Doctor of Philosophy / Department of Anatomy and Physiology / Thomas J. Barstow / The primary aim of this dissertation was to evaluate the factors that contribute to the cardiorespiratory and vascular responses following exercise conditioning and microgravity deconditioning. The first study of this dissertation (Chapter 2) revealed that exercise training in the head down tilt posture, which places increases central blood volume compared to upright, results in cardiorespiratory adaptations in both upright and head down tilt postures which are not completely expressed with exercise training in the upright posture. These findings suggest that augmentation of the ventricular volume load during exercise training may result in adaptations that transfer across multiple body positions. In the second and third studies measurements of blood velocity and flow were performed via Doppler ultrasound. In Chapter 3 we observed that in the brachial and femoral arteries blood moves with a slightly blunted parabolic velocity profile that is very stable across a range of mean arterial pressures and downstream limb resistances. We concluded that these findings support the current calculations of shear rate based on the assumptions of laminar flow. With these assumptions confirmed, the investigation in Chapter 4 could be performed. We observed that acute exposure to a sustained antegrade shear rate, via unilateral forearm heating, increased measurements of flow-mediated dilation and the overall rate of adjustment for forearm blood flow and vascular conductance during dynamic handgrip exercise. These findings suggest that one potential stimulus for improvements in vascular function and health following exercise conditioning may be exposure to elevations in antegrade shear. Lastly in Chapter 5 we changed focus to the cardiorespiratory deconditioning following long-duration microgravity exposure. We retrospectively reviewed and analyzed previous investigations of microgravity deconditioning and demonstrated that the decrease in maximal O2 consumption ( O2max) occurs as a function of duration of exposure and that both convective and diffusive O2 transport pathways substantially contribute to this decline. In addition we reviewed the current literature and highlighted potential mechanisms, across several organ systems, which may contribute to this decline in O2max. Collectively, these studies revealed the breath of plasticity for cardiorespiratory adaptations to a variety of stressors.

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Many college students struggle to perform well on exams in the early morning. Although students drink caffeinated beverages to feel more awake, it is unclear whether these actually improve performance. After consuming coffee (caffeinated or decaffeinated), college-age adults completed implicit and explicit memory tasks in the early morning and late afternoon (Experiment 1). During the morning, participants ingesting caffeine demonstrated a striking improvement in explicit memory, but not implicit memory. Caffeine did not alter memory performance in the afternoon. In Experiment 2, participants engaged in cardiovascular exercise in order to examine whether increases in physiological arousal similarly improved memory. Despite clear increases in physiological arousal, exercise did not improve memory performance compared to a stretching control condition. These results suggest that caffeine has a specific benefit for memory during students' non-optimal time of day-early morning. These findings have real-world implications for students taking morning exams.

To regular exercise and a healthy diet, the American Heart Association (AHA) strongly recommends rope jumping, and according to previous studies, rope jumping is considered a very strenuous exercise. Therefore the purpose of this study was to determine the steady state metabolic cost of repetitive jumping on the Digi-Jump machine, and to determine if exercise on this device is more or less strenuous than similar exercise with a jump rope. We also evaluated relative intensity of this type of exercise, based on each person’s VO2max as measured on a treadmill. Twenty – seven subjects completed two trials, one jumping trial at a rate of 120 jumps per minute (JPM) with the jumping height set at .5 inch for 5 min, and one graded exercise test (GXT) using the Bruce protocol. Oxygen uptake (VO2), heart rate (HR), respiratory exchange ratio (RER), and rating perceived exertion (RPE) were measured each minute during each trial. Results of this study indicated that steady state VO2 during the 5 min jump test was reached at the 3rd min (p < .05), therefore we equated all other variables (HR, RE, RPE) steady state to be from 3rd min. Average jumping steady state VO2 was 31.1 ± 5.5 ml/kg/min, while average VO2max was 56.4 ± 12 ml/kg/min, thus steady state VO2 during jumping trial was 57.1% of VO2max. Average jumping steady state HR was 149. 2 ± 20.1 bpm, while mean GXT HR was 184.7 ± 9.9 bpm, thus steady state HR during jumping trial was 80.9% of their maximal HR obtained during GXT. Average jumping steady state RER was .99 ± .6,while average GXT RER was 1.15 ± .07, thus steady state RER during jumping trial was 86%, and average jumping steady state RPE was 13.5 ± 1.5, while average GXT RPE was 17.9 ± 1, thus steady state RPE during jumping trial was 75.2%. These data indicate that jumping is a strenuous activity, even if the trial is done on Digi – Jump machine without rope.

Although there is an abundance of research investigating the effects of exercise on cognitive function, few studies have investigated acute effects of exercise on performance of tasks involving executive function. Furthermore, the effects of different exercise intensities on multiple tests of executive function have received little attention. The purpose of this study was to examine the acute effects of 20-minutes of stationary cycling exercise at varying exercise intensities on executive function performance and to determine these acute effects immediately following exercise as well as after 10 and 30-minute delays following exercise. University students (N = 88) completed baseline measures of executive function (stop-signal task [SST] and Stroop task [ST]) and a graded cardiovascular exercise test on Visit 1. On Visit 2, participants were stratified by gender and fitness level and randomized to one of four conditions: high-intensity interval training (HIT), high, moderate or low-intensity steady-state exercise performed on a cycle ergometer. The ST and SST were performed immediately following exercise and again at 10- and 30-minutes post-exercise. Immediately following exercise, ST response times were significantly different (p < .05), demonstrating faster response times for the high and moderate intensity exercise (p < .05), while improvements in SST response inhibition were revealed for the HIT (p < .01) condition. At 10-minutes post-exercise, moderate and low-intensity conditions revealed improvements in ST response times (p <.05), with enhanced SST response inhibition evident in the HIT, moderate and low-intensity conditions (p < .05). At 30-minutes post-exercise, ST response times continued to show improvements from baseline for the moderate and low-intensity conditions (p < .05), while SST response inhibition trended back towards baseline levels (p > .05). The present outcomes demonstrate beneficial effects of exercise, regardless of intensity, for up to 38 minutes post-exercise. Future research should focus on mechanisms that would account for these effects and factors that support enhanced executive function performance with exercise training. / Thesis / Master of Science (MSc)

While the benefits of both cardiovascular exercise and resistance training have been well documented, there is a lack of evidence for the order of exercise that is most effective when both are done in the same day. This study was designed to look at two groups of participants performing both resistance (R) and cardiovascular (C) training in the same day to determine if their order, resistance before cardiovascular (R-C) or cardiovascular before resistance (C-R), matter with regard to changes in body composition, maximal strength, and maximal aerobic capacity. The participants were 17 women between the ages of 30 and 55 years, with a BMI of ≥25 or body fat percentage ≥30% and no apparent risk of heart disease. They were randomly assigned into two groups (R-C = 9; C-R = 8) performing 30 minutes of cardiovascular exercise at 60-70% of their estimated VO2MAX and 7 exercises for 3-4 sets of 6 repetitions at their 6-repetition maximum with the R-C group performing the resistance training first and the C-R group performing the cardiovascular training first. There were three days of testing pre- and post-intervention for body weight, percent fat, fat mass, lean body mass, maximal bench press, maximal deadlift, and VO2MAX. There were no significant differences between groups in any of the variables, although there were trends toward significance in the maximal deadlift (R-C +13.5±8.6kg, ES = 1.15; C-R +6.8±5.6kg, ES = 0.42) and VO2MAX (R-C +2.8±2.4 ml/kg/min, ES = 0.41; C-R +0.9±1.0 ml/kg/min, ES = 0.31). Neither group lost significant amounts of body weight. However, there were significant pre- to post-intervention changes in percent fat, fat mass, lean body mass, maximum deadlift, maximum bench press, and VO2MAX for the C-R group and percent fat, fat mass, maximum deadlift, maximum bench press, and VO2MAX for the R-C group. There were also practically significant between group differences with the C-R group improving more in body fat percentage (ES = 0.89) and lean body mass (ES = 0.68) and the R-C group improving more in 1RM deadlift (ES = 1.50) and VO2MAX (ES = 1.57).

Self-control exertion leads to performance decrements during tasks demanding of muscular and cardiovascular systems (Bray et al., 2008; Marcora et al., 2009). Several reviews have also implicated self-control depletion with the psychobiological state of fatigue (Hagger et al., 2010; Van Cutsem et al., 2017). In this state, individuals have also been noted to report higher levels of perceived exertion when exercising at vigorous intensities (MacMahon et al., 2014; Marcora et al., 2009; Wagstaff et al., 2014). The purpose of this study was to investigate physical performance and ratings of perceived exertion during a self-paced maximum distance cycling trial (MDT) following a short bout of mentally-fatiguing cognitive activity (thought-suppression). Recreationally active participants (N = 16, Mage = 20.94) completed one familiarization session and two testing sessions. All visits were separated by ≥ 72-hours. Control and experimental trials were counterbalanced, with either a 6-minute bout of thought-logging (control) or a 6-minute bout of thought-suppression (experimental) being performed prior to each respective MDT. Ratings of perceived exertion (RPE) were solicited from participants across three sensory domains relevant to MDT task performance (Leg-muscle, Respiration, Mental). Thought-suppression was perceived to be significantly more demanding than the control task, which resulted in significantly higher ratings of mental fatigue (p = 0.04, 2 = 0.26). Distance travelled on the MDT was not significantly different following thought suppression, relative to control trials (p = 0.84, 2 = 0.00). Similarly, a repeated-measures ANOVA showed no differences in HR between conditions (p = 0.95, 2 = 0.00). Despite these similarities, ratings of perceived leg-muscle exertion (RPE-L) were significantly higher during the MDT following thought-suppression (p = 0.05, 2 = 0.24). RPE-R (respiration) and RPE-M (mental) ratings also trended towards higher scores following the experimental manipulation, although they did not differ significantly. RPE-L was perceived to be significantly higher than both RPE-R and RPE-M in both conditions on the MDT (ps < 0.05). RPE-M was rated significantly lower than RPE-L and RPE-R during MDTs in both conditions (ps < 0.05). Results indicate that performing a demanding self-control exertion task for a short duration leads to increased feelings of mental fatigue. The observed levels of fatigue were also associated with higher than normal ratings of perceived exertion during cycling tasks of equal demands and performance. / Thesis / Master of Science (MSc) / Any thought, emotion or behaviour that an individual modifies in order to better suit their goals occurs as a result of self-control exertion. Research indicates that just like the exertion of muscular strength, exerting self-control impacts subsequent attempts to do so. Using a mentally-demanding task, we induced states of self-control depletion which left individuals feeling mentally-fatigued. As a result of this state, participants needed to exert themselves harder in order to complete a task that was perceived less demanding, when non-fatigued.