned to one of four groups differentiated on the basis of the type and frequency of information provided for learning. Subjects were required to learn to distribute their weight on their feet at a 70:30 ratio. Following a pretest, one group of subjects was positioned by experimenter-provided manual guidance at the hips until 70% of their weight was on one foot, as determined by a bathroom scale. This guidance was provided on every trial for 10 blocks of 12 trials (GD100%). A second group was provided with guidance on every third trial (GD33%), with the other two trials being performed without any assistance. A third group was verbally provided with KR regarding the percentage of body weight on the test foot after every trial (KR100%) while the final group was given KR after every third trial (KR33%). Following acquisition, retention tests were performed 10 minutes, one day, and one week later during which no feedback or guidance was given. RESULTS: No difference between groups was found at the pretest, but an analysis of variance performed on the accuracy of achieving the 70% goal in retention revealed main effects for technique and frequency. These effects were overshadowed by a significant interaction of these variables with retention test. Analysis of this interaction revealed that the most accurate performance was exhibited by the KR33% group while the GD100% group consistently exhibited the poorest learning. The GD33% and KR100% groups showed a decrease in performance accuracy with time following practice. DISCUSSION AND CONCLUSION: These results indicate that infrequent KR was the most effective technique in learning to modify weight-bearing status and that frequent manual guidance during practice is ineffective for learning this task. The next step is to determine whether these findings hold in subjects with various orthopedic and neurological conditions.

Effects of long-term gait training using visual cues in an individual with Parkinson disease.

BACKGROUND AND PURPOSE: In an attempt to improve the gait of people with Parkinson disease (PD), researchers have examined the effect of visual cues placed on the floor. These studies typically have used a single session of training with such cues and have not examined the long-term carryover of such training. In the present study, therefore, gait was analyzed during uncued, cued, and retention phases, each lasting 1 month. SUBJECT: A 78-year-old woman who had been diagnosed with PD 12 years previously (Hoehn and Yahr classification of disability, stage III) volunteered for the study. METHODS: During the initial uncued gait phase, the subject was required to walk a distance of 10 m as many times as she could in 30 minutes, 3 times per week for 4 weeks. During the 4-week cued gait phase, visual cues were placed on the floor along the 10-m walkway. The cues were initially 110% of the uncued step length and were later increased to 120%. Following this cued gait phase, the subject's gait was recorded periodically for 1 month without cues available. Step length, gait speed, and 2-dimensional lower-limb kinematics were compared within and across the 3 experimental phases. Celeration lines were calculated for the initial uncued phase and then extrapolated across the cued training and uncued retention phases. Binomial tests were used to analyze the significance of changes from the initial phase of the experiment. RESULTS: Step length (0.53-0.56 m) and gait speed (0.77-0.82 m x s(-1)) were essentially unchanged during uncued gait training after the first day; however, during the cued gait phase, gait speed improved, from 0.87 m x s(-1) to 1.13 m x s(-1), as step length was increased with visual cues. Improvements in step length (0.68 m) and gait speed (1.08 m x s(-1)) were still evident 1 month following the removal of the cues. Analyses of angle-angle diagrams and phase-plane portraits revealed that training with visual cues increased hip and knee range of motion and engendered more stable motor control of the lower limb. DISCUSSION AND CONCLUSION: In contrast to previous studies in which the benefits of visual cueing were relatively short-lived, in this study, 1 month of gait training with visual cues was successful in establishing a lasting improvement in gait speed and step length while increasing the stability of the underlying motor control system.

Can mental practice increase ankle dorsiflexor torque?

BACKGROUND AND PURPOSE: Mental practice has been shown to be effective in increasing the force production of the abductor digiti minimi muscle in the hand. The aim of this study was to determine whether mental practice could produce strength gains in the larger ankle dorsiflexor muscles, which are important during walking. SUBJECTS: Twenty-four subjects were randomly assigned to a physical practice group, a mental practice group, or a control group (8 subjects per group). METHODS: In the practice groups, subjects either physically or mentally practiced producing maximal isometric contractions for 3 sets of 10 repetitions, 3 times per week for 4 weeks. Changes in mean peak isometric torque normalized to body weight and the resulting percentage of improvement were analyzed across the 3 groups. RESULTS: Differences in raw torque production after training in the 2 practice groups resulted in significant percentages of improvement for the physical practice group (25.28%) and the mental practice group (17.13%), but not for the control group (-1.77%). The 2 practice groups were not statistically different in their maximal torque-generating capacity after training. DISCUSSION AND CONCLUSION: These findings show that mental practice in people without impairments can lead to an increase in torque production similar to that produced by physical practice. Such a technique may prove to be a useful adjunct to traditional treatment options aimed at increasing muscle strength.

The effect of cane length on the haptic perception of height.

PURPOSE: The purpose of this investigation was to determine whether the ability to haptically perceive object height is a function of the length of cane being wielded by blindfolded individuals. METHOD: Fifteen sighted females between the ages of 18 and 25 years volunteered to participate in the study. Five different heights of wooden blocks were haptically explored with four different cane lengths (0.92, 1.22, 1.37 and 1.67 m), cane length order being randomized across 2 days of testing. Subjects were asked to report whether the explored block's height was taller, shorter, or equal to that of a previously presented standard block. The percentages of correct judgments for each cane and block height combination were subjected to statistical analysis. RESULTS: The analysis revealed significant main effects for cane length, F (3, 42) = 9.47, p < 0.0001, and block height, F (4, 56) = 17.69, p < 0.0001. The interaction of cane length and block height was not significant, F < 1. The accuracy of haptic perception improved with decreased cane length and increased difference in height from the standard block. CONCLUSIONS: Contrary to previous research on haptic perception in which probe length was found not to affect judgment accuracy, the present study found a marked influence of cane length on perceptual accuracy. This finding indicates that length is an important property that should be taken into account when prescribing canes for the visually impaired.

Acute effects of stretching on the neuromechanical properties of the triceps surae muscle complex.

Previous research has shown that an acute bout of passive muscle stretching can diminish performance in certain movements where success is a function of maximal force and/or power output. Two possible mechanisms that might account for such findings are a change in active musculotendinous stiffness and a depression of muscle activation. To investigate the likelihood of these two mechanisms contributing to a post-stretch reduction in performance, we examined the acute effects of stretching on the active stiffness and muscle activation of the triceps surae muscle group during maximal single-joint jumps with movement restricted to the ankle joint. Ten males performed both static (SJ) and countermovement (CMJ) jumps before and after passively stretching the triceps surae. Electrical activity of the triceps surae during each jump was determined by integrating electromyographic recordings (IEMG) over the course of the movement. Triceps surae musculotendinous stiffness was calculated before and after stretching using a technique developed by Cavagna (1970). Following stretching, a significant decrease [mean (SD) 7.4 (1.9)%; P<0.05] in jump height for the CMJ occurred, but for the SJ, no significant ( P>0.05) change in jump height was found. A small but significant decrease [2.8 (1.24)%; P<0.05] in stiffness was noted, but the magnitude of this change was probably not sufficient for it to have been a major factor underlying the decline in CMJ performance. Paradoxically, after stretching, the SJ exhibited a significant ( P<0.05) decrease in IEMG, but the IEMG for the CMJ remained unchanged ( P>0.05). It appears that an acute bout of stretching can impact negatively upon the performance of a single-joint CMJ, but it is unlikely that the mechanism responsible is a depression of muscle activation or a change in musculotendinous stiffness.

Distributed Control in Rapid Sequential Aiming Responses.

The preparation and on-line control of short, rapid sequential aiming responses were studied in 3 experiments. Participants (N = 12 in Experiments 1 and 2, and 20 in Experiment 3) produced 3-segment responses (a) within self-initiation, simple reaction time (RT), and choice RT paradigms (Experiment 1); (b) without visual feedback under self-initiation conditions (Experiment 2); and (c) with and without visual feedback under simple RT conditions (Experiment 3). In all conditions in which participants initiated movement in response to an external imperative signal, the 2nd response segment was performed consistently slower than preceding and succeeding response segments. That pattern of segmental movement times was found whether or not visual feedback was available but was not evident when participants self-initiated their responses with or without visual feedback. The findings rule out the possibility that subjects' use of visual feedback is responsible for the slowing of the 2nd response segment under RT conditions and suggest that the programming of rapid sequential aiming responses can be distributed in pre- and postinitiation intervals.