The Effects of Music Salience on the Gait Performance of Young Adults.

BACKGROUND: The presence of a rhythmic beat in the form of a metronome tone or beat-accentuated original music can modulate gait performance; however, it has yet to be determined whether gait modulation can be achieved using commercially available music. OBJECTIVE: The current study investigated the effects of commercially available music on the walking of healthy young adults. Specific aims were (a) to determine whether commercially available music can be used to influence gait (i.e., gait velocity, stride length, cadence, stride time variability), (b) to establish the effect of music salience on gait (i.e., gait velocity, stride length, cadence, stride time variability), and (c) to examine whether music tempi differentially effected gait (i.e., gait velocity, stride length, cadence, stride time variability). METHODS: Twenty-five participants walked the length of an unobstructed walkway while listening to music. Music selections differed with respect to the salience or the tempo of the music. The genre of music and artists were self-selected by participants. RESULTS: Listening to music while walking was an enjoyable activity that influenced gait. Specifically, salient music selections increased measures of cadence, velocity, and stride length; in contrast, gait was unaltered by the presence of non-salient music. Music tempo did not differentially affect gait performance (gait velocity, stride length, cadence, stride time variability) in these participants. CONCLUSIONS: Gait performance was differentially influenced by music salience. These results have implications for clinicians considering the use of commercially available music as an alternative to the traditional rhythmic auditory cues used in rehabilitation programs.

A new quantitative method for evaluating freezing of gait and dual-attention task deficits in Parkinson's disease.

People with Parkinson's disease (PD) can exhibit disabling gait symptoms such as freezing of gait especially when distracted by a secondary task. Quantitative measurement method of this type of cognitive-motor abnormality, however, remains poorly developed. Here we examined whether stepping-in-place (SIP) with a concurrent mental task (e.g., subtraction) can be used as a simple method for evaluating cognitive-motor deficits in PD. We used a 4th generation iPod Touch sensor system to capture hip flexion data and obtain step height (SH) measurements (z axis). The accuracy of the method was compared to and validated by kinematic video analysis software. We found a general trend of reduced SH for PD subjects relative to controls under all conditions. However, the SH of PD freezers was significantly worse than PD non-freezers and controls during concurrent serial 7 subtraction and SIP tasking. During serial 7 subtraction, SH was significantly associated with whether or not a PD patient was a self-reported freezer even when controlling for disease severity. Given that this SIP-based dual-task paradigm is not limited by space requirements and can be quantified using a mobile tracking device that delivers specifically designed auditory task instructions, the method reported here may be used to standardize clinical assessment of cognitive-motor deficits under a variety of dual-task conditions in PD.

Work activities and musculoskeletal discomforts amongst active older Albertans on alternative employment trajectories.

BACKGROUND: Bridge employment (scheduled paid work after retirement age) may promote successful aging and continued health, as work can be an important component of daily physical activity. Appropriate work demands for older adults are neither well-established nor well-applied, however, and excessive loading or increased perceptions of discomfort may negate the health benefits of work activity. OBJECTIVE: This study examined work status and musculoskeletal discomfort (MSD) amongst older Albertans. METHODS: 1044 Albertans aged 55 years and older participating in an organized 'Games' received a research package. Enclosed in the package were an introductory letter, a return envelope, and modified versions of validated questionnaires examining leisure and work activities, activity frequency, and perceptions of musculoskeletal health. RESULTS: 228 respondents were classified into one of three employment trajectory groups: fully retired, fully employed, or bridge employed. Groups differed in age, and both employed groups more frequently reported MSDs in all body areas. Bridge employed reported increased 'occasional' frequency of musculoskeletal injury risk factors, while both groups reported similar overall ratings of work-related exertion. CONCLUSIONS: The increased MSDs reported by bridge employed adults may be the result of irregularity of work activity and soft tissue loading. Detailed examination of work demands and musculoskeletal injuries amongst bridge employed adults could help define safer levels for less regular work activity.

Obstacle Avoidance amongst Parkinson Disease Patients Is Challenged in a Threatening Context.

We examined whether people with Parkinson disease (PD) have difficulty negotiating a gait obstruction in threatening (gait path and obstacle raised above floor) and nonthreatening (gait path and obstacle at floor level) contexts. Ten PD patients were tested in both Meds OFF and Meds ON states, along with 10 age-matched controls. Participants completed 18 gait trials, walking 4.7 m at a self-selected speed while attempting to cross an obstacle 0.15 m in height placed near the centre point of the walkway. Kinematic and kinetic parameters were measured, and obstacle contact errors were tallied. Results indicated that PD patients made more obstacle contacts than control participants in the threatening context. Successful crossings by PD patients in the threatening condition also exhibited kinematic differences, with Meds OFF PD patients making shorter crossing steps, with decreased initiation and crossing velocities. The findings from this study lend support to the theory that PD patients rely on directed attention to initiate and control movement, while providing indication that the motor improvements provided by current PD pharmacotherapy may be limited by contextual interference. These movement patterns may be placing PD patients at risk of obstacle contact and falling.

Selective attentional processing to fall-relevant stimuli among older adults who fear falling.

Fear of falling is known to affect more than half of community-dwelling older adults over 60 years of age. This fear is associated with physical and psychological effects that increase the risk of falling. The authors' theory is that attentional processing biases may exist in this population that serve to perpetuate fear of falling and subsequently increase fall risk. As a starting point in testing this proposition, the authors examined selective attentional processing bias to fall-relevant stimuli among older adults. Thirty older adult participants (M(age) = 70.8 ± 5.8), self-categorized to be Fearful of Falling (FF, n = 15) or Non-Fearful of Falling (NF, n = 15) completed a visual dot-probe paradigm to determine detection latencies to fall-threatening and general-threat stimuli. Attentional processing was defined using three index scores: attentional bias, congruency index, and incongruency index. Bias indicates capture of attention, whereas congruency and incongruency imply vigilance and disengagement difficulty, respectively. Both groups showed an attentional bias to fall-threat words but those who were fearful of falling also showed an incongruency effect for fall-threat words. These findings confirm that selective attentional processing profiles for fall-relevant stimuli differ between older adults who exhibit fear of falling and those who do not have this fear. Moreover, in accordance with current interpretations of selective attentional processing, the incongruency effect noted among fall-fearful older adults presents a possibility for a difficulty disengaging from fall-threatening stimuli.

Walking with music is a safe and viable tool for gait training in Parkinson's disease: the effect of a 13-week feasibility study on single and dual task walking.

This study explored the viability and efficacy of integrating cadence-matched, salient music into a walking intervention for patients with Parkinson's disease (PD). Twenty-two people with PD were randomised to a control (CTRL, n = 11) or experimental (MUSIC, n = 11) group. MUSIC subjects walked with an individualised music playlist three times a week for the intervention period. Playlists were designed to meet subject's musical preferences. In addition, the tempo of the music closely matched (±10-15 bpm) the subject's preferred cadence. CTRL subjects continued with their regular activities during the intervention. The effects of training accompanied by "walking songs" were evaluated using objective measures of gait score. The MUSIC group improved gait velocity, stride time, cadence, and motor symptom severity following the intervention. This is the first study to demonstrate that music listening can be safely implemented amongst PD patients during home exercise.

Obstacle crossing among people with Parkinson disease is influenced by concurrent music.

Multitasking situations exacerbate gait impairments and increase the risk of falling among people with Parkinson disease (PD). This study compared obstacle negotiation among 10 subjects with PD and 10 nonparkinsonian control (CTRL) subjects in two test conditions differentiated by the presence of music played through a personal music player. Subjects walked the length of a 10 m walkway at a self-selected pace, crossing a 0.15 m obstacle placed at the midpoint of the walkway. The results indicated that subjects with PD crossed the obstacle slower than CTRL subjects and that concurrent music differentially altered obstacle crossing behaviors for the CTRL subjects and subjects with PD. Subjects with PD further decreased obstacle-crossing velocities and maintained spatial parameters in the music condition. In contrast, CTRL subjects maintained all spatiotemporal parameters of obstacle crossing with music. The alterations to crossing behaviors observed among the subjects with PD support our previous suggestion that listening to music while walking may be an attentionally demanding task.

Challenging context affects standing reach kinematics among Parkinson's disease patients.

The standing reach movement requires coordinated activation of postural and focal motor responses. For PD patients, both components of this reaching task exhibit evidence of motor deficit. In the present experiment, we examined these motor responses during a standing reaching task in a challenging environmental context. PD patients (n=10) and control participants (n=8) were asked to reach and drink from a glass while standing on a raised platform (0.6m) with and without an additional anterior platform. Removal of the anterior platform placed participants in a higher postural threat context. Displacement data were captured from markers on relevant body landmarks to provide reach end-point and whole-body movement kinematics. Our results showed that PD patients delayed trunk flexion and peak end-point velocity during the forward reach phase and peak centre of mass velocity during the transport phase for a challenged standing reach. These behaviours, in combination with the bradykinetic motor control observed in PD patients, could contribute to the frequent falls observed among the PD population.

Novel challenges to gait in Parkinson's disease: the effect of concurrent music in single- and dual-task contexts.

OBJECTIVE: To investigate the effect of concurrent music on parkinsonian gait in single- and dual-task contexts. DESIGN: A counterbalanced repeated-measure design. SETTING: A university balance research laboratory. PARTICIPANTS: People with idiopathic Parkinson's disease (PD) (n=10) (67+/-7 y) and healthy age-matched (65+/-6 y) control subjects (n=10). INTERVENTION: Subjects walked at a self-selected pace along an unobstructed walkway in 4 differing test conditions. Test conditions were differentiated by the presence of music accompaniment (no music/music) and the presence of a secondary cognitive task (single/dual). Single- and dual-task conditions were randomized; trials were blocked by the presence of music and counterbalanced between subjects. Music was self-selected by subjects. The cognitive task consisted of serial subtractions (3's). Subjects were not instructed to attend to the music nor were they provided with instructions regarding task prioritization. MAIN OUTCOME MEASURES: Mean gait velocity, stride length, and the percentage of the gait cycle spent in double-limb support. RESULTS: Gait among the PD patients was adversely affected by concurrent music. In contrast, gait performance in the control subjects showed no significant difference between no music and music conditions. The added requirement of a cognitive task differentially influenced gait performance in PD patients and control subjects, with PD patients displaying a further decrease in spatiotemporal parameters of gait and control subjects displaying a marginal improvement. CONCLUSIONS: Gait impairments associated with PD are exacerbated in the presence of concurrent music, an effect that is further exaggerated by the addition of a cognitive task. These results have implications for patient safety in multitasking situations.

Visual guidance for hand advance but not hand withdrawal in a reach-to-eat task in adult humans: reaching is a composite movement.

Many animal species use reaching for food to place in the mouth (reach-to-eat) with a hand, and it may be a primitive movement. Although researchers (I. Q. Whishaw, 2005; A. N. Iwaniuk & I. Q. Whishaw, 2000; M. Gentiluci, I. Toni, S. Chieffi, & G. Pavesi, 1994) have described visual guidance of reaching in both normal and brain-injured human and nonhuman primates, researchers have not described the contribution of vision during advance of the limb to grasp food and during withdrawal of the limb with food to the mouth. To evaluate visual contributions, the authors monitored eye movements in young adults as they reached for food with and without vision. Participants visually engaged the target prior to the 1st hand movement and disengaged it as the food was grasped. Visual occlusion slowed limb advance and altered digit shaping but did not affect withdrawal. The dependence on visual control of advance but not withdrawal suggests that the reach-to-eat movement is a composite of 2 basic movements under visual and tactile/proprioceptive guidance, respectively.

Parkinsonian deficits in context-dependent regulation of standing postural control.

This study explored whether patients with Parkinson's disease alter the regulation of upright standing according to constraints imposed by the environmental context. The provision of context-dependent adaptations was inferred from the presence of adjustments to standing postural control that would serve to reduce fall risk when balance was challenged by a threatening environmental context. Participants were asked to stand as still as possible in two environmental context conditions that differed in the level of imposed postural threat: LOW threat and HIGH threat. Eight levodopa dependent patients with Parkinson's disease (PD) and eight age-matched control subjects (CTRL) provided the subject sample. PD patients were tested following a 12-h withdrawal of anti-Parkinsonian medications and approximately 1h post-medication. The CTRL group showed altered postural control in the HIGH threat condition, in a manner that was indicative of appropriate context-dependent regulation of standing. PD patients, in the non-medicated or medicated states, did not modify stance regulation when the environmental context heightened postural threat. Our results extend the current understanding of Parkinsonian deficits in the context-dependent regulation of postural control to include upright standing.

The effect of anxiety on the regulation of upright standing among younger and older adults.

We tested the hypothesis that fall anxiety would differentially influence the regulation of upright standing among younger and among older adults. Fall anxiety was imposed by a manipulation of environmental context that increased the threat to postural control by introducing the potential for injurious consequences should a fall occur. Fifteen younger and 15 older adults participated in this study. Regardless of age, postural control was more conservative when fall anxiety increased, however, age did not affect how anxiety influenced the regulation of postural control. Our findings imply that the motor consequences of fall anxiety are no more pervasive for older adults than for younger adults, and that age does not alter the ability to accommodate to environmental demands that heighten fall anxiety.

Age-dependent differences in the time course of postural control during sensory perturbations.

BACKGROUND AND AIMS: With research demonstrating that older adults are more likely to sustain a loss of balance than younger adults, the need for an account of age-related differences in postural control is apparent. Several measures of balance reported in the literature have assessed balance using an average or summative measure over the course of a trial, typically lasting several seconds. One limitation related to these measures is the inability to assess the time-course of postural control occurring throughout the trial. To this end, the current investigation assessed the temporal changes in balance both as a function of age and sensory environment. METHODS: Postural control was assessed from 10 older adults (69.3+/-4.7 years) and 10 younger adults (22.1+/-1.7 years) over the course of fifteen seconds in three different sensory environments. The sensory manipulations involved sway-referenced rotation of the floor and/or the visual surround. RESULTS: Significant differences (p=0.001) in overall postural stability were observed between the two groups on all three sensory conditions. Additionally, time-course changes were observed between the two groups when the environment did not cause sensory conflict (sway-referenced floor or room only). However, when the environment created a situation of sensory conflict (sway-referenced floor and room) both groups followed the same time-course of postural changes. CONCLUSIONS: Interestingly, the time course of postural control for the older adults on the easiest condition was mimicked by the younger adults on a more challenging condition. However, when faced with sensory conflict there were no group differences in the time course of postural control. The findings suggest an age-related decline in the temporal control of posture in altered sensory environments.

Parkinsonian deficits in sensory integration for postural control: temporal response to changes in visual input.

This study investigated the effect of Parkinson's disease (PD) on the time course for postural control following the removal and reinsertion of visual information. Twelve medicated PD patients (PD) and 12 age matched control (CTRL) subjects performed two 45-s quiet standing trials, during which visual feedback was available (0-15s), deprived (15-30s), and then restored (30-45s). The 45s test trial was divided into 5s time bins to compare the time-based effect of sensory reorganization during deprivation and reintegration. Results revealed an increase in Elliptical Sway Area (ESA) following visual deprivation for both groups; this increased ESA remained significantly higher than the baseline level for the duration of the deprivation period among PD patients and returned to baseline the level among CTRL. Despite elevated ESA at the end of visual deprivation among PD patients, neither group showed a change in ESA after visual information was restored. These results indicate a PD-associated deficit with the reorganization of sensory priorities for postural control, and may implicate the basal ganglia as being critical for integration of sensory information for postural control.

Motor deficits in Parkinsonian reaching: dopa-sensitivity influenced by real-world task constraint.

Parkinson's disease (PD) patients can perform many daily activities, but movement deficits are evident. Those deficits may be increased when the required movement is constrained in accuracy. Variable improvements in performance with PD medication have been demonstrated, and sensitivity to task constraint has been evident in some studies. The authors quantified both specific movement deficits and improvements for PD patients in a reaching task. PD patients (N=8) both on and off medication showed a need for greater ongoing control in movements with higher task-accuracy constraints. Increased task-accuracy constraints further compromised movement timing and structure among PD patients who were off medication, suggesting that unmedicated PD patients may typically compensate by using more conscious control of movement, resulting in increased slowing and segmentation of components when higher task accuracy is required.

Age-dependent differences in the attentional demands of obstacle negotiation.

BACKGROUND: Although the attention directed to gait does increase as an impending obstacle nears, it remains unclear whether the allocation of attentional resources differs between the precrossing phase of obstacle negotiation and the crossing phase of this task. This study compared the attentional demands associated with steady-state walking and the precrossing and crossing phases of an obstacle-negotiation task between young and older adults. METHODS: Fifteen younger and 15 older adults participated in this study. Participants were required to perform a verbal reaction time task during three events: (1) steady-state unobstructed gait, (2) precrossing (the final full stride prior to obstacle crossing), and (3) obstacle crossing. RESULTS: The attention directed during precrossing exceeds that of steady-state walking for both younger and older adults. Younger adults direct more attention to gait during precrossing than they do during crossing. However, precrossing is equally attentionally demanding as crossing for older adults, and both of these events require more attention than does steady-state gait in this age group. CONCLUSIONS: The task of obstacle negotiation, from precrossing through obstacle crossing, is attentionally demanding for elderly persons, and fall risk, due to a compromised availability of attentional resources, does occur prior to obstacle crossing in this age group.

Obstacle negotiation kinematics: age-dependent effects of postural threat.

This study investigated whether obstacle negotiation kinematics among younger (YA) and older adults (OA) are influenced by postural threat. Obstacle negotiation kinematics among YA and OA were examined under four conditions of postural threat. Seventeen older and 15 YA negotiated a fixed virtual obstacle while walking at a self-determined velocity along a 7.2 m walkway. Postural threat was manipulated by varying the width (0.60 vs. 0.15 m) and height (0.00 vs. 0.60 m) of the walkway. Increasing postural threat resulted in elevated levels of physiological arousal and altered crossing kinematics for all subjects. Specifically, crossing step length, lead limb velocity, trail limb velocity, and whole body center of mass (COM) velocity decreased and lead limb crossing height increased in the condition of greatest postural threat compared with the condition of least postural threat. Although both YA and OA altered obstacle negotiation kinematics under conditions of postural threat, the changes observed among older adults were considerably different from those of YA. In particular, OA demonstrated more marked reductions in the crossing velocity of the lead limb, trail limb, and COM than YA between the condition of least postural threat and the condition of greatest postural threat. The results of this study reveal that postural threat influences negotiation kinematics among YA and OA and illustrate that age-dependent differences exist for obstacle negotiation kinematics when postural threat increases. These findings may imply a beneficial effect of fear of falling on reducing fall probability among healthy OA.

The allocation of attention during locomotion is altered by anxiety.

We tested the hypotheses that: (1) anxiety regarding the possibility of falling alters the attentional demands of gait; and (2) this alteration in the attentional requirements of gait occurs independently of gait pattern accommodations. Sixteen younger and 15 older adults participated in this study. Subjects walked at a self-determined velocity along a 7.2-m walkway under four conditions of postural threat; the walking conditions varied depending on the width constraints of the walkway (60 cm vs 15 cm) and the height of the walking surface (0 cm vs 60 cm). Attentional demands of locomotion in each condition of testing were assessed using the dual-task methodology, in which participants verbally responded to an auditory cue as quickly as possible while continuing to walk. Our findings revealed that: (1) participants were successful in verbally responding to the auditory cue without modifying their gait pattern; (2) reaction times increased for all subjects when walking in the condition of greatest postural threat; (3) the attentional demands for locomotion varied with the phase of the gait cycle for younger adults but not for older adults; (4) the phase-dependent effect for younger adults disappeared in the condition of greatest postural threat, while reaction time scores for older adults systematically increased; and (5) increases in reaction time persisted despite significant changes in gait kinematics. Our findings confirm that anxiety increases the attentional demands for locomotion and provide further explanation for age-dependent increases in the attentional demands of gait. Furthermore, our findings confirm that fall-related anxiety predicates an increase in the allocation of attention to locomotor control that is independent of gait pattern adjustments.

Attentional demands for static postural control after stroke.

OBJECTIVE: To assess the attentional demands associated with postural control among people who have had a stroke. DESIGN: Nonrandomized matched case-control study. SETTING: University research laboratory in Canada. PARTICIPANTS: Six individuals who had suffered a left or right cerebral ischemic attack in the past year and a sample of 6 age- and gender-matched controls. Participants in the stroke group had a mean age of 64.17+/-13.14 years; control participants had a mean age of 64.00+/-13.91 years. Mean National Institute of Health Stroke Scale scores for these patients were 7.67+/-4.92 at the time of stroke and 1.66+/-1.36 at the time of testing. None of the patients were taking medications that would alter cognitive status or balance abilities. INTERVENTION: Participants performed a verbal reaction-time test while engaged in 3 postural tasks (sitting, standing, standing with feet together). MAIN OUTCOME MEASURE: Reaction time: latency between visual stimulus and verbal response. RESULTS: Reaction times in the stroke group differed significantly in all conditions from the controls (410+/-72 ms vs 320+/-54 ms, P<.01). A significant interaction was found between group and postural task (P=.05), with reaction-time scores showing a progressive increase in postural task difficulty among participants who had suffered a stroke. Post hoc comparisons revealed that sitting reaction-time scores were significantly slower than reaction-time scores for feet together standing (P=.008) among participants in the stroke group. CONCLUSION: Individuals who have suffered a stroke showed increased attentional demands for tasks of static postural control compared with healthy, age-matched participants.

Is the prioritization of postural control altered in conditions of postural threat in younger and older adults?

Background. The purpose of this study was to determine if the prioritization of postural control over secondary task performance is altered in younger and older adults under different conditions of postural threat. Methods. Fifteen healthy older adults (mean age = 69.53 +/- 5.78) and 15 younger adults (mean age = 22.00 +/- 2.17) performed Brooks' Spatial Letter Task (BST) while standing in four conditions of postural threat. Galvanic skin conductance (GSC) was collected to measure changes in physiological arousal. BST task duration was used to measure changes in cognitive performance, and center of pressure (COP) area was used to determine changes in postural stability across each of the testing conditions. A prioritization index was calculated based on the relative change in BST and COP across testing conditions. This measure was used to quantify changes in the relationship between postural control and secondary task performance under conditions of postural threat. Results. Measures of GSC increased in younger and older adults in response to conditions of increased postural threat. Prioritization index scores revealed that a greater number of older adults than younger adults prioritized postural control over secondary task performance under conditions of increased postural threat. Conclusions. Environmental contexts that alter postural threat may lead to modifications in the prioritization between postural control and secondary task performance among older adults. This relationship may have implications for postural control under situations that do not afford deterioration in secondary task performance.