Doctor of Philosophy

dissertationThrough the use of in vitro methods, previous research in animal models has attempted to isolate the effects of local metabolic factors, normally associated with exercising skeletal muscle, on vascular reactivity and thus blood flow regulation. Utilizing an in vitro vessel approach and human skeletal muscle feed arteries, the purpose of these studies was to determine if local factors, such as heat and acidosis, could alter vascular reactivity and thus contribute to reduced sympathetically induced vasoconstriction (functional sympatholysis) and exercise hyperemia. Specifically, it was hypothesized that heat and acidosis will suppress vasocontracile function in human skeletal muscle feed arteries. The first study investigated the effect of temperature on ?1- adrenergic receptor stimulation using phenylephrine (PE). Cooling to 35 °C or heating to 39 °C both resulted in an attenuated PE-induced vasocontraction, while smooth muscle function, as determined by KCl, remained unchanged. The goal of the second study was to determine if the potent vasodilator, nitric oxide (NO), could be a factor mediating the heat-induced attenuation in PE-induced contraction observed in the first study. Heating again reduced PE-induced vasocontraction, and was restored with NO blockade. Using molecular approaches, it was determined that heating did not change the density of ?1-receptors, but increased endothelial nitric oxide synthase (eNOS) protein expression. The third study sought to determine the effect of acidosis on vascular reactivity. Increasing levels of acidosis resulted in graded reductions in ?1- receptor-induced vasocontraction, which was in part due to reduced smooth muscle function as assessed by KCl. Increasing acidosis maintained maximal vasorelaxation and suggested enhanced sensitivity to both the endothelium-dependent agonist acetylcholine (ACh) and the endotheliumindependent NO donor sodium nitroprusside (SNP). Collectively, these results indicate that local factors normally associated with exercise-induced increases in skeletal muscle metabolism (i.e. heat and acidosis) are, in fact, capable of altering feed artery vascular reactivity in humans, and therefore likely play a role in sympatholysis in vivo

The Acute Impacts of Resistance Training Performed with and without Blood Flow Restriction on Lower Body Muscular Power

International Journal of Exercise Science 16(6): 1320-1333, 2023. The American College of Sports Medicine recommends resistance training using at least 70% one repetition maximum to improve muscular strength and hypertrophy; however, these intensities may not be safe for all populations. A training technique that has been reported to elicit increases in strength and muscle size uses low intensity resistance training or low load training in combination with blood flow restriction (BFR) to the working muscle. Although the acute effects of BFR on muscle strength and size are well established, the effects of BFR on muscular power are not definitively known. Resistance trained males (n = 14) completed three experimental sessions in which lower body power output and vertical jump height were measured pre and post exercise protocol. The barbell back squat was performed with either low load and blood flow restriction, high load (90% 1 RM, HL), or control (CON). A significant mean difference between pre (M = 46.35 ± 5.61 cm) and post (M = 43.63 ± 4.59 cm) vertical jump heights following 15 repetitions at 20% 1 RM with BFR was observed (p = 0.034), but not with HL or a CON. A decrement in vertical jump height was experienced after an acute bout of BFR with low load resistance exercise. Low load resistance exercise with BFR or high intensity resistance exercise may not be beneficial as part of a warm-up to acutely enhance vertical jump or power output

Exercise Performance and Physiological Responses: The Potential Role of Redox Imbalance

Increases in oxidative stress or decreases in antioxidant capacity, or redox imbalance, are known to alter physiological function and has been suggested to influence performance. To date, no study has sought to manipulate this balance in the same participants and observe the impact on physiological function and performance. Using a single-blind, placebo-controlled, and counterbalanced design, this study examined the effects of increasing free radicals, via hyperoxic exposure (FiO2 = 1.0), and/or increasing antioxidant capacity, through consuming an antioxidant cocktail (AOC; vitamin-C, vitamin-E, α-lipoic acid), on 5-kilometer (km) cycling time-trial performance, and the physiological and fatigue responses in healthy college-aged males. Hyperoxic exposure prior to the 5 km TT had no effect on performance, fatigue, or the physiological responses to exercise. The AOC significantly reduced average power output (222 ± 11 vs. 214 ± 12 W), increased 5 km time (516 ± 17 vs. 533 ± 18 sec), suppressed ventilation (VE; 116 ± 5 vs. 109 ± 13 L/min), despite similar oxygen consumption (VO2; 43.1 ± 0.8 vs. 44.9 ± 0.2 mL/kg per min), decreased VE/VO2 (35.9 ± 2.0 vs. 32.3 ± 1.5 L/min), reduced economy (VO2/W; 0.20 ± 0.01 vs. 0.22 ± 0.01), increased blood lactate (10 ± 0.7 vs. 11 ± 0.7 mmol), and perception of fatigue (RPE; 7.39 ± 0.4 vs. 7.60 ± 0.3) at the end of the TT, as compared to placebo (main effect, placebo vs. AOC, respectively). Our data demonstrate that prior to exercise, ingesting an AOC, but not exposure to hyperoxia, likely disrupts the delicate balance between pro- and antioxidant forces, which negatively impacts ventilation, blood lactate, economy, perception of fatigue, and performance (power output and 5 km time) in young healthy males. Thus, caution is warranted in athletes taking excess exogenous antioxidants

Physiological Responses to Speed-Matched Running on Non-Motorized Assault AirRunner versus Traditional Treadmills in Active Females: A Pilot Study

International Journal of Exercise Science 15(4): 1262-1273, 2022. Treadmills are utilized as a training tool to improve aerobic fitness, but precise understanding of intensity and the corresponding physiological strain is critical for optimizing exercise prescription and associated adaptations. Running on non-motorized, curved treadmills may result in greater oxygen uptake (VO2), increased heart rate (HR), and increased rating of perceived exertion (RPE) compared to traditional motorized treadmills. The purpose of this study was to investigate the physiological responses on non-motorized versus traditional motorized treadmills during speed-matched running. Participants were 4 college-aged, recreationally active females. HR, VO2, respiratory exchange ratio (RER), and RPE were monitored during 3 speed-matched stages of incremental exercise in two conditions: the non-motorized Assault AirRunner and a traditional motorized treadmill, as well as for 5 minutes post-exercise. VO2, RER, and HR were greater in the Assault condition (ESVO2 = 0.998, ESRER = 0.839, ESHR = 0.972, p \u3c 0.05). While not significant between groups, RPE showed a greater increase with increasing speeds in the Assault condition (ES = 0.728), as did RER (ES = 0.800, p \u3c 0.05). Cumulative excess-post exercise oxygen consumption (EPOC) during a five-minute period post-exercise was also greater in the Assault condition, and HR and RER remained higher five minutes post-exercise in the Assault condition (ESEPOC = 0.738, ESHR = 1.600, ESRER = 2.075, p \u3c 0.05). The Assault AirRunner elicited greater physiological responses (VO2, carbohydrate usage, and HR) in response to speed-matched running in comparison to a traditional motorized treadmill in active college-aged females. Collectively, aerobic exercise conducted on the Assault AirRunner has a greater physiological and perceived intensity and need to be taken into consideration when designing and implementing training programs or testing

Auditory verbal hallucinations in first-episode psychosis: a phenomenological investigation

Background In dimensional understanding of psychosis, auditory verbal hallucinations (AVH) are unitary phenomena present on a continuum from non-clinical voice hearing to severe mental illness. There is mixed evidence for this approach and a relative absence of research into subjective experience of AVH in early psychosis. Aims To conduct primary research into the nature of subjective experience of AVH in first-episode psychosis. Method A phenomenological study using diary and photo-elicitation qualitative techniques investigating the subjective experience of AVH in 25 young people with first-episode psychosis. Results AVH are characterised by: (a) entity, as though from a living being with complex social interchange; and (b) control, exerting authority with ability to influence. AVH are also received with passivity, often accompanied by sensation in other modalities. Conclusions A modern detailed phenomenological investigation, without presupposition, gives results that echo known descriptive psychopathology. However, novel findings also emerge that may be features of AVH in psychosis not currently captured with standardised measures