No description available.

Team lifting is required in many workplaces, particularly where heavy and awkward lifts are prevalent. Despite the known risk factors associated with team lifting, it remains under researched, with almost no 4-person lifting studies. The purpose of this thesis was to investigate how members of a 4-person team coordinate their actions during a lifting task that involved an unexpected release from a single team member. It involved a novel approach to investigating the mechanisms associated with joint action and whether these mechanisms may alert the remaining lifters that a release is imminent, where the goal was to elicit an unexpected response from the group. Data collected for a previous team lifting study was used. Six groups of four male participants (n = 24) performed 30 lifts with a constructed 60 kg lifting apparatus designed to transition between a rectangular (2 x 4 ft or 61 x 122 cm) and a square (2 x 2 ft or 61 x 61 cm) configuration. A total of 8 trials (4 per configuration) were designated as “drop trials”. Vertical force at the hands and right-side electromyography (EMG) of the biceps brachii (BB), anterior deltoid (AD), upper trapezius (UT), and the lumbar erector spinae (LES) was collected for each participant. Means and standard deviation of vertical force was compared from the pre-drop phase for both drop and non-drop (lift) trials. No significant differences were found between drop and non-drop trials during the pre-drop phase. A comparison of time to peak force and time to peak muscle activity was performed for lifters adjacent to the release position. These times were compared against a 25 to 150 ms window to determine whether the muscle activity was considered reflexive or anticipatory to the dropped load. A small proportion of the peak muscle activity values were considered anticipatory (6 BB and 2 LES), suggesting that while it is possible for the dropper to disguise the release, perhaps joint action provides insight to the other lifters. The complex mechanisms that support joint action, their connection to biomechanics and their role in team lifting warrants further research in order to determine how large of a role they might play. / Thesis / Master of Science in Kinesiology

The anatomical structure of the extrinsic finger muscles suggests that posture may play a role in the production of enslaved forces in the fingers. This phenomenon also appears dependent on contraction conditions. The purpose of this thesis was to determine the effect of: (i) wrist posture on the enslaving effect (EE) during ramp and isotonic exertions, and (ii) the rate of force development on EE and accuracy during ramp exertions. Twelve male participants performed 3 submaximal finger flexion and extension trials with the index and ring fingers at 30° wrist flexion, neutral, and 30° wrist extension. Trials consisted of a 5 second isotonic contraction at 25% MVC (maximum voluntary contraction), and two ramp contractions. Ramp contractions were performed at 25% MVC/s and 10% MVC/s up to 50% MVC, a 0.5 second hold, and decreased to zero at the same rate. Surface electromyography was recorded from the compartments of extensor digitorum and flexor digitorum superficialis and analyzed at 25% of maximum. Wrist posture had a significant effect on EE during extension exertions (F4, 44 > 2.6, p < 0.05); specifically, higher EE, error, and muscle activity were found at shorter muscle lengths. Contraction condition significantly affected EE for both index (p = 0.001) and ring finger exertions (p = 0.001). In the fingers adjacent to the task finger, descending phase EE was higher than the ascending phase, which appeared independent of muscle activity. This thesis found that, in extension exertions, neural factors affecting EE were dependent on muscle length, while mechanical factors appeared dependent on the type of exertion. These findings further our knowledge of the complex relationship between neural and mechanical control of the hand and fingers. / Thesis / Master of Science (MSc)

The present research was undertaken to investigate the effects of two independent variables considered potentially important to the reduction of fear through systematic desensitization. The first independent variable investigated was the importance of making covert motor responses when instructions were given to imagine motor behavior. Electromyographic measures were obtained on subjects' covert muscular activity as they imagined themselves raising their arms. The subjects were then classified, on the basis of their average electromyographic responsiveness, as high-responders (those showing relatively high levels when imaging movement) and low-responders. A 2 X 2 analysis of covariance showed a significant difference in the posttreatment scores of the high- and low responders on performance measures, the high-responders performing better. The difference between the two instruction groups was not statistically significant. Additional analyses indicate the importance of the instruction variable is mitigated by the extent to which subjects actually follow the particular instructions given. These data imply electromyography may be used in clinical practice as an assessment tool to determine which subjects are likely to respond to systematic desensitization. They also suggest the possibility of using response measures to train self-monitoring of imagery. Concerning the imagery construct, the present study offers an empirical alternative to the traditional conceptualization. The data obtained support the utility of the analysis of imagery advanced in this paper.

No description available.

Objective: To investigate the potential etiology of a loss of neck control injury in female standard ballroom dancers. The median frequency (MF) as measured by electromyography (EMG) of the left upper trapezius (UT), left splenius capitius (SPL), and right sternocleidomastoid (SCM) of injured dancers was compared to non-injured dancers. This comparison was performed to identify whether dancers with a history of loss of neck control have a greater amount of fatigue than those with no history of this particular injury. Design and Setting: A 2 x 6 factorial design was used for this investigation. The independent variables were group (injured vs. non-injured) and time (before and after the three rounds of dancing). The dependent variables were MF as measured by EMG, range of motion, and neck length. All testing was performed at the university biomechanics laboratory and ballroom dance studio. Subjects: Twenty female subjects (10 injured group {mean height 167.40 ± 4.12 cm and weight 59.30 ± 5.41 kg}, 10 non-injured group {mean height 166.76 ± 4.62 cm and weight 58.93 ± 5.30 kg}), with at least one year experience in competitive ballroom dancing, in the standard division participated in this study. All subjects competed at a Dancesport competition either in the novice, pre-championship, and/or amateur standard classifications. Inclusion criteria for the injured group included female ballroom dancers who had a loss of neck control episode. Measurements: Surface EMG activity was recorded from the left UT, left SPL, and right SCM muscles before and after dancing the five standard dances. Results: The decrease in EMG MF was not significant between groups. There was no difference in neck lengths from the external occipital protuberance to inferior angle of the scapula between groups. There were also no significant differences in range of motion of left and right lateral flexion and extension in either group from pre to post dancing. Conclusions: Based on the results of this study, subjects with a history of neuromuscular neck injury did not appear to have acute fatigue of the three muscles studied here following the routine used in this study.

Differences between humans and extant apes in the pelvis and its key muscle attachment sites are thought to reflect a trade-off between arboreal and bipedal locomotor abilities. Human pelvic morphology enables the hamstrings to effectively power the hip hyperextension necessary for efficient bipedal locomotion, but this morphology is thought to reduce the capacity of these muscles to powerfully extend the hip when in a flexed position typical of arboreal locomotion. This research tested whether the enlarged human gluteus maximus may have been shaped by the continued importance of climbing among humans, as it has been suggested that it plays a compensatory role during powerful hip extension due to the reduced ability of the hamstrings. Musculoskeletal modeling and electromyography were used to assess the relative function of the gluteus maximus and the hamstrings in a human participant across two movement trials that required different amounts of hip extension: 1) bipedal walking, and 2) standing from a deep squat. It was hypothesized that the gluteus maximus would perform more effectively than the hamstrings to power hip extension from the flexed position of the squat. Differences in relative muscle activity across the two motions support this hypothesis in general, and implications for the evolutionary significance of the human gluteus maximus are that this muscle plays an important and likely compensatory role with the hamstrings during both standing up from a squat and bipedal walking. Results support the growing body of research that indicates that it is important to consider a broader range of human locomotive repertoires as of evolutionary significance, beyond solely terrestrial bipedal locomotion. / Graduate

Cross education is the phenomenon by which the untrained limb will experience a gain in strength following a unilateral resistance training program. However, little is known as to the underlying adaptation occurring in the untrained limb. Purpose: To examine the effect of dynamic unilateral resistance training on the strength and neuromuscular adaptations of both the trained and untrained legs. Methods: Eight previously untrained males (22.38±2.92 y, 1.73±0.08 m, 75.26±14.53 kg) completed a four-week unilateral resistance training program, while another eight untrained males (24.00±4.57 y, 1.84±0.05 m, 94.21±16.14 kg) served as controls. Isometric leg extension strength, leg press 1 repetition maximum (1RM), leg extension 1RM, root mean square of the maximal electromyographic amplitude (EMG), submaximal EMG, dynamic neuromuscular economy (NME) and the slope of NME-power output relationship were determined before and after training to assess the changes in strength and neuromuscular adaptations of the vastus lateralis (VL) and rectus femoris (RF) in both the trained and untrained legs. The unilateral resistance training program was conducted on the dominant leg (DOM) in the unilateral resistance training group (URT) and was compared to the dominant leg of the control group (CON). Cross education was measured in the nondominant leg (NON) for both groups. The unilateral resistance training program was completed three days per week for a total of twelve training sessions. Exercises included in the training program were unilateral leg press, unilateral leg extension, bilateral chest press and bilateral low row. All data was analyzed using one-way analysis of covariance of the post-testing values using the pre-testing values as the covariate. Further analysis of the EMG and NME data was performed using magnitude-based inferences. Results: The URT group improved their isometric (DOM:11.03%, NON:4.98%), leg press (DOM:77.63%, NON:64.88%) and leg extension (DOM:46.76%, NON:16.43%) strength after the four weeks of resistance training. There was no difference between the groups in isometric strength in the dominant (p=0.188) or nondominant (p=0.948) leg. For leg extension 1RM, there was a significant difference between groups in the dominant leg (p=0.018), but not the nondominant leg (p=0.482). However, there were significant group differences in both the dominant (p=0.003) and nondominant (p=0.034) leg for leg press 1RM. In terms of maximal EMG, the training groups improved in the vastus lateralis (DOM:29.81%, NON:31.44%) and rectus femoris (DOM:20.71%, NON:6.26%) individually, as well as in total EMG (DOM:24.78%, NON:17.57%). There was a Likely Positive or Very Likely Positive effect of unilateral resistance training on the changes in maximal EMG of the vastus lateralis and rectus femoris in both the dominant and nondominant legs. There was a Likely Positive effect of unilateral resistance training on the submaximal EMG of the dominant vastus lateralis at 75 and 125 watts. Conversely, in the rectus femoris, there was Unclear effects of unilateral resistance training on the submaximal EMG of the dominant leg. There was no consistent effect of unilateral resistance training on submaximal EMG values of the vastus lateralis in the nondominant leg. However, the rectus femoris in the nondominant leg experienced a Likely Positive effect of unilateral resistance training on submaximal EMG. NME improved in the URT group in the VL at 75 (DOM:9.73%, NON:13.42%), 100 (DOM:8.76%, NON:8.21%), and 125(DOM:24.26%, NON:12.8%) watts and in the RF at 75 (DOM:22.25%, NON:15.73%), 100(DOM:24.85%, NON:17.05%) and 125 (DOM:30.99%) watts. In terms of neuromuscular economy, there was a Likely Positive or Very Likely Positive effect of unilateral resistance training on most measures of NME on both the vastus lateralis and rectus femoris in both the dominant and nondominant legs. In terms of NME slope, there was only a Likely Positive effect of unilateral resistance training on the dominant vastus lateralis. Conclusion: Based on these results, it appears that the cross education of strength from unilateral resistance training is modality-specific. Furthermore, the NME of both the vastus lateralis and rectus femoris in both legs appear to improve following unilateral resistance training. However, in the nondominant leg, the improvement in NME appears to be due solely to the increase in maximal EMG, whereas the improved NME in the dominant leg is due to both an increase in maximal EMG and a decrease in submaximal EMG.

Flat affect (i.e., diminished expressivity) and self-reported anhedonia (i.e., lack of pleasure) are associated with many psychiatric disorders. There is a need to examine the relationship between specific anhedonia subtypes and flat affect in a non-clinical sample. Forty-seven undergraduate students (59% male; mean age 20.37; SD = 4.74) completed self-report questionnaires assessing four subtypes of anhedonia - consummatory/anticipatory by social/non-social. Participants then viewed 15 randomly-presented pictures (five neutral, ten negative) from the International Affective Pictures System while facial muscle activity (electromyography; EMG) was recorded. Male participants reporting a greater level of anhedonia, particularly consummatory social anhedonia, showed greater EMG activity change in the corrugator supercilii muscle to negative pictures, as compared with neutral pictures. Females showed the opposite pattern: more consummatory social anhedonia related to less EMG activity change in the corrugator muscle. In summary, consummatory social anhedonia in particular showed a strong relationship with facial expressivity that interacted with sex. In the presence of more consummatory social anhedonia, males show more negative facial reactions to negative stimuli while females show a more flattened affect. These findings may help explain discrepancies in existing research examining anhedonia and flat affect in clinical populations and have implications for etiology and treatments.

Schizotypy is a sub-threshold syndrome associated with schizophrenia. Much of the research on schizotypy concerns its component features, one of which being blunted or constricted affect. While several investigations have addressed this common “negative” symptom within the context of schizophrenia, few have focused on schizotypy directly, and none have utilized psychophysiological measurement to examine affective constriction. The present investigation uses facial electromyography (EMG) to measure patterns of affective expression within a psychometrically defined schizotypal population when presented threatening and distressing pictures from the IAPS. Twenty-eight individuals with elevated schizotypal features and 20 healthy controls were recruited for this investigation. The participants observed the series of pictures and provided self-report ratings of affective valance and arousal while their physiological responses were recorded. The protocol used here closely matched that used by Bradley and Lang (2007) and produced a similar pattern of results across all participants on selfreported ratings and physiological measures. Results further suggest that those with schizotypal features did not differ from control participants in self-reported ratings of negative affect or autonomic arousal. A three-way interaction in facial EMG measurement revealed that while schizotypic males demonstrated the expected pattern of blunted facial affective expression, schizotypic females displayed the opposite pattern. That is, females with psychometrically schizotypy demonstrated significant elevations in negative facial affective expression while viewing distressing pictures. We argue that these findings reflect unidentified sex differences in affective expression in schizotypy, and we discuss implications for assessment and diagnostic procedures among individuals with personality disorders