L-citrulline and malate are amino acids within the body that have the potential to affect muscular endurance during athletic performances. Purpose: This study intended to test the effectiveness of CM on muscular performance and fatigue during a lower body resistance protocol. Methods: Twelve trained males completed a lower body resistance training protocol for two sessions, one using CM (8.0g) and the other with placebo (PL), within a randomized, double blind, counterbalanced study. Results: CM supplementation increased repetitions in leg press, hack squat and leg extension. Blood lactate was significantly increased post-exercise compared to pre-exercise, but no significant difference was found between CM and placebo. In addition, no significant differences were found for systolic blood pressure, diastolic blood pressure, or HR between the CM and PL groups. Conclusion: These findings suggest CM attenuates muscular fatigue during a specific lower body exercise protocol.

This paper presents the design of an underactuated lower body exoskeleton to assist with walking. It reduces the amount of bodyweight going through the user's leg by providing a supporting force to the user that is engaged and disengaged depending on the stage of the gait cycle the user is in. It is engaged when the leg is in stance, effectively pushing between the ball of the foot and the hips, and is disengaged during leg swing. This support force is provided by a linear actuator on each leg that consists of a compression spring, ball screw, and motor. It works by having the motor turn the ball screw, which moves a metal plate to either compress or decompress the spring. The actuator is designed to always be able to extend, to avoid limiting the user's motion. The spring is disengaged while the leg is in swing in order to reduce any impedance to the user's natural stride. The exoskeleton is also designed to minimize any range of motion limitations to reduce its restrictiveness. The exoskeleton was found to be able to provide 19 lbs (85 N) of support to the user per leg. / Master of Science / Exoskeletons are external devices worn to assist the user's natural movement or strength. This paper outlines the design of an exoskeleton that assists the user in walking by providing a supporting force on any leg that the user's weight is on. This effectively reduces the load on the user's legs, which could help reduce leg strain and fatigue. The exoskeleton releases this force when weight is removed from the leg to allow the user to easily swing their leg forward to step. The exoskeleton was designed to minimize limitations to the range of motion of the leg joints while walking, squatting, or sitting to ensure that the exoskeleton did not feel restricting or uncomfortable. Testing revealed that the exoskeleton was able to provide a supporting force of approximately 19 lbs (85 N) to the user per leg and met all the joint range of motion requirements to avoid restrictiveness.

An underactuated exoskeleton design for walking assistance is presented and evaluated. The exoskeleton uses one motor per leg and makes use of a pantograph to reduce the overall profile and allow the exoskeleton to closely follow the shape of the user's leg. Support is provided between the ball of the user's foot and their waist by compressing a spring in parallel with the user's leg during Stance Phase. The exoskeleton has a mass of 14.0 kg (30.8 lbs) and was tested up to a supplied spring force of 323.6 N (72.75 lbf) which equates to around 161.8 N (36.38 lbf) of assistive force at the waist. Range of motion tests showed minimal restriction at the knee and ankle, but some restriction of the hip. Human subject experiments using a simple gait detection method based on GRF at walking speeds from 0.45 m/s to 1.12 m/s (1.0 mph to 2.5 mph) were performed and showed an increase in the time between actual heel strike and predicted heel strike of approximately 0.05 seconds to 0.1 seconds. Lastly, calculations are presented examining the effect of exoskeleton assistance on the biological joint moments and optimizing the actuator design to reduce power consumption. The actual performance of the exoskeleton is compared with the calculations based on the joint angles during a typical walking cycle. / Master of Science / A design for an exoskeleton capable of providing walking assistance without requiring a motor for every joint is presented and evaluated. The exoskeleton uses one motor per leg and makes use of a pantograph to reduce the required size and allow the exoskeleton to closely follow the shape of the user's leg. Support is provided between the ball of the user's foot and their waist by compressing a spring attached beside the user's leg while the user's foot is on the ground. The exoskeleton weighs 14.0 kg (30.8 lbs) and was tested up to a supplied spring force of 323.6 N (72.75 lbf) which equates to around 161.8 N (36.38 lbf) of assistive force at the waist. Range of motion tests showed minimal restriction at the knee and ankle, but some at the hip. Testing with a human participant using a simple method for determining when to apply support and remove it based on the forces measured at the user's foot were performed at walking speeds of 0.45 m/s to 1.12 m/s (1.0 mph to 2.5 mph). These tests showed an increase in the time between when the heel of the foot initially hits the ground and when the exoskeleton code determined that it occurred of approximately 0.05 seconds to 0.1 seconds. Lastly, calculations are presented examining how exoskeleton assistance affects what is felt at the joints of the user and determining what spring stiffness would best reduce the power required from the motors. The actual performance of the exoskeleton is compared with the calculations based on the joint angles during normal human walking.

Precooling, or a reduction in core temperature (Tc) has been demonstrated to be a potent enhancer of endurance running performance, however there is no known mechanism for this improvement. By holding the exercise workload constant, changes in variables such as running economy (RE), heart rate, and ventilation (VE) can be determined as a result of precooling. Improved running economy, or a reduced oxygen cost of a specific workload, is linked to improved exercise performance. Purpose: To determine the changes in flexibility, RE, heart rate, VE, and Tc during running at a constant workload following cool water immersion and to determine any sex-specific responses. Methods: Fourteen well-trained runners (8 males and 6 females) completed four treadmill runs at a sex-specific velocity (8.0 mph for females and 8.6 mph for males). The first two runs served as accommodation trials. The third and fourth runs were preceded by either cool water immersion (24.8oC) for 40 minutes or quiet sitting. Oxygen consumption, heart rate, Tc, VE, and flexibility were measured during both experimental trials. Results: Running economy did not change as a result of the precooling treatment, whereas Tc and heart rate were reduced by 0.4oC and 5 beats per minute, respectively. Minute ventilation was reduced in the female subjects only (1.4 liters/min). Sex differences were apparent in Tc, heart rate, VE, and flexibility response. Conclusion: While the precooling procedure was effective in reducing Tc and heart rate, RE did not change. Thus, improvements in RE cannot explain the dramatic enhancements of endurance running performance that often occur post-cooling. Differences between male and female subjects in response to precooling were identified, most notably in VE.

Doctor of Philosophy / Department of Kinesiology / Carl Ade / During exercise, muscle blood flow (Q ̇m) increases to match metabolic demand of the active skeletal muscle. In order for this matching to take place, ‘competition’ between local vasodilating metabolites and sympathetically mediated vasoconstriction, termed “functional sympatholysis,” must take place. A key feature of functional sympatholysis is that it is driven largely by metabolic rate (i.e., a higher work rates lead to greater sympatholysis), but may also be largely dependent on nitric oxide bioavailability and oxidative stress in certain disease states (e.g., hypertension). Thus, evaluation of these factors may provide valuable insight into the vascular control mechanisms during exercise in both health and disease. Therefore, the purpose of this dissertation was to 1) determine the role metabolic rate and blood flow on mediating functional sympatholysis, 2) determine the role of nitric oxide bioavailability on functional sympatholysis with high salt intake, a risk factor for primary hypertension, and 3) determine the effect of increases in nitric oxide bioavailability on functional sympatholysis in primary hypertension patients. In the first investigation (Chapter 1), we increased the relaxation phase of the contraction-relaxation cycle to increase active skeletal muscle blood flow (Q ̇m) and see if this would impact vasoconstriction of the active skeletal muscle. We showed that a decreased relaxation time led to greater functional sympatholysis. Interestingly, despite a lower metabolic rate (15% and 20% MVC), we showed that there was no difference in vasoconstriction between the increased relaxation times. These results may show that increases in Q ̇m play a role in functional sympatholysis when mechanical compression is minimized. In the second investigation (Chapter 2), we sought to determine if high dietary sodium (HS) intake would impact functional sympatholysis. We showed that HS intake (15g/day for 7 days) did not impact functional sympatholysis during exercise. Importantly, we show a significant increase in mean arterial pressure (i.e., pressor response) during handgrip exercise. These findings show the deleterious changes in blood pressure, but further work is needed to pinpoint specific mechanisms causing the responses. In the final investigation (Chapter 3), we used an acute nitrate rich (NR) supplement to improve NO bioavailability in hypertensive post-menopausal women (PMW), and observe the impact on functional sympatholysis. We provide novel evidence that functional sympatholysis is improved (~50%) with a NR supplement. The finding that a NR supplement can attenuate vasoconstriction in hypertensive PMW sheds light on the complexities of hypertension, functional sympatholysis and NO bioavailability. The current results indicate that the ‘competition’ between vasodilating metabolites and sympathetically mediated vasoconstriction can be independently modified in health and disease. In individuals with impairment to local vasodilation (e.g., hypertension), the ability to increase functional sympatholysis and muscle blood flow may lead to improvements in cardiovascular health. Taken together, the present results suggest that modifying duty cycle, sodium intake, and NO bioavailability are important factors to be considered with regard to overall cardiovascular health.

No description available.

The purpose of this study was to examine the effects of increased self-efficacy on three separate jump tests. Forty-seven students (18 females & 29 males) from Utah State University were randomly assigned to a treatment or control group. Participants performed a vertical jump test, a standing broad jump test, and a 30-s Bosco test on three separate days over a span of 1 week. The treatment group (n = 24) were given false, positive feedback about their performance while the control group (n = 23) were told their true results. Self-efficacy was measured pre and post using the Physical Self-Efficacy scale (PSE) and was found to increase more for the treatment group than the control group. A 3 x 2 ANOVA showed a significant improvement for the Bosco test but no significance for the other two tests, suggesting that self-efficacy has an effect on power endurance but not explosive power.

Osteoarthritis (OA) is a group of diseases entailing degradation of joints, and has been designated as one of the key conditions for special attention during the World Health Organization’s Bone and Joint Decade (2000-2010) (Brooks & Hart, 2000). Research has demonstrated that body weight is the number one modifiable risk factor associated with the onset and progression of knee OA (Felson, 1996). However, exercise programs that aim to initiate weight loss and improve pain and function in knee OA often increase loading on the knee joint, contributing to degeneration of the knee and progression of the disease (Miyazaki et al, 2002). The introduction of a new anti-gravity treadmill, which utilizes a technology called Lower Body Positive Pressure (LBPP), allows the examination of the relationship between weight, knee pain and knee loading via knee acceleration during exercise. The null hypothesis states that there will be no significant difference in knee pain, knee function and knee joint acceleration when comparing full weight bearing and LBPP treadmill walking exercise in a young knee OA population. Twenty-two overweight/obese patients with mild or moderate early-onset knee OA were recruited to complete two 25 minute treadmill walking sessions (one full weight-bearing and one LBPP walking session) one week apart and two walkway walking sessions. Knee pain and knee acceleration were recorded. Paired t-tests and ANOVAs were used to compare conditions. On average, an LBPP of 12.3% body weight reduction reduced knee pain in our population. Knee pain was significantly lower during LBPP walking than during full weight-bearing walking. Knee acceleration decreased with increasing LBPP. Heel strike and toe-off data from walkway walking trials illustrated significantly different knee acceleration about the knee (slow walking loads were lower / fast walking were higher), as compared to treadmill walking sessions. This study illustrates that treadmill walking at a minimal level of LBPP can decrease knee pain and attenuate knee joint loads while allowing patients to complete exercise programs aimed at initiating weight loss and improving pain and function in knee OA. LBPP appears to be a promising tool for rehabilitation for those with painful knee OA and other lower body musculoskeletal conditions.

Knee osteoarthritis (OA) is a degenerative joint condition characterized by progressive joint pain, swelling, and loss of muscle and joint function for which there is no known cure. Current research indicates that the most important modifiable risk factor for the development and progression of knee OA is obesity, a condition that is increasingly common in older adults. Established treatment guidelines for knee OA recommend regular exercise for disease management. However, for obese patients weight-bearing exercise elicits large joint forces that can exacerbate symptoms and influence disease progression. Using a new anti-gravity treadmill capable of generating a lifting force called lower body positive pressure (LBPP), obese patients with knee OA can engage in regular physical activity while minimizing joint loading. The aim of this study was to assess the effect of a 12-week, anti-gravity treadmill walking (AGTW) program on knee pain and function in obese older adults with knee OA. The alternate hypothesis was that there would be a difference between Knee Injury and Osteoarthritis Outcome Score (KOOS) results before and after the anti-gravity treadmill walking program. A group of 25 participants with a mean (SD) age of 64.2 (6.1) years and BMI of 33.0 (6.8) kg/m2 completed AGTW twice per week for 12 weeks at a body weight percentage that minimized knee pain. Knee symptoms and function (KOOS), knee pain during full weight-bearing treadmill walking (FTW), isokinetic quadriceps and hamstring muscle strength, cardiovascular fitness (YMCA submaximal cycle ergometer test), general health status (SF-12), and activity level (average daily pedometer readings) were assessed at baseline and following the completion of the 12-week program using paired t-tests and Wilcoxon signed rank sum tests (α = 0.05). Improvements between baseline and outtake were found in all KOOS subscales, as well as hamstring and quadriceps thigh muscle strength. Knee pain during full FWB and AGTW decreased following the 12-week program. No significant differences were found in cardiovascular fitness, SF-12 scores, or average daily pedometer readings. The results of this study suggest that anti-gravity treadmill walking increases thigh muscle strength, reduces knee pain, and increases functional capacity during daily activities, including FTW in older, obese individuals with knee OA. Anti-gravity treadmill technology has the potential to improve the health and functional capacity of at-risk knee OA individuals, and advance current methods of rehabilitation and long-term management of chronic symptomatic knee OA.

Osteoarthritis (OA) is a group of diseases entailing degradation of joints, and has been designated as one of the key conditions for special attention during the World Health Organization’s Bone and Joint Decade (2000-2010) (Brooks & Hart, 2000). Research has demonstrated that body weight is the number one modifiable risk factor associated with the onset and progression of knee OA (Felson, 1996). However, exercise programs that aim to initiate weight loss and improve pain and function in knee OA often increase loading on the knee joint, contributing to degeneration of the knee and progression of the disease (Miyazaki et al, 2002). The introduction of a new anti-gravity treadmill, which utilizes a technology called Lower Body Positive Pressure (LBPP), allows the examination of the relationship between weight, knee pain and knee loading via knee acceleration during exercise. The null hypothesis states that there will be no significant difference in knee pain, knee function and knee joint acceleration when comparing full weight bearing and LBPP treadmill walking exercise in a young knee OA population. Twenty-two overweight/obese patients with mild or moderate early-onset knee OA were recruited to complete two 25 minute treadmill walking sessions (one full weight-bearing and one LBPP walking session) one week apart and two walkway walking sessions. Knee pain and knee acceleration were recorded. Paired t-tests and ANOVAs were used to compare conditions. On average, an LBPP of 12.3% body weight reduction reduced knee pain in our population. Knee pain was significantly lower during LBPP walking than during full weight-bearing walking. Knee acceleration decreased with increasing LBPP. Heel strike and toe-off data from walkway walking trials illustrated significantly different knee acceleration about the knee (slow walking loads were lower / fast walking were higher), as compared to treadmill walking sessions. This study illustrates that treadmill walking at a minimal level of LBPP can decrease knee pain and attenuate knee joint loads while allowing patients to complete exercise programs aimed at initiating weight loss and improving pain and function in knee OA. LBPP appears to be a promising tool for rehabilitation for those with painful knee OA and other lower body musculoskeletal conditions.