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This investigation examined the effects of 4 weeks of non-dominant arm suspension on the functional and structural characteristics of the triceps brachii muscle of 6 normo-active college age males (age: 23.3 ±0.8 yrs, height: 176.1 ±3.7 cm, weight: 75.9 ±5.8 kg). The primary intent of this study was to determine if arm suspension is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding suspension in a standard arm sling and immediately following removal of the sling. To suspend the arm the sling was worn during waking hours. Subjects were allowed to remove the sling during sleep and bathing. Specific instructions were given to avoid use of the arm. Torque production (Nm) during maximal isometric extensions at 90° significantly declined (p<0.05) in response to arm suspension (53.93 ±5.07 to 47.90 ±5.92; 12%). There was no significant change (p>0.05) in the force-velocity attributes of the triceps over the other measured velocities (60, 90, 120, 180, 240, 300°/sec). Cross-sectional muscle area (CSA) of the upper arm diminished significantly (44.26 +2.66 to 42.43 ±2.54 cm2; 4%) following the 4 weeks of unloading (p<0.05). Histochemical analysis of individual muscle fibers demonstrated reductions in fiber CSA of 27 and 18% for type I and type II fibers, respectively, however these changes were not statistically significant (p>0.05). Amplitude of the IEMG signal during maximal isometric contraction of the long head of the triceps fell (p<0.05) by 21 in response to the 4 week suspension period. The changes in triceps muscle structure and function found with arm suspension are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings suggest that arm suspension may provide a useful model for simulating the effects of microgravity on human skeletal muscle. / School of Physical Education

The perception of isometric forces was examined under normal conditions, during sustained constant force contractions, and during vibration of the muscle tendon. In these experiments a contralateral limb matching procedure was employed, and force and the brachial biceps and triceps electromyogram (EMG) were recorded from each arm. Under normal conditions it was found that smaller forces were consistently overestimated in magnitude. During sustained constant force contractions the matching forces exerted by the unfatigued arm increased linearly as did the EMG of the fatiguing muscle. These results are consistent with force judgements being made with respect to the excitatory input to the reference muscle. It was further determined that during fatigue subjects were unable to dissociate the force of exertion from the motor command generating the contraction. Muscle tendon vibration increased the variability of force judgements and resulted in the overestimation of forces. This appeared to be due to co-contraction of the antagonist triceps muscle during vibration of the contracting biceps. The increase in the perceived magnitude of force during vibration is again consistent with the centrally-mediated theory of force perception.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Physics. / Microfiche copy available in Archives and Science. / Includes bibliographical references. / by Patricia Canty. / M.S.

The present study investigated the patterns of interlimb organization during the concurrent performance of asymmetrical reaching movements. The inherent tendency towards interlimb synchronization often constrains activities requiring the two limbs to move over different distances or at different movement speeds. The study of bimanual coordination has shown that the amount of interlimb interference during bilateral performance of asymmetrical actions, is regulated according to the magnitude characteristics of the variable used to introduce the asymmetry between the limbs. The purpose of the present study was to examine the relationship between the degree of interlimb decoupling and the magnitude of the asymmetry between the limbs. Asymmetry was systematically manipulated by scaling the magnitude of the interlimb difference in final target distance, during bimanual performance of reaching movements. The degree of interlimb decoupling was reflected in the movement time, muscle activity onset and joint torque relationship between the limbs. / Decoupling of the asymmetrical limb movements was effected by an earlier onset of the antagonist muscles in the constrained limb which scaled the amount of muscle torque production and therefore the stiffness of the limb during the acceleration phase of the movement. Thus, the movement amplitude differentiation was achieved by an initial accelarative impulse attributed to the differential control of the muscle torque production at each joint. On the other hand, the interactive forces played a secondary role in the degree of decoupling process. Overall, the degree of decoupling scaled according to the magnitude of the interlimb difference in distance; the greater the asymmetry, the greater the differentiation between the limbs. However, systematic variations of the interlimb asymmetry in distance gave rise to a wide variety of individual decoupling trends. Bimanual practice of the asymmetrical reaching tasks did not result in the development of more independent limb movements. The results of the present study have implications to human factor design and ergonomics.

The purpose of this dissertation was to determine if the CNS produces relatively simple alterations in muscle activity to accomplish goal-directed reaching motions of the upper limb under a variety of movement conditions. / To this end, six subjects performed goal-directed arm movements in the horizontal plane. Two movement amplitudes (300 mm and 400 mm) were completed at a moderate speed (1050 mm/s) and as-fast-as possible. The speed and amplitude conditions were repeated for the 45$ sp circ$ and 90$ sp circ$ movement directions. Finally, each of the movement conditions mentioned thus far, were performed within the right and left sections of the work-space. Surface electro-myographic activity was recorded from the pectoralis major, posterior deltoid, biceps brachii short head, brachioradialis, triceps brachii long head, and triceps brachii lateral head. Motion recordings were obtained with a spatial imaging system that monitored the positions of infrared emitting diodes attached to the subject's upper arm and forearm-hand complex. / Several simplification schemes were found to be operative at the level of the electro-myogram. These include: (a) simple timing relationships for agonists between joints and agonist/antagonist intermuscle latencies within each joint; (b) tightly coupled timing between agonists within a single joint; (c) for a particular movement direction, the form and shape of EMG burst activity followed a strategy associated with modulation of pulse height and width; (d) the slope, duration, and onset were further affected by the direction of hand movement which resulted in the greatest RMS-EMG signal amplitude, changing in a predictable manner, and finally (e) there was tuning in which elbow muscles were activated earlier for goal-directed arm movements in the left area of the work-space.

M.Tech. (Chiropractic) / Aim: The aim of this study was to determine the effects of chiropractic adjustment therapy (CAT) to the cervical spine on the reflex motorneuron excitability of C5 and C6 nerves on the biceps brachii muscle bilaterally. This study was also aimed at measuring the subsequent increase in strength of the biceps brachii muscle. Method: A selection of 30 participants, male or female and between the ages of 18 and 40 were recruited. Participants had to meet all the inclusion criteria and present with no contra-indications. Only one group was used as each participant served as their own control. Participants were seen seven times over a period of three weeks. The measurements were taken during the 1st, 4th and 7th consultations. On the 2nd, 3rd, 5th and 6th consultations only treatment was applied. On the 7th consultation only data was collected and no treatment was done. Results: Statistically significant improvement of dynamometry and electromyographic measurements were noted over the consultation periods on both sides. No conclusion could be made regarding the comparison of dynamometer and sEMG measurements of the biceps brachii between each consultation and between each side (left and right) over the study period. Conclusion: Based on the results obtained in this research it may be deduced that CAT may have an effect on the neurological system and further more an effect by increasing motorneuron excitability at sites distant to the spine itself. These results are important to the Chiropractic profession as it shows that CAT does not only produce a segmental response, but that there are wide spread effects on structures distant to the spinal column. The extent of the effects CAT can elicit on the nervous system requires further investigation.

No description available.

No description available.

Submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, Durban, South Africa, 2016. / Background The electromyographic response post-spinal manipulation may support the elucidation of the underlying neurophysiological mechanism of spinal manipulation on motor activity as well as on arthrogenic muscle inhibition. The literature shows conflicting evidence regarding the excitatory or inhibitory nature of the reflexive electromyographic response and the excitability of the homonymous motor neuron pool post-spinal manipulation. The current study investigated whether the electromyographic response post-spinal manipulation is affected by a facilitated golgi tendon organ Ib inhibitory di-synaptic spinal reflex as part of the convergent input on the homonymous motor neuron pool excitability. Objectives The objectives of this placebo-controlled, single-blinded, repeated measures design were: 1) to determine electrical activity and muscle force of the biceps brachii muscle immediately before and after an Activator Adjusting II Instrument placebo spinal manipulation, 2) to determine electrical activity and muscle force of the biceps brachii muscle immediately before and after a C5/C6 spinal manipulation, 3) to compare the electrical activity and muscle force of the biceps brachii muscle between the control and intervention groups pre- and post-test. Method Each participant performed three sets of modified stretching of the biceps brachii muscle with two minute rest intervals between each set in a single appointment, of which at a standardized fourth second during each set an intervention was applied to the ipsilateral C5/C6 segment. The first intervention (AAI 1) entailed the application of an Activator II Adjustment Instrument placebo spinal manipulation; the second intervention (AAI 2) entailed the application of an Activator II Adjustment Instrument placebo spinal manipulation; and the third intervention (SMT) entailed the application of spinal manipulation. One-second electromyography (EMG) segments were taken during the force plateau of each set; the EMG signal was processed through Root Mean Square (RMS) analysis and the muscle force data were obtained by using the Biopac - MP 150 Data Acquisition system and AcqKnowledge analysis software. Results The objective data analysis revealed a noteworthy scientific finding of a medical anomalous inverse relationship between the muscle force and EMG RMS immediately post-spinal manipulation. The immediate post-SMT intervention revealed an increase in the biceps brachii muscle force by 4.76 % and a decrease in the biceps EMG RMS by 9.03 % with a summation of percentage difference between the muscle force and EMG RMS of 13.79 %. The immediate post-placebo AAI 1 intervention showed a decrease in the biceps EMG RMS by 1.86 % and a decrease in the biceps brachii muscle force by 0.85 % with a summation of percentage difference between the muscle force and EMG RMS of 1.01 %. The immediate post-placebo AAI 2 intervention showed a decrease in the biceps EMG RMS by 0.05 % and a decrease in the biceps brachii muscle force by 1.97 % with a summation of percentage difference between the muscle force and EMG RMS of 1.92 %. Conclusion Further research is warranted to add statistical significance to the inverse relationship between muscle force and EMG RMS observed immediately post-spinal manipulation. This knowledge obtained, may have clinical relevance for rehabilitation practitioners and physical therapists by providing evidence based support for the suggestion that optimal management of patients with muscle weakness suspected to be of arthrogenic nature could include the application of spinal manipulation to the segmentally innervated facet joints before traditional strength training is initiated. / M