Movement Initiation Time Research Articles

Facilitation of action planning in children with autism: The contribution of the maternal body odor

Imitation is a key socio-cognitive skill impaired in individuals with Autism Spectrum Conditions (ASC). It is known that the familiarity with an actor facilitates the appearance of imitative abilities. Here, we explore whether a highly familiar and socially relevant stimulus presented in the olfactory modality is able to improve spontaneous imitation as early as at the level of action planning. A group of 20 children with ASC and 20 controls observed their own mother or the mother of another child performing a reach-to-grasp action towards an object, under the exposure to their maternal odor, the odor of the mother of another child or no odor. Subsequently, children acted upon the same object with no specific instruction to imitate. Child’s movement initiation time (MIT) served as an indicator of motor planning facilitation induced by action observation. Results suggest that for children with ASC (but not controls) MIT was significantly lower when exposed to the maternal odor both when interacting with a familiar or an unfamiliar model. In the former case, the performance is comparable to controls. The familiar model in the absence of any olfactory cue is able to induce a facilitation effect, but the maximal facilitation on MIT is evident when maternal odor and familiar model are paired. We hypothesize that for children with ASC the maternal odor provides relevant social motivation for taking advantage of others’ actions when planning movements in an imitative context.

Facilitation of learning induced by both random and gradual visuomotor task variation

Motor task variation has been shown to be a key ingredient in skill transfer, retention, and structural learning. However, many studies only compare training of randomly varying tasks to either blocked or null training, and it is not clear how experiencing different nonrandom temporal orderings of tasks might affect the learning process. Here we study learning in human subjects who experience the same set of visuomotor rotations, evenly spaced between −60° and +60°, either in a random order or in an order in which the rotation angle changed gradually. We compared subsequent learning of three test blocks of +30°→−30°→+30° rotations. The groups that underwent either random or gradual training showed significant (P < 0.01) facilitation of learning in the test blocks compared with a control group who had not experienced any visuomotor rotations before. We also found that movement initiation times in the random group during the test blocks were significantly (P < 0.05) lower than for the gradual or the control group. When we fit a state-space model with fast and slow learning processes to our data, we found that the differences in performance in the test block were consistent with the gradual or random task variation changing the learning and retention rates of only the fast learning process. Such adaptation of learning rates may be a key feature of ongoing meta-learning processes. Our results therefore suggest that both gradual and random task variation can induce meta-learning and that random learning has an advantage in terms of shorter initiation times, suggesting less reliance on cognitive processes.

Impairments in Estimation of Target Velocity in SCA 6

Objective: Perception during visual motion is a fundamental function for the equilibrium system. Neural substrates for these systems are still incompletely known. We examined the role of cerebellum for those systems in Spinocerebellar ataxia type 6 patients. Method: Seven SCA6 patients and 7 age-matched normal controls participated in this study. Two tasks were tested. Task 1 examined subjects’ ability to estimate the timing of a target movement indicated by a finger movement. Task 2 examined the ability to match the remembered velocity of visual pattern movement. Results: In Task 1, when the target was always visible, the difference between the 2 groups was not significant at 2°/s and 5°/s of target movement. At 8°/s, there was significant difference between them. During the 50% target blanking condition, the patients showed lower successful ratios at 5°/s and 8°/s, respectively. In Task 2, when both subject groups fixated a stationary spot, there was no significant difference between the two groups at 2°/s and 5°/s. However, at 8°/s, the difference was significant. When a fixation spot was not presented, the difference was significant at all three velocities. Conclusion: Most SCA6 patients exhibited a larger variability in their timing estimation, and their estimations significantly lagged compared with controls. The present findings shed light on the mechanisms of estimation of target velocity and timing of movement initiation and support the conclusion that the cerebellum is involved in these functions.

Perceptual Skill Identification in a Complex Sport Setting

Decision making in sports has been extensively studied over the last two decades, with a particular focus on differences in visual search strategies and movement initiation times between experts and novices. The current study expands this paradigm by identifying situation, gender, and expertise specific gaze strategies in performing defensive actions in beach volleyball. Sixty-four beach volleyball players were confronted with 96 scenes displaying 3 attacking variations. The experimental set-up allowed participants to react as they would on court, while decision accuracy and movement initiation time were measured using a 10-camera-VICON-system. Furthermore, gaze behavior was recorded pursuing a novel integrated and automated approach with a high resolution eye tracker (EyeSeeCam, 220 Hz). First analyses show that elite players differ from near-elite players by having a higher percentage of correct decisions combined with a later movement initiation time. Apparently, elite players optimize the time available for information pick-up before initiating their defensive action.

Corticospinal excitability during preparation for an anticipatory action is modulated by the availability of visual information

To intercept rapidly moving objects, people must predict the right time to initiate their actions. The timing of movement initiation in interceptions is thought to be determined when a perceptual variable specifying time to contact reaches a criterion value. If a response needs to be aborted, the performer must make a decision before this moment. It has been recently shown that the minimal time to suppress an anticipatory action takes longer during motion extrapolation than during continuous visual information. In experiment 1, we sought to determine whether or not the availability of visual information would 1) affect the latency to inhibit an anticipatory action, and 2) modulate the level of excitability in the motor cortex (M1). The behavioral results showed that the absence of visual information prolonged the latency to stop the movement as previously reported. The neurophysiological data indicated that corticospinal excitability levels were affected by the availability of visual information. In experiment 2, we sought to verify whether corticospinal excitability levels would also differ between the two visual conditions when the task did not involve response suppression. The results of experiment 2 indicated that excitability levels did not differ between visual conditions. Overall, our findings indicated that the buildup of motor activation can also play a role in determining different latencies to inhibit an anticipatory action. They also suggest that the buildup of motor activation in the corticospinal pathways can be strategically modulated to the requirements of the task during continuous visual information.

Human movement onset detection from isometric force and torque measurements: A supervised pattern recognition approach

Recent research has successfully introduced the application of robotics and mechatronics to functional assessment and motor therapy. Measurements of movement initiation in isometric conditions are widely used in clinical rehabilitation and their importance in functional assessment has been demonstrated for specific parts of the human body. The determination of the voluntary movement initiation time, also referred to as onset time, represents a challenging issue since the time window characterizing the movement onset is of particular relevance for the understanding of recovery mechanisms after a neurological damage. Establishing it manually as well as a troublesome task may also introduce oversight errors and loss of information. The most commonly used methods for automatic onset time detection compare the raw signal, or some extracted measures such as its derivatives (i.e., velocity and acceleration) with a chosen threshold. However, they suffer from high variability and systematic errors because of the weakness of the signal, the abnormality of response profiles as well as the variability of movement initiation times among patients. In this paper, we introduce a technique to optimise onset detection according to each input signal. It is based on a classification system that enables us to establish which deterministic method provides the most accurate onset time on the basis of information directly derived from the raw signal. The approach was tested on annotated force and torque datasets. Each dataset is constituted by 768 signals acquired from eight anatomical districts in 96 patients who carried out six tasks related to common daily activities. The results show that the proposed technique improves not only on the performance achieved by each of the deterministic methods, but also on that attained by a group of clinical experts. The paper describes a classification system detecting the voluntary movement initiation time and adaptable to different signals. By using a set of features directly derived from raw data, we obtained promising results. Furthermore, although the technique has been developed within the scope of isometric force and torque signal analysis, it can be applied to other detection problems where several simple detectors are available.

Motor timing and motor sequencing contribute differently to the preparation for voluntary movement

Two crucial processes preceding voluntary action are determining the time for movement initiation and planning of the specific sequence of motor output. In this study we aimed to differentiate the neural activity related to motor timing and motor sequencing and to examine over what time periods they contribute to premovement activity during the readiness for voluntary action. Eighteen participants performed self-initiated voluntary finger movements in a readiness potential paradigm, both during EEG measurement and during fMRI. The finger movement task involved three conditions: (1) simple repetitive sequences; (2) increased demand on the sequencing of movement order; and (3) increased demand on the timing of movement initiation. Functional MRI and 64 channels EEG were conducted in two separate sessions. Motor timing and motor sequencing were found to involve different neural processes occurring at different times prior to movement initiation. Motor timing involved greater activation in lateral prefrontal regions over the earliest part of premovement activity, from 1200 ms before movement onset. Motor sequencing involved greater activation of dorsal premotor and parietal areas and was reflected in central and parietal scalp regions only over the later part of premovement activity, within 600 ms of movement onset. We suggest that different neural processes contribute to different aspects of the intended action over different time periods during the preparation for movement, and it is the coordinated activity of these multiple regions that is represented in premovement activity during the readiness for voluntary action.

Palmar arch dynamics during reach-to-grasp tasks

The relationship between arm transport and grip aperture scaling has traditionally been used to study the control of reaching and grasping. Since the palmar concavity forms a postural base of the hand, intuitively it should play an essential role in hand shape modulation during grasping. This role however has not yet been investigated. This study investigated whether hand shape modulation was initiated at the palmar level or at the level of the finger joints during two types of power grasps (spherical, cylindrical). Hand shape modulation was studied in eight healthy adults and was characterized by the change in palmar arch movement during three phases of the reach-to-grasp tasks, traditionally defined as arm transport, hand preshaping and object contact. Palmar arch kinematics changed significantly during arm transport for both types of grasp (spherical 47.4%, cylindrical 63.7%). Approximately 16% more modulation was observed when grasping the cylindrical as compared to the spherical object. This was counterbalanced by relatively less modulation during the preshaping and object contact phases compared to the spherical grasp. These results showed that the three grasping phases occurred concurrently in a common time window. Furthermore, an increase in the duration of either one of the components impacted the execution of the others. A secondary finding was that hand shape modulation began at the same time or within 125 ms of the initiation of arm transport for both grasp types. In most cases (60%), movement in the palmar arch occurred prior to movement at the metacarpophalangeal joint (MCP) of the index and middle fingers. The same was observed when palmar arch modulation was compared with the time of movement initiation in the proximal interphalangeal (PIP) joints of the index and middle fingers (60-75%). Thus palmar and finger joint movement were initiated almost simultaneously and hand shape modulation began early in the reach-to-grasp task. The findings show that hand shape and arm transport were modulated together and suggest that prehensile movement, including both palmar arch and finger configuration, is planned as early as the intent to grasp.

The Response Activation Model and Cross-Modal Facilitation and Inhibition of Return: A Trajectory Analysis

Non-informative spatial cues presented prior to a goal-directed movement influence not only movement initiation time but also the spatial characteristics of the movement trajectories. These trajectory effects are thought to stem from an integration of competing motor responses. In the present experiments, trajectories of rapid aiming movements were examined under the constraints of a cue-target inhibition of return (IOR) paradigm. Aiming movements were made to targets that were preceded by a cue stimulus in the same or different location. Four experiments were conducted in which the modality of the cue and target stimulus was manipulated across vision and audition. Although facilitation effects were present under the cross modality protocols, IOR effects were observed only for same cue-target pairings. At short stimulus onset asynchronies, limb trajectories deviated toward the target that had just been cued, particularly when the cue occurred in left space. These trajectory effects are consistent with response activation models of selective attention and movement preparation.

Testing Basal Ganglia Motor Functions Through Reversible Inactivations in the Posterior Internal Globus Pallidus

To test current hypotheses on the contribution of the basal ganglia (BG) to motor control, we examined the effects of muscimol-induced inactivations in the skeletomotor region of the internal globus pallidus (sGPi) on visually directed reaching. Injections were made in two monkeys trained to perform four out-and-back reaching movements in quick succession toward four randomly selected target locations. Following sGPi inactivations the following occurred. 1) Peak velocity and acceleration were decreased in nearly all sessions, whereas movement duration lengthened inconsistently. 2) Reaction times were unaffected on average, although minor changes were observed in several individual sessions. 3) Outward reaches showed a substantial hypometria that correlated closely with bradykinesia, but directional accuracy was unaffected. 4) Endpoint accuracy was preserved for the slow visually guided return movements. 5) No impairments were found in the rapid chaining of out-and-back movements, in the selection or initiation of four independent reaches in quick succession or in the quick on-line correction of initially misdirected reaches. 6) Inactivation-induced reductions in the magnitude of movement-related muscle activity (EMG) correlated with the severity of slowing and hypometria. There was no evidence for inactivation-induced alterations in the relative timing of EMG bursts, excessive cocontraction, or impaired suppression of antagonist EMG. Therefore disconnecting the BG motor pathway consistently produced bradykinesia and hypometria, but seldom affected movement initiation time, feedback-mediated guidance, the capacity to produce iterative reaches, or the ability to abruptly reverse movement direction. These results are discussed with reference to the idea that the BG motor loop may regulate energetic expenditures during movement (i.e., movement "vigor").

On-Line Control of Grasping Actions: Object-Specific Motor Facilitation Requires Sustained Visual Input

Dorsal stream visual processing is generally considered to underlie visually driven action, but when subjects grasp an object from memory, as visual information is not available, ventral stream characteristics emerge. In this study we use paired-pulse transcranial magnetic stimulation (TMS) to investigate the importance of the current visual input during visuomotor grasp. Previously, the amplitude of the paired-pulse motor evoked potentials (MEPs) in hand muscles before movement onset have been shown to predict the subsequent pattern of muscle activity during grasp. Specific facilitation of paired-pulse MEPs may reflect premotor-motor (PMC-M1) cortex connectivity. Here we investigate the paired-pulse MEPs evoked under memory-cued and visually driven conditions before grasping one of two possible target objects (a handle or a disc). All trials began with a delay period of 1200 ms. Then, a TMS pulse served as the cue to reach, grasp and hold the target object for 0.5 s. Total trial length was 5 s. Both objects were continually visible in both conditions, but the way in which the target object was designated differed between conditions. In the memory-cued condition, the target object was illuminated for the first 200 ms of the trial only. In the visually driven condition, the target object was illuminated throughout the 5 s trial. Thus, the conditions differed in whether or not the object to be grasped was designated at the time of movement initiation. We found that the pattern of paired-pulse MEP facilitation matched the pattern of object-specific muscle activity only for the visually driven condition. The results suggest that PMC-M1 connectivity contributes to action selection only when immediate sensory information specifies which action to make.

Planning and on-line control of catching as a function of perceptual-motor constraints

Two experiments were conducted in order to investigate the adaptability and associated strategies of the human perceptuo-motor system to deal with changing constraints. In a catching task, perceptual-motor constraints were internally controlled by coupling movement onset of the catch and the illumination circuit in the lab: upon the first movement of the catcher, all lights went out within 3 ms. The authors studied (a) how much movement time catchers prefer if no visual information is available after movement onset, and (b) how movement execution changes under such temporal constraints. It was hypothesised that, in order to accomplish successful catching behaviour, (1) movement initiation would be postponed in order to allow sufficient information uptake before the lights went out, and (2) an alternative control strategy would have to be mobilised, since on-line control becomes inappropriate when catching in the dark. In the first experiment, the adaptation process to the light–dark paradigm was investigated. In the second experiment, the conclusions from experiment 1 were challenged under varying ball speeds. In order to maintain catching performance, subjects initiated the catch approximately 280 ms before ball-hand contact. Next to changes in temporal structure of the catch and subtle kinematic adaptations, evidence for a change in the control mode emerged: while an on-line control strategy was adopted under normal illumination, catching movements seemed to be executed as planned in advance when catching in the dark. Additionally, perceptual constraints seem to determine the time of movement initiation, rather than motor constraints. These results emphasize the capability of the human perceptuo-motor system to adjust promptly to new task constraints.

FC18.2 On feature selection for brain computer interfaces

Currently, Brain Computer Interfaces (BCI) are of limited practical use requiring prolonged user training. BCI usability can improve by developing methods for EEG feature selection that allow for a more intuitive link between user intention and device control and which can provide multiple degrees of freedom in command selection. EEG was recorded from 28 electrodes forming an array over the left sensorimotor cortex in normal subjects with approval of a Local Ethics Committee. Right wrist muscle EMG was also recorded. Subjects viewed a PC monitor randomly presenting a set of five spatially distinct target positions corresponding to neutral, flexed, extended, ulnar and radial deviations of the wrist. When presented with a new target subjects were required to move (or imagine move) their wrist to the target as fast as possible creating datasets of repeats of 20 different movement (or imagined movement) combinations. Continuous wavelet transform was used to extract spatio-temporal characteristics of the EEG signals relative to time of movement initiation or target appearance in case of imagined motion. Using PCA, 10 principal components generated 95% correct classification of pre-movement EEG with actual direction of motion. During imagined movement classification success reduced to 67%. In contrast, SVM classification of the imagined movement data outperformed PCA with up to 87% correct classification for intended direction of movement. During imagined movement SVM outperforms PCA. However, SVM is computationally demanding. We conclude that a hybrid method combining merits of both PCA and SVM may have potential for use in BCI intention detection.

Prediction in the timing of pursuit eye movement initiation revealed by cross-axis vestibular–pursuit training in monkeys

The smooth-pursuit system interacts with the vestibular system to maintain the image of a moving target on the fovea. Efficient tracking performance requires information about the velocity and the initiation of target motion. Previous studies in monkeys have shown that training with orthogonal pursuit and whole body rotation results in adapted eye movement direction during chair rotation. In addition, the latency of the pursuit shortens and initial eye velocity increases in a task-dependent manner. To examine whether these adapted eye movements are predictive pursuit, we studied whether our monkeys could predict the timing of smooth eye movement initiation during chair rotation. Two young Japanese monkeys were rotated horizontally in a trapezoidal waveform (20 degrees/s, +/-10 degrees) with random inter-trial intervals. A laser spot was moved vertically with the same trajectory at a constant delay ranging from 100 to 700 ms after the onset of the chair motion. The monkeys were required to pursue the spot. After this training, the latencies of pursuit eye movements following the onset of chair motion were examined in the presence of the target motion. The target was also briefly (for 500-700 ms) extinguished at 80 ms after the onset of chair rotation. Pursuit eye movements after training were initiated before the onset of target motion and the latencies were proportional to the delays used for training. The latencies and response magnitudes of pursuit with or without target blanking were similar. The auditory-pursuit training did not induce an initial pursuit response similar to that induced by vestibular-pursuit training. These results indicate that smooth eye movements during the chair rotation after the vestibular-pursuit training included a predictive pursuit component. The monkeys' estimate of the delays revealed by the latencies of pursuit was shorter by 22-36% than the actual delays.

Effects Of Caffeine And Lorazepam On The Performance Of Female Soccer Players

Cue utilization theory posits that high arousal narrows attention. Individuals also tend to produce over learned responses at higher levels of arousal. In skilled sport performers, then, high arousal may benefit performance by allowing them to avoid being distracted and focusing their visual attention on areas they have learned are information rich. PURPOSE To examine the effect of high arousal (caffeine induced), low arousal (lorazepam induced), and placebo-control (ascorbic acid) on perceptual and physical performance in female university soccer players. METHODS Speed and accuracy of decision making, strength, power and endurance were tested in 14 athletes (20.1 ± 2.9 yrs) after ingesting 5 mg/kg caffeine (high arousal), 1 mg lorazepam (low), and 200mg ascorbic acid (placebo-control) in a randomized, double-blind design. The somatic-anxiety and self-confidence subscales of the Competitive State Anxiety Inventory-2 were used to examine the perceived impact of the three substances. To test perceptual performance, athletes assumed a ready position and moved in response to 24 life-size video clips of soccer passes to their right and left. Movement initiation time relative to ball contact, and response accuracy were recorded. Strength, power, and endurance were assessed through grip strength, vertical jump, and a run to exhaustion on a treadmill. Cardiovascular function was monitored through resting heart rate and blood pressure. RESULTS The three substances did not produce significant effects with respect to resting heart rate, blood pressure, perceptions of somatic-anxiety and self-confidence, or movement initiation time. However; response accuracy was higher with lorazepam than ascorbic acid (p<0.05), grip strength was greater with caffeine than lorazepam or ascorbic acid (p<0.05), vertical jump was impaired with lorazepam compared to caffeine and ascorbic acid (p<0.01), and the trend towards a longer duration run to exhaustion with caffeine approached statistical significance (p=0.055). CONCLUSIONS The higher levels of arousal produced by caffeine and lower levels of arousal produced by lorazepam did not noticeably affect the speed of decision making. However; ingestion of caffeine and lorazepam led to differences in physical performance indicating that athletes were differently affected by them. The use of caffeine to boost arousal may provide some physical benefits to athletes without compromising perceptual capabilities.

Behavioral and immunohistochemical effects of chronic intravenous and subcutaneous infusions of varying doses of rotenone

Mitochondrial toxins such as the complex 1 inhibitor rotenone are widely used as pesticides and may be present in military environments. Administration of rotenone can induce biochemical and histological alterations similar to those of Parkinson's disease in rats. However, only a subset of animals show these effects and it is unclear whether more subtle alterations are caused by chronic administration of rotenone in those animals that appear resistant to its toxic effects on dopaminergic nerve terminals. To address this question, vehicle or rotenone (2.0, 2.5, or 3.5 mg/kg/day) was administered intravenously or subcutaneously for 21 days to adult rats, and rotenone effects on survival, motor behavior, and striatal tyrosine hydroxylase immunoreactivity (TH-IR) were examined. Both intravenous and subcutaneous rotenone induced a dose-dependent decrease in survival rates. Surviving animals showed a decrease in spontaneous rearing. Locomotor activity and movement initiation time were also altered in some of the experimental groups. Confirming previous results, TH-IR in the striatum was markedly decreased in rats that fell ill early in the study and in a few of the surviving rats with high rotenone doses. However, none of the surviving rats receiving 2.0 mg/kg/day showed TH-IR loss reminiscent of Parkinson's disease, and loss of striatal TH-IR across doses was not correlated with motor behavior in individual rats. Thus, chronic administration of low doses of rotenone induces motor anomalies even in animals that do not develop histological signs of Parkinson's disease, indicating a pervasive neurological effect of moderate mitochondrial dysfunction in vivo.

Instructions emphasizing velocity, accuracy, or both in performance and kinematics of overarm throwing by experienced team handball players.

On motor tasks like the overarm throw, velocity and accuracy are two important parameters of performance that may be incompatible and require different strategies in the execution of the motor task. The purpose was to investigate the effects of instruction (emphasizing velocity, accuracy, or both) on performance and kinematics of overarm throwing. Results for 9 experienced male team handball players (M age = 24 +/- 2.2 yr.) showed type of instruction affected the maximal ball velocity. The difference in ball velocity reflected the significant difference in maximal linear velocity of the wrist, elbow, and hip segments together with their absolute timing before ball release. The subjects did not seem to change their throwing technique, i.e., the relative timing of movement initiation of the different body segments.

Interaction between discrete and rhythmic movements: reaction time and phase of discrete movement initiation during oscillatory movements

This study investigates a task in which discrete and rhythmic movements are combined in a single-joint elbow rotation. Previous studies reported a tendency for the EMG burst associated with the discrete movement to occur around the expected burst associated with the rhythmic movement (e.g., [Exp. Brain Res. 99 (1994) 325; J. Neurol. Neurosurg. Psychiatry 40 (1977) 1129; Hum. Mov. Sci. 19 (2000) 627]). We document this interaction between discrete and rhythmic movements in different task variations and suggest a model consisting of rhythmic and discrete pattern generators that reproduces the major results. In the experiment, subjects performed single-joint elbow oscillatory movements (2 Hz). Upon a signal, they initiated a movement that consisted of a shift in the midpoint of the oscillation (MID), a shift in the amplitude of the oscillation (AMP), or a combination of both (MID + AMP). These shifting movements were performed either in a reaction time or in a self-paced fashion. The tendency for the EMG bursts associated with the discrete and rhythmic movements to synchronize was found similarly in all three tasks and instruction conditions, but the synchronization was most pronounced in the self-initiated discrete movement. Reaction time was increased for the combined task (MID + AMP), indicating higher control demands due to a combination of discrete and rhythmic components. This EMG burst synchronization was reproduced in a model based on a half-center oscillator with activation signals that produce either rhythmic or discrete activity. This activity was interpreted as torques driving a simple limb model. Summation of discrete and rhythmic activation signals of the pattern generators was sufficient to simulate the EMG burst synchronization. Further, simulation data reproduced the modulation of the reaction time as a function of the phase of the discrete movement.

INSTRUCTIONS EMPHASIZING VELOCITY, ACCURACY, OR BOTH IN PERFORMANCE AND KINEMATICS OF OVERARM THROWING BY EXPERIENCED TEAM HANDBALL PLAYERS

On motor tasks like the overarm throw, velocity and accuracy are two important parameters of performance that may be incompatible and require different strategies in the execution of the motor task. The purpose was to investigate the effects of instruction (emphasizing velocity, accuracy, or both) on performance and kinematics of overarm throwing. Results for 9 experienced male team handball players (M age = 24 ± 2.2 yr.) showed type of instruction affected the maximal ball velocity. The difference in ball velocity reflected the significant difference in maximal linear velocity of the wrist, elbow, and hip segments together with their absolute timing before ball release. The subjects did not seem to change their throwing technique, i.e., the relative timing of movement initiation of the different body segments.

Aerobic exercise intervention improves aerobic capacity and movement initiation in Parkinson's disease patients

Parkinson's Disease (PD) is a progressive neurologic disorder, which includes an inability to activate appropriate muscle activity. Very little research has analyzed aerobic exercise for PD patients. The purpose of this study was to investigate the effect of a 16 week aerobic exercise intervention on aerobic capacity and movement initiation (MI) time for PD patients. With 8 PD subjects (Hoehn & Yahr stage 2), 4 completed the exercise intervention. Peak VO_2scores significantly improved (26%) Choice MI improved from 532 ms to 415 ms, while simple MI improved from 285 ms to 261 ms. The improvement in aerobic capacity suggests that PD patients may benefit from exercise just as much as a normal population. The change in MI indicates that aerobic exercise may reduce the detrimental effects of neuromuscular slowing within PD patients, by improving the subjects' ability to initiate and perform appropriate movement patterns.