Lawrence Abraham

University of Texas at Austin | UT · Department of Kinesiology and Health Education

Objective This study examined whether “hang”, an extended period of greatly reduced or zero vertical velocity of the head and trunk created by inter-segmental interactions, would be seen during skilled volleyball player spike jumps. Method: Fifteen skilled volleyball hitters (eight men and seven women, age 23.26 ± 3.22 years, height 1.86 ± 0.08 m,...

The authors investigated how varying the required low-level forces and the direction of force change affect accuracy and variability of force production in a cyclic isometric pinch force tracking task. Eighteen healthy right-handed adult volunteers performed the tracking task over 3 different force ranges. Root mean square error and coefficient of...

In a previous study, we found that hang-time can have potential benefits on athlete performance during volleyball spikes, but hang-time usually comes at a cost of decreased peak height. To address this loss in peak height, we tested whether the trajectories of the " non-performing segments " (legs and non-hitting arm) can be modified to maximize th...

This study examined pilot data exploring approaches to testing whether the existing explanation about the biomechanics of hang-time in a basketball jump shot proposed by Bishop and Hay (1979) is applicable for spike jumps in volleyball and to identifying possible additional factors that could have an influence on hang-time in volleyball. Kinematics...

In a study of the cues involved in spontaneous alternation in which the first turn took place in one maze and the second turn in a different maze, we found: (1) identical levels of significant, above-chance, alternation whether the mazes were parallel or perpendicular to each other; (2) blinding did not affect alternation rates; and (3) bilateral v...

Understanding the effects of age and gender on pinch strength, variability, and accuracy and how one's hand function changes with age better enables those in the preventative and rehabilitative fields to combat these losses. The present study examined fine motor maximum pinch strength [maximum voluntary isometric contraction (MVIC)] as well as the...

This paper attempts to identify the factors which enable certain highly skilled divers to enter the water without apparent splash. Twelve national and international caliber competitive platform divers each performed four fall-ins from a 7.5-m platform. Two kinds of rip entries (non-seething and seething), as well as non-rip entries, were filmed abo...

Activity patterns of four major muscles were studied in the support leg during a standard one foot balance test. Electromyographic (EMG) activity of the tibialis anterior (TA), peroneus longus (PL), gluteus medius (GM), and adductor magnus (AM) was recorded from 10 boys (aged 7-9 yr) during 30 s balance trials. Rectified, low-pass filtered EMG data...

The UTeach secondary mathematics and science teacher preparation program has recently undergone national replication based on its ability to increase recruitment and retention of mathematics and science teachers, of which there is a national shortage. The Noyce Scholarship program represents a primary effort of the National Science Foundation to in...

Therapeutic effects of functional electrical stimulation (FES) cycling for persons with spinal cord injury (SCI) are limited by high rates of muscular fatigue. FES-cycling performance limits and surface mechanomyography (MMG) of 12 persons with SCI were compared under two different stimulation protocols of the quadriceps muscles. One strategy used...

The University of Texas at Austin's Cockrell School of Engineering, College of Education, UTeach Natural Sciences program and the Austin Independent School District are collaborating to develop and deliver UTeachEngineering, an innovative, design-based curriculum for preparing secondary teachers to meet the growing need for engineering teachers in...

To examine the usefulness of a biomechanical measure, resistance torque (RT), in quantifying spasticity by comparing its use with a clinical scale, the modified Ashworth scale (MAS), and quantitative electrophysiological measures. This is a correlational study of spasticity measurements in 34 adults with traumatic brain injury and plantarflexor spa...

A prospective, case-control design. To develop a kinematic model that characterizes frequently observed movement patterns in patients with low back pain (LBP). Understanding arthrokinematics of lumbar motion in those with LBP may provide further understanding of this condition. Digital fluoroscopic video (DFV) was used to quantify the magnitude and...

A clinical prediction rule (CPR) has been reported to identify patients with low back pain who are likely to benefit from stabilization exercises. The aim of this study was to characterize the spinal motion, using digital fluoroscopic video, of a subgroup of subjects with low back pain. Twenty subjects who were positive on the CPR were compared wit...

Although both starting position and stretching velocity play an important role in reflex response, their interaction with stretch reflexes has not been thoroughly investigated. This study examined the interaction effect of starting position and stretching velocity on the reflex threshold angle (RTA) of the stretch reflex in the soleus muscle of nor...

Methodological reliability. Develop a measurement technique to assess dynamic motion of the lumbar spine using enhanced digital fluoroscopic video (DFV) and a distortion compensated roentgen analysis (DCRA). Controversy over both the definition and consequences of lumbar segmental instability persists. Information from static imaging has had limite...

Synergy generally refers to the coordinated action of several motor elements to produce a specific motor task, either intentionally or automatically. One example is motor irradiation, a sudden spread of synergistic muscular coactivation resulting from a forceful single joint movement. To investigate this type of synergy pattern, a quantitative EMG...

Fundamental to intralimb coordination in the lower extremity, ankle-knee synergy induced by motor irradiation has long been employed to secure facilitation of paralyzed muscles. This study, a companion research subsequent to the time amplitude analysis of surface electromyography in part 1, was to investigate the recruitment strategy of irradiated...

This study examined the extent to which a battery of tests could detect a reduction of plantarflexor spasticity resulting from cryotherapy. The tests included a traditional qualitative spasticity scale, three potential quantitative spasticity measures and a measure of voluntary ankle muscle function. Twenty-six adult traumatic-brain-injured subject...

To investigate a possible ankle-knee synergy, experiments with normal subjects were performed to compare changes of the quadriceps motor pool excitability due to ankle position and effort. Vastus medialis H reflex amplitude was examined during ankle isometric contractions conditioned by different ankle positions (dorsiflexion, neutral, and plantarf...

Rapid, goal-directed elbow flexion movements were examined under interacting conditions of inertial loading and resistance to movement initiation. The resistance ceased when movement began, resulting in quick release movements. Inertial load slowed the movement and lengthened the agonist and antagonist electromyographic (EMG) burst durations. The q...

The activity of certain muscles that cross the elbow joint complex (EJC) are affected by forearm position and forearm movement during elbow flexion/extension. To investigate whether these changes are based on the musculoskeletal geometry of the joint, a three-dimensional musculotendinoskeletal computer model of the EJC was used to estimate individu...

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Although the Modified Ashworth Scale (MAS) is commonly used to assess the severity of muscle spasticity for ankle plantarflexors, its reliability has only been established for elbow muscles. Interrater reliability, intrarater reliability and temporal (between-days) reliability were examined in this study. Also, interrater reliability for use of the...

This paper describes the development and evaluation of a musculoskeletal model that represents human elbow flexion-extension and forearm pronation-supination. The length, velocity, and moment arm for each of the eight musculotendon actuators were based on skeletal anatomy and joint position. Musculotendon parameters were determined for each actuato...

This study of plantar flexor spasticity describes relationships among a traditional qualitative spasticity scale, three potential quantitative spasticity measures and a measure of voluntary ankle muscle function. Thirty-four volunteer adult patients with traumatic brain injuries participated. There were 28 males and 6 females; the mean age was 30.3...

Two criteria reported in recent literature were compared with the criterion of 95% probability (using analysis of variance) for their abilities to detect significant differences in M-waves due to repositioning of the ankle joint during human soleus H-reflex testing. Data from five normal adult males were analyzed using all three rejection criteria,...

The human elbow joint complex (EJC) is an intricate joint which produces combinations of movements that are unique within the human body and that are involved in performing many important tasks. This paper discusses an on-going study to predict muscle force patterns in elbow flexion-extension. Four musculotendon actuators are included in this preli...

This paper describes a musculoskeletal model that represents human elbow flexion-extension and forearm pronation-supination. Musculotendon parameters and the skeletal geometry were determined for the musculoskeletal model in the analysis of ballistic elbow joint complex movements. The key objective was to develop a computational model, guided by op...

The dynamics of planar human body motion, solved with a non-iterative matrix formulation, is presented. The approach is based on applying Newton-Euler equations of motion to an assumed 15 body segment model resulting in a system of 48 equations. The system of equations was carefully ordered to result in a banded system (bandwidth = 10) which is sol...

In order to examine interactions between centrally initiated postural activity preceding voluntary arm movements and compensatory postural activity, we studied patterns of postural muscle activity preceding a vigorous bilateral reach and grasp task or triggered by support surface motion. The reaching task required movement onset to be coincident wi...

In this study we evaluated the physiological and biomechanical responses of 'elite-national class' (i.e., group 1; N = 9) and 'good-state class' (i.e., group 2; N = 6) cyclists while they simulated a 40 km time-trial in the laboratory by cycling on an ergometer for 1 h at their highest power output. Actual road racing 40 km time-trial performance w...

Previous evidence has shown a marked increase in motoneuronal excitability during muscle contraction and decreased post-contraction excitability. This post-contraction inhibition has been shown to persist up to 800 msec following the end of contraction (Gottlieb and Agarwal, 1973) and apparently continues with gradual recovery up to one minute (Eno...

This paper describes the research background and computer graphics techniques used to model the musculoskeletal system of the human arm. The model is part of an on-going research project that integrates computational dynamics, biomechanical data acquisition, and computer graphics workstations to study the musculoskeletal function of the human upper...

Rapid 90 degree elbow flexions were performed under varying loads (X1, X2, X3 moment of inertia) and varying resistance to movement initiation (0, 40, 70% maximal isometric torque). Surface EMG from biceps brachii and triceps brachii and movement kinematics were measured. Increasing load increased reaction time (RT), movement time to 45 and to 90 d...

A study was conducted of ten subjects to evaluate electromyographic (EMG) correlates to learning during manual control tracking. Subjects were seated in front of a CRT screen and manually tracked two different trajectories on two different days. The surface EMG signal was gathered from the supinator longus muscle and RMS-averaged over one-half-seco...

An experiment was conducted to evaluate various methods for smoothing human motion data that has been subjected to noise during the filming and digitization process. Orthogonal accelerometers were attached to the subject's leg, and records of complex dynamic kicking motions were recorded on film and simultaneously sampled through an A/D converter o...

The purpose of this investigation was to examine and compare the simultaneous electromyographic activity from surface and implanted wire electrodes of an antagonist pair of muscles during a reversal stretching technique. Previous studies reported increased electromyographic activity of a muscle being stretched during antagonist muscle activation. F...

To the Editor In a postscript to an article published in the January 1987 issue of Physical Therapy, Ms. Sandra Condon and Dr. Robert Hutton took issue with one of our recent publications on the same topic.¹ Specifically, Condon and Hutton claimed that we had “misquoted the findings” of an earlier study from their laboratory² and that we drew erron...

Among modern stretching techniques none has clearly been shown to be the most effective for increasing range of motion. The most common stretching method comparisons are between static stretching (SS) and one or more Proprioceptive Neuromuscular Facilitation (PNF) technique(s). The two most frequently implemented PNF techniques are: contract-relax...

The effects of 3 stretching methods on the motor pool excitability of the soleus muscle as measured by the Hoffmann reflex have been compared with the objective of revealing central nervous system influences promoting muscle compliance to lengthening. The H-wave was reduced slightly throughout the static stretch method. The contract-relax (CR) meth...

In order to better understand the organization of the locomotor control system, we examined the temporal patterns of distal hindlimb muscle responses to brief electrical stimulation of cutaneous nerves during walking on a treadmill. Electromyographic recordings were made from twelve muscles; stimuli were applied individually to three nerves at rand...

Chronic recordings were made of electromyographic (EMG) activity, tension, and length of distal hindlimb muscles in six cats performing a variety of normal motor tasks. Muscles studied thoroughly or in part were medial gastrocnemius, lateral gastrocnemius, plantaris, soleus, flexor digitorum brevis, flexor digitorum longus, flexor hallucis longus,...

In order to better understand the organization of the locomotor control system, we examined the temporal patterns of distal hindlimb muscle responses to brief electrical stimulation of cutaneous nerves during walking on a treadmill. Electromyographic recordings were made from twelve muscles; stimuli were applied individually to three nerves at rand...

The 2nd author (1972) proposed that the caudate nucleus was involved in processing sensory (especially vestibular) cues for egocentric spatial orientation. The present experiments examined the effect of caudate nucleus lesions on a return from passive transport (RPT) task, which has been shown to depend on vestibular input. In Exp I, 18 male Long-E...

25 male Long-Evans rats were trained to return to a water spout after being passively transported away from it along paths containing a 90° turn. The task was successfully relearned after enucleation. Subsequent vestibular nucleus damage produced a severe, lasting deficit in this task when compared with the effects of cerebellar cortex lesions. In...

This study was designed to measure the interaction of 8 weeks of endurance running and chronic ethanol consumption upon skeletal muscle mitochondria. Male Sprague-Dawley rats were assigned to 1 of 4 groups; ethanol diet sedentary (SED-E), ethanol diet trained (RUN-E), control diet sedentary (SED-E), and control diet trained (RUN-C). The ethanol gro...

While a wealth of evidence has implicated the nigrostriatal dopamine system in the initiation of movement, most or all of these movements have been in a conditioned avoidance framework, and on the order of 3-14 seconds in latency. It is proposed here that an elucidation of dopaminergic involvement in movement initiation requires a behavioral paradi...

The relationship between voluntary movement initiation (VMI) and caudate nucleus dopamine receptor dynamics was analyzed in two rat strains. Charles River CD/F F-344 (CR-CD/F) and Zivic-Miller CD (ZM-CD) rats (male, 125-150 g) were trained to rapidly release and reset a response lever to avoid electric shock. Whereas 86% of all CR-CD/Fs completed t...

The responses of 157 neural units in the magnocellular (mc) and parvocellular (pc) components of the medial geniculate nucleus (MG) and other nuclei of the posterior (PO) thalamic group were recorded and analyzed. Units were tested for a response to electrical stimulation of the vestibular nerve, natural auditory and electrical cochlear nerve stimu...

The rostral projections of the vestibular system were investigated in cats by applying electrical stimulation separately to the vestibular and cochlear nerves while recording from the medial geniculate body and the anterior suprasylvian region of the cerebral cortex. Complete ablation of the cerebellum and transection of the medial longitudinal fas...

A technique for vestibular neurotomy in the rat has been developed. Removal of the tympanic membrane and ossicles through the external auditory meatus permits access to the auditory bulla. After the pterygopalatine artery has been cauterized, and the electrode may be introduced through the oval widow. The vestibular branch of the VIII nerve can the...

The primary purpose of this study was to observe the relationship between muscle activation of the right hand with the force produced at the fingertips in an isometric precision pinch tracking task. Thirty right-handed subjects, 15 males and 15 females, with a mean age 23.5 (SD 3.5) years, free from any neurological disorder or physical ailment, ha...