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The learning and retention adaptations of muscle activity were studied during a novel multi-joint task. Electromyographic (EMG) signals were recorded from the posterior deltoid, long and lateral heads of the triceps, pectoralis major, biceps and brachioradialis muscles. These data were assayed in a pattern recognition analysis (SVD) to ascertain the minimum number of 'common features' or waveforms (W's) required to describe the set of input EMG patterns (IP). / Fifteen participants performed targeted arm movements, which incorporated the shoulder and elbow articulations, as fast and as accurately as possible in the horizontal plane. Both experimental (E) and control (C) groups were employed. The E group was trained (Day 1 to Day 4) and tested both pre- and post-learning. They were further re-tested during a retention period (RET) consisting of 1, 2, 4, 6 and 8 week post-learning sessions. The C group was tested before and after learning and at the end of the RET period. (Abstract shortened by UMI.)

The present thesis investigated the process of gross motor skill acquisition in the context of how movement pattern characteristics are organized and modified as a result of learning. The process of multisegmental skill acquisition was studied using performance production measures as a window to explore stable and transient changes in the movement control process. Bernstein's principles of exploitation of motion dependent torques, and the minimization of the degree of freedom were tested. / Twenty male subjects performed a total of 240 trials, as fast and accurate as possible, over 4 sessions for two tasks with different level of complexity (10 subjects per task). Kinematic and EMG data were acquired for a two segment model of the arm using a lightweight, adjustable manipulandum, and surface EMG for the PDL, PEC, TRI, and BIC muscles. Movement organization characteristics were revealed by wave pattern analyses performed with a phase breakdown technique, CCCF on torque partitioning components, and the CFs on the muscle activation waveforms. / The experimental protocol allowed enough practice for the tasks to be learned resulting in PT decrease. Consistent adaptations in movement organization were revealed by all three levels of analysis. Improvement in the performance production measures were in the same direction for both learning conditions, and the rate of change within experimental sessions decreased over time. The significant adaptations in movement organization occurred at the critical phases of each task (i.e. the power absorption--phase simple task, and the reversal phase--complex task). The EMG and joint torque components demonstrated significant amplitude and profile changes particularly during the critical phases. The subjects learned to perform the tasks faster by compensating the motion dependent torques components with the muscle torques in time and amplitude. This finding was consistent with the principle of exploitation of motion dependent torques which was enhanced with learning. Significant task specific motor program adaptations were revealed by the SVD analysis. The minimization of the degree of freedom hypothesis is consistent with the increasing covariation observed over learning between the antagonists PEC and BIC in the simple task, and for both the agonists PDL and TRI and antagonists PEC and BIC in the complex task. In addition the results justified the use of waveform analysis on performance production measures, as a method that can reveal important adaptation details in the underlying control mechanisms for gross motor skill.

Patellofemoral pain syndrome (PFPS) is one of the most common, but least understood, knee disorders. Fulkerson (1997) believes that pathology may result from an excessive valgus force being applied to the patella. Researchers have historically examined quadriceps strength and neuromuscular activity and knee kinematics. However, results from these works have not provided conclusive answers. Powers (2003) has theorized that other structures can influence knee function, and researchers have shown that PFPS subjects can exhibit hip weakness and demonstrate altered hip kinematics during functional activities. Although they provide preliminary evidence regarding hip influences, investigations that simultaneously examine hip and knee function in PFPS subjects are needed. The primary purpose of this study was to determine functional performance, strength, neuromuscular activity (amplitudes and onset timing differences), and kinematics of the hip and knee for people diagnosed with PFPS. Eighteen females diagnosed with PFPS and 18 asymptomatic female controls participated. Subjects initially completed a 10-cm visual analog scale. Next, they completed two functional performance tests and underwent a strength assessment for the hip abductors, hip external rotators, and knee extensors. Surface electromyography (EMG) electrodes and reflective markers were donned in order to collect EMG and kinematic data during a stair-stepping task. For this purpose, subjects ascended and descended two 20-cm high steps at a standardized rate. Seven PFPS and seven control subjects were retested five to seven days later to establish measurement reliability. A repeated measures analysis of variance was used to determine group differences. Correlation coefficients were calculated to identify associations between pain and dependent measures; intraclass correlation coefficients were calculated to determine measurement reliability for both control and PFPS subjects. Results from this study showed group differences for functional performance, strength, and EMG amplitudes but none for onset timing differences or kinematics. A strong association was found between pain and hip external rotator strength and EMG amplitudes during stair-stepping. Most tests provided reliable measures with repeat testing. PFPS subjects demonstrated quadriceps dysfunction but even greater hip weakness that was correlated more with pain. Contemporary rehabilitation has focused on quadriceps strengthening; however, results from this study support the importance of the hip.

This study examined muscle activation and relative joint angles during a conventional deadlift while using either a double‐pronated or overhand/underhand (OU) grip. Ten weight‐trained individuals performed the deadlift with 60% and 80% of their 1‐repetition maximum, with three different grip variations. EMG recordings were taken of the left and right biceps brachii, brachioradialis, upper trapezius, and upper latissimus dorsi. Motion capture was used to measure angles of the wrist, elbow, knee, and hip. With an OU grip, significant bilateral asymmetry was seen in EMG activity of biceps brachii and brachioradialis. Mean wrist and elbow angle also showed significant bilateral asymmetry when using an OU grip. Training recommendations for the OU grip deadlift should emphasize the need to vary which hand is supinated/pronated to avoid muscle imbalances and possible injury. Furthermore, it may be preferential to use a double‐pronated grip to avoid asymmetric training altogether.

The purpose of this study was to quantify the EMG activity of selected lower limb muscles during cycling, and to define the relationship between pedal shaft width and muscular involvement. This study has particular significance to the female cyclist who by virtue of pelvic width may have a less efficient pedalling force, or an imbalance of applied muscular force. Variables analyzed were hip, knee, ankle range of motion (ROM), biceps femoris(BF), vastus lateralis(VL), rectus femoris(RF), and vastus medialis(VMO) muscle activity. Significant differences among three different pedal shaft widths were determined through use of repeated measures oneway ANOVA, Newman-Keuls post hoc test. The hip ROM, biceps femoris, and vastus medialis EKG activity results of the present study appeared to indicate that different pedal shaft widths had an effect on changes in the ROM and EMG activity. This study indicated that the hip ROM values increased with an increase in the pedal shaft width. In contary, an increase in pedal shaft width significantly decreased the muscle activity in the vastus medialis while two inch pedal shaft width significantly decreased the muscle activity in the biceps femoris. / School of Physical Education

Prolonged periods in sitting or standing may negatively influence worker health. Integration of sit-stand workstations has attempted to mitigate these deleterious effects, and has generated positive results in terms of postural discomfort, injury risk and worker fatigue. Identification of how identical tasks are affected by sitting and standing is necessary to take advantage of loading differences between these configurations. The purpose of this research was to determine if differences in workplace configurations between seated and standing postures created changes in posture or muscular activity levels during manual materials handling tasks. Twenty male and twenty female participants performed four manual materials handling tasks: a 40N static push, a 40N static pull, a weighted bottle transfer set at 15% of the participant’s maximal arm elevation force, and a light assembly task in sitting and standing. Upper extremity electromyography was collected at 8 sites, and changes in local joint moments and body discomfort were calculated. Interactions between task and sit/stand configuration resulted in increases of up to 500% in some joint moments, 94% in EMG activity and 880% in some local body discomfort regions when tasks were completed in sitting. A main effect of sitting appeared primarily in joint moments and muscle activity, and generally resulted in increased loading in sitting. Important exceptions existed, which included resultant wrist joint loading 8.2 times larger in standing, and foot/shank discomfort increasing by up to 609%. Task differentially affected all EMG outputs, as well as most local joint moments and body discomfort regions. Future recommendations regarding upper extremity exposures during manual materials handling tasks should consider placing workers in standing postures instead of seated ones to minimize musculoskeletal loading to the upper extremity. In addition, the effects of task and sit/stand configuration should be considered in order to leverage differences between these positions, with tasks in standing generally resulting in decreased musculoskeletal disorder risks.

Nearly every voice teacher is aware of problems encountered by students with tightness in the throat or jaw muscles. Classes in vocal pedagogy attempt to solve problems such as these through indirect inference and mental images using psychological and empirical (observation) teaching methods. In fact, many voice teachers will freely admit that singing is mostly a matter of imagination.Traditional teaching methods in voice (an area open to much charlatanism) generally deny the existence of a direct, explicit solution reached through creative problem solving. The purpose of this study was to supply a comparison (through means of accepted research techniques) between students who received traditional instruction in voice and those who received additional scientific information in the form of electromyographic biofeedback to assist them in overcoming the problems of tension or tightness in the muscles supporting the larynx.The population sample of this study consisted of two groups of college voice students suffering from tension problems in the neck and throat.The experimental group consisted of six males and four females, ranging in age from 19 to 43. The control group was made up of nine females and one male ranging in age from 19 to 32.Each subject in the experimental group participated in 10 biofeedback training sessions of approximately one half-hour in length receiving 15 minutes of actual biofeedback during each session. The control group did not receive biofeedback but did receive pre- post-test electromyograms.Data from the two groups was subjected to statistical analysis using the T-test and F-test and the following conclusions were made. In comparing the pre-test means with the post-test mean of the experimental group, a T-test indicated a significant difference at both the 5% and 1% levels of confidence. An F-test between the post-test means of both the experimental and control groups indicated that variations in data did not appear to be due to chance, but to a cause (biofeedback).The null hypothesis was rejected at the 1% level of confidence as a result of the T-test between the post-test means of both the experimental and control group (assuming that the control post-test mean is the population mean). This allows a restatement of the hypothesis in the positive form: There is a significant difference between singers with tension problems in the laryngeal musculature who receive electromyographic biofeedback training and those who do not.The control group clearly showed no significant difference in the pre-test, post-test means at the 1% level of confidence.

Evolutionary accounts of empathy often focus on the ways in which empathy-motivated helping can give rise to indirect fitness benefits. These accounts posit that empathy is adaptive insofar as it motivates strategic helping behavior, but they neglect a key feature of the empathic process – it can prepare one to act effectively within a shared environment. In particular, adopting the affective and motivational states of others provides a rapid and automatic way to avoid danger and threat, which play a disproportionately large role in shaping behavior. Based on the idea that empathic processes facilitate adaptive reactions to threat, I conducted four experiments to test the hypothesis that empathic reactions reflect withdrawal motivation. In the first experiment I used electroencephalography (EEG) to measure baseline right-frontal cortical asymmetry, a reliable neural correlate of withdrawal motivation. I then assessed empathic reactions to images of children ostensibly taken from a charity campaign. Participants who showed greater right-frontal cortical asymmetry also showed stronger empathic reactions to the images. In the second study I used self-report measures fear and anger to assess dispositional withdrawal- and approach-motivation, respectively. This time, participants indicated their empathic reactions to targets experiencing happiness and targets experiencing sadness. Empathy for both types of targets was positively related to fear and negatively related to physical aggression, again supporting a link between empathy and withdrawal motivation. In the third study I measured state withdrawal motivation by using facial electromyography (EMG) to assess disgust expressions towards charity images. These expressions were positively correlated with empathic reactions, demonstrating that state withdrawal motivation is also positively related to empathy. In the final study I manipulated approach and withdrawal emotions by having participants make emotional facial expressions. Focusing on fear and anger, I found that participants were more empathic when making fearful faces than when making angry faces, although these results must be interpreted with caution, as the manipulation may not have had the intended effects on emotional state. Taken together, these four studies provide converging evidence of an association between withdrawal motivation and empathy, supporting the idea that empathy plays a role in the adaptive response to threat.

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.