Abstract Not Provided. / Thesis / Master of Science (MSc)

A great deal of research has shown decrements in force and power following static stretching. There has been little research investigating the acute effects of static stretching of the antagonist on the expression of strength and power. The purpose of this study was to investigate the effects of static stretching of the antagonist muscles on a variety of strength and power measures. Sixteen active males were tested for vertical jump height and isokinetic torque production in a slow knee extension (KES) at 60°/s and a fast knee extension (KEF) at 300°/s. Electromyography was taken during knee extension tests for the vastus lateralis and the biceps femoris muscles. Participants performed these tests in a randomized counterbalanced order with and without prior antagonist stretching. All variables for stretching and non-stretching treatments were compared using paired t tests at an alpha of .05. Paired samples t tests revealed a significant (p = .034) difference between stretch KEF and non-stretch KEF conditions. There was no significant (p > .05) difference between KES stretch and non-stretch conditions. Vertical jump height was significantly (p = .011) higher for the stretching treatment than the non-stretching treatment. Vertical jump power was also significantly higher (p = .005) in the stretch versus the non-stretch condition. Paired samples t test indicated no significant (p > .05) difference between testing conditions for electromyography, represented as a percentage of maximal voluntary contraction (MVC). These results suggest that stretching the antagonist hamstrings prior to high speed isokinetic knee extension increases torque production. It also demonstrated that stretching the hip flexors and dorsi flexors may enhance jump height and power. Practitioners may use this information to acutely enhance strength and power performances.

Yes / When lying supine, due to the reaction force from the mattress acting mostly through the heel, an external knee-extension joint-torque is induced that keeps the knee fully extended. This torque becomes zero if the feet are hung over the end of the support. This study investigated, in patients with knee-osteoarthritis (knee-OA) who routinely sleep supine, whether a change to such a sleeping position would ameliorate the knee pain and associated physical problems they suffer. Patients were recruited (General-Practitioners Centre, UK) over a 9-month period; those eligible (51/70) were randomly allocated to an intervention (65% female; age 71.5 [11.3] yrs; BMI, 29.20 [5.54] kg/m2; knee-OA severity, 20 mild–mod/3 severe) or control group (63% female; age, 68.3 [9.7] yrs; BMI, 28.69 [5.51] kg/m2; knee-OA severity, 17 mild–mod/2 severe). The primary outcome was improvements (0 [worst] to 100 [best]) in knee pain at 3 months and was rated in the Knee-Injury-and-Osteoarthritis-Outcome-Score questionnaire (KOOS). Secondary outcomes were improvements (0–100) in the other four KOOS-subscales. There were no differences between groups in KOOS outcomes at baseline, and there were no changes in KOOS outcomes in the control group at 3 months. Relative to the baseline KOOS values in Knee-Pain (50.1), Symptoms (52.5), Activities-of-Daily-Living (53.8) and Quality-of-Life (31.5), were all seen to improve at 3 months in the intervention group (by between 11.9 and 12.9); however, when comparing to controls, only the improvements in the subscale Activities-of-Daily-Living (which improved by 12.2) were statistically significant. Findings indicate that for those with knee-OA who routinely sleep supine, sleeping with the feet over the end of the mattress (to prevent the knee being pushed into/held in full extension) can help ameliorate the physical problems they suffer.

Master of Science / Department of Kinesiology / Thomas Barstow / Previously in our laboratory, capillary blood flow (QCAP) kinetics were found to be significantly slower than femoral artery (QFA) kinetics following the onset of knee extension exercise. If the increase in QCAP does not follow a similar time course to QFA, blood must be flowing into the leg but not to the working muscle. One possible explanation for this discrepancy is that blood flow also increases to the nonworking lower leg muscles. Purpose: To determine if cuffing below the knee alters the kinetics of QFA and QCAP during knee extension exercise, and provide insight into the potential mechanisms controlling the rapid increase in QFA. Methods: Subjects performed a ramp max test to determine the work rate at which gas exchange threshold (GET) occurred. At least four constant work rate trials in each condition were conducted at work rates eliciting ~80% GET. Trials were performed with and without below knee occlusion. Pulmonary gas exchange, near-infrared spectroscopy, QFA and mean arterial pressure (MAP) measurements were taken. Muscle oxygen uptake (VO2m) and deoxy[hemoglobin + myoglobin] were used to estimate QCAP. Conductance (C) was calculated (QFA/MAP) and the percent change from baseline at 60s into exercise was calculated to indicate a time course of change. Results: There was no significant difference between the uncuffed and cuffed conditions (P>0.05). The mean response times (MRT) of QFA were 18.7 ± 14.2s (uncuffed) and 24.6 ± 14.9s (cuffed). QCAP MRTs were 51.8 ± 23.4s (uncuffed) and 56.7 ± 23.2s (cuffed), which were not significantly different from the time constants (τ) of VO2m (39.7 ± 23.2s (uncuffed) and 46.3 ± 24.1s (cuffed)). However, the MRT of QFA was significantly faster (P<0.05) than the MRT of QCAP and τVO2m. τVO2m and MRT QCAP were significantly correlated. The QFA and C percent increase from baseline at 60s were significantly different from MAP but not from each other. Conclusion: Cuffing below the knee did not significantly change the kinetics of QFA, QCAP or VO2m. Estimated QCAP kinetics tracked VO2m following exercise onset, while changes in QFA appeared to be primarily driven by an increase in C, not an increase in MAP.

Introduction: Isokinetic testing is used in rehabilitation settings on a regular basis, yet there is a lack of consistency in rest period usage among protocols. Purpose: The purpose of this study was to establish an optimal rest period that would allow reproducibility of strength during a common isokinetic strength-test. Methods: Twentyseven healthy college-aged males underwent isokinetic strength testing to determine peak torque at 60, 180 and 300 deg/sec, respectively. Work:rest ratios of 1:3, 1:8 and 1:12 were counterbalanced between sets. A 3 X 3 repeated measures ANOVA was used to analyze the data. The p < .05 level of significance was used for all tests. Results: There was no significant difference in either knee extension or knee flexion peak torque when comparing work:rest ratios. Conclusion: These findings suggest that a 1:3 work:rest ratio is sufficient during a common isokinetic strength test.

High-tone extensor thrust is common to those with cerebral palsy and those suffering spinal cord injuries. It is a muscle-control phenomenon that causes the body to straighten spastically. One goal of this thesis is to design a dynamic seating system that moves with respect to the wheelchair frame, allowing the seat to move with the user during an extensor thrust and reduce forces. One unique challenge is that the seat needs to remain rigid during normal functional activities and only become dynamic when an involuntary thrust is detected. A second goal of this thesis is to design a control scheme that is able to differentiate between these two types of motion. These design goals are initially investigated with a hinged-seatback system, instrumented with sensors to allow for the detection of thrusts and to actively control seating components. A full seating system is then built to allow for full-body extensor thrusts, involving the seatback, seat bottom, and leg rest of the wheelchair. This system is analyzed for effectiveness of reducing forces on the body during an extensor thrust. Another serious problem for this segment of the population is pressure ulcers. These are caused by prolonged pressure on the skin from weight-bearing bony prominences. Various seating system configurations are known to help with pressure relief. The three standard configurations for a chair are tilt, recline, and standing. The final goal of this thesis is to measure and compare the effectiveness of these three methods for their ability to relieve pressure on the seat bottom. To accomplish this, a powered wheelchair with built-in capabilities for recline and standing is mounted to a tilting mechanism. Test subjects are used to experimentally compare the effectiveness of each method for pressure reduction using pressure mats on all weight-bearing surfaces. A 2D model is also developed and validated with the experimental results.

Background: Sagittal plane external flexion moment in early stance has been reported to be both higher and lower in people with medial knee OA compared to control subjects. Purpose: Sagittal plane knee joint kinetics and kinematics were compared between people with medial compartment OA and healthy subjects. Subjects with OA and low pain scores were also compared to those with OA and moderate pain scores. Subjects: Forty people with medial knee OA and 40 age and sex matched control subjects. Method: Knee alignment and OA severity were measured from radiographs. Frontal and sagittal plane moments and knee flexion angle during gait were measured using a three dimensional motion analysis system and force plates. The Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) was used to measure pain; this score was used to divide the OA group into low pain and moderate pain OA groups. The relationship between knee flexion moment in early stance and gait speed, knee flexion angle and pain was also determined. Results: Subjects with OA had lower gait speed and cadence, and higher double limb support time. Peak knee adduction moment (first 50% of the gait cycle) was higher in the OA group. The knee flexion moment in early stance did not differ between groups; however the knee extension moment in late stance was lower in the knee OA group. The moderate pain group walked more slowly than the low pain group. The knee adduction moment, sagittal plane moments and knee flexion angle in stance did not differ between OA groups. A positive correlation was found between knee flexion moment and knee flexion angle in early stance in the knee OA group; the correlations between knee flexion moment and pain and gait speed were not significant. Conclusion: No differences were found in the knee flexion moment or stance phase knee flexion angle between the groups compared in this study, and therefore the results do not contribute to resolution of the controversy in the literature. Participants with knee OA in this study had relatively mild to moderate disease severity, which may have contributed to the non-significant findings. / Thesis (Master, Rehabilitation Science) -- Queen's University, 2009-08-27 00:37:29.466

The rapid growth of an older demographic is an increasing concern around the world. Older people have been reported to suffer from physiological and neuromuscular declines in several systems including skeletal muscles, central nervous system, cardiovascular processes and respiratory function. These age-related changes are often reflected through impairments in functional performance of occupational tasks as well as activities of daily living. This may make an older population more prone to musculoskeletal disorders and injuries. In addition, health problems and injury risks are likely amplified by factors such as obesity. Obesity has emerged as a serious health concern in the United States in recent decades. However, obesity-related changes in performance and motor control as well as how they will be modified by gender, specifically among older adults, are still largely unexplored. As motor variability has recently been reported to be associated with fatigue development and may have the potential to reveal underlying mechanisms of neuromuscular control, the main goals of this study were to investigate the influence of gender and obesity on motor performance, neuromuscular control and endurance in the elderly, by examining differences in motor variability during intermittent submaximal isometric exertions of the knee and hand. Fifty-two older participants with age over 65 were recruited into four groups: obese male (9), obese female (13), non-obese male (15) and non-obese female (15). The obese groups consisted of those whose BMI was greater than 30 kg/m2. Participants were asked to perform intermittent (15s on and 15s off) isometric handgrip and knee extensions at 30% MVC until exhaustion. Force and muscle activations of the Vastus Lateralis, Rectus Femoris, Extensor Carpi Radialis and Flexor Carpi Radialis muscles were collected through the endurance task. Motor variability was quantified using the coefficient of variation (CV) and sample entropy (SaEn) of the surface electromyography (EMG) and force signals. Motor variability during exercise differed both between males and females, and between obese and non-obese people, reflecting different motor strategies employed in order to prolong endurance. Overall, across all individuals, we observed a significant positive correlation between cycle-to-cycle variability of knee extensor muscle activation during the baseline period of the task and endurance time. As for gender differences, males exhibited longer endurance times than females, and seemed to achieve that through utilizing a motor strategy involving a more variable (higher CV) and less complex (lower SaEn) agonistic muscle activity. Since this was accompanied by a lower fluctuation in the force signal (lower CV) and a higher complexity of force (SaEn), we interpreted this to be a motor strategy involving more variable recruitment of synergistic and antagonistic motor units during the knee extension task to prolong endurance time, among males compared to females. As for obesity differences, there were no obesity-related changes in endurance time. However, obese individuals exhibited a greater cycle-to-cycle variability that was positively correlated with endurance time during the knee extension task, indicating a larger alteration in the recruitment of motor units across successive contractions, which contributed to comparable endurance time and performance with their non-obese counterparts. During the hand-grip tasks, variabilities in force and muscle activity followed similar trends as the knee extension task. However, there were no significant gender or obesity differences in endurance time, and there also weren't any significant correlations between any of the dependent variables with endurance time. Thus, this study was a basic investigation into changes in motor variability and how it was associated with the development of fatigue among older adults; and the potential influences of gender and obesity on the relationships. Two tasks of high relevance to both occupational life and activities of daily living, i.e. knee extension and hand-grip were considered. Our findings enhance the theoretical understanding of the underlying neuromuscular control patterns and their relationship with fatigue for different individuals. Given that both aging and obesity rates are rising continuously and becoming a substantial health and safety problem especially in the occupational environment, the results from this study are both timely and critical for practical design applications, especially by recognizing the importance of having a variable motor pattern in task performance, even among older adults. / MS

Introduction: Impaired isometric muscle strength and muscle endurance in adults with Fontan circulation has previously been reported. However, the knowledge if corresponding impairment is present in children and adolescents with Fontan circulation is scarce. Aim: The aim was to examine the isometric muscle strength and muscle endurance of the lower limbs in children and adolescents with Fontan circulation in comparison to age and sex matched controls. Method: In this cross-sectional study 43 children and adolescents (6-18 years) with Fontan circulation and 43 controls were included. Isometric knee extension and plantar flexion muscle strength was assessed using dynamometry (Newton:N). Unilateral isotonic heel-lift until exhaustion was used for evaluation of lower limb muscle endurance. Analysis on group level (n=43) and for the subgroups 6-12 years (n=18) and 13-18 years (n=25) was performed. Results: On group level the children and adolescents with Fontan circulation had impaired isometric plantar flexion strength for the left leg compared to controls (393.9±181.1N vs. 492.5±241.6N, p=0.04). In addition, they had impaired isometric knee extension strength bilaterally (right 222.8±101.1N vs. 293.0±164.9N, p=0.02, left 220.7±102.7N vs. 279.5±159.1N, p=0.05). In contrast, lower limb muscle endurance did not differ. In subgroup analysis, the impaired isometric strength was only present in the group of adolescents. Conclusion: Adolescents with Fontan circulation had impaired isometric muscle strength compared to controls. However, no corresponding differences were found in children. Further, lower limb muscle endurance did not differ. This implies that the impaired isometric muscle strength may develop during adolescence whereas the impaired muscle endurance may occur later. / Del av en multicenterstudie

Azyklische Beinstreckbewegungen stellen mit der Erzeugung hoher Absprunggeschwindigkeiten in vielen Sportarten wesentliche Teilleistungen dar, die durch Gelenkleistungen der unteren Extremitäten limitiert werden. An maximal willentlich ausgeführten Beinstreckbewegungen mit dem Ziel größtmöglicher Endbeschleunigung des Körperschwerpunkts hat die kniestreckende Muskulatur den größten Anteil. Mit geeigneten Muskelparametern lässt sich das Kontraktionsverhalten und damit die mechanische Antriebsleistung von Muskeln unter verschiedenen Arbeitsbedingungen kennzeichnen und das Training wirksam steuern. In dieser Arbeit wurde ein Instrumentarium zur individuellen Bestimmung von Muskelparametern der Kraft-Geschwindigkeit-Längen-Relation für die Kniestrecker entwickelt. Dies beinhaltete ein isokinetisches Testprogramm das die von antagonistischen Einflüssen isolierte Kraftdiagnose der kniestreckenden Muskulatur gewährleistet. Mit den in den Tests erhobenen Eingangsdaten konnten mit einem wirklichkeitsnahen Geometriemodell, inverser Dynamik und einem Optimierungsverfahren plausible Muskelparameter, u. a. die maximale Muskelleistung, für sechs Kadersportler berechnet werden. Am Beispiel eines Strecksprungs ohne Sprunggelenkeinsatz wurde gezeigt, dass die berechneten Parameter zur muskelkraftgesteuerten Simulation in Muskel-Skelett-Modellen geeignet sind und so die Optimierung der sportlichen Technik unter Berücksichtigung der individuell limitierten Antriebsleistung im Kniegelenk möglich ist.