Thesis (Ph. D.)--University of North Texas, Aug., 2009. / Title from title page display. Includes bibliographical references.

Thesis (M. Sc.)--York University, 2002. Graduate Programme in Kinesiology and Health Science. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ71630.

Physical inactivity is a major risk factor for chronic disease; yet the majority of the population does not meet physical activity recommendations, with fatigue being a primary underlying reason. Common nutritional supplements such as caffeine (CAF) and carbohydrate (CHO) are frequently taken prior to and during exercise and can delay fatigue, particularly in trained athletes; but, whether these same reductions in fatigue translate to habitually sedentary individuals is less clear. The main goal of this research was to investigate the influence of nutritional aids: CAF, low-calorie CHO, and their combination CAF+CHO to delay physical and mental fatigue in healthy but sedentary men and women compared to endurance-trained counterparts. The minimum amount of CHO that could elicit a benefit without eliciting a metabolic response when ingested remains unclear. Thus, our first aim was to evaluate glycemic response after ingestion of CHO drinks ranging from 0-6% CHO; and, to determine effects of two methods of CHO administration (ingest and oral rinse without ingestion) on sustained attention during a mentally fatiguing cognitive task. In agreement with evidence that “low calorie beverages” do not appear to alter blood glucose, a 0.4% CHO solution (<2 g CHO) elicited the most similar response to artificially sweetened placebo and was evaluated further. Compared to oral rinse of a small amount (<2 g) of CHO or control (0 g CHO), ingestion of an equivalent “dose” (<2 g CHO) in the 0.4% CHO solution maintained sustained attention, providing evidence that ingesting a low-CHO drink may be more effective than simply rinsing, in a fasted state. Oral rinse of CHO did not, however, provide any benefit compared to rinsing a control solution. Our second aim was to evaluate the efficacy of ingesting a moderate dose of CAF (3 mg/kg), low-CHO, and the combination of CAF+CHO on exercise capacity in trained (ET) versus sedentary (SED) groups. As expected, CAF reduced perceived effort during exercise and increased endurance capacity (longer total time to volitional fatigue and longer duration before rating vigorous intensity exercise as “very hard”), for ET and SED. However, addition of <2 g CHO did not provide further improvement with CAF; or any benefit when ingested alone, compared to placebo. CAF and CHO did not influence blood glucose but CAF resulted in higher blood lactate compared to no-CAF. As expected, ET had higher fat oxidation than SED; and, CAF increased CHO oxidation but not fat oxidation. CAF tended to maintain maximal voluntary contractile (MVC) strength in the quadriceps after exercise; but, CAF did not influence voluntary muscle activation or appear to have a direct effect on skeletal muscle since electrically evoked strength was not altered with CAF. Since acute exercise also benefits cognition independent of CAF or CHO, our third aim was to determine: (1) the effect of moderate intensity exercise (MOD-EX) on sustained attention in comparison to seated rest; and 2) whether CAF provides additional benefit to sustained attention and perceptual measures when combined with exercise. As expected, compared to an equivalent duration of rest, MOD-EX improved sustained attention following mental fatigue in both groups; and, when coupled with CAF, provided greater benefit to sustained attention and perceived mental energy. Although CAF’s beneficial effect on sustained attention persisted after exercise to volitional fatigue, it did not improve perceptual measures of reduced mental energy and increased mental fatigue at the point of physical fatigue. Our research investigated nutritional aids that are not only beneficial for athletes, but also widely consumed by the general population despite their lack of regular physical activity. In response to public health recommendations for reducing sugar intake, low-sugar/low-calorie drinks have been heavily marketed to the population despite much research to support their efficacy. Our findings suggest that low-CHO can be ergogenic during a sedentary mental task in a fasted state, perhaps through central mechanisms. Although CHO mouth rinse is evidenced to be efficacious for exercise performance without ingestion, we did not find that ingestion of low-CHO provides any significant benefit during moderate to vigorous exercise following a small meal. However, a moderate dose of CAF was ergogenic for both ET and SED. Future work should not only investigate additional exercise interventions; but also different CHO and CAF doses and administration protocols, and their relative metabolic implications.

No description available.

Children and adolescents are regular consumers of caffeine, and their consumption is increasing. Caffeine has been shown to affect the later behaviour of rats and mice when exposed to the drug daily before birth and during the lactational period of development. However, to date, little research has investigated the effects caffeine consumption may have on adolescent brain development, and the behavioural consequences of this. The present study, therefore, investigated the effects of repeated caffeine exposure on adolescent rats on behavioural measures of anxiety. During middle and later adulthood, the rats’ activity and emotional reactivity were assessed by means of frequencies of rearing, ambulation, immobility, defaecation and urination recorded in an open field, as well as their occupancy of corners and centre squares of the field, and their partial emergence and latencies to fully emerge from a small darkened chamber into a brightly lit arena. The results showed that those rats treated with caffeine were probably more emotionally reactive than untreated controls, as suggested by more immobility, defaecation and urination. There were also effects on rearing and ambulation that might have arisen from increased impulsivity. Overall, the results suggest that exposure to caffeine during adolescence produces some small but significant increases in emotionality in adulthood. This study may have clinical implications, as it is possible that people exposed to caffeine as adolescents, may show increased anxiety later in life.

Children and adolescents are regular consumers of caffeine, and their consumption is increasing. Caffeine has been shown to affect the later behaviour of rats and mice when exposed to the drug daily before birth and during the lactational period of development. However, to date, little research has investigated the effects caffeine consumption may have on adolescent brain development, and the behavioural consequences of this. The present study, therefore, investigated the effects of repeated caffeine exposure on adolescent rats on behavioural measures of anxiety. During middle and later adulthood, the rats’ activity and emotional reactivity were assessed by means of frequencies of rearing, ambulation, immobility, defaecation and urination recorded in an open field, as well as their occupancy of corners and centre squares of the field, and their partial emergence and latencies to fully emerge from a small darkened chamber into a brightly lit arena. The results showed that those rats treated with caffeine were probably more emotionally reactive than untreated controls, as suggested by more immobility, defaecation and urination. There were also effects on rearing and ambulation that might have arisen from increased impulsivity. Overall, the results suggest that exposure to caffeine during adolescence produces some small but significant increases in emotionality in adulthood. This study may have clinical implications, as it is possible that people exposed to caffeine as adolescents, may show increased anxiety later in life.

Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 48-59)

No description available.

Most sleep loss research has concentrated on long duration, repeated measures performance of low-level, monotonous tasks, such as vigilance and reaction time, in support of the theory that sleep loss induces a decline in Non-Specific arousal while having no specific effects on functioning. Numerous studies have shown the beneficial effects of caffeine on this type of performance measure. Recent studies have been conducted on executive functioning tasks that are short, novel, and stimulating. These measures display a sensitivity to sleep loss after 36h that is not compensated by waking countermeasures such as motivation and caffeine. These findings suggest Specific effects of sleep loss, contrary to the Non-Specific theory, particularly on tasks associated with frontal lobe activation. Similarities between performance deficits following brain lesions and those observed in sleep loss subjects form the basis of a neuropsychological model of sleep function. This thesis was an endeavour to document the findings of executive functioning sensitivity following 27 and 36 hours of sleep loss, testing the effect of two common countermeasures, caffeine and a nap. It was established that the critical period of sleep loss for executive functioning performance is at 36 hours. Sleep deprivation effects for periods shorter than 36 hours can be countered by a waking countermeasure, caffeine. It was further established that a 2-hour prophylactic nap opportunity inhibited sleep deprivation effects at 36-hr performance testing for executive functions. The systematic analysis of the effects of sleep loss on language skill, a complex task which is possibly an executive functioning task associated with frontal lobe activation but largely neglected in the literature, detected an increase in variability in language skill, and a propensity towards production errors in speech, but not writing, at 36 hours without sleep. This effect was not observed at 27 hours. The findings are discussed in support of a hypothetical consolidated model of Specific and Non-Specific Effects of sleep loss.

No description available.