Location versus task relevance: The impact of differing internal focus of attention instructions on motor performance.

Impaired performance while executing a motor task is attributed to a disruption of normal automatic processes when an internal focus of attention is used. What remains unclear is whether the specificity of internally focused task instructions may impact task performance. The present study assessed the implications of changing the attentional focus of novice and skilled golfers by measuring behavioural, neurophysiological and kinematic changes during a golf putting task. Over six blocks of ten putting trials each, attention was directed either externally (towards the target) or internally in one of two ways: 1) proximal (keeping the elbows extended and the hands gripping the putter); or 2) distal (keeping the weight evenly distributed between both legs) to the critical elements of the task. Results provided evidence that when novice participants use an internal focus of attention more closely associated with task performance that their: 1) execution; 2) accuracy; 3) variability of surface electromyography (sEMG) activity; and 4) kinematics of the putter movement are all adversely affected. Skilled golfers are much more resilient to changes in attentional focus, while all participants interpret a distal internal focus of attention similar to an external focus. All participants produced decreased activity in the muscle (tibialis anterior) associated with the distal (less task relevant) focus of attention even when the "internal" focus was on the lower extremity. Our results provide evidence that the skill level of the participant and the distance of the internal focus of attention from the key elements of a motor skill directly impact the execution, muscle activity, and movement kinematics associated with skilled motor task performance.

Fitts's Law using lower extremity movement: Performance driven outcomes for degenerative lumbar spinal stenosis.

A paucity of objective outcome measures exists for assessing movement disorders, including degenerative lumbar spinal stenosis (LSS). Fitts's Law provides a novel approach to clinical outcome measurement since performance is resistant to learning, and task difficulty can be altered. The objective of the present study was to compare, using a Fitts's task, movement performance of individuals with and without LSS to determine if motor difficulties that arise with LSS impede the planning, initiation, or execution of deliberate lower limb movements. Twelve pre-surgical LSS patients and twelve control participants from the community performed a Fitts's Law (foot reaching) task, while LSS participants also completed pain and disability questionnaires. Fitts's Law was evident for both groups, however the LSS group's movements were more adversely impacted as task difficulty increased. Specifically, the LSS group's movement time and time to peak velocity (ttPV) increased as task index of difficulty increased, while peak velocity decreased. Correlations between ttPV and leg pain, and with stenosis impairment severity respectively, provided evidence that less support leg pain and less stenosis impairment severity yield faster ttPV in the moving leg at the highest index of difficulty. Therefore a lower extremity Fitts's Law task captured differences in the planning and execution of leg movements between healthy and LSS populations.

Lumbar spinal stenosis and lower extremity motor control: the impact of walking-induced strain on a performance-based outcome measure.

OBJECTIVE: The primary objective of this study was to quantify the lower extremity movements and capabilities of a population with lumbar spinal stenosis (LSS) compared with healthy age-matched controls under conditions of strain and no strain. The secondary objective was to identify challenging movement conditions for a population with LSS, on a lower limb aiming task with different levels of difficulty, compared with healthy age-matched controls under conditions of strain and no strain. METHODS: Using a nonrandomized, controlled, before-and-after design, LSS patients (n = 16) and healthy controls (n = 16) performed 2 blocks of great toe-pointing movements to a series of projected squares. Following block 1, participants completed a 12-minute progressive exercise treadmill test. Pointing movements were analyzed using 3D motion analysis. Behavioral and kinematic measures evaluated performance. RESULTS: Both groups' reaction times (RTs) lengthened as task difficulty increased. An interaction revealed that LSS patients were more adversely impacted by task difficulty, F (3,372) = 4.207; P = .006. The progressive exercise treadmill test facilitated RT for both groups, F (1,124) = 5.105; P = .026. Control participants showed less variability in time-to-peak velocity poststrain, a benefit not shared by LSS patients, t (31) = 2.149; P = .040. CONCLUSION: A lower extremity movement task captured differences under strain between healthy and LSS populations. The lower extremity Fitts' Law task accurately measured differences between healthy and LSS participants. For the subjects in this study, strain was sufficient to prevent LSS patients from demonstrating improvement in the variability of the ballistic phase of movement execution, whereas LSS patients' movement performance remained unchanged. This study also showed that regardless of strain, as task difficulty increased, LSS patients were more adversely impacted in the planning and execution of their lower limb movements than healthy control participants. The lower extremity motor control task (Fitts' task) can be used as a performance-based outcome measure to measure differences between healthy and LSS populations.