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Biomedical subjects

F A Harris

Publications and source records attributed to F A Harris.

9 recordsLinked to original sources
PubMed1979

Treatment with a position feedback-controlled head stabilizer.

A position feedback-controlled head stabilizer has been developed to provide cerebral palsied individuals with resistive exercise to strengthen the neck musculature. This apparatus detects "involuntary" head motion and stabilizes the head by applying opposing forces; it also can be used to facilitate muscular contraction by resisting the subject's voluntary movements. The purpose of the present study was to determine whether voluntary head control in cerebral palsied individuals can be improved through systematic exercise using the stabilizer to strengthen the muscles of the neck and improve their balance of action. The findings support the author's contention that this is possible. The apparatus consists of a helmet and shoulder pads, interconnected so that the head is supported in the helmet by a manipulator arm. At its lower end, the manipulator arm is attached to the shoulder pad mounting frame via a gimbal assembly which allows head movement in two planes of tilt (pitch, or forward-and back, and roll, or side-to-side). Feedback control circuitry is so arranged that any deviation of the head from the desired position leads to actuation of pneumatic cylinders, which apply torques to the manipulator gimbal axes so as to oppose or conteract the incipient head movement. It is particularly significant that none of these patients participating in these experiments were at all apprehensive about or resisted being placed in the apparatus. (Even the youngest subject to use the apparatus--five year old-- did not mind being restrained by the shoulder pads or having his head gripped by helment.) While JG utilized the safety release valve quite often during the first few head control training sessions, he soon became confident enough in the action of the stabilizer that he did not even bother to grip the handle of the release valve. While DA had the action of safety valve explained and demonstrated for her, she never bothered to use it even from the outset of her experience with the stabilizer. Thus, it seems that the football shoulder pads use to stabilize the shoulders and the hockey helmet used to grip and manipulate the head actually make the apparatus attractive to younger patients, while the padding thereby provided makes it comfortable enough to be tolerated well by older individuals. And, the subject's knowing that he has an override control by means of which he can assert command over the entire system appears to be of psychological benefit in establishing confidence in both the apparatus and the investigator.

Adolescent↗
PubMed1978

Muscle stretch receptor hypersensitization in spasticity. Inapproprioception, Part III.

The author's concept of Inapproprioception, which accounts for athetoid movements in terms of defective proprioceptive feedback (i.e., distortion of afferent signals representing limb position) is extended here to explain spasticity in cerebral palsy was well. Descending activation of gamma efferents supplying hypertonic muscles may be excessive, leading to hypersensitization of stretch receptors in those muscles (the exact distribution of muscles affected varying with the individual). The result is exaggerated reflex activation of alpha motoneurons in response to the slightest muscle stretch. Even passive tension due to gravitational forces, which is inescapable, results in excessive impulse discharge from sensitized stretch afferents and thus leads to reflex contractions simply in response to shifts in body position. The affected muscles shorten to a length corresponding to the elevated level of reflexly originating motoneuron discharge, manifesting excessive tone even in the contracted state. The distribution of hypertonicity thus induced usually follows a predictable pattern and can be modified using slow passive stretch of hypertonic muscles to relax them, followed by facilitated voluntary contraction to strengthen weak antagonists, and progressing to functional reciprocal usage of agonists and antagonists to achieve proper muscle balance. Application of this procedure leads to improved posture, balance and ambulation in subjects with spastic cerebral palsy.

Adolescent↗
PubMed1978

Correction of muscle imbalance in spasticity.

A summary is presented of observations made and results obtained during evaluation and preliminary treatment of twenty-one predominantly spastic cerebral palsied subjects, whose neuromuscular function was studied in each of four positions (supine, prone, kneeling and sitting on the floor) and in three dynamic situations (rising to standing, maintaining standing balance, and ambulating). A description is given of the procedures utilized to; (i) correct the imbalance of muscle tone imposing abnormal "resting" joint positions and limiting the range of their voluntary movements, and (ii) assist them in developing the sensorimotor function requisite for postural stability and voluntary motor control, involving exercises performed in each of the four positions and in transitions between them. Resistance exercises performed with the investigator and independent exercises both were included in the program. Case studies of a six-year-old spastic with "pre-athetoid" tendencies, an 11-year old spastic and a 32-year-old spastic are provided to illustrate typical initial evaluations, therapeutic activities subsequently utilized to improve neuromuscular function, and results thereby obtained.

Adult↗