Speed Of Limb Movement Research Articles

Exploring the Effects of LED Lighting Training Program on Motor Performance among Young Athletes

ABSTRACT The aim of this study was to examine the effects of a BATAK Pro™ training program in combination with regular sport-specific training as compared with sport-specific training alone on motor performance among young athletes. Twenty-two athletes (aged 11–16 years) were recruited and randomly assigned to either an active control group or BATAK training group. The BATAK training program consisted of 2–3 sets of 4–5 exercises, biweekly for 12-weeks. The assessment of motor performance included upper limb movement speed, agility, reactive agility, acceleration, sprinting, and Y-Balance test. Within-group analyses revealed performance increases in the 10-m sprint test (−2.6%), and in Y-Balance test variables, specifically in anterior direction (4.0–5.4%), posteromedial direction (6.6–8.0%) and in posterolateral direction (10.7–14.6%) in the BATAK group. This study reports for the first time that the use of LED lighting devices in addition to sport-specific training promotes increases in motor skills, particularly in dynamic stability. More studies are needed to confirm whether the training-induced benefits of this novel performance tool are significantly better as compared to other approaches, and whether these results can be translated into on-field performance outcomes, not only in terms of critical motor development but also in a meaningful increase of creative actions.

Physical fitness and physical activity levels in people with alcohol use disorder versus matched healthy controls: A pilot study.

Low physical fitness and physical inactivity have been recognized as prominent behavioral risk factors for cardiovascular diseases and an independent risk factor for all-cause mortality. To date, no studies have ystematically assessed physical fitness and physical activity in patients with alcohol use disorders (AUD) vs. a healthy comparison group. The aim of this cross-sectional study was to assess and compare the physical fitness and physical activity levels in patients with AUD against healthy controls. Thirty inpatients with AUD (22 males, 40.4±10.5 years, illness duration=9.7±9.3 years) and 30 age-, gender- and body mass index (BMI)-matched healthy controls were included. All participants performed the Eurofit test battery and the International Physical Activity Questionnaire. Patients also completed the Positive Affect and Negative Affect Scale (PANAS) and Alcohol Use Disorders Identification Test (AUDIT). The PANAS positive and negative scores were 30.1±7.5 and 27.6±8.2; the AUDIT score was 27.3±7.0. Patients with AUD had a reduced whole body balance (flamingo balance test: 12.1±5.1 vs. 8.7±3.9 attempts; p=0.005), speed of limb movement (plate tapping: 13.3±2.7 vs. 11.6±2.2s, p=0.007), explosive leg muscle strength (standing broad jump: 151.8±34.9 vs. 174.2±33.7cm; p=0.01), abdominal muscular endurance (sit-ups: 15.9±5.7 vs. 19.8±7.1; p=0.02), and running speed (shuttle run: 25.4±4.5 vs. 23.1±4.0s). Patients with AUD were also significantly less physically active than healthy controls (1020.9±578.8 vs. 1738.7±713.3 MET-minutes/week; p<0.001). Backward regression analyses demonstrated that older age and higher BMI explained lower physical fitness levels, whereas longer illness duration and impaired explosive muscle strength explained lower total physical activity levels. The current findings suggest that lower physical fitness and physical activity are emerging as prominent modifiable risk factors in patients with AUD. Future research should explore the benefits of specific rehabilitation interventions aimed at increasing physical activity and physical fitness in this vulnerable group.

Wii-based exercise program to improve physical fitness, motor proficiency and functional mobility in adults with Down syndrome.

People with Down syndrome (DS) usually display reduced physical fitness (aerobic capacity, muscle strength and abnormal body composition), motor proficiency impairments (balance and postural control) and physical functional limitations. Exergames can be an appealing alternative to enhance exercise engagement and compliance, whilst improving physical fitness and motor function. This study aims to analyse the effects of a Wii-based exercise program on physical fitness, functional mobility and motor proficiency of adults with DS. Twenty-seven adults with DS were randomly allocated to an experimental group (Wii; n=14) or control group (n=13). Participants in the experimental group completed a 2-month Wii-based exercise program, with three 1-h sessions per week that included training games for aerobic endurance, balance and isometric strength. Participants completed assessments regarding anthropometric measures, physical fitness, functional mobility and motor proficiency. Mixed ANOVA analysis showed a significant group by time interaction for aerobic endurance, explosive leg power and flexibility. Independent samples t-test for change scores indicated significant between-group differences favouring the experimental group regarding speed of limb movement, trunk strength and functional mobility, as well as a trend towards significance on body weight. Mann-Whitney's U test for change scores demonstrated between-group differences favouring the experimental group for visceral fat as well as running speed and agility. Large within-group effect sizes were observed for explosive leg power (d=1.691), body weight (d=1.281), functional mobility (d=1.218), aerobic endurance (d=1.020), speed of limb movement (d=0.867) and flexibility (d=0.818) in the experimental group. Our findings suggest that Wii-based exercise can be an effective tool to improve physical fitness, functional mobility and motor proficiency of adults with DS, including crucial measures such as aerobic capacity and lower limb strength. Exergames using Wii Fit or other equipment can be appealing alternatives for adults with DS to engage in regular physical activity, preventing sedentary behaviour and decreasing the risk to develop cardiovascular diseases.

Changes in Motor Skills of Children who Train Sports Swimming at the Initial Stage of School Education (in an Annual Training Cycle)

This paper presents an empirical approach to the changes in motor skills of children who train sports swimming at the initial stage of school education in an annual training cycle. Swimming belongs to the disciplines in which training starts at the age of 6-7. The proper selection of candidates to train certain disciplines is a complex process as they should be chosen from a large population of children, both girls and boys, having specific somatic and motor characteristics which, developed in the long-term, will enable them to achieve sports mastery. The aim of the research was to define which changes in motor skills occur in girls who train sports Aim: swimming in an annual training cycle. The Subject group consisted of 85 girls aged 7 who attended four elementary schools in Szczecin, Poland. 36 of them belonged to the Swimmers group and they were all members of the Municipal Swimming Club (MKP) in Szczecin. The Control group consisted of 49 girls who attended the same elementary schools. All subjects took part in two examinations (carried out in the school year 2009/2010. Physical ability tests were conducted in gyms. Motor skills were assessed with EUROFIT Test Battery which is the most reliable and accurate tool according to scientific research. The research revealed changes in both groups (Sw, C) in terms of all eight tests. Examination II proved statistically significant improvement of results in both groups (Sw, C) in comparison to Examination I. Changes between Examination I and Examination II results were most visible in the Swimmers groups in terms of balance, agility, static strength, functional strength and agility run. Changes between Examination I and Examination II were similar in both groups (Sw, C) in terms of speed of limb movement, explosive strength and torso strength. Progressive changes in motor skill of subjects are a positive phenomenon in the physical development of a child. Swimming training resulted significantly in positive changes in terms of motor skills of subject who were at the initial stage of swimming trainings, compared to their non-training peers. Participation in organized, regular sports classes results in the development of motor (physical) skills of children.

Improvement in functional performance with high-speed power training in older adults is optimized in those with the highest training velocity.

To identify whether variability in limb movement velocity during high-speed power training (HSPT) may impact physical functioning in older adults. 42 older men and women (71.3±6.6 years) were randomized to lower extremity HSPT (n=28) or control (CON; n=14) (Analysis 1) for 12weeks. A second analysis (Analysis 2) allocated HSPT into high-velocity (n=14) or low-velocity (n=14) based on a limb movement speed above or below the median average velocity during the 12-week HSPT intervention. Habitual gait speed, maximal gait speed, timed up-and-go, and the short physical performance battery were measured at baseline and 12weeks. Change scores were compared between HSPT and CON (Analysis 1), and high-velocity, low-velocity, and CON (Analysis 2) using ANCOVA. Statistical significance was accepted at p<0.05. Analysis 1 There were no group differences in habitual gait speed, maximal gait speed, or timed up-and-go between HSPT and CON (all p>0.05). Short physical performance battery was greater in HSPT (0.96±0.19) compared to CON (0.10±0.26; p=0.01). Analysis 2 There were no group differences in the change in habitual GS (p=0.33) among high-velocity, low-velocity and CON. There were significant group differences in the change in maximal GS (p=0.007), timed up-and-go (p=0.03), and short physical performance battery (p=0.03). There is considerable variation in self-selected maximal limb velocity during HSPT in older adults. In the present cohort, an average limb velocity of 0.88m/s during HSPT was necessary to ensure optimal improvement in functional performance for older adults, but this threshold will need further investigation.

A comparison of physical fitness in patients with bipolar disorder, schizophrenia and healthy controls

Purpose: To compare the physical fitness of inpatients with bipolar disorder, schizophrenia and healthy controls.Method: Twenty-two inpatients with bipolar disorder, and 22 age-, gender- and body mass index-matched inpatients with schizophrenia and healthy controls were included. All participants performed the Eurofit test battery and the International Physical Activity Questionnaire. One way analyses of variance with post hoc Scheffe were applied to examine differences.Results: Both patient groups were significantly more physically inactive and had a significantly impaired speed of limb movement, explosive muscle strength and abdominal muscular endurance compared to the healthy controls. No significant differences between the patient groups were found.Conclusions: The results suggest that physical fitness and physical activity participation are similar among inpatients with bipolar disorder and schizophrenia but markedly lower than healthy controls. Chronic inpatients with lower levels of physical activity may particularly benefit from rehabilitation interventions aimed at increasing physical fitness.Implications for RehabilitationPhysical fitness should receive similar attention in the treatment of bipolar disorder and schizophrenia.Sedentary patients with a longer duration of illness need additional support in changing lifestyle behaviours.Rehabilitation should not only consider cardio-respiratory fitness but also muscular endurance, muscular strength and balance.

Limb movement frequency is a significant modulator of the ventilatory response during submaximal cycling exercise in humans

Human experimentation investigating the contribution of limb movement frequency in determining the fast exercise drive to breathe has produced controversial findings. To evaluate the role of limb movement frequency in determining the fast exercise drive to breathe, endurance runners and recreationally-active controls performed two sinusoidal exercise protocols on a cycle ergometer. One protocol was performed at constant workload with sinusoidal pedaling cadence, and a second with sinusoidal workload at constant cadence. Metabolic rate (VO2) increases and means were matched between these two experiments. The ventilatory response was significantly faster when limb movement speed was varied, compared to when pedal loading was varied (18.49±15.6s vs. 50.5±14.5s, p<0.05). Ventilation response amplitudes were significantly higher during pedal cadence variation versus pedal loading variation (3.99±0.25 vs. 2.58±0.17L/min, p<0.05). Similar findings were obtained for endurance athletes, with significantly attenuated ventilation responses to exercise versus control subjects. We conclude that fast changes in limb movement frequency are a potent stimulus for ventilation at submaximal workloads, and that this response is susceptible to attenuation through training.

Health-related physical fitness in patients with bipolar disorder vs. healthy controls: An exploratory study

BackgroundLow physical fitness has been recognized as a prominent behavioral risk factor for cardiovascular diseases and an independent risk factor for all-cause mortality. To date, no studies have systematically assessed physical fitness in patients with bipolar disorder. The aim of the current study was to assess and compare the physical fitness in patients with bipolar disorder against healthy controls. MethodsThirty patients with bipolar disorder (16♂, 40.8±11.6 years) and 30 age-, gender- and body mass index (BMI)-matched healthy controls were included. All participants performed the Eurofit test battery and the International Physical Activity Questionnaire. Patients were screened for psychiatric symptoms using the Quick Inventory of Depressive Symptomatology and Hypomania Checklist-32. ResultsPatients with bipolar disorder had a reduced speed of limb movement (15.8±5.7 vs. 11.8±2.2s; p<0.001), explosive leg muscle strength (134.9±49.0 vs. 167.6±32.3cm; p=0.003) and abdominal muscular endurance (11.5±7.8 vs. 18.3±7.6; p<0.001). Backward regression analyses demonstrated that longer illness duration, higher body mass index, higher levels of depression and a lower physical activity level explained the variance in physical fitness. LimitationsOur data are cross-sectional and cannot establish cause and effect. ConclusionsThe current findings suggest that a lower physical fitness is emerging as an eminent modifiable risk factor for somatic co-morbidity in people with bipolar disorder. In particular less physically active persons, those with a longer illness duration and those with higher levels of depression might benefit from specific rehabilitation interventions aimed at increasing physical fitness.

The Left Hand Second to Fourth Digit Ratio (2D:4D) Is Not Related to Any Physical Fitness Component in Adolescent Girls

IntroductionThe second to fourth-digit-ratio (2D:4D), a putative marker of prenatal androgen action and a sexually dimorphic trait, has been suggested to be related with fitness and sports performance, although results are not univocal. Most studies however focus on a single aspect of physical fitness or one sports discipline.MethodsIn this study the 2D:4D ratio of 178 adolescent girls (age 13,5–18 y) was measured on X-rays of the left hand. The relation between 2D:4D digit ratio and multiple aspects of physical fitness (balance, speed of limb movement, flexibility, explosive strength, static strength, trunk strength, functional strength, running speed/agility, and endurance) was studied by correlation analyses and stepwise multiple regression. For comparison the relation between these physical fitness components and a selected number of objectively measured anthropometric traits (stature, mass, BMI, somatotype components and the Bayer & Bailey androgyny index) are presented alongside the results of 2D:4D digit ratio.ResultsLeft hand 2D:4D digit ratio (0.925±0.019) was not significantly correlated with any of the physical fitness components nor any of the anthropometric variables included in the present study. 2D:4D did not enter the multiple stepwise regression for any of the physical fitness components in which other anthropometric traits explained between 9,2% (flexibility) and 33,9% (static strength) of variance.ConclusionUnlike other anthropometric traits the 2D:4D digit ratio does not seem to be related to any physical fitness component in adolescent girls and therefore most likely should not be considered in talent detection programs for sporting ability in girls.

Effect of Speed and Gender on Rate of Velocity Development Quadriceps/Hamstrings Ratios

PURPOSE: There is speculation that the ratio of quadriceps to hamstrings rate of velocity development (RVD) differs between genders and speeds due to the male bias in limb movement speed. The purpose of this study was to determine if males and females demonstrated different lower body muscle group RVD ratios when testing across a velocity spectrum. METHODS: 119 male (n=57) and female (n=62) university kinesiology students (age 23.29±2.13 years, height 170.98±10.25 cm, weight 71.29±16.15 kg) performed 5 maximal reciprocal concentric/concentric knee extension and flexion repetitions on a Biodex System 3 isokinetic dynamometer at 13 random speeds between 30 and 400 d/s. RVD is the measured ROM traveled from 0 to the target velocity, therefore, a lower value equates to greater limb acceleration. Quadriceps/hamstrings ratios were determined by dividing peak extension RVD by peak flexion RVD and multiplying by 100. ANOVA was used to determine the differences between male and female ratios, as well as the differences of the ratios across the velocity spectrum. RESULTS: Males and females demonstrated no significant differences in peak quadriceps/hamstrings RVD ratios when compared across speeds. However, there was a significant (p <0.05) main effect for speed on the RVD ratios. As testing speeds increased, the quadriceps/hamstrings RVD ratios decreased. Ratios decreased from 76.97%+19.31 to 64.10%+6.73 between 30 and 400 d/s respectively. CONCLUSION These results demonstrate that although males had less RVD at all speeds, there was no difference in RVD ratios by gender. The data also indicate that peak RVD in the hamstrings and quadriceps increases with increasing velocity while the ratios decline. This is due to the fact that the hamstrings slow down at a greater rate than the quadriceps causing the ratio to decrease. This is contrast to the increasing ratios seen in torque development. Therefore, training protocols may need to be moderated at very high velocities to insure that hamstring exercise is within the velocity range capability.

Physical fitness profile of elite athletes with intellectual disability

The aim of this study was to investigate the physical fitness profile of high-performance athletes with intellectual disability (ID) in comparison with able-bodied individuals. Participants were 231 male and 82 female athletes. All evaluations were done using the EUROFIT physical fitness test. In comparison with population data, both male and female athletes with ID score better for flexibility and upper body muscle endurance, but have similar or lower values for running speed, speed of limb movement, and strength measures. Compared with age-matched physical education students, male athletes with ID score better for running speed and flexibility, and worse for strength. Female athletes with ID score not different from able-bodied individuals for flexibility, running speed, and upper body muscle endurance, but worse for strength measures. Athletes with ID also have poorer cardio respiratory endurance capacity compared with sportive peers without ID. Furthermore, male athletes have a more differentiated profile depending upon their sports discipline, compared with female athletes. It can be concluded that high-performance athletes with ID reach physical fitness levels that are equal to or lower than those of able-bodied sportive counterparts. Further research should investigate the importance of reduced muscle strength to be the limiting factor.

The relationship between peak height velocity and physical performance in youth soccer players

Longitudinal changes in height, weight and physical performance were studied in 33 Flemish male youth soccer players from the Ghent Youth Soccer Project. The players' ages at the start of the study ranged from 10.4 to 13.7 years, with a mean age of 12.2 ± 0.7 years. Longitudinal changes were studied over a 5 year period. Peak height velocity and peak weight velocity were determined using non-smoothed polynomials. The estimations of peak height velocity, peak weight velocity and age at peak height velocity were 9.7 ± 1.5 cm · year−1, 8.4 ± 3.0 kg · year−1 and 13.8 ± 0.8 years, respectively. Peak weight velocity occurred, on average, at the same age as peak height velocity. Balance, speed of limb movement, trunk strength, upper-body muscular endurance, explosive strength, running speed and agility, cardiorespiratory endurance and anaerobic capacity showed peak development at peak height velocity. A plateau in the velocity curves was observed after peak height velocity for upper-body muscular endurance, explosive strength and running speed. Flexibility exhibited peak development during the tear after peak height velocity. Trainers and coaches should be aware of the individual characteristics of the adolescent growth spurt and the training load should also be individualized at this time.

Familial Resemblance In Physical Fitness

Given the positive relationship between health related physical fitness and health status, insight in determinants of physical fitness might be useful for intervention and/ or health promotion campaigns. These determinants can be influenced by genetic and non-genetic relationships between family members. PURPOSE To quantify familial resemblance in physical fitness components. METHODS 148 fathers (47y ± 0.7) of the “Leuven Longitudinal Study on Lifestyle, Fitness and Health”, 103 mothers (44.4y ± 2.6), 60 sons (17.3y ± 1.8) and 45 daughters (17. 1y ± 2.2) performed physical fitness tests to quantify muscular strength (isometric, explosive, functional and trunk), maximal aerobic performance, speed of limb movement, flexibility and balance. Pearson product moment correlations were calculated between all family members to estimate familial resemblance in physical fitness characteristics. RESULTS Largest correlations between genetically related family members were found for isometric strength (0.24–0.70), maximal aerobic performance (0.16–0.42) and flexibility (0.14–0.37). High father-mother-correlations were found for isometric strength (0.48), maximal aerobic performance (0.42) and speed of limb movement (0.28). For trunk strength significant parent-son correlations were observed (0.31–0.34) and the spousal correlation was 0.22, although it was not significant. Family members' scores for balance and explosive strength did not correlate significantly. CONCLUSIONS As first degree family members share on average 50% of their genetic material, correlations found in this study for isometric strength, maximal aerobic performance and flexibility suggest a component of genetic transmission. However, as the spousal correlations for isometric strength, maximal aerobic performance and speed of limb movement are quite high (0.28–0.48), assortative mating and/or shared environmental factors are presumably also causing part of the variance of these variables. No clear patterns can be derived from the familial correlations in balance and explosive strength, suggesting larger individual environmental influences. Supported: The Flemish Policy Research Center Sport, Physical Activity and Health is supported by the Flemish Government.

Generational Differences In Physical Fitness

PURPOSE To document the generational differences in male adolescents and to study the father-son correlations in physical fitness. METHODS Between 1969 and 1974, Belgian male adolescents were observed in the Leuven Growth Study of Belgian Boys and, in 2003, their sons participated in the last phase of the Leuven Longitudinal Study of Lifestyle, Fitness and Health. Height, weight, BMI were measured, and the Leuven fitness test battery was administered in 77 father-son pairs observed about 33 years apart but, at the same age level (15.7 ± 1.75 yrs). Generational differences were tested and father-son correlations calculated. RESULTS Present-day male adolescents are taller, heavier and perform less well in static strength, flexibility and speed of limb movement than their fathers during their adolescence. No differences were found for BMI, explosive strength or power, muscular endurance, and running speed. Father-son correlations were rather high (above .40) for isometric strength, power, speed of limb movement and flexibility. Non-significant correlations were observed for running speed and muscular endurance. CONCLUSIONS Present-day male adolescents perform worse than their fathers during their adolescence, and relatively high father-son correlations were observed, indicating genetic and/or cultural transmission. Supported: The Flemish Policy Research Center Sport, Physical Activity and Health is supported by the Flemish Government.

Generational Differences In Physical Fitness

PURPOSE To document the generational differences in male adolescents and to study the father-son correlations in physical fitness. METHODS Between 1969 and 1974, Belgian male adolescents were observed in the Leuven Growth Study of Belgian Boys and, in 2003, their sons participated in the last phase of the Leuven Longitudinal Study of Lifestyle, Fitness and Health. Height, weight, BMI were measured, and the Leuven fitness test battery was administered in 77 father-son pairs observed about 33 years apart but, at the same age level (15.7 ± 1.75 yrs). Generational differences were tested and father-son correlations calculated. RESULTS Present-day male adolescents are taller, heavier and perform less well in static strength, flexibility and speed of limb movement than their fathers during their adolescence. No differences were found for BMI, explosive strength or power, muscular endurance, and running speed. Father-son correlations were rather high (above .40) for isometric strength, power, speed of limb movement and flexibility. Non-significant correlations were observed for running speed and muscular endurance. CONCLUSIONS Present-day male adolescents perform worse than their fathers during their adolescence, and relatively high father-son correlations were observed, indicating genetic and/or cultural transmission. Supported: The Flemish Policy Research Center Sport, Physical Activity and Health is supported by the Flemish Government.

Practicing a Maximal Performance Task: A Cooperative Strategy for Muscle Activity

The effect of practice on predicting elbow flexion movement time was studied. Participants (N = 18) performed 400 elbow flexion trials to a target in the horizontal plane. The trials were distributed equally over four sessions. The goal was to decrease the movement time (MT) for the same degree of accuracy. The electromyographic (EMG) activity of the biceps and triceps brachii was monitored with standard Beckman Ag/AgCl surface electrodes. The EMG measures formed two variable sets within one prediction equation. One variable set was composed of the onset of muscle activity relative to the start of movement (motor time) and the duration of muscle activity. The other variable set consisted of the mean amplitude value of the entire burst and of the first 30 ms (Q30) of activity. As the maximal speed of limb movement increased, the duration of muscle activity (motor time and EMG duration) decreased, and the magnitude of muscle activity (MAV and Q30) increased. Most of the change in the duration of muscle activity occurred in Session 1, while the magnitude of muscle activity continued to increase until Session 3. Multiple regression analysis revealed a cooperative strategy between the magnitude and duration of muscle activity. Early in learning, participants adjusted the magnitude of muscle activity to increase limb movement speed. As practice continued, alterations in the duration of muscle activity became more important, while the magnitude changes were less involved. Late in learning, both dimensions of muscle activity were used to decrease MT. We suggest that the interplay between the magnitude and duration of muscle activity may be due to: (a) cognitive factors related to the division of attention in a motor skill, (b) an increase in the frequency of motor unit firing that affects both dimensions of muscle activity, or (c) some combination of (a) and (b).

Associations between daily physical activity and physical fitness in Flemish males: A cross-sectional analysis.

The relationship of physical activity to several components of physical fitness was investigated in a sample of 166 males 40 years of age. In addition to Pearson correlations, multivariate canonical correlations were calculated. Physical activity during work (work index), sport (sport index), and leisure time (leisure time index) was assessed by the Baecke questionnaire. Physical fitness included cardiorespiratory fitness measures, the body mass index (BMI), the sum of seven skinfold thicknesses (SKI), percentage body fat (PFAT), balance, and several tests of muscle strength and endurance, flexibility, and speed of limb movement. More than 86% of the variance was shared by the two first canonical variables. The first canonical variable can be interpreted as a health-related fitness function. Carciorespiratory fitness, balance, speed of limb movement, explosive strength, and trunk muscle strength are clearly related to this function. From the physical activity measures, the Baecke sport index correlated significantly with this health-related fitness function. The second canonical variable can be explained as a fatness function, since body weight, BMI, SKI, and PFAT showed the highest correlations with the variable. The Baecke work index was inversely related to this canonical variable. The sample was also divided into physical activity groups in order to look for differences in physical fitness. The data indicate that physical activity during work was modestly, but inversely related to adiposity. Sport activity was beneficially associated to several fitness components, including cardiorespiratory fitness, trunk muscle strength, and upper body muscular endurance. Am. J. Hum. Biol. 11:587-597, 1999. Copyright 1999 Wiley-Liss, Inc.

Low sensitivity of dorsal spinocerebellar neurons to limb movement speed.

This paper reports the effect of limb movement speed on dorsal spinocerebellar tract (DSCT) activity recorded while the cat hindlimb was passively moved through two types of foot trajectories (figure eight and step cycle) at different speeds. While nearly all the DSCT neurons sampled (151/159; 94.5%) were significantly modulated by the direction of foot movement in these trajectories, they were only modestly influenced by movement speed. We quantified the speed effect and also accounted for intrinsic cell variability by computing a variability index (VI) between pairs of responses to trajectories made either at the same or at different speeds. The distribution of same-speed VIs across cells indicated a mean variability of about 10% over a trajectory cycle, whereas the two-speed distributions indicated a mean change of about 25% for a two- to fourfold change in movement speed. We also examined the relative contribution of movement speed to the activity of each DSCT cell by means of a multivariate regression model that also included as predictors the position, movement direction, and interactions between movement and position. We found that 28 of 103 (27.2%) neurons were not sensitive to movement speed. The rest were modulated in varying degrees by changes in speed, and the speed modulation depended on limb position for most of them (54/75). Overall, DSCT speed sensitivity resembles the 0.3-power relationship used to describe the velocity sensitivity of muscle spindles for large muscle stretches. We examined this by recording muscle spindle activity during these passive foot trajectories and found that their speed sensitivity was within the range observed for the DSCT and explained by the 0.3-power law. In total, movement speed accounted for about 15% of the variance in DSCT activity across cells, while the directional component of movement accounted for about 45%. The results suggest a separate processing of sensory information about the two components of movement velocity: namely, its direction and magnitude.

EFFECTS OF REPETITIVE DYNAMIC CONTRACTIONS UPON ELECTROMECHANICAL DELAY

1918 The effects of repeated, maximal effort, isotonic contractions upon electromechanical delay (EMD) was studied. Over a period of four days, 18 subjects performed a total of 400 ballistic goal-directed elbow flexion trials on a manipulandum in the horizontal plane. Twenty-four hours separated test days 1 and 2 and test days 3 and 4 with a one-week rest period between test days 2 and 3. A potentiometer and microswitches at the elbow axis of rotation allowed angular displacement and movement time to be recorded. The electromyographic (EMG) activity of the biceps brachii (BB) was monitored using Beckman surface electrodes. There was a significant increase in the speed of limb movement. The mean power frequency and duration of EMD were resistant to ballistic elbow flexion training, while root-mean-square amplitude followed the same pattern of changes as did movement kinematics. In contrast, the end portion of agonist activity (END) was more adaptable as both its mean power frequency and root-mean-square amplitude varied with movement kinematics. Similar to EMD, the duration of END remained stable. We conclude that changes in movement kinematics were a result of alterations in motor unit recruitment during the END portion of agonist activity and not during the EMD period.

Practice Effects on the Timing and Magnitude of Antagonist Activity during Ballistic Elbow Flexion to a Target

This study examined changes in antagonist timing and magnitude in response to ballistic elbow flexion practice. Seventeen men performed 400 ballistic elbow flexion trials to a target in the horizontal plane over 4 days of testing. A potentiometer and microswitch system at the elbow axis of rotation of a manipulandum recorded angular displacement and movement onset. Surface electrodes (Beckman Ag/AgCl) monitored the triceps brachii lateral head, and the electromyographic (EMG) signals were bandpassed between 20 and 300 Hz. The antagonist EMG burst was divided in two: early low-level activity (ANT1), and the large portion of the burst which occurs near target achievement (ANT2). Movement time decreased from 178 ms on the first test day to 136 ms on the last session. As practice improved the speed of limb movement, onset of the first component (ANT1) remained unchanged, while the second component (ANT2) started earlier. The magnitude of both portions of the antagonist burst increased from the first to last test day, but the change in ANT2 relative to ANT1 was more pronounced. These findings are used to explain discrepant observations in the literature for the temporal measure.