Peak Angular Velocity Research Articles

Blowfly flight characteristics are shaped by environmental features and controlled by optic flow information

Blowfly flight consists of two main components, saccadic turns and intervals of mostly straight gaze direction, although, as a consequence of inertia, flight trajectories usually change direction smoothly. We investigated how flight behavior changes depending on the surroundings and how saccadic turns and intersaccadic translational movements might be controlled in arenas of different width with and without obstacles. Blowflies do not fly in straight trajectories, even when traversing straight flight arenas; rather, they fly in meandering trajectories. Flight speed and the amplitude of meanders increase with arena width. Although saccade duration is largely constant, peak angular velocity and succession into either direction are variable and depend on the visual surroundings. Saccade rate and amplitude also vary with arena layout and are correlated with the 'time-to-contact' to the arena wall. We provide evidence that both saccade and velocity control rely to a large extent on the intersaccadic optic flow generated in eye regions looking well in front of the fly, rather than in the lateral visual field, where the optic flow at least during forward flight tends to be strongest.

Lumbopelvic Landing Kinematics and EMG in Women with Contrasting Hip Strength

Hip muscle weakness has been associated with altered lower extremity mechanics and the increased likelihood of receiving treatment for low back problems, although biomechanical injury mechanisms focused on the trunk have not been investigated. The purpose of this study was to compare lumbopelvic kinematic variables and muscle activation of the trunk and gluteal muscles in females with strong and weak hip muscle strength during a demanding single-leg task. Twenty-two asymptomatic females were categorized into a strong or weak group (11 per group) as determined by isometric hip extension and abduction dynamometry profiles. Participants performed a single-leg landing task during which three-dimensional lumbopelvic kinematics and trunk (lumbar erector spinae, external obliques, and rectus abdominis) and gluteal (gluteus maximus and gluteus medius) muscle activities were recorded. Peak lumbopelvic angular displacement, total angular excursion, and mean and peak angular velocity during the first 0.5 s of landing were reported. Mean normalized EMG and muscle cocontraction index (between the lumbar erector spinae and the external obliques) were also reported. Significant between-group differences existed for each of the following: peak displacement, excursion, velocity, and muscle activity. Differences in peak angular displacement occurred in the frontal plane, whereas excursion differences were observed in all planes. Differences in peak velocity were noted in the sagittal and frontal planes. Weaker subjects showed increased muscle activation (across all muscles except the rectus abdominis) and cocontraction index. Individuals with diminished hip muscle strength exhibit greater lumbopelvic angular displacement, velocity, and muscle activity during the single-leg landing task. Future studies targeting hip strengthening may provide more insight to rehabilitation protocols as well as the relation between hip strength, low back motion, and muscle activity.

Quantifying Upper-Arm Rehabilitation Metrics for Children through Interaction with a Humanoid Robot

The objective of this research effort is to integrate therapy instruction with child-robot play interaction in order to better assess upper-arm rehabilitation. Using computer vision techniques such as Motion History Imaging (MHI), edge detection, and Random Sample Consensus (RANSAC), movements can be quantified through robot observation. In addition, incorporating prior knowledge regarding exercise data, physical therapeutic metrics, and novel approaches, a mapping to therapist instructions can be created allowing robotic feedback and intelligent interaction. The results are compared with ground truth data retrieved via the Trimble 5606 Robotic Total Station and visual experts for the purpose of assessing the efficiency of this approach. We performed a series of upper-arm exercises with two male subjects, which were captured via a simple webcam. The specific exercises involved adduction and abduction and lateral and medial movements. The analysis shows that our algorithmic results compare closely to the results obtain from the ground truth data, with an average algorithmic error is less than 9% for the range of motion and less than 8% for the peak angular velocity of each subject.

Do we use a priori knowledge of gravity when making elbow rotations?

In this study, we aim to investigate whether motor commands, emanating from movement planning, are customized to movement orientation relative to gravity from the first trial on. Participants made fast point-to-point elbow flexions and extensions in the transverse plane. We compared movements that had been practiced in reclined orientation either against or with gravity with the same movement relative to the body axis made in the upright orientation (neutral compared to gravity). For each movement type, five rotations from reclined to upright orientation were made. For each rotation, we analyzed the first trial in upright orientation and the directly preceding trial in reclined orientation. Additionally, we analyzed the last five trials of a 30-trial block in upright position and compared these trials with the first trials in upright orientation. Although participants moved fast, gravitational torques were substantial. The change in body orientation affected movement planning: we found a decrease in peak angular velocity and a decrease in amplitude for the first trials made in the upright orientation, regardless of whether the previous movements in reclined orientation were made against or with gravity. We found that these decreases disappeared after participants familiarized themselves with moving in upright position in a 30-trial block. These results indicate that participants used a general strategy, corresponding to the strategy observed in situations with unreliable or limited information on external conditions. From this, we conclude that during movement planning, a priori knowledge of gravity was not used to specifically customize motor commands for the neutral gravity condition.

Tennis forehand kinematics change as post-impact ball speed is altered

Peak joint angles and joint angular velocities were evaluated for varying speed forehands in an attempt to better understand what kinematic variables are most closely related to increases in post-impact ball velocity above 50% of maximal effort. High-speed video was used to measure three-dimensional motion for 12 highly skilled tennis players who performed forehands at three different post-impact ball speeds: fast (42.7 ± 3.8 m/s), medium (32.1 ± 2.9 m/s), and slow (21.4 ± 2.0 m/s). Several dominant-side peak joint angles (prior to ball impact) increased as post-impact ball speed increased from slow to fast: wrist extension (16%), trunk rotation (28%), hip flexion (38%), knee flexion (27%), and dorsiflexion (5%). Between the aforementioned peak joint angles and ball impact, dominant-side peak angular velocities increased as ball speed increased from slow to fast: peak wrist flexion (118%), elbow flexion (176%), trunk rotation (99%), hip extension (143%), knee extension (56%), and plantarflexion (87%). Most kinematic variables changed as forehand ball speed changed; however, some variables changed more than others, indicating that range of motion and angular velocity for some joints may be more closely related to post-impact ball speed than for other joints.

Quantitative Relationship between Axonal Injury and Mechanical Response in a Rodent Head Impact Acceleration Model

A modified Marmarou impact acceleration model was developed to study the mechanical responses induced by this model and their correlation to traumatic axonal injury (TAI). Traumatic brain injury (TBI) was induced in 31 anesthetized male Sprague-Dawley rats (392±13 g) by a custom-made 450-g impactor from heights of 1.25 m or 2.25 m. An accelerometer and angular rate sensor measured the linear and angular responses of the head, while the impact event was captured by a high-speed video camera. TAI distribution along the rostro-caudal direction, as well as across the left and right hemispheres, was determined using β-amyloid precursor protein (β-APP) immunocytochemistry, and detailed TAI injury maps were constructed for the entire corpus callosum. Peak linear acceleration 1.25 m and 2.25 m impacts were 666±165 g and 907±501 g, respectively. Peak angular velocities were 95±24 rad/sec and 124±48 rad/sec, respectively. Compared to the 2.25-m group, the observed TAI counts in the 1.25-m impact group were significantly lower. Average linear acceleration, peak angular velocity, average angular acceleration, and surface righting time were also significantly different between the two groups. A positive correlation was observed between normalized total TAI counts and average linear acceleration (R(2)=0.612, p<0.05), and time to surface right (R(2)=0.545, p<0.05). Our study suggested that a 2.25-m drop in the Marmarou model may not always result in a severe injury, and TAI level is related to the linear and angular acceleration response of the rat head during impact, not necessarily the drop height.

Individual differences in the biomechanical effect of loudness and tempo on upper-limb movements during repetitive piano keystrokes

The present study addressed the effect of loudness and tempo on kinematics and muscular activities of the upper extremity during repetitive piano keystrokes. Eighteen pianists with professional music education struck two keys simultaneously and repetitively with a combination of four loudness levels and four tempi. The results demonstrated a significant interaction effect of loudness and tempo on peak angular velocity for the shoulder, elbow, wrist and finger joints, mean muscular activity for the corresponding flexors and extensors, and their co-activation level. The interaction effect indicated greater increases with tempo when eliciting louder tones for all joints and muscles except for the elbow velocity showing a greater decrease with tempo. Multiple-regression analysis and K-means clustering further revealed that 18 pianists were categorized into three clusters with different interaction effects on joint kinematics. These clusters were characterized by either an elbow-velocity decrease and a finger-velocity increase, a finger-velocity decrease with increases in shoulder and wrist velocities, or a large elbow-velocity decrease with a shoulder-velocity increase when increasing both loudness and tempo. Furthermore, the muscular load considerably differed across the clusters. These findings provide information to determine muscles with the greatest potential risk of playing-related disorders based on movement characteristics of individual pianists.

The impact of contractile mode and work volume on the prediction of cortisol concentrations from flywheel-based resistive exercise workouts

To assess cortisol concentrations (CC) from flywheel ergom eter resistive exercise, subjects performed three differe nt leg press workouts on the device. Comprised of ten-repetition sets, the workouts entailed 1): a three-set protocol composed of concentric and eccentric actions (CE3), as well as concentric-only paradigms comprised of 2): three (CO3) and 3): six (CO6) sets. Venous blood draws, collected before workouts and at one and 30 minutes post-exercise, measured CC. ANOVA yielded CC results similar to studies that employed standard resist ive exercise equipment. However multivariate regression revealed body mass, peak angular velocity and average power were strong predictors of post-exercise CC. Separate multivariate analyses of the CE3 and pooled concentric-only (CO3 and CO6 combined) data show differences in level of explained (r 2 ) variance, which was likely due to the ergometer's operation. Constant torque ex ertion throughout the CE3 bout meant performance was continual only for that workout and evoked more explained variance versus the concentric-only trials. The current ergometer was originally intended for use aboard manned spacecraft and is a prototype to newer flywheel-based resistive exercise devices. Future research should assess responses to workouts in a bed rest model to determine which protocol best abates CC to further aid future in-flight exercise.

Kinematics, kinetics, and electromyogram of ankle during drop landing: A comparison between dominant and non-dominant limb

The biomechanical difference between the dominant and non-dominant limb has seldom been studied during double-leg landing. The objective of this study was to evaluate the effectiveness of limb laterality on the ankle kinematics, kinetics and electromyogram (EMG) during drop landing. Sixteen healthy adults were recruited and dropped individually from platforms with three different heights (0.32 m, 0.52 m, and 0.72 m). The ground reaction force, ankle joint kinematics, and surface EMG of tibialis anterior (TA) and lateral gastrocnemius (LG) were measured in both lower extremities. Two-way analysis of variance was used to analyze the effects of laterality and dropping height. The peak angular velocities in dorsiflexion and abduction were significantly higher in the dominant ankle, whereas the pre- and post-landing EMG amplitudes of the TA were significantly higher in the non-dominant limb. Compared with the dominant side, the non-dominant ankle has a more effective protective mechanism in that excessive joint motion is restrained by greater ankle flexor activity. Compared with the non-dominant side, the dominant ankle joint is in greater injury risk during drop landing, and data measured in the dominant limb may produce more conservative conclusions for injury protection or prediction.

Investigation of high-speed badminton racket kinematics by motion capture

The kinematics of a badminton racket during a smash stroke was observed in this study with the purpose of investigating stroke dynamics and racket behaviour. Motion capture measurements of the racket during several smash strokes performed by three players of different skill levels indicated a clear increase in racket velocity at impact with increasing skill level. Variations between translational and rotational contributions to the impact speed could also be seen between the players. The advanced player produced a much higher peak angular velocity and also relied much less on translation, with a translational velocity of only 8% of the total velocity versus the 20% for the recreational player. It is proposed that, as an alternative to shuttlecock speeds, racket head speed measurements can be used as an indicator of performance, and can also provide some insight into the interaction between the racket and player.

Kinematic Variables Quantifying Upper-Extremity Performance After Stroke During Reaching and Drinking From a Glass

Background. Three-dimensional kinematic analysis provides quantitative and qualitative assessment of upper-limb motion and is used as an outcome measure to evaluate impaired movement after stroke. The number of kinematic variables used, however, is diverse, and models for upper-extremity motion analysis vary. Objective. The authors aim to identify a set of clinically useful and sensitive kinematic variables to quantify upper-extremity motor control during a purposeful daily activity, that is, drinking from a glass. Methods. For this purpose, 19 participants with chronic stroke and 19 healthy controls reached for a glass of water, took a sip, and placed it back on a table in a standardized way. An optoelectronic system captured 3-dimensional kinematics. Kinematical parameters describing movement time, velocity, strategy and smoothness, interjoint coordination, and compensatory movements were analyzed between groups. Results. The majority of kinematic variables showed significant differences between study groups. The number of movement units, total movement time, and peak angular velocity of elbow discriminated best between healthy participants and those with stroke as well as between those with moderate (Fugl-Meyer scores of 39-57) versus mild (Fugl-Meyer scores of 58-64) arm impairment. In addition, the measures of compensatory trunk and arm movements discriminated between those with moderate and mild stroke impairment. Conclusion. Kinematic analysis in this study identified a set of movement variables during a functional task that may serve as an objective assessment of upper-extremity motor performance in persons who can complete a task, such as reaching and drinking, after stroke.

Prediction of Resultant Testosterone Concentrations from Flywheel-Based Resistive Exercise

Numerous variables impact resultant testosterone concentrations (TC) that foretell the efficacy of workouts. Identifying variables may aid the development of in-flight exercise prescription. To identify variables that predict the variance in TC from flywheel ergometer exercise, 17 subjects did 3 workouts in a randomized order. Comprised of 10-repetition leg press sets, workouts entailed either: 1) 3 sets of both concentric and eccentric muscle actions (CE3), and concentric-only actions done for 2) three (CO3), or 3) six (CO6) sets. Venous plasma TC were collected before and at 1 and 30 min postexercise. The last two collection points served as criterion measures. Body mass, delta blood lactate levels, peak angular velocity, average power, and total work from workouts were used to predict the variance in TC. Predictor variables accounted for significant levels of variance at both 1 and 30 min post-exercise for both the CE3 and the concentric-only (CO3 and CO6 bouts combined) workouts using multivariate regression. Inclusion of eccentric variables (only collected from the CE3 bout; r2 = 0.90) predicted nearly twice the variance than the concentric-only (r2 = 0.54) workouts. Body mass and average power indices were the best predictors of the variance in post-workout TC. Since a flywheel-based device is used to abate in-flight muscle atrophy and strength losses, exercise prescriptions may wish to monitor these indices as they impacted post-workout TC to the greatest extent. Future research should assess why eccentric variables increased the amount of explained variance from flywheel ergometer workouts.

Acute Effects of High-Intensity Dumbbell Exercise After Isokinetic Eccentric Damage: Interaction between Altered Pain Perception and Fatigue on Static and Dynamic Muscle Performance

This study aimed to determine whether high-intensity dumbbell exercise involving both concentric and eccentric contractions would provide a temporary alleviation of delayed-onset muscle soreness (DOMS). It also examined the effect of alleviated muscle soreness on dynamic muscle performance using a stretch-shortening cycle (SSC; peak angular acceleration and velocity of the elbow during both lowering and concentric phases) to provide indirect evidence that DOMS contributes to the dynamic performance decrement after eccentric injury. Thirteen untrained adults performed 30 maximal isokinetic eccentric contractions of the elbow flexors to induce eccentric damage. Five sets of arm curls using a dumbbell (equivalent to 70% of isometric maximal voluntary contraction) were then performed until failure on days 1, 2, 3, and 5 of recovery. Muscle soreness significantly decreased after each session of dumbbell exercise (p = 0.001). Isometric strength further decreased immediately after dumbbell exercise, indicating muscle fatigue (p < 0.001). Dynamic performance variables were less affected by fatigue, however, with performance being reduced only for peak lowering velocity (p < 0.001). Other measures of dynamic performance were relatively constant after dumbbell exercise, particularly on days 2 and 3 when soreness was greatest. It was concluded that high-intensity concentric/eccentric dumbbell exercise was able to temporarily alleviate DOMS and that this reduction in soreness served to counter the effect of peripheral muscle fatigue during dynamic activities. Practical applications of this study are that after eccentric damage, alleviation of muscle soreness through an optimal warm-up may be helpful to temporarily recover dynamic muscle performance. Free-weight loading is one suggested technique to temporarily manage DOMS.

Biomechanical Gender Differences of the Ankle Joint During Simulated Half-Squat Parachute Landing

A search of the literature did not reveal known gender differences in biomechanics during parachute landing. Eight male and eight female healthy adults participated in this experiment. Each individual jumped from platforms with three different heights (low: 0.32 m; medium: 0.52 m; and high: 0.72 m) and landed on flat ground in a standard half-squat parachute landing technique. The ground reaction force (GRF) normalized to bodyweight (BW), ankle joint kinematics, and the surface electromyogram (EMG) signals of the tibialis anterior (TA) and lateral gastrocnemius (LG) were measured. Two-way ANOVA was used to analyze the effects of the dropping height and gender factors. The anterior-posterior GRF (men 1.01 BW; women 0.79 BW), rate of loading (men 260 BW x s(-1); women 127 BW x s(-1)), and absolute EMG amplitude of TA (pre-landing: men 219 microv; women 129 microv; post-landing: men 573 microv; women 288 microv) in the men's group were significantly higher than in the women's group, whereas peak angular velocity of dorsiflexion in the women's group (1627 degrees x s(-1)) was significantly higher than in the men's (1188 degrees x s(-1)). Women are prone to transform the kinetic energy to the ankle motion, whereas men are more likely to transform it to friction. The co-contraction of the ankle flexor and extensor differs between genders. These factors may be associated with the higher incidence of parachute injuries among women reported by some authors.

Human discrimination of rotational velocities

Vestibular reflexes are critically important for stabilizing gaze and maintaining posture, but comparatively little is known about conscious perceptions of vestibular stimuli and how they may relate to balance function. We used psychophysical methods to determine the ability of normal subjects and a vestibular-deficient subject to discriminate among velocities of earth-vertical sinusoidal rotations. Discrimination thresholds in normal subjects rose from 2.26 deg/s at a peak velocity of 20 deg/s up to 5.16 deg/s at 150 deg/s. The relationship between threshold and peak angular velocity was well described by the power law function DeltaI = 0.88I(0.37), where I is the magnitude of the stimulus and DeltaI is the discrimination threshold. The subject with bilateral vestibular hypofunction had thresholds more than an order of magnitude worse than normals. The performance of normal subjects is much better than that predicted by Weber's Law, which states that discrimination thresholds increase proportionally with stimulus magnitude (i.e., DeltaI/I = C, where C is the "Weber fraction"). This represents a remarkable exception to other sensory systems and may reflect the vestibular system's ability to stabilize gaze and maintain posture even at high stimulus intensities. Quantifying this relationship may help elucidate the role of higher-level processes in maintaining balance and provide information to diagnose and guide therapy of patients with central causes for imbalance.

Biomechanical analysis of the penalty-corner drag-flick of elite male and female hockey players

The aim of this study was to analyse the kinematic sequencing in the penalty-corner drag-flicks of elite male and female field hockey players of international calibre. Thirteen participants (one skilled male drag-flicker and six male and six female elite players) participated in the study. An optoelectronic motion analysis system was used to capture the drag-flicks with six cameras, sampling at 250 Hz. Select ground reaction force parameters were obtained from a force platform which registered the last support of the front foot. Twenty trials were captured from each subject. Both player groups showed significantly (p < 0.05) smaller ball velocity at release, peak angular velocity of the pelvis, and negative and positive peak angular velocities of the stick than the skilled subject. Normalised ground reaction forces of the gender groups were also smaller than that of the skilled drag-flicker. By comparing these players we established that the cues of the skill level are a wide stance, a whipping action (rapid back lift) of the stick followed by an explosive sequential movement of the pelvis, upper trunk and stick.

Quantitative measurement of spastic ankle joint stiffness using a manual device: A preliminary study

Quantitative measurement of ankle joint stiffness following stroke could prove useful in monitoring the progress of a rehabilitation programme. The objective of this study was to design a manual device for use in the clinical setting. Manual measurement of spastic ankle joint stiffness has historically been conducted using hand-held dynamometers or alternative devices, but some difficulties have been reported in controlling the velocity applied to the ankle during the measurement. In this study, a manually operated device was constructed with a footplate, a torquemeter and a potentiometer. It was mechanically designed to rotate around an approximated axis of the ankle joint and to measure ankle joint angular position and its corresponding resistive torque. Two stroke hemiplegic subjects pariticapted in a pilot study. The results suggested that difficulty in controlling the applied velocity might be complemented by presenting torque data as a function of peak angular velocity in each stretching cycle. Moreover, the results demonstrated that the device could potentially apply a wide range of angular velocities and provide potentially useful clinical information. Quantitative data successfully acquired using this method included the approximate ankle angular position, where the velocity-dependent characteristics of stiffness was notably initiated and its corresponding torque and velocity.

Effects of vocalization on elbow motion during reaching in persons with hemiparetic stroke

To observe the effect of self-vocalization on the quality of movement of each arm during a reaching task in people with left hemiparetic stroke. The design of this study is a single-blinded, within subject, repeated measures design. Fourteen right-handed participants with left hemiparetic stroke were requested to perform a reaching task with each arm, with and without self-vocalization. A 3-D motion analysis system measured the peak angular velocity, time to peak angular velocity, and movement unit in elbow motion. In the unaffected dominant right arm, movements during the reaching task with vocalization were faster, smoother, and more efficient than without vocalization. The peak angular velocity (p < 0.05) and time to peak angular velocity (p > 0.05) increased. The movement unit decreased significantly (p < 0.05). However, in the affected non-dominant left arm, the movement with vocalization was slower, rougher, and less efficient. The peak angular velocity decreased (p > 0.05). Time to peak angular velocity (p < 0.05) and the movement unit increased significantly (p < 0.05). Self-vocalization provided a positive effect on reaching movement of the dominant side but a negative effect on reaching movement of the non-dominant side in right handed persons with left hemiparetic stroke.

A Comparison of Age Level on Baseball Hitting Kinematics

We propose that learning proper hitting kinematics should be encouraged at a young age during youth baseball because this may help reinforce proper hitting kinematics as a player progresses to higher levels of baseball in their adult years. To enhance our understanding between youth and adult baseball hitting, kinematic and temporal analyses of baseball hitting were evaluated with a high-speed motion analysis system between 12 skilled youth and 12 skilled adult baseball players. There were only a small number of temporal differences between youth and adult hitters, with adult hitters taking significantly greater time than youth hitters during the stride phase and during the swing. Compared with youth hitters, adult hitters a) had significantly greater (p < .01) lead knee flexion when the hands started to move forward; b) flexed the lead knee over a greater range of motion during the transition phase (31 degrees versus 13 degrees); c) extended the lead knee over a greater range of motion during the bat acceleration phase (59 degrees versus 32 degrees); d) maintained a more open pelvis position at lead foot off ground; and e) maintained a more open upper torso position when the hands started to move forward and a more closed upper torso position at bat-ball contact. Moreover, adult hitters had greater peak upper torso angular velocity (857 degrees/s versus 717 degrees/s), peak left elbow extension angular velocity (752 degrees/s versus 598 degrees/s), peak left knee extension angular velocity (386 degrees/s versus 303 degrees/s), and bat linear velocity at bat-ball contact (30 m/s versus 25 m/s). The numerous differences in kinematic and temporal parameters between youth and adult hitters suggest that hitting mechanics are different between these two groups.

Does Endurance Fatigue Increase the Risk of Injury When Performing Drop Jumps?

Although from an athletic performance perspective it may be beneficial to undertake drop jump training when fatigued (principle of "specificity" of training), such endurance fatigue may expose the body to a greater risk of injury if it causes an increase in peak impact accelerations. This study aimed to determine if endurance fatigue resulted in an increase in tibial peak impact acceleration and an associated change in knee kinematics when completing plyometric drop jumps. Fifteen females performed drop jumps from 3 heights (15, 30, and 45 cm) when fatigued and nonfatigued. Treadmill running was used to induce endurance fatigue. The following variables were assessed: tibial peak impact acceleration, knee angle at initial ground contact, maximum angle of flexion, range of flexion, and peak knee angular velocity. Fatigue resulted in significantly greater (p < 0.05) tibial peak impact acceleration and knee flexion peak angular velocity in drop jumps from 15 and 30 cm, but not from 45 cm. Fatigue had no effect on any of the knee angles assessed. The neuromuscular system was affected negatively by endurance fatigue at 15 and 30 cm, indicating that coaches should be aware of a potential increased risk of injury in performing drop jumps when fatigued. Because from the greater drop height of 45 cm the neuromuscular system had a reduced capacity to attenuate the impact accelerations per se, whether nonfatigued or fatigued, this would suggest that this height may have been too great for the athletes examined.