Purpose: The aim of this study was to investigate the effects of a maximal repeated-jumps task on force production, muscle activation and kinematics, and to determine if changes in performance were dependent on gender. Methods: Eleven male and nine female athletes performed continuous countermovement jumps for 60 s on a force platform while muscle activation was assessed using surface electromyography. Performances were videotaped and digitized (60 Hz). Data were averaged across three jumps in 10-s intervals from the initial jump to the final 10 s of the test. Results: No interaction between time and gender was evident for any variable; therefore, all results represent data collapsed across gender. Preactivation magnitude decreased across time periods for anterior tibialis (AT, P < .001), gastrocnemius (GAS, P < .001) and biceps femoris (BF, P = .03), but not for vastus lateralis (VL, P = .16). Muscle activation during ground contact did not change across time for BF; however, VL, G, and AT showed significant reductions (all P < .001). Peak force was reduced at 40 s compared with the initial jumps, and continued to be reduced at 50 and 60 s (all P < .05). The time from peak force to takeoff was greater at 50 and 60 s compared with the initial jumps (P < .05). Both knee fexion and ankle dorsifexion were reduced across time (both P < .001), whereas no change in relative hip angle was evident (P = .10). Absolute angle of the trunk increased with time (P < .001), whereas the absolute angle of the shank decreased (P < .001). Conclusions: In response to the fatiguing task, subjects reduced muscle activation and force production and altered jumping technique; however, these changes were not dependent on gender.

Introduction: Baseball pitching is considered one of the most intense aspects within the game of baseball, as well as the most complicated dynamic throwing task in all of sports. The biomechanics of pitching have been heavily investigated in an attempt to identify optimal pitching mechanics in terms of pitching performance. Previous quantified upper body kinetics research has concluded that improved muscle strength is needed in attempting to achieve adequate upper body kinetics and efficient pitching performances. Therefore, it is the purpose of this research study to compare the lower extremity muscle and upper extremity muscle activation patterns and kinematic variables associated with the curveball pitch and the fastball pitch when pitching from the wind-up and stretch position. Methods: Twelve skilled (competed at the NCAA collegiate level) baseball pitchers volunteered to be research subjects for this study. The participants were fitted with six surface electromyography (EMG) bipolar electrodes (Delsys Inc., Boston, Massachusetts) on the stride leg biceps femoris, medial gastrocnemius, ipsilateral side (throwing arm side) lower trapezius, upper trapezius, triceps brachii and biceps brachii. Each participant underwent maximum voluntary isometric contraction (MVIC) testing and then performed a pitching analysis. All EMG variables of interest were normalized using MVIC data and then compared between pitching types and pitch delivery. Shoulder rotation, shoulder abduction, elbow flexion and extension, elbow angular velocity and pelvis rotation were determined using motion capture (Motion Analysis Corp., Santa Rosa, SA) and Visual 3D software (C-Motion Inc., Germantown, MD). Paired t-tests and factorial analyses were performed using SPSS (p ≤ 0.05). Results and Discussion: Significant differences in the peak and mean muscle activity for the fastball and curveball pitched from wind-up and stretch position were observed. Significant differences in the kinematic variables between the fastball and curveball from the wind- up and stretch were also observed. These findings suggest that upper and lower muscle activity could be associated with enhanced pitching technique and pitching performance. Pitching kinematic differences associated with the diverse pitch types as well as the multiple pitch deliveries may impact the overall “wear and tear” on a pitcher’s health and pitching arm. Conclusions: Many differences were found, between both the pitching type and the pitching delivery as well as the kinematic variables. These findings suggest that upper and lower muscle activity could be associated with enhanced pitching technique and pitching performance to keep a baseball pitcher healthy and on the pitching mound longer into the season, decreasing the rate of injury. Shoulder rotation and pelvis rotation, as well as the elbow angular velocity and elbow flexion-extension, have an impact on the pitcher’s ability to stay off the disabled list and in the game longer. Determining pitch types along with delivery types that enhance the pitcher’s ability to stay active without injury will provide a way to make the game of baseball safer for the future generation of all stars.

The need to characterize normal and pathological human movement has consistently driven researchers to develop new tracking devices and to improve movement analysis systems. Movement has traditionally been captured by either optical, magnetic, mechanical, structured light, or acoustic systems. All of these systems have inherent limitations. Optical systems are costly, require fixed cameras in a controlled environment, and suffer from problems of occlusion. Similarly, acoustic and structured light systems suffer from the occlusion problem. Magnetic and radio frequency systems suffer from electromagnetic disturbances, noise and multipath problems. Mechanical systems have physical constraints that limit the natural body movement. Recently, the availability of low-cost wearable inertial sensors containing accelerometers, gyroscopes, and magnetometers has provided an alternative means to overcome the limitations of other motion capture systems. Inertial sensors can be used to track human movement in and outside of a laboratory, cannot be occluded, and are low cost. To calculate changes in orientation, researchers often integrate the angular velocity. However, a relatively small error or drift in the measured angular velocity leads to large integration errors. This restricts the time of accurate measurement and tracking to a few seconds. To compensate that drift, complementary data from accelerometers and magnetometers are normally integrated in tracking systems that utilize the Kalman filter (KF) or the extended Kalman filter (EKF) to fuse the nonlinear inertial data. Orientation estimates are only accurate for brief moments when the body is not moving and acceleration is only due to gravity. Moreover, success of using magnetometers to compensate drift about the vertical axis is limited by magnetic field disturbance. We combine kinematic models designed for control of robotic arms with state space methods to estimate angles of the human shoulder and elbow using two wireless wearable inertial measurement units. The same method can be used to track movement of other joints using a minimal sensor configuration with one sensor on each segment. Each limb is modeled as one kinematic chain. Velocity and acceleration are recursively tracked and propagated from one limb segment to another using Newton-Euler equations implemented in state space form. To mitigate the effect of sensor drift on the tracking accuracy, our system incorporates natural physical constraints on the range of motion for each joint, models gyroscope and accelerometer random drift, and uses zero-velocity updates. The combined effect of imposing physical constraints on state estimates and modeling the sensor random drift results in superior joint angles estimates. The tracker utilizes the unscented Kalman filter (UKF) which is an improvement to the EKF. This removes the need for linearization of the system equations which introduces tracking errors. We validate the performance of the inertial tracking system over long durations of slow, normal, and fast movements. Joint angles obtained from our inertial tracker are compared to those obtained from an optical tracking system and a high-precision industrial robot arm. Results show an excellent agreement between joint angles estimated by the inertial tracker and those obtained from the two reference systems.

Alteration in the tension or stiffness of the vocal folds, mediated by the cricothyroid (CT) muscle activation, is one of the laryngeal strategies attributed to devoicing during speech production. While some studies have reported a consistent increase in CT activity associated with voiceless sounds in comparison to their voiced cognates during speech (Kagaya & Hirose, 1975; Dixit & MacNeilage,1981; Lofqvist, McGarr & Honda, 1984; Löfqvist et al., 1989; Hoole et al., 2004), other studies have suggested that closer relation of CT activity to supra-segmental characteristics of the utterance rather than voicing contrasts (Hirose & Gay, 1972; Hirose and Ushijima,1978; Collier, Lisker, Hirose & Ushijima, 1979). The purpose of this study was to test the hypothesis that during intervocalic syllable production, CT muscle activity was consistently higher for voiceless sounds than their voiced cognates, to assist in vowel devoicing, when pitch, intensity, stress and aspiration were kept controlled. Simultaneous recordings of thyroarytenoid and cricothyroid muscle activity, video-nasendoscopy, and audio signals were obtained from eight, gender-matched adult speakers during intervocalic (VCV) syllable production. The speech sounds represented contrasts in manner of production including, plosives, affricates and fricatives with their voiced-voiceless and aspirated-unaspirated cognates Two voicing transition events were identified and marked on the EMG signals: Vowel-Consonant Transition (VC) and Consonant-Vowel Transition (CV).The mean amplitude of CT muscle activity during voicing transitions (VC, CV) was calculated over a 60 ms time window preceding the acoustic event. CT muscle activity was normalized to a percent of mean maximum activity and compared between voiced/voiceless and aspirated/unaspirated cognates across different categories of speech sounds, subjects and, VC and CV transitions. During the VC transition of intervocalic syllable production of voiceless and voiced speech sounds, a consistent increase in CT muscle activation was not observed across all subjects suggesting that CT activity is not essential for devoicing. Four of the eight subjects (M1, M4, F2, F3) showed consistently higher CT activity for voiceless than voiced sounds while, four of the eight subjects (M2, M3, F1, F4) either did not show any increase in CT muscle activity or showed an inconsistent pattern of increase. The magnitude of difference in CT activity between voiceless and voiced sounds ranged from 3-24% with the highest difference for voiceless fricatives, followed by voiceless aspirated stop plosives and voiceless affricates, and with least difference for unaspirated stop plosives. During consonant vowel (CV) transition of intervocalic syllable production seven of the eight subjects showed lower or comparable levels of CT EMG activity for voiceless speech sounds in comparison to their voiced cognates. Results of one-tailed unpaired t-test revealed that four of the eight participants, M1 [t (60.69) = 10.17, p < .001], M4 [t (8.88) = 57.03, p < .001], F2 [t (5.88) = 35.20, p < .001] and F3 [t (8.91) = 51.00, p < .001], showed significantly higher CT activity for the voiceless than voiced sounds during the VC transition of intervocalic syllable production but the results were not significant for subjects M2, M3, F1 and F4. No statistically significant difference was found between aspirated and unaspirated cognates for all the eight subjects on a two-tailed, unpaired t-test. No gender differences were observed in the findings.

It is well established that cathodal transcranial direct current stimulation (tDCS) can decrease the excitability of the primary motor cortex (M1) in humans. Despite the cortical inhibition caused by cathodal tDCS, it remains unknown how this intervention alters unrestrained dynamic reaching movements qualitatively. Accordingly, we designed this study to examine how cathodal tDCS impacts unrestrained dynamic reaching as measured by qualitative kinematic features and electromyography (EMG). Ten young, healthy adult subjects were recruited to participate in a two day protocol involving repetitively reaching to two different targets (large and small) both before and following cathodal tDCS applied over the contralateral M1 during one session and before and following sham tDCS over the same brain region during another session. We discovered that cathodal tDCS was not able to alter the kinematic features of reaching in these subjects but did degrade the EMG performance, specifically by increasing the amount of co-contraction between muscle pairs. Because co-contraction is an indicator of relatively unskilled performance, these results seem to indicate that cathodal tDCS of M1 preferentially disrupts the learning or execution of highly coordinated muscle firing patterns during dynamic reaching. This work adds to the growing body of knowledge about how tDCS applied over M1 affects our movements. Moreover, it leads us to believe that tDCS can be utilized to assist in rehabilitation of patient populations who suffer from neurological dysfunctions but EMG assessments may need to be included in order to more effectively assess the patient performance.

Numerous agencies have accumulated evidence since 1964 which implicates habitual cigarette smoking as a causal or facilitating factor in the development of many circulatory and respiratory diseases. This study sought to identify those psychological variables which possibly contribute to the maintenance of cigarette smoking and therefore, had two main purposes. First, this study investigated the individual and simultaneous physiological changes, i.e., Electroencephalography, Electromyography, Heart Rate, Blood Pressure and Skin Temperature that occurred during and immediately after the smoking of one cigarette. Second, the study investigated the hypothesis that smoking frequency would decrease when individuals were trained via biofeedback procedures to increase 8-12 Hz occipital EEG activity as a substitute for smoking. Three male, very heavy smokers (35 or more cigarettes per day ) and three male moderate smokers (15-24 cigarettes per day) physiologies were monitored while smoking, non-smoking and while they were provided with 8-12 Hz occipital EEG biofeedback training using a multiple baseline design. Results of the study indicate that of the six smokers physiologically monitored, four or more of the smokers demonstrated the following physiological changes while actually smoking one cigarette: the percent of time producing 4-8 cycles per second bra .in waves increased (S2 ,S3 ,S5); heart rate (beats per minute) increased (Sl,S2,S3,S4,S5,S6); and the percent of time producing 8-12 cycles per second (Hz) brain waves decreased (Sl,S2,S3,S4,S5,S6). Immediately after the smoking of one cigarette, four or more of the smokers demonstrated an increase in their rates (Sl,S2,S3,S4,S5, S6) and subjects 1,4,5 and 6 demonstrated an over-the-entire-session decrease in their skin temperatures. There did not appear to be any specific consistent brain wave changes across the subjects. However, the following subject-specific brain wave changes were evident: Subject 1 data indicates an increase in Alpha brain waves (8-12 Hz), a decrease in Theta brain waves (4-8 Hz), and a decrease in Beta brain waves (12-20 Hz). Subject 2 data indicates a decrease in Alpha brain waves, an increase in Theta brain waves, and a decrease in Beta waves. Subject 3 data indicates an Alpha wave decrease, Theta wave increase, and Beta wave increase. Subject 4 data indicates an Alpha wave decrease, Theta wave increase, and no observable change in Beta activity. Subject 5 data indicates an Alpha increase, a Theta decrease, and no observable change in Beta activity. Subject 6 data indicates an Alpha decrease, a non-observable change in Theta production and an increase in Beta activity. During the training period, when the smokers were given music feedback whenever they produced 8-12 Hz, four of the six smokers learned to increase the percent of time producing 8-12 Hz, (Sl,S2,S5, S6). Two of these four smokers were able to continue producing high levels of 8-12 Hz activity without the use of biofeedback equipment (Sl,S2). These smokers had quit smoking completely at the end of a six-month follow-up period. These two smokers were contacted by phone at the eight-month follow-up period and reported they were still absent from any cigarette smoking. The four smokers who could not increase their 8-12 Hz activity without the use of 8-12 Hz auditory feedback (Phase D) decreased their frequency of cigarette smoking at the six-month follow-up period as follows: Subject 3, from 38 to 15 cigarettes smoked per day; Subject 4, from 50 to 44 cigarettes smoker per day; Subject 5, from 18 to 8 cigarettes smoked per day; and Subject 6, from 17 to 10 cigarettes smoked per day. Possible reasons why Subjects 1 and 2 quit smoking are discussed and directions for future research are presented.

The ability of an organism to modulate its feeding behavior is an important focus of feeding ecology studies. Modulation is the ability to distinctly and consistently alter a behavior to accommodate different stimuli. The goal of this study was to examine the ability of the nurse shark Ginglymostoma cirratum to modulate its food capture behavior with different sizes and types of food items. This was carried out through kinematic and electromyographic analysis. Eight sub-adult specimens of G. cirratum were filmed feeding on two different food types (squid and fish) and sizes (gape size and larger than gape size). Filming consisted of high-speed videography utilizing a low-light digital video system. Kinematic variables related to lower jaw movement, mouth width, and head angle were measured from video footage. Up to twelve muscles in each of six specimens were implanted with bipolar electrodes to measure the onset and duration of motor activity. There were no significant differences between food sizes and any of the kinematic variables. Only two muscles showed significant differences in onset time based on food size. In regards to food types, squid bites were significantly faster than fish bites, but when examined proportionately to bite duration only the time to jaw closure remained significantly different. The motor pattern of G. cirratum demonstrates an anterior to posterior sequence, which corresponds to the anterior to posterior kinematic sequence. Little cranial elevation is present during feeding sequences and is not thought to contribute significantly to feeding. Ginglymostoma cirratum is a stereotyped, inertial suction feeder. There is little evidence that there is modulation in feeding behavior based on food size or food type. If modulation does exist in the feeding behavior, it is more likely to occur after prey capture while the prey is being processed and manipulated prior to transport. Initial observations suggested that a novel behavior termed 'spit-suck manipulation' is utilized for larger prey items.

Doctor of Philosophy / In this thesis, three experiments were conducted to monitor: (i) muscle oxygenation and electromyographic activity of the biceps brachii after exercise-induced muscle damage (ii) muscle oxygenation after downhill walking-induced muscle damage, and, (iii) muscle oxygenation following a bout of vigorous concentric exercise. Maximal eccentric exercise (EE) of biceps brachii resulted in significantly increased mean resting oxygen saturation and decreased deoxyhaemoglobin. During isometric contractions at 50% and 80% of subjects’ maximum voluntary torque (MVT), oxygen desaturation and resaturation kinetics and volume were significantly decreased after EE, and these declines were significantly prevalent over the following 6 days. Additionally, a significant shift in median frequency intercept (measured by electromyography; EMG) towards lower frequencies was observed during isometric contractions at both 50% and 80% MVT after EE in the exercised arm. After an exhaustive session of downhill walking, another form of EE, resting total haemoglobin and oxyhaemoglobin decreased. Furthermore, during isometric contractions at 30%, 50% and 80% of MVT, prolonged and significant increases were observed in oxygen desaturation and resaturation kinetics and volumes after ambulatory EE. In contrast to the two EE experiments, concentric contractions did not evoke any prolonged changes in muscle oxygenation. Collectively, the findings of this thesis revealed significant and prolonged changes in muscle oxygenation at rest and during exercise, following sessions of strenuous eccentric exercise. Although not clear, the possible mechanism responsible for the changes in muscle oxygenation after EE could be increased resting muscle oxygen utilization due to probable muscle damage and a subsequent requirement of energy demanding repair processes. Concentric exercise resulted in fatigue, but it did not affect muscle oxygenation. Although a prolonged reduction in EMG median frequency intercept was observed after EE, this was not closely time-associated with the biochemical, anthropometric or functional markers of muscle damage.

A range of signal processing techniques have been adopted and developed as a methodology which can be used in developing an intelligent surface electromyography (SEMG) signal classifier. An intelligent SEMG signal classifier would be used for recognising and treatment of musculoskeletal pain and some neurological disorders by physiotherapists and occupational therapists. SEMG signals displays the electrical activity from a skeletal muscle which is detected by placing surface electrodes placed on the skin over the muscle. The key factors of this research were the investigation into digital signal processing using various analysis schemes and the use of the Artificial Neural Network (ANN) for signal classification of normal muscle activity. The analysis schemes explored for the feature extraction of the signals were the Fast Fourier Transform (FFT), Short Time Fourier Transform (STFT), Continuous Wavelet Transform (CWT), Discrete Wavelet Transform (DWT) and Discrete Wavelet Packet Transform (DWPT).Traditional analysis methods such as FFT could not be used alone, because muscle diagnosis requires time-based information. CWT, which was selected as the most suitable for this research, includes time-based information as well as scales, and can be converted into frequencies, making muscle diagnosis easier. CWT produces a scalogram plot along with its corresponding frequency-time based spectrum plot. Using both of these plots, overviewed extracted features of the dominant frequencies and the related scales can be selected for inputs to train and validate an ANN. The purpose of this research is to classify (SEMG) signals for normal muscle activity using different extracted features in an ANN. The extracted features of the SEMG signals used in this research using CWT were the mean and median frequencies of the average power spectrum and the RMS values at scales 8, 16, 32, 64 and 128. SEMG signals were obtained for a 10 second period, sampled at 2048 Hz and digitally filtered using a Butterworth band pass filter (5 to 500 Hz, 4th order). They were collected from normal vastus lateralis and vastus medialis muscles of both legs from 45 male subjects at 25%, 50%, and 75% of their Maximum Voluntary Isometric Contraction (MVIC) force of the quadriceps. The ANN is a computer program which acts like brain neurons, recognises, learns data and produces a model of that data. The model of that data becomes the target output of an ANN. Using the first 35 male subjects' data sets of extracted features, the ANN was trained and then validated with the last 10 male subjects' data sets of the untrained extracted features. The results showed how accurate the untrained data were classified as normal muscle activity. This methodology of using CWT for extracting features for analysing and classifying by an ANN for SEMG signals has shown to be sound and successful for the basis implementation in developing an intelligent SEMG signal classifier.

Based on a thesis in Electrical Engineering, 1965. / Bibliography: p.79-86. / Contract DA-36-039-AMC-03200(E).