Lower Peak Velocity Research Articles

Difference between vertical and horizontal saccades across the human lifespan

The purpose of the study was to analyze vertical saccade parameters (latency, peak velocity, amplitude gain), and compare them to those of horizontal saccades in a cross-sectional study across the ages of the human lifespan. One hundred and thirty one participants (62 males) between the ages of 3 and 86 years made vertical prosaccades of 2–44° in response to a dot stimulus projected on a screen. A subset of participants also made horizontal prosaccades of 2–60° under the same conditions. The El-Mar (Downsview, Ontario, Canada) eye tracker was used to record binocular eye movements. Measures of saccadic latency, peak velocity and amplitude gain were calculated for each participant. Differences between saccade parameters for upward & downward saccades were calculated. Vertical saccade parameters were evaluated as a function of age and age related differences between vertical and horizontal saccade parameters were determined. There was no significant difference between upward and downward saccades and no effect of age for either latency or peak velocity. Downward saccades had significantly higher gains than upward saccades (p = 0.0001) and this difference increased significantly with age (p = 0.001). Vertical saccadic latency initially decreased from about 400 ms at 4 years of age, remained stable for a period of time and then increases again in later life. The lowest peak velocities were found in participants under 20 and over 70 years of age, while the highest peak velocities were seen in participants between 20 and 60 years of age. The majority of vertical saccades were hypometric. Saccadic amplitude gains varied depending on both the stimulus size (p = 0.0001) and age (p = 0.0001) of participants. Vertical saccades are most accurate for small amplitudes and for participants between 20 and 30 years of age. Vertical saccades had significantly longer latencies than horizontal saccades (p = 0.0001) but there was no significant effect of age. Vertical saccades had lower peak velocities than horizontal saccades in very young children but this difference decreased with age (p = 0.0015). Large vertical saccades were more hypometric than their horizontal counterparts across all ages. The observed differences in saccadic parameters could be related to the different areas in the brain used for saccadic generation, different periods and/or mechanisms of development and senescence within the visual system and brain and/or the effects of differential use.

Kinematic Components of the Reach-to-Target Movement After Stroke for Focused Rehabilitation Interventions: Systematic Review and Meta-Analysis.

Background: Better upper limb recovery after stroke could be achieved through tailoring rehabilitation interventions directly at movement deficits.Aim: To identify potential; targets for therapy by synthesizing findings of differences in kinematics and muscle activity between stroke survivors and healthy adults performing reach-to-target tasks.Methods: A systematic review with identification of studies, data extraction, and potential risk of bias was completed independently by two reviewers. Online databases were searched from their inception to November 2017 to find studies of reach-to-target in people-with-stroke and healthy adults. Potential risk-of-bias was assessed using the Down's and Black Tool. Synthesis was undertaken via: (a) meta-analysis of kinematic characteristics utilizing the standardized mean difference (SMD) [95% confidence intervals]; and (b), narrative synthesis of muscle activation.Results: Forty-six studies met the review criteria but 14 had insufficient data for extraction. Consequently, 32 studies were included in the meta-analysis. Potential risk-of-bias was low for one study, unclear for 30, and high for one. Reach-to-target was investigated with 618 people-with-stroke and 429 healthy adults. The meta-analysis found, in all areas of workspace, that people-with-stroke had: greater movement times (seconds) e.g., SMD 2.57 [0.89, 4.25]; lower peak velocity (millimeters/second) e.g., SMD −1.76 [−2.29, −1.24]; greater trunk displacement (millimeters) e.g. SMD 1.42 [0.90, 1.93]; a more curved reach-path-ratio e.g., SMD 0.77 [0.32, 1.22] and reduced movement smoothness e.g., SMD 0.92 [0.32, 1.52]. In the ipsilateral and contralateral workspace, people-with-stroke exhibited: larger errors in target accuracy e.g., SMD 0.70 [0.39, 1.01]. In contralateral workspace, stroke survivors had: reduced elbow extension and shoulder flexion (degrees) e.g., elbow extension SMD −1.10 [−1.62, −0.58] and reduced shoulder flexion SMD −1.91 [−1.96, −0.42]. Narrative synthesis of muscle activation found that people-with-stroke, compared with healthy adults, exhibited: delayed muscle activation; reduced coherence between muscle pairs; and use of a greater percentage of muscle power.Conclusions: This first-ever meta-analysis of the kinematic differences between people with stroke and healthy adults performing reach-to-target found statistically significant differences for 21 of the 26 comparisons. The differences identified and values provided are potential foci for tailored rehabilitation interventions to improve upper limb recovery after stroke.

Age-related changes in upper limb motion during typical development.

Background and aimUnderstanding the maturation of upper limb (UL) movement characteristics in typically developing (TD) children is key to explore UL deficits in those with neurodevelopmental disorders. Three-dimensional motion analysis (3DMA) offers a reliable tool to comprehensively evaluate UL motion. However, studies thus far mainly focused on specific pre-defined parameters extracted from kinematic waveforms. Here, we investigated age-related differences in UL movement characteristics over the entire movement cycle in TD children.Participants and methodsWe assessed the non-dominant UL of 60 TD children (mean age 10y3m±3y1m) using 3DMA during eight tasks: reaching (forwards (RF), upwards (RU), sideways (RS)), reach-to-grasp (sphere (RGS), vertical cylinder (RGV)) and activities-of-daily-living mimicking tasks (hand-to-head (HTH), hand-to-mouth (HTM), hand-to-shoulder (HTS)). We investigated differences between four age-groups (5-7y, 8-10y, 11-12y, 13-15y) in: (1) spatiotemporal parameters (movement duration, peak velocity, time-to-peak velocity and trajectory straightness), and (2) 12 UL joint angles, using Statistical Parametric Mapping (SPM).ResultsWe found that the 5-7y children moved with lower peak velocity and less straight trajectories compared to the 11-12y group (peak velocity: RS, HTS, p<0.01; trajectory: RU, RS, RGV, HTS, p<0.01) and the 13-15y group (peak velocity: RF, RS, RGS, RGV, HTH, HTS, p<0.01; trajectory, all tasks, p<0.01). The 5-7y children showed increased scapular protraction compared to older children (8-10y and 11-12y, HTS), as well as increased scapular medial rotation compared to the 13-15y group (RGS). During RU, the 5-7y children moved more towards the frontal plane (shoulder), unlike the 13-15y group. Lastly, the 5-7y group used less elbow flexion than older children (11-12y and 13-15y) during HTH and HTS.Discussion and conclusionIn conclusion, our results point toward a maturation in UL movement characteristics up to age 11-12y, when UL motion seemed to reach a plateau. The reference values provided in this study will help to further optimize the interpretation of UL deficits in children with neurodevelopmental disorders.

Definition and quantification of ‘ride’ during running

‘Ride’ is a term that has been used occasionally to describe the feel of a shoe while running, yet it has never formally been defined nor have there been any suggestions of how to objectively measure ‘ride’. In this study, we proposed a definition for ‘ride’, relating to the smoothness of the transition of the foot through the stance phase of gait, and suggested that the peak velocity in the anterior–posterior direction derived from the centre of pressure would be an appropriate measure to quantify ‘ride’. Then, we used experimental evidence to advocate the appropriateness of this assessment. Thirteen participants ran over 160 metres in two pairs of shoes with different midsole compliance, and subjectively evaluated the ‘ride’ and comfort of each shoe. Centre of pressure was measured from pressure-sensing insoles and the peak velocity in the anterior–posterior direction was taken from the transition from heel to forefoot. It was found that individuals were able to perceive the ‘ride’ of a shoe and the shoe with the lower peak velocity coincided with a significantly higher rating of ‘ride’ and comfort (p < 0.001). However, it was not always the shoe with the softer midsole that had a smoother ‘ride’, as 5 out of 13 participants had a smoother ‘ride’ in the stiff midsole. Further research is required to understand why certain individuals have a smoother ‘ride’ in a compliant versus a stiff midsole. This concept could prove useful in the real world and could possibly be implemented within a shoe store to help guide the selection of a shoe.

Comparisons of recovery, external and internal load by playing position and match outcome in professional soccer

Abstract AIMS To compare the internal and external load and the recovery by playing position and the match outcome (wins, losses or draws) in professional soccer. METHODS 23 male professional soccer athletes from a team of the first division of the Brazilian Championship took part into the study (age 26.1 ± 3.8 years old, weight 77.5 ± 5.0 kg, height 177.6 ± 5.1 cm). During the games, athletes were monitored by GPS and the variables of external loads were taken. Additionally, the session rating of perceived exertion (session RPE) and the perceived recovery scale (PRS) were collected 30 minutes and 40h after the end of the matches, respectively. RESULTS The external load was greater on full-backs and defense midfielders (p 20 km/h, covering higher distances >20 km/h; these stimuli makes them to perceive less recovered than defenders, defense and attack midfielders (p<0.05). Moreover, the defenders are those who cover lower distances by the minute and the defense midfielders are those who present the lower Peak Velocity (p<0.05). There were no significant differences between GPS variables, internal load and recovery. In addition, it was found a correlation between the external and the internal load (r=0.66; p=0.001). CONCLUSIONS The GPS variables and the perceived recovery are influenced by the playing position, but not by the match outcome.

Acute Effects of the Elevation Training Mask on Strength Performance in Recreational Weight lifters.

Jagim, AR, Dominy, TA, Camic, CL, Wright, G, Doberstein, S, Jones, MT, and Oliver, JM. Acute effects of the elevation training mask on strength performance in recreational weightlifters. J Strength Cond Res 32(2): 482-489, 2018-The Elevation Training Mask 2.0 (ETM) is a novel device that purportedly simulates altitude training. The purpose of this study was to investigate the acute effects of the ETM on resistance exercise performance, metabolic stress markers, and ratings of mental fatigue. Twenty male recreational weight lifters completed 2 training sessions of back squat and bench press (6 sets of 10 repetitions at 85% of 5-repetition maximum and seventh set to failure) as well as a maximal effort sprint test (18% body mass) with the mask (ETM) and without the mask (NM). Training evaluation included baseline and postexercise blood lactate and oxygen saturation measures. Performance evaluation included peak and average velocity bar velocity, total volume load, total work, total repetitions completed, and sprint performance. Adverse side effects were reported in 12% (n = 3) of participants, which included feelings of light headedness, anxiety, and discomfort. No differences were found in repetitions or total workload in back squat (p = 0.07) or bench press (p = 0.08) between conditions. A lower peak velocity was identified during the back squat, bench press, and sprint test in the ETM condition (p = 0.04). Blood lactate values were lower after bench press and sprint during the ETM condition (p < 0.001). Significantly lower ratings of alertness and focus for task were found after squat, bench press, and sprint test in the ETM condition compared with the NM condition (p < 0.001). Wearing the ETM during bouts of resistance training did not hinder the ability to achieve desired training volumes during the resistance training session. However, wearing the ETM does seem to attenuate the ability to maintain working velocity during training bouts and negatively influence ratings of alertness and focus for task.

The Fluid Dynamical Performance of the Carpentier-Edwards PERIMOUNT Magna Ease Prosthesis.

The aim of the present in vitro study was the evaluation of the fluid dynamical performance of the Carpentier-Edwards PERIMOUNT Magna Ease depending on the prosthetic size (21, 23, and 25 mm) and the cardiac output (3.6–6.4 L/min). A self-constructed flow channel in combination with particle image velocimetry (PIV) enabled precise results with high reproducibility, focus on maximal and local peek velocities, strain, and velocity gradients. These flow parameters allow insights into the generation of forces that act on blood cells and the aortic wall. The results showed that the 21 and 23 mm valves have a quite similar performance. Maximal velocities were 3.03 ± 0.1 and 2.87 ± 0.13 m/s; maximal strain Exx, 913.81 ± 173.25 and 896.15 ± 88.16 1/s; maximal velocity gradient Eyx, 1203.14 ± 221.84 1/s and 1200.81 ± 61.83 1/s. The 25 mm size revealed significantly lower values: maximal velocity, 2.47 ± 0.15 m/s; maximal strain Exx, 592.98 ± 155.80 1/s; maximal velocity gradient Eyx, 823.71 ± 38.64 1/s. In summary, the 25 mm Magna Ease was able to create a wider, more homogenous flow with lower peak velocities especially for higher flow rates. Despite the wider flow, the velocity values close to the aortic walls did not exceed the level of the smaller valves.

Predator counteradaptations: stealth echolocation overcomes insect sonar-jamming and evasive-manoeuvring defences

Although bat–insect interactions are often described as an ‘evolutionary arms race’, conclusive evidence for bat counterstrategies to insect defences has been difficult to acquire. Previous studies have indicated that some bats use low-amplitude, ‘stealth’ echolocation to counter moth hearing. However, actual bat–insect interactions have not been documented to validate this finding. We hypothesized that the bat Corynorhinus townsendii uses stealth echolocation to overcome prey defences. We measured C. townsendii call intensities as they attacked tethered moths in the field and in a large outdoor flight cage. We also used three-dimensional videography to document C. townsendii and Myotis volans , which uses intensities more typical of aerial-hawking bats, as they attacked free-flying moths in a flight cage. Source levels of C. townsendii calls were 93.6 ± 6.1 dB at 0.1 m in open field conditions and 81.9 ± 6.9 dB in the more enclosed flight cage, values that are 20–45 dB lower than other aerial-hawking bats under similar conditions. Sound levels arriving at prey were mostly below known thresholds for eliciting late-attack defences. Free-flying moths were 49–66% less likely to exhibit evasive manoeuvring and sonar-jamming defences during attacks by C. townsendii compared to M. volans . Prey also exhibited lower peak velocities and accelerations during attacks, factors that are known to affect bat capture success. Accordingly, C. townsendii had 31% higher capture success against moths overall and 52% higher capture success against the sonar-jamming moth Bertholdia trigona . We conclude that stealth echolocation is an evolutionary counteradaptation to insect defences because there is no known benefit for C. townsendii to use low-amplitude calls outside of predator–prey interactions, and such calls come with considerable cost in reduced prey detection distances.

Saccades evoked in response to electrical stimulation of the posterior bank of the arcuate sulcus.

To test the hypothesis that the premotor cortex in and behind the caudal bank of the arcuate sulcus can generate saccades, we stimulated electrically the periarcuate region of alert rhesus monkeys. We were able to produce saccades from sites of the premotor cortex that were contiguous with the frontal eye fields and extended up to 2mm behind the smooth pursuit area. However, premotor sites often elicited saccades with ipsiversive characteristic vectors, lower peak velocities, and flatter velocity profiles when compared to saccades evoked from the frontal eye field.

Comparison of Frequency of Referral to Cardiothoracic Surgery for Aortic Valve Disease in Blacks, Hispanics, and Whites

Racial differences in prevalence and in intervention rate of those with severe aortic stenosis have been reported. Our objective was to evaluate health disparities in referral to cardiothoracic surgery (CTS) for aortic stenosis in black and Hispanic compared with white patients before the transcatheter aortic valve replacement program was started in our community. Using a retrospective cohort design, we identified all patients >40years, who had been captured with aortic valve disease from January 2011 to June 2016. Clinical and echocardiographic data were collected manually. Exposure was race/ethnicity; outcome was referral to CTS. Multivariable logistic regression analysis was conducted with variables that had significance of p <0.20 in univariate model. We included 952 patients in the final analysis (423 white, 376 black, and 153 Hispanic). Compared with whites, black subjects were significantly younger, had more advanced degrees of kidney disease, were more likely to have Medicaid as payer, and had more atherogenic co-morbidities. Black patients had significantly higher aortic valve area indexed for body surface area, more aortic regurgitation, lower peak velocities, lower transvalvular gradients, less calcified valves, and fewer patients in aortic stenosis stage D. The adjusted odds ratio for CTS referral was 0.48 for blacks (p <0.001) and 0.86 for Hispanics (p= 0.73) compared with whites. In conclusion, after adjusting for clinical and echocardiographic variables, black patients were less likely to be referred to CTS for treatment of aortic valve disease. We found no difference in the referral pattern of Hispanic compared with white patients.

Preece-Baines Model 1 to Estimate Height and Knee Height Growth in Boys and Girls From Merida, Mexico.

Height and body segments in children have differential pubertal growth characteristics. Lower leg length is a sensitive indicator of child's nutritional status. The purpose of this study was to estimate differential timing and tempo of height and knee height (KH) growth in 9- to 17-year-old boys (n = 475) and girls (n = 500) from Merida, Mexico. In this cross-sectional study, the Preece-Baines growth curves-model 1 (PB 1) was fitted to the anthropometric data for height and KH. Based on the PB 1 model, KH had earlier age at maximum increment than height in boys (height = 12.37 years, KH = 11.54 years) and girls (height = 11.01 years, KH = 10.93 years). Peak velocity of these 2 dimensions was different in both sexes (boys: height = 7.11 cm/yr, KH = 2.25 cm/yr; girls: height = 5.14 cm/yr, KH = 1.45 cm/yr). Differences ( P <.001) by sex were also observed for the estimated size at peak velocity and final size of height and KH. When compared to height, KH was shown to have earlier adolescent growth spurt and a smaller difference between final size and the size at maximum (peak) velocity indicating an earlier age for achieving adult size. Overall, the studied boys and girls had short estimated final size, an earlier age at maximum increment, and a lower peak velocity in height than urban Guatemalan peers, the only regional reference available.

Choice of Balloon-Expandable Versus Self-Expanding Transcatheter Aortic Valve Impacts Hemodynamics Differently According to Aortic Annular Size

We sought to determine whether balloon-expandable valve (BEV) and self-expanding valve (SEV) affect valve hemodynamics differently according to native aortic annulus size. Transcatheter aortic valve replacement can achieve superior prosthetic valve hemodynamics compared with surgical aortic valve replacement, particularly in patients with small aortic annulus. One hundred ninety-three consecutive transcatheter aortic valve replacement patients were grouped into tertiles defined by computed tomography derived aortic annulus systolic perimeter. The predischarge echocardiogram was analyzed for prosthetic valve hemodynamics. Tertile perimeter cutoffs were 73 and 80mm. STS score decreased as annulus size increased (7.8% vs 7.6% vs 6.0%, p ≤0.05 for small, medium, and large annulus, respectively). In patients with small aortic annulus, SEV was associated with significantly higher dimensionless index (0.64 vs 0.53, p= 0.02) and lower peak velocity (1.8 vs 2.4m/sec, p <0.001) and a trend toward lower mean gradient (7.5 vs 10.0mm Hg, p= 0.07) compared with BEV. These differences were attenuated and absent in patients with medium and large annulus, respectively. Few patients had moderate/severe paravalvular leak, with no association with valve type or annulus size. There was no difference in mortality between tertiles or valve type at 30days or 1year. There was no association between aortic annulus perimeter and 1-year mortality by univariate analysis (hazard ratio 1.00, 95% CI 0.95 to 1.05, p= 0.86) or multivariate analysis (hazard ratio 1.02, 95% CI 0.95 to 1.09, p= 0.60). In conclusion, SEV hemodynamics was superior to BEV in patients with small aortic annulus. This difference was diminished in patients with larger aortic annulus. This study highlights the importance of valve selection in patients with small aortic annulus.

The effects of steady swimming on fish escape performance

Escape maneuvers are essential to the survival and fitness of many animals. Escapes are frequently initiated when an animal is already in motion. This may introduce constraints that alter the escape performance. In fish, escape maneuvers and steady, body caudal fin (BCF) swimming are driven by distinct patterns of curvature of the body axis. Pre-existing muscle activity may therefore delay or diminish a response. To quantify the performance consequences of escaping in flow, escape behavior was examined in bluegill sunfish (Lepomis macrochirus) in both still-water and during steady swimming. Escapes executed during swimming were kinematically less variable than those made in still-water. Swimming escapes also had increased response latencies and lower peak velocities and accelerations than those made in still-water. Performance was also lower for escapes made up rather than down-stream, and a preference for down-stream escapes may be associated with maximizing performance. The constraints imposed by pre-existing motion and flow, therefore, have the potential to shape predator-prey interactions under field conditions by shifting the optimal strategies for both predators and prey.

A Neural Control Model for Horizontal Visual, Auditory and Auditory-Visual Bisensory Stimuli Elicited Saccades

To provide a comprehensive investigation of goal-oriented saccades, experiments are designed to trigger fast eye movements by different types of targets, including visual, auditory, and auditory-visual bisensory stimuli. Human saccades are recorded using a high speed eye tracking system. Data is analyzed to produce parameter estimates using system identification technique for a 3rd-order linear horizontal saccadic eye movement model. Saccade characteristics are explored and compared. The auditory-visual stimuli provide the greatest saccade accuracy. Auditory saccades show lower peak velocity and longer duration. Saccade latent period is relatively independent of saccade amplitude, but there is a significant reduction in the bisensory saccades. Neural inputs of saccades are estimated and analyzed as well. Auditory saccades exhibit lower agonist pulse magnitude and longer agonist pulse duration. Antagonist onset delay is longer in auditory saccades. Post saccade phenomena are caused by the post-inhibitory rebound burst of the antagonist motoneurons. There is a higher incidence of dynamic overshoot in auditory saccades than visual saccades, with more in the abducting direction than the adducting direction.

Eye and hand movement strategies in older adults during a complex reaching task.

The kinematics of upper limb movements and the coordination of eye and hand movements are affected by ageing. These age differences are exacerbated when task difficulty is increased, but the exact nature of these differences remains to be established. We examined the performance of 12 older adults (mean age = 74) and 11 younger adults (mean age = 20) on a multi-phase prehension task. Participants had to reach for a target ball with their preferred hand, pick it up and place it in a tray, then reach for a second target ball and place that in the same tray. On half the trials (stabilising condition), participants were required to hold the tray just above the surface of the table with their non-preferred hand and keep it as still as possible. Hand and eye movements were recorded. Older adults took longer to complete their movements and reached lower peak velocities than the younger adults. Group differences were most apparent in the stabilising condition, suggesting that the added complexity had a greater effect on the performance of the older adults than the young. During pickup, older adults preferred to make an eye movement to the next target as soon as possible, but spent longer fixating the current target during placement, when accuracy requirements were higher. These latter observations suggest that older adults employed a task-dependent eye movement strategy, looking quickly to the next target to allow more time for planning and execution when possible, but fixating on their hand and successful placement of the ball when necessary.

Does behavioral dissociation of real vs. pantomime movements only apply to visually guided action?

Pantomime reaching movements to imagined objects differ kinematically from real reaching movements to visual objects. It has been proposed that these differences may be related to the availability of online visual input. Specifically, real reaches are proposed to rely on online visual information localized largely in the left dorsal stream whereas pantomime reaches are proposed to rely on perceptual information processed in more widespread areas including the ventral stream and the right dorsal stream. Withdrawing the hand to place an object in the mouth is a natural and common movement; yet, it differs from other reaching movements in that it relies almost entirely on somatosensory guidance and may be mediated by a 'hard-wired' cortical motor representation that controls the arm, hand, and mouth. Given these differences, it could be hypothesized that hand-to-mouth movements might not be subject to the same real vs. pantomime dissociation as visually guided reaching. The present study used frame-by-frame video analysis and linear kinematics to analyze hand and mouth movements as participants withdrew the arm and hand to place either real or imagined food items into the mouth for eating. Pantomime hand-to-mouth movements were characterized by longer movement durations, lower peak velocities, and smaller openings of the mouth aperture to receive the food item than real hand-to-mouth movements. Nonetheless, mouth opening scaled to object size regardless of whether the food item was real or imagined. The results are discussed in relation to the idea that neurobehavioral dissociation of real vs. pantomime actions is a general feature of movement control that applies to both visually and nonvisually guided actions. Meeting abstract presented at VSS 2015. Language: en

Comparison of Lower Limb Segments Kinematics in a Taekwondo Kick. An Approach to the Proximal to Distal Motion.

In taekwondo, there is a lack of consensus about how the kick sequence occurs. The aim of this study was to analyse the peak velocity (resultant and value in each plane) of lower limb segments (thigh, shank and foot), and the time to reach this peak velocity in the kicking lower limb during the execution of the roundhouse kick technique. Ten experienced taekwondo athletes (five males and five females; mean age of 25.3 ±5.1 years; mean experience of 12.9 ±5.3 years) participated voluntarily in this study performing consecutive kicking trials to a target located at their sternum height. Measurements for the kinematic analysis were performed using two 3D force plates and an eight camera motion capture system. The results showed that the proximal segment reached a lower peak velocity (resultant and in each plane) than distal segments (except the peak velocity in the frontal plane where the thigh and shank presented similar values), with the distal segment taking the longest to reach this peak velocity (p < 0.01). Also, at the instant every segment reached the peak velocity, the velocity of the distal segment was higher than the proximal one (p < 0.01). It provides evidence about the sequential movement of the kicking lower limb segments. In conclusion, during the roundhouse kick in taekwondo inter-segment motion seems to be based on a proximo-distal pattern.

Movement planning and online control in multiple sclerosis: assessment using a Fitts law reciprocal aiming task.

We sought to quantify subtle changes in motor control in multiple sclerosis (MS) using a Fitts law reciprocal aiming task presented on a computer touchscreen. Upper-limb motor control is impaired in MS. However, many commonly used motor assessments do not detect subtle changes in motor function or differentiate between aspects of movement such as planning and online control. Fitts law states that movement time varies as a function of task difficulty, with smaller targets and greater distances making the task more difficult. We gave a Fitts aiming task to 22 patients with MS and 22 matched controls. We manipulated movement difficulty by changing the targets' size and distance apart. The patients spent a significantly longer time than the controls stationary in each target before starting the next movement, and had a lower peak velocity, suggesting deficits in movement planning. The patients also spent longer in the deceleration phase of each movement, indicating deficits in the online control of movement. The computerized Fitts task allows quick, easy, and sensitive measurement of subtle aspects of movement. This task should be useful in clinical and research settings for assessing MS motor symptoms, disease progression, and treatment efficacy.

Primary and submovement control of aiming in C6 tetraplegics following posterior deltoid transfer.

BackgroundUpper limb motor control in fast, goal-directed aiming is altered in tetraplegics following posterior-deltoid musculotendinous transfer. Specifically, movements have similar end-point accuracy but longer duration and lower peak velocity than those of age-matched, neurotypical controls. Here, we examine in detail the interplay between primary movement and submovement phases in five C6 tetraplegic and five control participants.MethodsAiming movements were performed in two directions (20 cm away or toward), with or without vision. Trials that contained a submovement phase (i.e., discontinuity in velocity, acceleration or jerk) were identified. Discrete kinematic variables were then extracted on the primary and submovements phases.ResultsThe presence of submovements did not differ between the tetraplegic (68%) and control (57%) groups, and almost all submovements resulted from acceleration and jerk discontinuities. Tetraplegics tended to make a smaller amplitude primary movement, which had lower peak velocity and greater spatial variability at peak velocity. This was followed by a larger amplitude and longer duration secondary submovement. Peak velocity of primary movement was not related to submovement incidence. Together, the primary and submovement phases of both groups were equally effective in reducing end-point error.ConclusionsC6 tetraplegic participants exhibit some subtle differences in measures of motor behaviour compared to control participants, but importantly feedforward and feedback processes work effectively in combination to achieve accurate goal-directed aiming.

Physiological response to a breed evaluation field test in Icelandic horses

This study examined the response in terms of heart rate (HR), respiratory rate (RR), haematocrit (Htc), rectal temperature (RT), and some plasma variables in Icelandic horses of different sexes and ages performing the riding assessment in a breed evaluation field test (BEFT). The study was conducted in Iceland on 266 horses (180 mares and 86 stallions, divided into four age groups; 4, 5, 6 and ⩾7 years old). RT and RR were recorded and blood samples were taken before the warm-up and after the riding assessment. Horse HR, velocity and distance were recorded during the warm-up, the riding assessment and a 5-min recovery period. The distance covered in the BEFT was 2.9±0.4 km (range: 1.8 to 3.8 km, n=248), the duration was 9:37±1:22 min:s (range: 5:07 to 15:32 min:s, n=260) and the average speed was 17.8±1.4 km/h (range: 13.2 to 21.3 km/h, n=248). Average HR was 184±13 b.p.m. (range: 138 to 210 b.p.m., n=102) and peak HR 224±9 b.p.m. (range: 195 to 238 b.p.m., n=102), and 36% of the BEFT was performed at HR ⩾200 b.p.m. Post-exercise plasma lactate concentration (Lac) was 18.0±6.5 mmol/l (range: 2.1 to 34.4 mmol/l, n=266), and there was an increase in total plasma protein, plasma creatine kinase and aspartate amino transferase concentration, as well as RR, RT and Htc. Stallions covered a longer total distance (in the warm-up and BEFT) (P<0.05), at a faster speed during BEFT (P<0.001) than mares and had higher Htc and lower HR and post-exercise Lac values. There were few effects of age, but the 4- and 5-year-old horses had lower Htc than older horses and 4-year-old horses had higher post-exercise RR than older horses, although they were ridden for a shorter distance, shorter duration and at lower peak velocity (P<0.1). The results showed that the riding assessment in the BEFT is a high-intensity exercise. The results also showed that aerobic fitness was higher in stallions and that age had a limited effect on the physiological response. It is suggested that these results should be used as a guide for the development of training programmes and fitness tests in Icelandic horses that would improve both performance and welfare of the horse.