Introduction: Recent evidence in isolated mitochondria and permeabilized muscle fibers in ex vivo using simultaneous measurements of O2 consumption and ATP production suggest that mitochondrial efficiency provides an additional mechanism to fine-tune oxidative phosphorylation rate to ATP demand in skeletal muscle. However, in the absence of a direct measurement of both VO2 and ATP synthesis from the same region of the contracting muscle, whether this mechanism plays a role in the skeletal muscle in vivo is still unknown. Purpose: Using a noninvasive approach combining phosphorus and proton magnetic resonance spectroscopy (31P/1H-MRS), the present study aimed to determine skeletal muscle ATP synthesis rate and muscle VO2 during a graded dynamic plantar flexion exercise to determine mitochondrial efficiency in contracting skeletal muscle contraction. Method: To measure mitochondrial efficiency under physiological conditions, we applied a recently developed methodological approach in ex vivo to human gastrocnemius muscle in vivo using 31P/1H-MRS noninvasive techniques. We conducted a series of constant workloads and ischemic protocols to assess oxidative ATP synthesis (ATPox) rate and Myoglobin-derived oxygen consumption (Mb-derived VO2). Specifically, during two separate visits, in 12 healthy, sedentary to recreationally active young male adults, we determined the ATPox rate by measuring the initial phosphocreatine (PCr) resynthesis rate during recovery and Mb-derived VO2 during 30 seconds of occlusion at the end of each given exercise workload. Results: The calculated mean power output during constant load performed by all subjects increased linearly at each incremental workload for both 1H and 31P visits. The mean percent coefficient of variation (CV%) at all exercise workloads (25% of WRmax= 6.0 ± 6.6, 50% of WRmax = 4.5 ± 2.7, 75% of WRmax = 4.9 ± 3.9, 100% = 7.0 ± 4.5) demonstrated high reliability and reproductivity in power output between each visit. The mean concentration of PCr consumption at the steady state remained constant between 25 and 50% of WRmax (28.6 ± 1.7 and 28.2 ± 1.4, respectively) but increased linearly beyond 50% of WRmax (75% = 22.9 ± 1.4 mM and 100%= 18.0 ± 1.4 mM, respectively). Mean intracellular pH was not significantly different between 25 and 50% of submaximal workloads (6.98 ± 0.02 and 6.97 ± 0.02, respectively). Intracellular pH dropped to 6.94 ± 0.02 during the last min of exercise at 75% of WRmax and further decreased at 100% of WRmax, (6.87 ± 0.03). The percentage of Mb oxygenation level and partial pressure of oxygen(PO2) at the steady state exhibited a consistent linear decline with increasing workload. Accordingly, a distinct and strong linear relationship was found between the MbO2 and workload (r2 = 0.71). Similarly, as the exercise workload increased, the ATPox synthesis rate also increased linearly throughout all exercise workloads (r2 = 0.45). In contrast, there was no significant change in Mb-derived VO2 with increased exercise workload averaged over a 30 s (r2 = 0.36) and 10 s time frame (r2 = 0.17). As a result, there was no significant correlation between ATPox synthesis rate and Mb-derived VO2 across exercise intensities. However, at rest, the P/O ratio in the gastrocnemius muscle was 1.95 ± 0.68, consistent with theoretical values and previous studies in mice. Conclusion: Despite the decrease in MbO2 (%), Mb-derived VO2 from both 30 and 10 s averages remained relatively constant during the ischemic protocol, likely due to O2 availability limitation induced by the prolonged occlusion and the slow time-resolution for measuring the dMb signal, which precluded the quantification of mitochondrial efficiency during exercise. However, mitochondrial efficiency calculated at rest was in agreement with previously documented values using other methodologies and thus can provide an additional parameter to more comprehensively evaluate mitochondrial function in vivo.

Abstract Predicting Location and Training Effectiveness (PLATE) Erik Bruenner Physical activity and exercise have been shown to have an enormous impact on many areas of human health and can reduce the risk of many chronic diseases. In order to better understand how exercise may affect the body, current kinesiology studies are designed to track human movements over large intervals of time. Procedures used in these studies provide a way for researchers to quantify an individual’s activity level over time, along with tracking various types of activities that individuals may engage in. Movement data of research subjects is often collected through various sensors, such as accelerometers. Data from these specialized sensors may be fed into a deep learning model which can accurately predict what movements a person is making based on aggregated sensor data. However, in order for prediction models to produce accurate classifications of activities, they must be ‘trained’. Training occurs through the process of supervised learning on large amounts of data where movements are already known. These training data sets are also known as ‘validation’ data or ‘ground truth’. Currently, generation of these ground truth sets is very labor-intensive. To generate these labeled data sets, research assistants must analyze many hours of video footage with research subjects. These research assistants painstakingly categorize each video, second by second, with a description of the activity the subject was engaging in. Using only labeled video, the PLATE project facilitates the generation of ground truth data by developing an artificial intelligence (AI) that predicts video quality labels, along with labels that denote the physical location that these activities occurred in. The PLATE project builds on previous work by a former graduate student, Roxanne Miller. Miller developed a classification system to categorize subject activities into groups such as ‘Stand’, ‘Sit’, ‘Walk’, ‘Run’, etc. The PLATE project focuses instead on development of AI to generate ground truth training in order to accurately detect and identify the quality of video data, and the location of the video data. In the context of the PLATE project, video quality refers to whether or not a test subject is visible in the frame. Location classifications include categorizing ‘indoors’, ‘outdoors’, and ‘traveling’. More specifically, indoor categories are further identified as ‘house’, ‘office’, ‘school’, ‘store’ or ‘commercial’ space. Outdoor locations are further classified as ‘commercial space’, ‘park/greenspace’, ‘residential’ or ‘neighborhood’. The nature of our location classification problem lends itself particularly well to a hierarchical classification approach, where general indoor, outdoor, or travel categories are predicted, then separate models predict the subclassifications of these categories. The PLATE project uses three convolutional neural networks in its hierarchical location prediction pipeline, and one convolutional neural network to predict if video frames are high or low quality. Results from the PLATE project demonstrate that quality can be predicted with an accuracy of 96%, general location with an accuracy of 75%, and specific locations with an accuracy of 31%. The findings and model produced by the PLATE project are utilized in the PathML project as part of a ground truth prediction software for activity monitoring studies. PathML is a project funded by the NIH as part of a Small Business Research Initiative. Cal Poly partnered with Sentimetrix Inc, a data analytics/machine learning company, to build a methodology for automated labeling of human physical activity. The partnership aims to utilize this methodology to develop a software tool that performs automatic labeling and facilitates the subsequent human inspection. Phase I (proof of concept) of the project took place from September 2021 to August 2022, Phase II (final software production) is pending. This thesis is part of the research that took place during Phase I lifetime, and continues to support Phase II development.

More than one-half of university students in the United States and Canada are not active enough to gain health benefits. Enjoyment of exercise proposes a feasible solution to the absence of motivation surrounding physical activity. The purpose of this study is to compare the differences in reported enjoyment between upper and lower body cycling graded exercise to exhaustion (GXT). Seven university students (23 ± 3 years old; 26 ± 4 kg/m2) performed two randomized graded exercise tests on different days: one for upper body, one for lower body. Feeling Scale (FS) measured the affective response during exercise. Post-exercise enjoyment values were recorded 15 minutes after concluding GXT using the Physical Activity Enjoyment Scale (PACES), which has been shown to be a valid and reliable measure of physical activity enjoyment. Paired t-tests were used to evaluate mean differences between upper and lower body GXT enjoyment scores. Rank biserial correlations and Cohen's d values were used to evaluate effect size for the non-parametric and parametric analyses. Alpha level was set a priori at p < 0.05. Means and standard deviations were calculated for PACES, age, and BMI. No significant differences were found for enjoyment (p=0.162) between upper (104.3 ± 12.6) and lower-body cycling (97.8 ± 15.3). Notable effect sizes were found for the PACES Total and several subscales (Enjoy/Hate, Pleasant, and Contentment). No significant differences were found for the FS at ventilatory threshold (p=0.586) or at maximal aerobic power (p=0.670) between the upper and lower body GXT trials. More research is needed to explore exercise enjoyment across different exercise modes and provide a more particular evaluation of PACES subscales. Further research should aim to compare enjoyment levels across different physical activity levels (e.g., low, moderate, high), between sexes and within diverse populations.

<p>Functional limitations place youth with cerebral palsy (CP) at an increased risk of physical inactivity and cardiovascular disease. The structure and function of the cardiovascular system of these adolescents has not been previously investigated. In the current cross-sectional study, endothelial function was assessed using flow-mediated dilation (FMD) in eleven adolescents with CP (age 13.2 ± 2.1 y) and compared to eleven healthy, age-and gender-matched control participants (12.4 ± 2.3 y). All participants with CP were ambulatory or ambulatory with assistive devices (lower leg brace) and classified as levels I-II according to the Gross Motor Function Classification System (GMFCS). Baseline arterial stiffness was examined through assessment of central and peripheral pulse wave velocity (cPWV, pPWV,) as well as carotid distensibility, a direct measure of central artery stiffness. A combination of B-mode ultrasound imaging and applanation tonometry was used to calculate carotid distensibility. Carotid intima-media thickness (IMT), a measure of vascular structure, was also quantified using B-mode ultrasound images and a semi-automated edge detection software program. cPWV was calculated using the distance (carotid to femoral via the subtraction method) and time delay between ventricular depolarization and the foot of the femoral waveform. pPWV was calculated from the femoral to dorsalis pedis artery using the distance between each site and time delay between the arrival of the foot of each corresponding waveform. Physical activity (PA) levels were assessed using a 7-day recall questionnaire. Anthropometric measurements as well as measures of resting systolic, diastolic and mean arterial blood pressures were similar in both groups. There were no group differences (p>0.05) in ivabsolute, relative or normalized FMD responses. Both groups also had similar values of carotid IMT as well as all measures of arterial stiffness including carotid distensibility, cPWV and pPWV (p>0.05). No group differences were found in the amount of time spent in light and moderate intensity PA; however, the control group participated in a significantly greater amount of vigorous intensity PA (CON: 196 ± 174 min. vs. CP: 38 ± 80 min). Pearson correlation coefficients with all participants revealed a significant positive relationship between age and cPWV (r=0.485 p=0.026) and negative relationship with carotid compliance (r=-0.436, p=0.048). These findings indicate that the arterial structure and function of youth with CP (GMFCS level I-II), examined in this study are not different from a healthy control group. Future research should include youth with CP of GMFCS levels III-V to gain further insight into the potential consequences of severe mobility impairments and functional limitations on levels of habitual PA and arterial health in this young, clinical population.</p> / Master of Science (MSc)

<p>Chronic resistance training leads to muscle hypotrophy in a wide range of populations however most resistance training studies are relatively small in sample size</p> <p>Three studies were conducted to better understand the sources of this variability. The first study employed a unilateral resistance training model to test the effects of relative training load and volume on the magnitude of hypertrophy and strength gains. This study showed that high relative training loads were no better than low training loads at inducing muscle hypertrophy provided that each set was performed to the point of muscular exhaustion. In agreement with previous finding, strength gains were greatest with the highest loads.</p> <p>The next two studies attempted to correlate various putative regulators of muscle hypertrophy with the magnitude of hypertrophy after 16 weeks of training in 23 subjects. Study two showed no association between the acute responses of testosterone, GH or IGF-1 and muscle hypertrophy but did show associations with androgen receptor content and acute phosphorylation of p70S6K. This suggests that local rather than systemic processes are the most important regulators of muscle hypertrophy.</p> <p>The third study tested whether the acute post exercise protein synthetic response to a single bout of resistance exercise is related to the magnitude of hypertrophy following training in the same subjects. Although previous work has shown that acute post exercise protein synthetic response is qualitatively similar to the magnitude of hypertrophy after chronic training with similar manipulations in different subjects, we did not see any relationship.</p> / Doctor of Philosophy (PhD)

High intensity exercise is believed to yield greater results on health and human performance than moderate intensity exercise. Extensive research indicates that not only do high-intensity interval training (HIT) and sprint interval training (SIT) produce significant improvements in cardiovascular fitness and disease, they may be more effective at improving long-term metabolic function, including insulin sensitivity (Si), by producing more mitochondria. Moreover, compliance rates for HIT and SIT participation are reported to be the same or better than traditional moderate intensity exercise. Because lack of time is often cited as major hindrance to exercise participation, SIT is also seen as a time efficient option to improve health and performance. It does appear, however, that repeated sessions of SIT are needed before overall improvements can be measured. SIT protocols employing maximal 30 sec sprints with ~5 min rest [a 1:9 work-to-rest ratio (W:R)], have garnered much of the research focus, while those using minimal rest periods, like Tabata which uses 20 sec sprints and 10 sec rest (2:1 W:R), have been ignored. This may omit a possible SIT option that could influence acute and chronic adaptations. The role of inflammatory cytokines on Si remains an area of continued research. While endurance exercise is thought to create an overall anti-inflammatory environment that stimulates improvement in Si, SIT is often viewed as pro-inflammatory. However, few studies have provided significant insight into cytokine release following SIT, and none haveexplored its impact on Si. In addition, the impact of W:R on cytokine remains speculative at best. Therefore, the examination of the effect of different sprint protocols of similar total work (kJ) on performance, metabolic function, and inflammatory response may provide valuable insight into these adaptive processes.

A dose response relationship between carbohydrate (CHO) ingestion and exercise performance has not been consistently reported. Additionally the underlying metabolic and neuromuscular explanations for an improvement in performance with increasing doses of CHO have not been fully explained. In Chapter 2 of this thesis 20 male cyclists completed 2 h of submaximal exercise followed by a time trial task (531 ± 48KJ). Three CHO electrolyte beverages, plus a control (water), were administered during a 2 h ride providing 0, 20, 39 or 64 g CHO·h-1 at a fluid intake rate of 1 L·h-1. Performance was assessed by time to complete the time trial task, mean power output sustained, and pacing strategy used. Mean task completion time (min:sec ± SD) for 39 g·h-1 (34:19.5 ± 03:07.1, p=0.006) and 64 g·h-1 (34:11.3 ± 03:08.5 p=0.004) of CHO were significantly faster than control (37:01.9 ± 05:35.0). The mean percentage improvement from control was -6.1% (95% CI: -11.3 to -1.0) and -6.5% (95% CI: -11.7 to -1.4) in the 39 and 64 g·h-1 trials respectively. The 20 g·h-1 (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared to control (p = 0.126) despite a mean improvement of -3.7% (95% CI -8.8 to 1.5%). These data demonstrate that consuming CHO at a rate between 39 to 64 g·h-1 is likely to be optimal for most individuals looking to utilise a single source CHO as an ergogenic aid during endurance performances lasting less than 3 hrs. Attempts have been made to try and understand the acute metabolic regulation that occurs when ingesting increasing amounts of CHO. However, no one study has fully investigated the metabolic mechanisms underlying graded increments of CHO ingestion. In Chapter 3 we aimed to utilise stable isotopes and blood metabolite profiles to examine the integrated physiological responses to CHO ingestion when ingested at rates throughout the range where performance gains appear greatest. Twenty well-trained male cyclists completed 2 h constant load ride (95% lactate threshold, 185 ± 25W) where one of three CHO beverages, or a control (water), were administered every 15 min, providing participants with 0, 20, 39 or 64 g CHO·h-1 at a fixed fluid intake rate of 1L·h-1. Dual glucose tracer techniques (6,6,2H2 glucose and U13C labelled glucose) were used to determine glucose kinetics and exogenous carbohydrate oxidation (EXO) during exercise. Endogenous CHO contribution was suppressed in the second hour of exercise when consuming 39 and 64 g·h-1 in comparison to 0 g·h-1 (-7.3%, 95%CI: -13.1 to -1.6 and -11.2%, 95%CI: -16.9 to -5.5 respectively). Additionally, consuming 64 g·h-1 suppressed the endogenous CHO contribution by -7.2% (95%CI: -1.5 to -13.0) compared to the 20 g·h-1 treatment. Exogenous CHO oxidation rate increased by 0.13 g·min-1 (95%CI: 0.10 to 0.15) and 0.29 g·min-1 (95%CI: 0.27 to 0.31) when consuming 39 and 64 g·h-1 in comparison to 20 g·h-1 of CHO. Peak exogenous CHO oxidation rates were 0.34 (0.06), 0.54 (0.09) and 0.78 (0.19) g·min-1 for 20, 39 and 64 g·h-1 respectively. Plasma NEFA concentration was 0.10 (95%CI: 0.07 to 0.13), 0.12 (95%CI: 0.10 to 0.16) and 0.16 (95%CI: 0.13 to 0.19) mmol.L-1 higher when consuming 0 g·h-1 in comparison to 20, 39 and 64 g·h-1 respectively. Both 39 and 64 g·h-1 were effective at sparing endogenous CHO stores of which it is estimated that most of this is liver glycogen sparing, but the measured response was highly variable between individuals. Consuming 39 g·h-1 of CHO appears to be the minimum ingestion rate required to have a significant metabolic effect that results in an increase in performance. Recent research has indicated a key role of endogenous CHO sensing and oral glucose sensing in maintaining central drive and peripheral function during endurance exercise tasks. Consuming 39 and 64 g·h-1 of CHO elicits the greatest improvements in performance and also demonstrate a similar metabolic response. The improvement in subsequent time trial performance when consuming 39 and 64 g·h-1 coincided with significant alterations in whole body substrate usage that lead to endogenous CHO sparing at the same ingestion rates. In Chapter 4 we aimed to utilise gold standard neuromuscular function assessment techniques, alongside novel measures, to investigate the effect of consuming different rates of CHO on neuromuscular function during and following prolonged cycling exercise. In a double-blind, randomised cross-over design, well-trained male cyclists (n=20, mean±SD, age 34 ± 10 y, mass 75.8 ± 9 kg, peak power output 394 ± 36 W, V̇O2max 62 ± 9 ml·kg-1·min-1) completed 2 familiarisation trials then 4 experimental trials. Trials involved a 2 h submaximal ride followed by a high intensity time trial task lasting approx. 35 min with each of 0, 20, 39 and 64 g·h-1 CHO ingestion rates during submaximal exercise. Each trial involved pre and post exercise assessments (MVC, Mwave twitch potentiation and force, motor unit recruitment and firing rate assessment using high density EMG) and during exercise (gross EMG amplitude). MVC peak torque values were reduced post exercise by -20.4 nM (95%CI: -26.5 to -14.4) in comparison to pre value on all trials with no differences between trials. The firing rates of early recruited motor units significantly increased by 1.55 pps (95%CI: 0.51 to 2.59) following exercise in comparison to pre-exercise rates. Gross EMG during the 2 h cycling bout revealed a main effect of treatment (p<0.01) but post hoc comparisons provided no clarity and likely reflect methodological issues. Consuming CHO at ingestion rates between 20 and 64 g·h-1 had little to no impact on the neuromuscular function of well-trained cyclists when comparing pre and post fatiguing exercise values. Despite differences in time trial completion time between trials, following exercise to fatigue in an endurance task, no post exercise differences were detected.

Metabolic Syndrome Insulin Resistance Is Associated with Discordant Distribution of GLUT4 and the Insulin Receptor in Fast-Twitch and Slow-Twitch Muscle Fiber Types We have previously shown that We have previously shown that strength training alone improved insulin responsiveness in sedentary controls but not in metabolic syndrome subjects. Immunoblots of metabolic syndrome subjects[apos] muscle homogenates showed training-related increases in GLUT4 and mitochondrial enzymes was half that seen in the controls. To determine if this was due to changes primarily in fast-twitch fibers (strength fibers), we performed immunohistochemical (IHC) studies on muscle sections from these subjects to quantify fiber-specific changes in GLUT4, phospho-AMPK, phospho-mTOR, ATP synthase, and the insulin receptor. Signal intensity in confocal microscopic images was digitally quantified and the amount in each fiber type was adjusted by the fiber composition and the average size of each fiber type. Fiber type was classified using monoclonal antibodies against slow-twitch (type 1 fibers) and fast-twitch (type 2a and 2b fibers) myosin heavy chains. At baseline, both groups had slightly more insulin receptor in slow-twitch fibers, and most of the ATP synthase (mitochondrial marker) was in fast-twitch fibers. In controls, 55% of GLUT4 was in slow-twitch fibers, whereas metabolic syndrome subjects had only 33% of their GLUT4 in slow-twitch fibers. The IHC data showed modest increases in GLUT4 (9-25%), and substantial increases of ATP synthase (55-95%), and insulin receptors (44-104%) in both fiber types in both groups. Training-related increases were seen in phospho-AMPK (25% in slow-twitch, 15% in fast-twitch) only in the control subjects but no change in phospho-mTOR in either subject group. At baseline, metabolic syndrome subjects[apos] muscle had 56% of insulin receptors expressed in slow-twitch fibers, but only 33% of the GLUT4 was in these fibers. Thus, the untrained muscle composition of the metabolic syndrome subjects exhibited a mismatch between insulin receptors and GLUT4 in their fiber-specific distributions. This mismatch may contribute to the insulin resistance seen in the metabolic syndrome and may be involved in the diminished insulin sensitivity response to strength training in these subjects.

Lack of Improvement in Insulin Responsiveness in the Metabolic Syndrome after Resistance Training Only May Be Due to Fewer Muscle Slow-Twitch Fibers and Decreased Activation of AMPK Ten non-diabetic subjects (fi Ten non-diabetic subjects (five males, five females) with the Metabolic Syndrome underwent eight weeks of supervised strength training. Training consisted of five weekly sessions. A brief orientation period was followed by two blocks of progressively increasing intensity training. Nine control subjects were trained at the same time following the same protocols. At the completion of training, strength and VO[sub]2[/sub]max increased by 10% in both groups, but body composition and body weight had not changed. Insulin responsiveness, quantified using a three hour euglycemic clamp procedure, did not improve in the insulin resistant Metabolic Syndrome subjects, but increased significantly (13%) in the control group. Control subjects had significantly more slow-twitch muscle fibers at baseline (50% vs. 36%). The fiber composition was not changed in either group by training. Expression of GLUT4, the principle insulin-responsive glucose transporter, increased significantly in both groups (39% in Metabolic Syndrome subjects, 76% in the control group). The muscle mitochondrial biogenesis pathway reflected by AMPK total expression and activation, and the muscle hypertrophy pathway as indicated by mTOR expression and activation were increased in both groups. Even though total AMPK and total mTOR increased about 40% in both groups, the change in activated phospho-AMPK was greater in the control group (38% vs. 8%), and the activated phospho-mTOR increased more in the Metabolic Syndrome group (50% vs. 25%). Since AMPK is predominantly expressed in slow-twitch muscle fibers and mTOR is expressed at higher levels in fast-twitch fibers, these data may reflect the difference in fiber composition between the two groups. Strength training resulted in qualitatively similar effects on muscle remodeling in persons at low risk or high risk for diabetes, but greater activation of AMPK was associated with increased insulin responsiveness. In Metabolic Syndrome subjects, resistance training alone activated muscle hypertrophy pathways and increased muscle GLUT4 expression, but did not improve insulin responsiveness.

Resistance training of healthy young men typically results in muscle hypertrophy and a shift in vastus lateralis composition away from type IIx fibers to an increase in IIa fiber content. Our previous studies of 8 wk of resistance training found that many metabolic syndrome men and women paradoxically increased IIx fibers with a decrease in IIa fibers. To confirm the hypothesis that obese subjects might have muscle remodeling after resistance training very different from healthy lean subjects, we subjected a group of nine obese male volunteers to progressive resistance training for a total of 16 wk. In these studies, weight loss was discouraged so that muscle changes would be attributed to the training alone. Detailed assessments included comparisons of histological examinations of needle biopsies of vastus lateralis muscle pretraining and at 8 and 16 wk. Prolonging the training from 8 to 16 wk resulted in increased strength, improved body composition, and more muscle fiber hypertrophy, but euglycemic clamp-quantified insulin responsiveness did not improve. Similar to prior studies, muscle fiber composition shifted toward more fast-twitch type IIx fibers (23 to 42%). Eight weeks of resistance training increased the muscle expression of phosphorylated Akt2 and mTOR. Muscle GLUT4 expression increased, although insulin receptor and IRS-1 expression did not change. We conclude that resistance training of prediabetic obese subjects is effective at changing muscle, resulting in fiber hypertrophy and increased type IIx fiber content, and these changes continue up to 16 wk of training.