The bilateral movement condition facilitates maximal but not submaximal paretic-limb grip force in people with post-stroke hemiparesis

OBJECTIVES: Although healthy individuals have less force production capacity during bilateral muscle contractions compared to unilateral efforts, emerging evidence suggests that certain aspects of paretic upper limb task performance after stroke may be enhanced by moving bilaterally instead of unilaterally. We investigated whether the bilateral movement condition affects grip force differently on the paretic side of people with post-stroke hemiparesis, compared to their non-paretic side and both sides of healthy young adults. METHODS: Within a single session, we compared: 1) maximal grip force during unilateral vs. bilateral contractions on each side, and 2) force contributed by each side during a 30% submaximal bilateral contraction. RESULTS: Healthy controls produced less grip force in the bilateral condition, regardless of side (- 2.4% difference), and similar findings were observed on the non-paretic side of people with hemiparesis (- 4.5% difference). On the paretic side, however, maximal grip force was increased by the bilateral condition in most participants (+11.3% difference, on average). During submaximal bilateral contractions in each group, the two sides each contributed the same percentage of unilateral maximal force. CONCLUSIONS: The bilateral condition facilitates paretic limb grip force at maximal, but not submaximal levels. SIGNIFICANCE: In some people with post-stroke hemiparesis, the paretic limb may benefit from bilateral training with high force requirements

Comparison of unilateral versus bilateral upper extremity task performance after stroke

BACKGROUND: Previous studies have suggested that practicing functional tasks bilaterally instead of unilaterally may improve paretic limb performance after stroke. OBJECTIVE: The purposes of this study were to determine whether the bilateral movement condition alters paretic limb performance of a functional task in people with post-stroke hemiparesis, and to identify specifically which parameters of performance may be affected. METHODS: In this single-session study, we examined immediate effects of the bilateral vs. unilateral movement condition on performance of a reach-grasp-lift-release task at preferred-speed in 16 people with mild to moderate post-stroke hemiparesis and in 12 healthy controls. Performance was quantified using motion analysis variables, including durations of the reach and grasp phases, reach path straightness, maximum thumb-index finger aperture, efficiency of finger movement, peak grip force, and timing of release. RESULTS: We found no evidence of immediate improvement in paretic-limb performance in the bilateral condition. In both groups, release timing occurred later when participants moved bilaterally instead of unilaterally, possibly representing a divided-attention effect. Other variables did not differ across conditions. CONCLUSIONS: Our findings suggest little immediate impact of the bilateral condition on motor performance of a reach-grasp-lift-release task at preferred speed, in people with mild to moderate hemiparesis

A spiral-like disk of ionized gas in IC 1459: Signature of a merging collision

The authors report the discovery of a large (15 kpc diameter) H alpha + (NII) emission-line disk in the elliptical galaxy IC 1459, showing weak spiral structure. The line flux peaks strongly at the nucleus and is more concentrated than the stellar continuum. The major axis of the disk of ionized gas coincides with that of the stellar body of the galaxy. The mass of the ionized gas is estimated to be approx. 1 times 10 (exp 5) solar mass, less than 1 percent of the total mass of gas present in IC 1459. The total gas mass of 4 times 10(exp 7) solar mass has been estimated from the dust mass derived from a broad-band color index image and the Infrared Astronomy Satellite (IRAS) data. The authors speculate that the presence of dust and gas in IC 1459 is a signature of a merger event

Person-specific changes in motor performance accompany upper extremity functional gains after stroke

In animal models, hundreds of repetitions of upper extremity (UE) task practice promote neural adaptation and functional gain. Recently, we demonstrated improved UE function following a similar intervention for people after stroke. In this secondary analysis, computerized measures of UE task performance were used to identify movement parameters that changed as function improved. Ten people with chronic post-stroke hemiparesis participated in high-repetition UE task-specific training 3 times per week for 6 weeks. Before and after training, we assessed UE function with the Action Research Arm Test (ARAT), and evaluated motor performance using computerized motion capture during a reach-grasp-transport-release task. Movement parameters included the duration of each movement phase, trunk excursion, peak aperture, aperture path ratio, and peak grip force. Group results showed an improvement in ARAT scores (p = 0.003). Although each individual changed significantly on at least one movement parameter, across the group there were no changes in any movement parameter that reached or approached significance. Changes on the ARAT were not closely related to changes in movement parameters. Since aspects of motor performance that contribute to functional change vary across individuals, an individualized approach to upper extremity motion analysis appears warranted

Need for speed: Better movement quality during faster task performance after stroke

BACKGROUND: Although slow and insufficient muscle activation is a hallmark of hemiparesis post-stroke, movement speed is rarely emphasized during upper extremity rehabilitation. Moving faster may increase intensity of task-specific training, but positive and/or negative effects on paretic-limb movement quality are unknown. OBJECTIVE: To determine whether moving quickly instead of at a preferred speed either enhances or impairs paretic limb task performance after stroke. METHODS: Sixteen people with post-stroke hemiparesis and 11 healthy controls performed reach-grasp-lift movements at their preferred speed and as fast as possible, using palmar and 3-finger grip types. We measured durations of the reach and grasp phases, straightness of the reach path, thumb-index finger separation (aperture), efficiency of finger movement, and grip force. RESULTS: As expected, reach and grasp phase durations decreased in the fast condition in both groups, showing that participants were able to move more quickly when asked. When moving fast, the hemiparetic group had reach durations equal to those of healthy controls moving at their preferred speed. Movement quality also improved. Reach paths were straighter and peak apertures were greater in both groups in the fast condition. The group with hemiparesis also showed improved efficiency of finger movement. Differences in peak grip force across speed conditions did not reach significance. CONCLUSIONS: People with hemiparesis are able to move faster than they choose to, and when they do, movement quality is improved. Simple instructions to move faster could be a cost-free and effective means of increasing rehabilitation intensity after stroke

Grip type and task goal modify reach-to-grasp performance in post-stroke hemiparesis

This study investigated whether grip type and/or task goal influenced reaching and grasping performance in post-stroke hemiparesis. Sixteen adults with post-stroke hemiparesis and twelve healthy adults reached to and grasped a cylindrical object using one of two grip types (3-finger or palmar) to achieve one of two task goals (hold or lift). Performance of the stroke group was characteristic of hemiparetic limb movement during reach-to-grasp, with more curved handpaths and slower velocities compared to the control group. These effects were present regardless of grip type or task goal. Other measures of reaching (reach time and reach velocity at object contact) and grasping (peak thumb-index finger aperture during the reach and peak grip force during the grasp) were differentially affected by grip type, task goal, or both, despite the presence of hemiparesis, providing new evidence that changes in motor patterns after stroke may occur to compensate for stroke-related motor impairment

Super-resolution provided by the arbitrarily strong superlinearity of the blackbody radiation

Blackbody radiation is a fundamental phenomenon in nature, and its explanation by Planck marks a cornerstone in the history of Physics. In this theoretical work, we show that the spectral radiance given by Planck's law is strongly superlinear with temperature, with an arbitrarily large local exponent for decreasing wavelengths. From that scaling analysis, we propose a new concept of super-resolved detection and imaging: if a focused beam of energy is scanned over an object that absorbs and linearly converts that energy into heat, a highly nonlinear thermal radiation response is generated, and its point spread function can be made arbitrarily smaller than the excitation beam focus. Based on a few practical scenarios, we propose to extend the notion of super-resolution beyond its current niche in microscopy to various kinds of excitation beams, a wide range of spatial scales, and a broader diversity of target objects