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Subacromial impingement accounts for significant burdens on the economy and individual quality of life. The development and progression of this disorder is thought to be related to overuse; however, little is known regarding biomechanical factors such as scapular kinematics, shoulder muscle recruitment and joint proprioception with respect to this disorder. The high degree of variability between individuals on these biomechanical measures limits our ability to make inferences behind the development of shoulder impingement. Here, biomechanical factors associated with impingement are investigated using within-subjects designs in order to reduce this inherent variability. Using modern clinical techniques, this dissertation is applicable towards treatment of shoulder impingement as well as scientific understanding of motor control and function in the presence of pain. This dissertation includes previously published and un-published co-authored material.

Cerebrovascular disease continues to be responsible for significant morbidity and mortality. There is a pressing need to better understand the biomechanics of both intracranial arteries and the extracranial arteries that feed these vessels. Histology and immunohistochemistry were performed on basilar and carotid arteries and elucidated their structural differences. Nonlinear optical microscopy (NLOM) provided collagen fiber orientation and distribution, which offered motivation for a more microstructrually-based model. Biaxial testing was performed on acute basilar and carotid arteries and cultured basilar arteries. We used a validated 2D, four fiber family constitutive relation to model passive biaxial stress-stretch behaviors of basilar and common carotid arteries, and we developed a new relation to model their active biaxial responses. Residual stress information from opening angles and collagen fiber orientation were used to create a 3D fiber distribution constitutive relation. Passive biaxial stress-stretch behavior of basilar arteries was modeled with the 3D fiber distribution constitutive relation and was combined with our new active relation to model the active response of basilar arteries. These data and 2D, four fiber family and active constitutive relation allow the first full comparison of circumferential and axial biomechanical behaviors between a muscular (basilar) and an elastic (carotid) artery from the same species. Our active model describes the responses by both types of vessels to four doses of the vasoconstrictor endothelin-1 (10^-10, 10^-9, 10^-8, 10^-7 M) and predicts levels of smooth muscle activation associated with basal tone under specific in vitro testing conditions. Cultured arteries revealed smooth muscle tone is necessary for vascular remodeling. Our 3D model allowed for the calculation of stress through the wall in passive basilar arteries. These results advance our understanding of the biomechanics of intracranial and extracranial arteries, which is needed to understand better their differential responses to similar perturbations in hemodynamic loading.

This study compared the center of mass behavior and muscle activation patterns during Chi running and normal running. The study included 10 participants, both male and female, who were recreational runners training at least 5 days a week. Thirty-second trials were collected continuously on a treadmill in the University of Texas Non-linear Biodynamics Laboratory. The variables being examined were the COM vertical position and COM acceleration in the A/P direction, the angle of lean, the gravitational moment about the ankle, and EMG amplitude and duration from four leg muscles. Although no significant differences were found between the two conditions for any of the dependent measures, there was a visible change in running form. A larger number of participants or a different set of dependent measures may be required to observe statistically significant differences. / text

Purpose: The purpose of this study was two-fold: (1) determine if muscle activation was greater in a BFR exercise condition compared to non-BFR exercise condition using MRI T2 mapping, and (2) determine if the muscle activation for both BFR and non-BFR exercise conditions differs between postbariatric surgery individuals and individuals in 2 control groups. Methods: Three groups participated: (1) a normal-BMI group, (2) a postbariatric surgery group, and (3) a matched group for the surgery individuals. Ultrasound imaging was used to find the optimal BFR pressure for each participant. All participants participated in both BFR and non-BFR exercises. Using a 3-Telsa MRI, a T2 map was imaged prior to and immediately following exercise. Analyses included within-group-across-condition comparisons and within-condition-across-group comparisons. The outcome variable of interest was the change in muscle activation determined via T2 mapping. Results: There was no statistical difference in the increase in muscle activation between BFR and non-BFR exercise conditions (p-value range 0.1091 to 0.9166). When comparing groups across conditions, we found that the surgery group elicited a significantly greater increase in activation compared to the normal-BMI group in every condition (p-value range 0.0014 to 0.0217) and in several muscles when compared to the matched group (p-value range 0.0060 to 0.0311). Other muscles compared to the matched group were not significantly different (p-value range 0.0683 to 0.129). No difference was found between the control groups (p-value range 0.2041 to 0.9557) in muscle activation for either condition. Conclusion: These results did not suggest a difference between BFR exercise and non-BFR exercise for the calf-raise protocol. Postbariatric surgery patients elicited an equal muscle activation response in some conditions and a greater muscle activation response in others when compared to both control groups. Further research is needed to determine whether a greater intensity or duration of exercise is needed to elicit an acute response to BFR and what factors are contributing to the increased muscle activation seen in the postbariatric surgery group.

A study involving the movement of small-sized nursery plant containers was conducted using surface electromyography (EMG) to assess the effect that glove type has on forearm and shoulder muscle activation. A total of 24 participants were asked to move weighted nursery containers simultaneously with both left and right hands (one onegallon, two one-gallon and one three-gallon) from a floor location to a table located twenty feet away while wearing one of four glove treatments (1. No Glove; 2. Thick Leather; 3. Grip Assist Mechanics; 4. Thin Nitrile). Muscle activation was evaluated as a percentage of the participants’ maximum voluntary exertion (MVE). The results show no glove effect difference for the smaller pot configuration. With the larger container treatments, muscle activity was affected by glove treatment, specifically for the left and right flexor and extensor radialis muscles.

Abstract Introduction: The prevalence of anterior cruciate ligament tear is around 7000 every year within the swedish population and 95% of reconstructive surgery was with a hamstring tendon graft. Six months post surgery a 13% decrease in knee flexion strength compared to non injured side. The need for a study that determine the role of gastrocnemius and foot position in knee flexion is lacking in the litterature and could benefit Physiotheraphy ACL rehabilitation. Purpose: of his study was to investigate M gastrocnemius medialis (MGM) activation in the ipsilateral knee after removal of hamstring tendon for ACLR, and se if ankle position alter knee flexion outcomes. Method: 3 women, mean age 24 years who underwent ACL reconstruction with hamstring graft on one leg was tested. The time since injury was 3, 6 and 7 years respectively with an mean ,5 years wait until surgery. Isokinetic knee flexion and extension testing was done in the Biodex system 3 pro. EMG electrodes measured medial gastrocnemius activation with and without ankle in dorsiflexion. Results: Knee flexion peak strength was higher by a mean of 3 Nm (3,5%) with dorsiflexed foot. Mean (MGM) activation remained the same with or without dorsiflexion. Overall knee flexion strength was higher by a mean of 5 Nm compared to the injured side. Conclusion: Knee flexion in the biodex with foot in dorsiflexion could allow for isometric plantarflexion and increas power output. Certain changes in inclusion criteria and methodology as well more studies is needed to come to a given conclusion. / nej

PowerCranks(tm) are claimed to increase economy of motion and cycling efficiency by reducing the muscular recruitment patterns that contribute to the resistive forces occurring during the recovery phase of the pedal stroke. However, scientific research examining the efficacy of training with PowerCranks(tm) is lacking. Therefore, the purpose of this study was to determine if five weeks of training with PowerCranks(tm) improves economy of motion (EOM), gross efficiency (GE), oxygen uptake (V.O2) and muscle activation patterns in trained cyclists. Sixteen trained cyclists were matched and paired into either a PowerCranks(tm) (PC) or Normal Cranks (NC) training group. Prior to training, all subjects completed a graded exercise test (GXT) using normal bicycle cranks. Additionally, on a separate day the PC group performed a modified GXT using PowerCranks? and cycled only until the end of the 200W stage (PCT). During the GXT and PCT, FeO2, FeCO2 and V.E were measured to determine EOM, GE and V.O2max. Integrated electromyography (iEMG) was also used to examine selected muscular activation patterns. Subjects then repeated the tests following the completion of training on their assigned cranks.

Despite a paucity of experimental evidence, clinical opinion remains that though LTrPs allow pain-free movement, they are primarily associated with deleterious motor effects and occur commonly in 'healthy' muscles. The primary aim of this study was to investigate the effects of LTrPs on the muscle activation patterns (MAPs) of key shoulder girdle muscles during scapular plane elevation of the arm in the unloaded, loaded and fatigued states. In connection with the main aim, a preliminary study was carried out to examine the frequency with which LTrPs occur in the scapular positioning muscles in a group of normal subjects. After establishing intra-examiner reliability for the clinical examination process, 154 healthy subjects volunteered to be screened for normal shoulder girdle function, then undergo a physical examination for LTrPs in the trapezius, rhomboids, levator scapulae, serratus anterior and the pectoralis minor muscles bilaterally. Of these 'healthy' subjects, 89.8% had at least one LTrP in the scapular positioning muscles (mean=10.65 ± 6.8, range=1-27), with serratus anterior and upper trapezius harbouring the most LTrPs on average (2.46 ± 1.8 and 2.36 ± 1.3 respectively). Consistent with clinical opinion, this study found that LTrPs occur commonly in the scapular positioning muscles. To investigate the motor effects of LTrPs, surface electromyography (sEMG) was used to measure the timing of muscle activation of the upper and lower trapezius and serratus anterior (upward scapular rotators), the infraspinatus (rotator cuff) and middle deltoid (arm abductor). These studies found that LTrPs housed in the scapular upward rotator muscles affected the timing of activation and increased the variability of the activation times of this muscle group and were also associated with altered timing of activation in the functionally related but LTrP-free infraspinatus and middle deltoid. Compared with the control group (all muscles LTrP-free), the MAPs of the LTrP group appeared to be sub-optimal, particularly in relation to preserving the subacromial space and the loading of the rotator cuff muscles. After the initial sEMG evaluations, the LTrP subjects were randomly assigned to one of two interventions: superficial dry needling (SDN) followed by post-isometric relaxation (PIR) stretching to remove LTrP s or sham ultrasound, to act as a placebo treatment where LTrPs remained. Where LTrPs were removed, a subsequent sEMG evaluation found MAPs to be similar to the control group in most of the experimental conditions investigated. Of particular note, when LTrPs had been treated and the subjects repeated the fatiguing protocol, the resultant MAP showed no significant difference with that of the control group in the rested state, suggesting treating LTrPs was associated with an improved response to fatigue induced by repetitive overhead movements. In conclusion, the findings indicate that LTrPs commonly occur in scapular positioning muscles and have deleterious effects on MAPs employed to perform scapular plane elevation and thus affect motor control mechanisms. Treating LTrPs with SDN and PIR stretching increases pressure-pain thresholds, removes associated taut bands and at least transiently optimises the MAP during scapular plane elevation. Discussion includes possible neuromuscular pathophysiology that might explain these results.

Early strength increase with training is normally attributed to neural adaptations but recent evidence suggests that muscle hypertrophy occurs earlier than previously thought. The purpose of this study was to examine the time course of adaptation through 20 days of training and 5 days of detraining. Twenty-two untrained subjects trained one arm every 2nd day for 20 days. Subjects performed isokinetic eccentric biceps training at 90°/s (6 sets of 8 reps). Muscle thickness (reported in cm) via ultrasound, strength (reported in Nm) and muscle activation (electromyography) were measured before, during and after training (9 time points). Muscle thickness increased after 8 days of training (3.66±0.11 to 3.90±0.12; p<0.05) and remained above baseline until the end of training (3.97±0.12). After 5 days of detraining muscle thickness decreased (3.97±0.12 vs. 3.85±0.11; p<0.05), but remained higher than baseline (p<0.05). Muscle thickness did not change significantly in the untrained arm at any time point. Strength in the trained arm decreased after 8 days of training (65.6±4.1 to 57.5±3.5; p<0.05) and remained suppressed throughout the study. Muscle activation amplitude increased after 14 days of training (p<0.05) and remained elevated throughout the study. In conclusion, biceps muscle thickness increases very rapidly with frequent intense eccentric training although this type of training appears to impair strength. These findings provide additional evidence that muscle hypertrophy may occur much faster than has been generally accepted.