Biomedical subjects

William A Sparrow

Publications and source records attributed to William A Sparrow.

7 recordsLinked to original sources

PubMed2006

Aging effects on visual reaction time in a single task condition and when treadmill walking.

Visual reaction time (RT) was measured in 10 older men (mean age, 71.1 years) and gender-matched controls (mean age, 26.3 years) when standing (single task) and when walking on a motor-driven treadmill (dual task). There were 90 quasi-randomly presented trials over 15 min in each condition. Longer mean and median RTs were observed in the dual task compared to the single task. Older males had significantly slower mean and median RTs (315 and 304 ms, respectively) than the younger group (273 and 266 ms, respectively) in both task conditions. There were no age or condition effects on within-subject variability. Both groups showed a trend of increasing RT over the 90 single task trials but when walking only the younger group slowed. These novel findings demonstrate high but sustained attention by older adults when walking. It is proposed that the motor task's attentional demands might contribute to their slower preferred walking speed.

Adult↗

PubMed2006

Learning to minimize energy costs and maximize mechanical work in a bimanual coordination task.

The authors addressed the hypothesis that economy in motor coordination is a learning phenomenon realized by both reduced energy cost for a given workload and more external work at the same prepractice metabolic and attentional energy expenditure. "Self-optimization" of movement parameters has been proposed to reflect learned motor adaptations that minimize energy costs. Twelve men aged 22.3 -/+ 3.9 years practiced a 90 degrees relative phase, upper limb, independent ergometer cycling task at 60 rpm, followed by a transfer test of unpracticed (45 and 75 rpm) and self-paced cadences. Performance in all conditions was initially unstable, inaccurate, and relatively high in both metabolic and attentional energy costs. With practice, coordinative stability increased, more work was performed for the same metabolic and attentional costs, and the same work was done at a reduced energy cost. Self-paced cycling was initially below the metabolically optimal, but following practice at 60 rpm was closer to optimal cadence. Given the many behavioral options of the motor system in meeting a variety of everyday movement task goals, optimal metabolic and attentional energy criteria may provide a solution to the problem of selecting the most adaptive coordination and control parameters.

Adult↗

PubMed2005

Aging effects on the metabolic and cognitive energy cost of interlimb coordination.

Many everyday motor tasks have high metabolic energy demands, and some require extended practice to learn the required coordination between limbs. Eight older (73.1 +/- 4.4 years) and 8 younger (23.3 +/- 5.9) men practiced a high-energy two-hand coordination task with both 180 degrees and 90 degrees target relative phase. The older group showed greater performance error in both conditions, and performance at 90 degrees was strongly attracted to antiphase coordination (180 degrees). In a retention test one week following the acquisition trials, the older group had learned the 180 degrees condition but did not learn the 90 degrees condition. Metabolic energy cost was not different between groups, but the older men showed higher heart rate and both conditions imposed greater cognitive demands as revealed in auditory probe reaction time. Older adults' motor learning may be inhibited by elevated heart rate at the same oxygen cost, increased cognitive cost, and an attraction toward more established low-energy in-phase or antiphase coordination.

Adult↗

PubMed2005

Control of lead and trail limbs during obstacle crossing following stroke.

BACKGROUND AND PURPOSE: Obstacle crossing is compromised following stroke. The purpose of this study was to quantify modifications during obstacle clearance following stroke. SUBJECTS: Twelve subjects with stroke and 12 subjects without stroke participated in the study. METHODS: Kinematic variables were measured while participants crossed a 4-cm-high obstacle. Subjects with stroke walked at a self-selected speed; subjects without stroke walked at a comparable speed and at a self-selected speed. RESULTS: Several modifications were observed following stroke with both groups walking at self-selected speeds. The affected lead limb was positioned closer to the obstacle before crossing. Affected trail-limb clearance over the obstacle was reduced. Both affected and unaffected lead and trail limbs landed closer to the obstacle after clearance. Swing time was increased in the affected lead limb after obstacle clearance. Fewer modifications were detected at matched walking speed; the trail limb still landed closer to the obstacle. DISCUSSION AND CONCLUSION: Modifications during obstacle crossing following stroke may be partly related to walking speed. The findings raise issues of safety because people with stroke demonstrated reduced clearance of a 4-cm obstacle and limb placement closer to the obstacle after clearance.

Aged↗

PubMed2003

The effects of improved strength on obstacle negotiation in community-living older adults.

Poor mobility has been associated with age-related deterioration in muscle strength. While previous work has examined the effects of improved strength on level walking, we have quantified the effects of a resistance-training program on obstructed gait tasks using biomechanical-dependent measures. Forty-five community-dwelling participants aged 62 years or older were randomised to either a control (n=16) or experimental group (n=29). The experimental subjects exercised for 24 weeks on a progressive resistance-training program designed to improve lower body strength. Dynamic strength was assessed at weeks 0 and 24 as well as specific laboratory gait kinetics and kinematics during stepping over an obstacle and negotiation of a raised surface set at 10, 20 and 30% of each subject's leg length. Significant strength improvements (P<0.05), ranging between 197 and 285%, were recorded in the experimental group. The strength gains in the experimental group were accompanied by significant increases in obstacle-crossing stride velocity (range 5.5-15.5%) due to increases in stride length and decreases in stride duration for both gait tasks. Significant changes in the peak vertical and anterior-posterior ground reaction forces as well as in kinematic variables associated with a safe obstacle traverse such as vertical obstacle heel clearance, limb flexion at obstacle crossing, horizontal foot placement and vertical landing velocity resulted in an improved crossing strategy in the experimental subjects. These findings provide evidence of significant improvements in obstructed gait function of community-living older adults associated with a systematic resistance-training program.

Age Factors↗

PubMed2002

The relationship between lower body strength and obstructed gait in community-dwelling older adults.

OBJECTIVES: To determine the relationship between lower body strength of community-dwelling older adults and the time to negotiate obstructed gait tasks. DESIGN: A correlational study. SETTING: The Biomechanics Laboratory, Deakin University, Australia. PARTICIPANTS: Twenty-nine women and 16 men aged 62 to 88 were recruited using advertisements placed in local newspapers. The participants were independent community dwellers, healthy and functionally mobile. MEASUREMENTS: Maximal isometric strength of the knee extensors and dynamic strength of the hip extensors, hip flexors, hip adductors, hip abductors, knee extensors, knee flexors, and ankle plantar flexors were assessed. The times to negotiate four obstructed gait tasks at three progressively challenging levels on an obstacle course and to complete the course were recorded. The relationship between strength and the crossing times was explored using linear regression models. RESULTS: Significant associations between the seven strength measures and the times to negotiate each gait task and to walk the entire course at each level were obtained (r = -0.38 to -0.55; P < .05). In addition, the percentage of the variance explained by strength (R(2)), consistently increased as a function of the progressively challenging level. This increase was particularly marked for the stepping over task (R(2) = 19.3%, 25.0%, and 27.2%, for levels 1, 2, and 3, respectively) and the raised surface condition (R2 = 17.1%, 21.1%, and 30.8%, for levels 1, 2, and 3, respectively). CONCLUSION: The findings of the study showed that strength is a critical requirement for obstructed locomotion. That the magnitude of the association increased as a function of the challenging levels suggests that intervention programs aimed at improving strength would potentially be effective in helping community-dwelling older adults negotiate environmental gait challenges.

Age Factors↗

PubMed2002

Visual perception of movement kinematics and the acquisition of "action prototypes".

Recognizing a class of movements as belonging to a "nominal" action category, such as walking, running, or throwing, is a fundamental human ability. Three experiments were undertaken to test the hypothesis that common ("prototypical") features of moving displays could be learned by observation. Participants viewed moving stick-figure displays resembling forearm flexion movements in the sagittal plane. Four displays (presentation displays) were first presented in which one or more movement dimensions were combined with 2 respective cues: direction (up, down), speed (fast, slow), and extent (long, short). Eight test displays were then shown, and the observer indicated whether each test display was like or unlike those previously seen. The results showed that without corrective feedback, a single cue (e.g., up or down) could be correctly recognized, on average, with the proportion correct between .66 and .87. When two cues were manipulated (e.g., up and slow), recognition accuracy remained high, ranging between .72 and .89. Three-cue displays were also easily identified. These results provide the first empirical demonstration of action-prototype learning for categories of human action and show how apparently complex kinematic patterns can be categorized in terms of common features or cues. It was also shown that probability of correct recognition of kinematic properties was reduced when the set of 4 presentation displays were more variable with respect to their shared kinematic property, such as speed or amplitude. Finally, while not conclusive, the results (from 2 of the 3 experiments) did suggest that similarity (or "likeness") with respect to a common kinematic property (or properties) is more easily recognized than dissimilarity.

Biomechanical Phenomena↗