Cross-education of strength is a neural adaptation defined as the increase in strength of the untrained contralateral limb after unilateral training of the opposite homologous limb. The neural mechanisms of the effect have remained elusive, although it appears to be a motor learning adaptation. Despite cross-education of strength being an inter-limb effect, no previous study has determined the influence of handedness and the direction of transfer (dominant to non-dominant or the reverse). Arguably, this is partly responsible for massive variation in the literature regarding the magnitude of the effect. The primary purpose of this document is to attempt to determine the central and peripheral neuro-physiological mechanisms controlling cross-education of muscular strength. Prior to determining the mechanisms of the effect, the influence of handedness and the preferred direction of transfer for cross-education of strength must be addressed. The secondary purpose is to determine the preferential direction of transfer of cross-education of strength in order to isolate the circumstances in which the effect is more pronounced. Two experiments were necessary to meet these objectives. <p>Experiment 1: The purpose was to determine the effect of the direction of transfer on cross-education in right-handed individuals. Subjects were randomized into a left-hand training (LEFT), right-hand training (RIGHT), or non-training control (CON) group. Strength training was 6 weeks of maximal isometric ulnar deviation, 4 times per week. The change in strength in the untrained limb was greatest in the RIGHT group (39.2%; p<.01), whereas no significant changes in strength were observed for the untrained limb of the LEFT group (9.3%) or for either of the CON group limbs (10.4% and 12.2%). There were no changes in muscle thickness of untrained limbs compared to CON. Changes in untrained limb EMG were not different compared to CON. Cross-education with hand strength training occurs only in the right-to-left direction of transfer in right-handed individuals. Cross-education of arm muscular strength is most pronounced to the non-dominant arm. <p>Experiment 2: The purpose of this study was to determine the central and peripheral mechanisms of cross-education of strength after actual and imagery training. Subjects were randomized into an actual training, imagery training, or non-training control group. A sub-sample of 8 subjects (4 actual, 4 imagery training) had brain activity during exercise assessed with functional magnetic resonance imaging (fMRI). Strength training was 6 weeks of maximal isometric handgrip ulnar deviation (Biodex) of the right arm, 4 times per week. Actual training was highly effective for increasing strength in trained (45.3%; p<.01) and untrained (47.1%; p<.01) limbs. Imagery training and control groups had no increases in strength for either arm. Muscle thickness increased only in the trained arm of the actual group (8.4%; p<.001). After actual training, there was an increase in activation of contralateral sensorimotor cortex and left temporal lobe during actual contractions with the untrained left arm (p<.001). Actual training was associated with a significantly greater change in agonist muscle activation pooled over both limbs, compared to the imagery and control groups (p<.05). Cross-education of strength is only significant after actual training, indicating that peripheral feedback is necessary for the effect. Cross-education of strength is accompanied by changes in cortical activation indicative of motor learning and the retrieval of memory of movement acquired by the trained limb. <p>General Conclusion: The neuro-physiological mechanism of cross-education of strength is that changes in cortical activation indicative of motor learning occur in both brain hemispheres after unilateral training. Cross-education of strength is influenced by strength asymmetries related to handedness, and the preferential direction of transfer is from dominant to non-dominant limb. Cross-education is a motor learning adaptation also reliant on peripheral feedback during training.

Background: Resistance training has proven to increase athletic performance, traditionally barbell training and Olympic Lifting have been used for this purpose. Sling training has recently been developed as a complement or substitution to traditional resistance training. Research has shown an increase in sport specific athletic performance and core stability with sling training. TRX Suspension Trainer is a newly developed sling training tool and to date no independent research has been done with the TRX. Purpose: To examine and compare muscle activation using TRX and the Olympic Lifting movement Hang Clean. Methods: 32 senior high school male soccer players participated in the study. Surface electromyographic (sEMG) data were collected on mm.erector spinae (back), m.gluteus maximus (glutes), m.vastus lateralis (quadriceps), m.semitendinosus (hamstrings) and m.gastrocnemius caput laterale (calf). Surface EMG data was collected when the subjects performed five different exercises, Hang Clean, TRX Squat Jump, TRX Front Squat and TRX Power Pull. In addition a Squat Jump was used as reference. Results: A similar muscle activation was found between Hang Clean (674 µV), TRX Squat Jump (684 µV) and TRX Front Squat (691 µV). TRX Power Pull showed the highest activation for mm.erector spinae and m.gluteus maximus but the lowest when comparing total muscle activation for all measured muscles. Conclusion: The similar amount of muscular activation for Hang Clean, TRX Squat Jump and TRX Front Squat indicates that the TRX Suspension Trainer can be used as a complement, for experienced athletes, or a substitution, for novice athletes, to traditional strength training. Coaches and athletic trainers should acknowledge the need and the importance of resistance training for athletic performance.

The delayed occurrence of fatigue while maintaining submaximal force output is a function that could be driven by the central nervous system (CNS). It has been found previously that mean EMG amplitude increases with fatigue. Endurance time has also been found to increase over repeated testing. The purpose of this study was to compare the muscle activation patterns and endurance times after training of the AdP muscle. This study analyzed surface EMG of the adductor pollicis (AdP) muscle in young, healthy adults during a sustained submaximal isometric fatiguing contraction before and after 4 weeks of muscular endurance task training. Eight participants (training group: n = 4 and control group: n = 4) carried out maximal voluntary contractions (MVCs) while sustaining isometric force of 20% MVC of thumb adduction before and after the four weeks of endurance training. EMG, recorded through surface electrodes, was measured before and after training in an effort to detect a possible CNS training effect. The endurance training group trained the AdP muscle at 20% MVC every other day for 4 weeks. Average force was calculated over 5 second time bins every 5% of endurance time (20 time bins total). A significant increase in endurance time was seen in the training group of this study. A significant effect of change for pre and post-training mean EMG amplitude across the two groups was found (p < .001). A significant interaction effect between pre and post training and control groups was also found (p = .016). There was also a significant deficit in increases of mean amplitude between the first and last time bins of the endurance task (pre and post) after training. This indicates that there is an effect of training on increasing endurance time which can be exhibited through changes in mean EMG amplitude. / text

Activity of skeletal muscles produce electrical signals that can be measured using electrodes placed on the skin surface over a target muscle or with electrodes inserted into the muscle. Such electromyographic (EMG) signals provide fundamental information about the intensity of the neural drive acting upon muscle. In addition, EMG signals are widely deployed as control sources for powered prosthetic limbs. One limitation related to recording EMG signals, however, is that signals arising from neighboring muscles may contribute significantly to the activity detected with electrodes placed over or within a given target muscle. Such unwanted contribution of signal from muscles other than the targeted muscle is referred to as cross-talk. Cross-talk was investigated in four neighboring muscles in the forearm with different electrode types and configurations: bipolar intramuscular, monopolar intramuscular, and bipolar surface EMG. Cross-correlation analysis was performed for every pairwise combination of EMG signal recorded. The peak correlation coefficient at near-zero time delay provided an index of the degree of cross-talk. Correlation coefficients dropped off exponentially with distance between recording electrodes. Bipolar intramuscular EMG had the narrowest pick-up range, with a length constant of 14.5 mm. Bipolar surface EMG had a longer length constant of 37.0 mm, whereas monopolar intramuscular EMG had the longest length constant of 64.5 mm. A second set of experiments indicated that correlation in EMG signals detected in different muscles was unlikely to have a neural basis. Therefore, because of their wide detection range, monopolar configurations including those involving intramuscular electrodes, should be avoided.

A lack of empathy is considered to be a hallmark feature of psychopathy. However, remarkably little research has specifically examined the relationship between psychopathy and empathy, and what does exist relies solely on self-report measures, which is problematic given psychopaths' propensity for dishonesty. This research signifies an attempt to develop an objective measure of empathy, using psychophysiological indices of emotional experience as indicators of an empathic response. Specifically, corrugator and zygomatic facial muscle activity, event-related heart rate, and acoustic startle reflex responses were measured while participants viewed brief films of individuals experiencing happy and sad emotional events.Pilot investigations of the films suggest they are appropriate for eliciting happy and sad empathic emotion, and the pattern of responses by undergraduates with high and low trait levels of empathy indicates the validity of the approach, and the promise of utilizing psychophysiological indices of emotional responding to measure situational empathy in an objective manner. In particular, participants demonstrated patterns of psychophysiological responses to the empathy-inducing films which both matched their self-reported emotional experiences as well as the emotional valence of the stimuli. Moreover, several of the psychophysiological indices were able to discriminate high and low empathy individuals, whereby low empathy participants exhibited less facial expressiveness and less modulation of the acoustic startle reflex to the empathy-inducing stimuli than their high empathy counterparts.The paradigm was then extended to a sample of male undergraduates with high and low levels of psychopathic traits, as assessed by the Psychopathic Personality Inventory-Revised. Results suggest a significant negative relationship between self-reported psychopathy and self-reported dispositional empathy, with high levels of psychopathy associated with low levels of dispositional empathy, particularly with respect to affective empathy. However, despite differences in dispositional empathy, psychopathic and non-psychopathic undergraduates were not easily discriminated on subjective or objective measures of situational empathy, with the exception of an anomalous pattern of zygomatic EMG activity exhibited by the psychopathic participants. The implications of these findings are discussed with respect to the nature of the empathic capabilities of psychopaths, as well as considerations of the methodological limitations of the current study and directions for future research.

To a person with an upper limb amputation or congenital defect, a well-functioning prosthesis can open the door to many work and life opportunities. A fundamental component of many modern prostheses is the myoelectric control system, which uses the myoelectric signals from an individual's muscles to control prosthetic movements. Though much research has been done involving the myoelectric control of arm and gross hand movements, more dexterous finger control has not received the same attention. Consequently, the goal of this study was to determine an optimal approach to the myoelectric signal classification of a set of typing motions. Two different movement sets involving the fingers of the right hand were tested: one involving digits two through five (4F - "four finger"), and the other involving digits one and two (FT - "finger/thumb"). Myoelectric data were collected from the forearm muscles of twelve normally-limbed subjects as they performed a set of typing tasks. These data were then used to test a series of classification systems, each comprising a different combination of system element choices. The best classification system over all subjects and the best classification system for each subject were determined for both movement sets. The optimal subject-specific classification systems yielded classification accuracies of 92.8 ± 2.7% for the 4F movement set and 93.6 ± 6.1% for the FT movement set, whereas the optimal overall classification systems yielded significantly lower performance (p<0.05): 89.6 ± 3.4% for the 4F movement set and 89.8 ± 8.5% for the FT movement set. No significant difference in classification accuracy was found between movement sets (p=0.802). A two-way repeated measures ANOVA (α=0.05) was used to determine both significance results. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2008-10-31 14:59:43.151

The game of rugby union has evolved over the years into a professional sport in which an increased incidence of injury is evident. This also applies to the shoulder joint. It appears that certain risk factors are associated with shoulder pathology among rugby players as well as among the general population. In a competitive sporting environment where high stress loads are placed upon the body and joints, this association may be even more pronounced. Despite the fact that numerous studies have investigated the various factors that potentially play a role in the occurrence of shoulder injuries among sports participants generally, similar studies involving rugby union players in particular are limited. Previous studies have investigated and profiled rugby players with regards to posture, shoulder isokinetic muscle strength and electromyographic patterns, but no study has yet investigated the relationship between these factors and the role they may play in the risk of being injured. It would be beneficial to have a better understanding of the interplay between these factors and to identify the most likely factors to predict and/or prevent shoulder injuries in rugby players. With this information at hand, it might be possible to identify players who are at risk of shoulder injuries in order that they may potentially benefit from effective “pre-habilitation” protocols. The aim of this study was to determine what the relationship between thoracic posture, isokinetic shoulder strength and scapulae muscle activation patterns in injured and uninjured rugby players was, and to determine which of these variables might predict shoulder injuries. Methods Ninety-one (91) uninjured semi-professional rugby union players’ shoulder joint range of motion differences (ROM) were manually tested with the hand-behind-the-neck and hand- behind-the-back method. The profiling and classification of the thoracic posture was performed using the New York Posture Test. Scapular muscle activation patterns were determined by means of electromyography (EMG) measuring the activation of the upper and lower trapezius, serratus anterior and infrapinatus muscles. The isokinetic muscle strength of the rotator cuff muscles was determined at 60°/sec (Kin-Com 500H) measuring concentric and eccentric forces during internal and external rotation. Results Some participants presented with non-ideal or unsatisfactory shoulder internal rotators (59%) and external rotators (85%) bilateral ROM differences. Of all the participants, 68% presented with an abnormal shoulder position in the lateral view, and the sequence of muscle activation of the scapula stabiliser muscles was found to be: serratus anterior; lower trapezius; infraspinatus and then upper trapezius. The isokinetic antagonist/agonist strength ratio for shoulder rotation during concentric muscle contraction was 64% for the non-dominant and 54% for the dominant shoulder. The corresponding ratios for the eccentric muscle contraction of the non-dominant and dominant shoulders were 67% and 61% respectively. The median muscle onset times of the backline players’ non-dominant infraspinatus muscles were 35.90 ms for ideal, 95.20 ms for non-ideal, and 93.90 ms for the unsatisfactory external rotators’ range of motion (ROM) differences. The median firing orders of the forwards’ dominant lower trapezius muscle was 3 for ideal, 1 for non-ideal, and 2 for unsatisfactory external rotators’ ROM differences. Among the forward shoulder group and the normal shoulder position group of the forwards respectively, the median muscle onset time of their non-dominant infraspinatus muscle was 113 milliseconds (ms) and 42 ms. Their non- dominant serratus anterior muscles’ median onset time was 78.85 ms among the players with a rounded back, and 31.90 ms among the players with a normal thoracic curvature. The backline players displayed a median non-dominant serratus anterior onset time of 47.45 ms (in the uneven shoulder group) versus 32.75 ms (in the even shoulder group). The median firing order of the backline players’ non-dominant infraspinatus muscle was third in the normally curved back group. Among the players with an abnormally rounded back, however, the median firing order changed to second. The median external rotation/internal rotation isokinetic strength ratio of the forward players was 63% (forward shoulders), versus 56.50% (normal shoulder position). This was for their non-dominant shoulders. Certain isokinetic shoulder strength ratios displayed statistically significant correlations with scapular muscle activation patterns but they were not clinically significant. Players who had sustained shoulder injuries during the season differed significantly from those who had not sustained injuries with regards to the following baseline measurements: age (the injured were older), height (the injured were taller) and non-dominant/dominant concentric external rotation ratio (the injured had a higher ratio). Among the backline players baseline differences occurred within age (the injured were older), weight (the injured were heavier), height (the injured were taller) and the body mass index (BMI) (the injured had a higher BMI). The variables that displayed statistically significant predictive values towards future injury were age (1.34 times increase for each year older), insufficient shoulder external rotator ROM differences (16.15 times increase if an unsatisfactory ROM difference occurs), uneven shoulders (4.43 times increase if shoulders were abnormally uneven) and the non- dominant/dominant concentric external rotation strength ratio (a 1.42 times increase for every 10% that the ratio increases). Conclusion Profiling of the group of players revealed that their non-ideal or unsatisfactory flexibility of shoulder external rotators, their forward shoulders in the lateral view, and their weakness of the shoulder external rotators did not result in abnormal scapular muscle activation patterns. Positive relationships were found between certain postural abnormalities (forward shoulders, a rounded back and uneven shoulders) and the delay of muscle onset times of infraspinatus and serratus anterior, as well as the firing order of infraspinatus. Forward shoulders increased antagonist/agonist isokinetic shoulder rotation strength ratios. Non-ideal or unsatisfactory flexibility of shoulder external rotators displayed positive relationships with altered infraspinatus muscle onset times and an altered lower trapezius muscle firing order. No clinically significant correlations were found between isokinetic shoulder strength ratios and scapulae muscle activation patterns. It appears that posture (uneven shoulders), has a higher predictive ability than shoulder strength imbalance (non-dominant/dominant concentric external rotation ratio) regarding future shoulder injury. However, age and especially external rotator ROM deficiency proved to be strong predictors of future shoulder injury in semi-professional rugby players. / Thesis (PhD (Human Movement Science))--North-West University, Potchefstroom Campus, 2013.

The game of rugby union has evolved over the years into a professional sport in which an increased incidence of injury is evident. This also applies to the shoulder joint. It appears that certain risk factors are associated with shoulder pathology among rugby players as well as among the general population. In a competitive sporting environment where high stress loads are placed upon the body and joints, this association may be even more pronounced. Despite the fact that numerous studies have investigated the various factors that potentially play a role in the occurrence of shoulder injuries among sports participants generally, similar studies involving rugby union players in particular are limited. Previous studies have investigated and profiled rugby players with regards to posture, shoulder isokinetic muscle strength and electromyographic patterns, but no study has yet investigated the relationship between these factors and the role they may play in the risk of being injured. It would be beneficial to have a better understanding of the interplay between these factors and to identify the most likely factors to predict and/or prevent shoulder injuries in rugby players. With this information at hand, it might be possible to identify players who are at risk of shoulder injuries in order that they may potentially benefit from effective “pre-habilitation” protocols. The aim of this study was to determine what the relationship between thoracic posture, isokinetic shoulder strength and scapulae muscle activation patterns in injured and uninjured rugby players was, and to determine which of these variables might predict shoulder injuries. Methods Ninety-one (91) uninjured semi-professional rugby union players’ shoulder joint range of motion differences (ROM) were manually tested with the hand-behind-the-neck and hand- behind-the-back method. The profiling and classification of the thoracic posture was performed using the New York Posture Test. Scapular muscle activation patterns were determined by means of electromyography (EMG) measuring the activation of the upper and lower trapezius, serratus anterior and infrapinatus muscles. The isokinetic muscle strength of the rotator cuff muscles was determined at 60°/sec (Kin-Com 500H) measuring concentric and eccentric forces during internal and external rotation. Results Some participants presented with non-ideal or unsatisfactory shoulder internal rotators (59%) and external rotators (85%) bilateral ROM differences. Of all the participants, 68% presented with an abnormal shoulder position in the lateral view, and the sequence of muscle activation of the scapula stabiliser muscles was found to be: serratus anterior; lower trapezius; infraspinatus and then upper trapezius. The isokinetic antagonist/agonist strength ratio for shoulder rotation during concentric muscle contraction was 64% for the non-dominant and 54% for the dominant shoulder. The corresponding ratios for the eccentric muscle contraction of the non-dominant and dominant shoulders were 67% and 61% respectively. The median muscle onset times of the backline players’ non-dominant infraspinatus muscles were 35.90 ms for ideal, 95.20 ms for non-ideal, and 93.90 ms for the unsatisfactory external rotators’ range of motion (ROM) differences. The median firing orders of the forwards’ dominant lower trapezius muscle was 3 for ideal, 1 for non-ideal, and 2 for unsatisfactory external rotators’ ROM differences. Among the forward shoulder group and the normal shoulder position group of the forwards respectively, the median muscle onset time of their non-dominant infraspinatus muscle was 113 milliseconds (ms) and 42 ms. Their non- dominant serratus anterior muscles’ median onset time was 78.85 ms among the players with a rounded back, and 31.90 ms among the players with a normal thoracic curvature. The backline players displayed a median non-dominant serratus anterior onset time of 47.45 ms (in the uneven shoulder group) versus 32.75 ms (in the even shoulder group). The median firing order of the backline players’ non-dominant infraspinatus muscle was third in the normally curved back group. Among the players with an abnormally rounded back, however, the median firing order changed to second. The median external rotation/internal rotation isokinetic strength ratio of the forward players was 63% (forward shoulders), versus 56.50% (normal shoulder position). This was for their non-dominant shoulders. Certain isokinetic shoulder strength ratios displayed statistically significant correlations with scapular muscle activation patterns but they were not clinically significant. Players who had sustained shoulder injuries during the season differed significantly from those who had not sustained injuries with regards to the following baseline measurements: age (the injured were older), height (the injured were taller) and non-dominant/dominant concentric external rotation ratio (the injured had a higher ratio). Among the backline players baseline differences occurred within age (the injured were older), weight (the injured were heavier), height (the injured were taller) and the body mass index (BMI) (the injured had a higher BMI). The variables that displayed statistically significant predictive values towards future injury were age (1.34 times increase for each year older), insufficient shoulder external rotator ROM differences (16.15 times increase if an unsatisfactory ROM difference occurs), uneven shoulders (4.43 times increase if shoulders were abnormally uneven) and the non- dominant/dominant concentric external rotation strength ratio (a 1.42 times increase for every 10% that the ratio increases). Conclusion Profiling of the group of players revealed that their non-ideal or unsatisfactory flexibility of shoulder external rotators, their forward shoulders in the lateral view, and their weakness of the shoulder external rotators did not result in abnormal scapular muscle activation patterns. Positive relationships were found between certain postural abnormalities (forward shoulders, a rounded back and uneven shoulders) and the delay of muscle onset times of infraspinatus and serratus anterior, as well as the firing order of infraspinatus. Forward shoulders increased antagonist/agonist isokinetic shoulder rotation strength ratios. Non-ideal or unsatisfactory flexibility of shoulder external rotators displayed positive relationships with altered infraspinatus muscle onset times and an altered lower trapezius muscle firing order. No clinically significant correlations were found between isokinetic shoulder strength ratios and scapulae muscle activation patterns. It appears that posture (uneven shoulders), has a higher predictive ability than shoulder strength imbalance (non-dominant/dominant concentric external rotation ratio) regarding future shoulder injury. However, age and especially external rotator ROM deficiency proved to be strong predictors of future shoulder injury in semi-professional rugby players. / Thesis (PhD (Human Movement Science))--North-West University, Potchefstroom Campus, 2013.

Human beings have been exposed to different cold conditions throughout time, and have through cold acclimation developed mechanisms to survive in these conditions. Cold acclimation can be elicited through exposure to natural cold climates, or artificially induced in a laboratory to study the body’s response to repeated cold exposures. Several studies looking at the effects of cold acclimation in humans have been conducted during the last 50 years, and have reported that cold acclimation can lead to a change in skin and core temperature, heat production and shivering. An accurate quantification of shivering thermogenesis (ST) during cold acclimation has not been done before, and most previous measurements of shivering during cold acclimation have been inaccurate and inadequate. In this study a Liquid Condition Suits (LCS) was used to elicit cold acclimation (10°C, 2hr daily, for 4 weeks) while an accurate measurement of the effect of cold acclimation on changes in muscle activity was conducted. In CHAPTER 2, results showed that four weeks of cold acclimation at 10°C did not change skin and core temperature, heat production or ST. The effects on shivering pattern and fuel selection were also analysed, but no effects of cold acclimation could be observed. These measurements were a part of a larger study, in which the effects of cold acclimation on changes in BAT were the main outcome measures. These data showed that an increase in BAT volume (45%) and activity (120%) were the only observed effects of cold acclimation. In CHAPTER 3, we set out to assess if changes in shivering from pre to post cold acclimation are associated with changes in BAT volume, and if the amount of BAT a participant possesses prior to cold acclimation can be used to predict changes in shivering intensity during cold acclimation. The interindividual variability in changes in thermal responses, heat production, shivering and BAT volume occurring between subjects during four weeks of cold acclimation was also addressed in this section.

Syftet med denna studie var att pröva olika teorier om stamning, avseende nivå av muskelspänning vid flytande tal. Tjugofyra försöksdeltagare ingick i studien, tolv stammande och tolv kontrolldeltagare. Försöksdeltagarnas muskelaktivitet i musklerna orbicularis oris (OO) och depressor labii inferior (DLI) uppmättes med hjälp av elektromyografi (EMG) vid flytande tal och vid en icke verbal uppgift, att puta med läpparna. De stammandes grad av stamning bedömdes med The Wright and Ayre Stuttering Self-Rating Profile (WASSP) och Stuttering Severity Instrument, fjärde upplagan, (SSI-4) för att korrelera denna med muskelaktiviteten. Ingen statistisk signifikant skillnad avseende muskelaktivitet mellan grupperna kunde påvisas, varken i flytande tal eller vid den icke verbala uppgiften. Det fanns inte heller något signifikant samband mellan den sammanlagda muskelaktiviteten av OO och DLI vid flytande tal och stamningsgrad uppmätt med SSI-4 respektive WASSP. Inget signifikant samband kunde heller ses mellan OO vid läpputning och stamningsgrad uppmätt med SSI-4 respektive WASSP. Ett negativt signifikant samband påvisades dock mellan muskelaktivering i OO vid flytande tal och självskattad stamningsgrad. Således kan resultatet tyda på att det varken finns någon muskulär hypertoni eller hypotoni i OO och DLI i stammandes flytande tal jämfört med en icke stammande kontrollgrupp. Resultatet indikerar även att det kan finnas tendens till låg muskelaktivering vid svårare stamning.