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Traditional approaches to exercise testing in children may not provide the most appropriate measures of a child's physiological responses to exercise, partly because they do not reflect children's normal intermittent activity patterns. The measurement of the rate and magnitude of change of oxygen uptake to dynamic exercise, oxygen uptake kinetics (V02 KINETICS provides an alternative approach to exercise testing. A submaximal, intermittent, pseudo-random binary sequence (PRBS) exercise test to measure V02 KINETICS may provide a useful method of measuring the metabolic responses of children to exercise. Traditional methods used in the analysis of V02 KINETICS require the fitting of explicit models in order to characterise the data. These models have not however been validated for use in children. As the responses to the PRBS protocol are analysed in the frequency domain, explicit models and their physiological correlates are not required to characterise the data. Another potential problem in the measurement of V02 KINETICS in children are the small work rate changes that can be employed to stimulate the exercise response whilst constraining the test to the aerobic range. In respiratory gas measurement, breath-by-breath variability (noise) can be large in comparison to the magnitude of the metabolic response and this signal noise can obscure some characteristics of the response. The aim of the study was to develop appropriate measurement techniques to reduce the effects of breath-by-breath variability and to apply the techniques to the measurement of V02 KINETICS in children. The main experimental study compared the V02 KINETICS of children with those of adults. Ten children (3 females) in the age range 8 to 13 and twenty adults (10 females) in the age range 20 to 28 years completed a PRBS test to measure V02 KINETICS and an incremental ramp protocol on a cycle ergometer (Bosch 550 ERG) to establish V02 MAX, T VENT and delta efficiency. Breath-by-breath respiratory gas analysis was undertaken using a respiratory mass spectrometer (MGA1100). Estimates of alveolar gas exchange were made using the algorithm of Beaver et al. (1981) and a post hoc value of an effective lung volume was calculated to minimise the breath-by-breath variability. A cross-correlation technique (CC) was used to filter out the effects of anomalous (nonphysiologic) V02 responses recorded during the PRBS protocol. Subsequent Fourier analysis of the auto-correlation and CC functions provided a description of V02 KINETICS in the frequency domain in terms of amplitude ratio and phase delay over the frequency range of 2.2-8.9mHz. At each of the frequencies assessed amplitude ratio was higher in children (P<0.001) than in either of the adult groups. Phase delay was also significantly shorter in children compared to adults males (P<0.01) and adult females (P<0.001) but this effect was not identifiable at any specific frequency. Maximal oxygen uptake was not significantly different in adult males (42.5 ml"kg "min) and children (44.7 ml-kg'-min') but was lower in adult females (36.9 ml"kg "min) than adult males (P<0.01) and children (P<0.001). Ventilatory threshold (% V02 MAX) was not different between groups. Delta efficiency was significantly lower in children than adult males (P<0.05) and adult females (P<0.01). These results support the contention that there are maturational differences between adults and children in the metabolic processes involved in the utilisation of oxygen during physical activity. It has been argued, theoretically, that in adults the control of V02 KINETICS is driven by ATP demand in the skeletal muscle. As the mitochondria] capacity and the concentration of oxidative enzymes is higher in children than in adults it is likely that the controlling factor(s) for V02 KINETICS in children also relates to some aspect of peripheral metabolism. It is suggested that the PRBS protocol, with appropriate noise reduction techniques, is considered a suitable method for investigating the metabolic responses of children to dynamic exercise.

Early research with beta-alanine (beta-ALA) supplementation has shown increases in muscle carnosine as well as improvements in body composition, exercise performance and blood lactate levels. Creatine monohydrate supplementation has been extensively researched for its effects on anaerobic exercise performance. Recently, a new line of studies have examined the combined effects beta-ALA and creatine supplementation on anaerobic exercise performance and lactate threshold. The purpose of the present study is to examine the acute and chronic effects of beta-ALA supplementation with and without creatine monohydrate on body composition, aerobic and anaerobic exercise performance, and muscle carnosine and phosphagen levels in college-aged recreationally active females. Thirty-two females were randomized in a double-blind placebo controlled manner into one of four supplementation groups including beta-ALA only, creatine only, beta-ALA and creatine combined and placebo. Participants supplemented for four weeks and reported for testing at baseline, day 7 and day 28. Testing sessions consisted of a resting muscle biopsy of the vastus lateralis, body composition measurements, a graded exercise test on the cycle ergometer for VO2max and lactate threshold, and multiple Wingate tests for anaerobic exercise performance. Results showed all supplementation strategies increasing muscle carnosine levels over placebo after four weeks, but not between groups. Muscle creatine increased for all groups after four weeks, but not between groups. There were improvements for all groups with body composition after four weeks, despite the present study not including a specific training protocol. There were no group differences observed for aerobic exercise, blood lactate levels, lactate threshold, ventilatory threshold, peak power, mean power, total work or rate of fatigue. There were some trends for anaerobic exercise indicating groups supplementing with creatine may have greater improvements, however, these findings were not statistically significant. The present study failed to show any additive effects of beta-ALA and creatine supplementation for body composition, aerobic exercise, lactate threshold or anaerobic exercise measures. This could be due to the small sample size resulting in low power and effect sizes. Previous research has demonstrated that four weeks of beta-ALA and creatine supplementation was enough time to increase muscle carnosine and phosphagen levels. However, perhaps more time is needed for performance adaptations to occur, especially without the addition of an exercise training component.

The vasodilatory effects of nitric oxide (NO) have attracted a lot of attention from many investigators who are interested in treatment for cardiovascular disease or hypertension. Recently, however, NO has drawn the attention of people who are looking for new avenues to improve their health, as well as effective ways to enhance exercise performance. In particular, NO, a potent vasodilator, is known to regulate blood flow to active muscles and improve muscle contractile efficiency during exercise, allowing participants to exercise much longer with less fatigue. Neo40TM contains 420mg of a nitric oxide blend with 75mg of caffeine. Therefore, the purpose of the current study was to investigate the effects of Neo40TM on cycling time trial performance and exercise efficiency in 15 moderately trained cyclists. The protocol was a double-blind, randomized, placebo-controlled, two-period, within-subjects crossover study. The treatments were Neo40TM, and a non-caloric similarly favored placebo (PLA). Fifteen participants were randomly assigned to ingest a Neo40 TM or PLA in lozenge form. Exercise performance was assessed by time to complete a simulated 20.15km time-trial course. Exercise efficiency was also measured by VO2 and lactate accumulation at standardized submaximal steady-state exercise intensities. Time-trial performance was enhanced by 2.1% when participants consumed Neo40TM compared to a PLA without a significant difference in rating of perceived exertion (RPE). Time to complete 6km, 10km, 19.5km and 20.15km of cycling was analyzed by gender. A significant difference was found in female subjects at all time points, but not in male subjects. We did not find significant treatment effects for VO2, respiratory exchange ratio (RER), RPE, heart rate (HR) and lactate concentration during steady state exercise. In conclusion, acute supplementation with Neo40TM improved time-trial performance by an average of 2.1% although there were no treatment effects in regards to factors related to work efficiency. / text

The purpose of this study was to: (a) determine if listening to music can reduce the potential aversiveness of an acute session of sprint interval training (SIT) by improving affect, motivation and enjoyment, and examine the effects of music on performance; and (b) evaluate participants’ attitudes and intentions towards SIT and determine if they would change after experiencing SIT. Twenty moderately active adults (22±4y), unfamiliar with interval exercise, completed an acute session of SIT under two different conditions: music and no music. The exercise consisted of four, 30-second Wingate Anaerobic Test (WAnT) bouts on a cycle ergometer, separated by 4 minutes of rest. Power output, ratings of perceived exertion (RPE), affect, motivation, and enjoyment of the exercise were measured. Attitudes and intentions towards SIT were evaluated at baseline and follow-up. Mixed-effects models were used to evaluate changes in the dependent measures over time and between the two conditions. Paired sample t-tests were conducted to compare differences between attitudes and intentions from baseline to follow-up. Peak and mean power over the course of the exercise session were higher in the music than no music condition (coefficients=49.72 [SE=13.55], 23.65 [SE=11.30], ps<0.05). A significant time X condition effect emerged for peak power (coefficients=-12.31 [SE=4.95], p<0.05). There were no between-condition differences for RPE, affect or motivation. Perceived enjoyment increased over time, and was consistently higher in the music condition (coefficient=7.00 [SE=3.05], p<0.05). Finally, attitudes and intentions towards SIT were positive at baseline and did not change upon study completion. Overall, the results suggest music enhanced in-task performance and enjoyment of an acute bout of SIT. Listening to music during intense interval exercise may be an effective strategy to facilitate participation in, and adherence to, this form of training. Furthermore, experiencing an intense SIT protocol does not alter pre-existing positive attitudes and intentions towards SIT. / Thesis / Master of Science in Kinesiology

Exerting cognitive control can lead to mental fatigue and impair self-regulation of subsequent physical performance. However, current understanding is limited due to a number of factors. First, studies have employed manipulations involving either high or low cognitive demands, failing to test whether a dose-response relationship exists between mental fatigue and physical performance. Second, the role of several psychological variables among the mental fatigue – physical performance relationship remains unclear. Third, current literature lacks generalizability in that existing findings have largely been derived from studies involving active samples performing physical tasks that the general population may not commonly engage in for health and fitness benefits. Lastly, there has been little research examining intervention strategies that may attenuate the effects of mental fatigue on physical activity behaviour. This dissertation aimed to advance our understanding of self-regulation of physical activity behaviour in response to mental fatigue by addressing shortcomings within the literature discussed above. Study 1 examined whether a dose-response relationship exists for mental fatigue and physical performance. Results showed a performance threshold exists between 4 and 6 minutes of exposure to a mentally fatiguing cognitive control task. Beyond this threshold, task self-efficacy also showed uniform reductions which mediated the mental fatigue – physical performance change relationship. Findings are consistent with previous research and reveal self-efficacy is a key variable that accounts for the negative effects of mental fatigue on physical performance. Study 2 investigated the hypothesis that offering a performance contingent monetary incentive would attenuate the negative carryover effects of mental fatigue on physical performance. Findings showed mental fatigue caused characteristic declines in physical performance; however, incentives countered the effects of mental fatigue and led to performances equal to those witnessed in a non-fatigued state. Interestingly, incentives did not provide any additional benefit for performance when not fatigued. Findings support motivational accounts of self-regulation, although incentives may lack practicality and may not be a cost-effective means to alter exercise behaviour. Study 3 examined the effect of mental fatigue on intended physical exertion and exercise performance reflective of current public health guidelines for physical activity in a sample comprised of insufficiently active university students. Findings showed mental fatigue alters the amount of physical effort people are willing to invest in an exercise workout and follow through with those intentions by doing less work and exercising at a lower heart rate intensity. These are the first results showing people may deliberately adjust their physical effort to cope with mental fatigue. Study 4 investigated whether heart rate biofeedback moderates the effects of mental fatigue on vigorous-intensity exercise reflective of current public health physical activity guidelines and the effects of mental fatigue on pre-exercise motivational cognitions. Results showed mental fatigue was associated with decreases in intended physical effort and commitment to vigorous-intensity exercise goals which corresponded with reductions in exercise intensity (i.e., HRAVE) and total work performed when people exercised without feedback. However, HR biofeedback attenuated the negative carryover effects of mental fatigue on exercise behaviour, restoring exercise intensity and performance to levels witnessed in a non-fatigued state. Similar to incentives, biofeedback offered no further benefits for performance when not fatigued. Findings align with predictions of Control Theory and suggest biofeedback using widely available physical activity monitors in combination with goals can improve intensity-based physical activity guideline adherence when confronted with barriers such as mental fatigue. / Thesis / Doctor of Philosophy (PhD) / Effortful cognitive control exertion can lead to mental fatigue and impair self-regulation of subsequent physical performance. However, current understanding is limited due to a number of factors. This thesis addressed several gaps in the literature through a systematic examination of potential mediators and moderators of the mental fatigue - physical performance relationship. Findings revealed downstream physical performance impairments are dependent on exceeding a critical mental fatigue threshold. Reductions in pre-exercise cognitions including self-efficacy, intended physical exertion and goal commitment all correspond with negative changes in exercise performance. Evidence also highlights the generalizability of fatigue-induced effects by demonstrating that insufficiently active people engaging in exercise for health and fitness benefits down-regulate exercise performance in the face of mental fatigue. Incentives and heart rate biofeedback can attenuate the effects of mental fatigue on physical performance. Collectively, evidence provides insight for theories of self-control and can be interpreted within Muller and Apps (2018) neurocognitive framework of motivational fatigue.

Thoracic loads (i.e., a heavy backpack) commonly used in occupational and recreational settings significantly challenge human physiological systems and increase the work of breathing, which may promote respiratory muscle fatigue and negatively impacts whole body performance during physical tasks. Accordingly this thesis: (Chapter number: II) designed a laboratory based protocol that closely reflects occupational demands and (III) assessed the effect that load carriage (LC) has upon physiological and respiratory muscle function. Consequently the thesis addressed (IV) acute, (V) chronic and (VI) functional inspiratory muscle loading strategies to assess the limitations and trainability of the respiratory muscles to load carriage performance. The novel laboratory protocol, performed wearing a 25 kg backpack load, combined submaximal load carriage (LC; 60 min treadmill march at 6.5 km·h-1) and self-paced time trial exercise (LCTT; 2.4 km) to better reflect the physiological demands of occupational performance (between trials mean difference -0.34 ± 0.89 min, coefficient of variation 10.5%). Following LC, maximal inspiratory muscle pressure (PImax) and maximal expiratory muscle pressure (P¬Emax) were reduced by 11% and 13% respectively (P<0.05), and further by 5% and 6%, respectively (P< 0.05), after LCTT. Acute inspiratory loading (2 × 30 forced inspiratory efforts 40% PImax) following an active warm-up (10 min lactate turnpoint) failed to improve LCTT despite a transient increase in PImax of ~7% (P<0.05). Chronic inspiratory loading (6 wk, 50% PImax, 30 breaths twice daily) increased PImax (31%, p<0.05) reduced HR and perceptual responses post-LC, and improved LCTT (8%, P< 0.05) with no change in a placebo control. Combining IMT with functional core muscle exercises improved PImax and LCTT by 7% and 4% respectively (P< 0.05), which was greater than traditional IMT alone. Acute, chronic and functional inspiratory muscle loading strategies did not protect against respiratory muscle or locomotor muscle fatigue during LC and LCTT.

The glycemic index (GI) of a pre-exercise meal has been shown to affect substrate oxidation during exercise and may influence exercise performance. Previous research in this area has focused on continuous, moderate intensity exercise. The purpose of this study was to examine the effects of low and high glycemic index (GI) pre-exercise meals on metabolism and performance during soccer-specific intermittent exercise. Thirteen trained male soccer players (22.3 ± 3.3 yrs) participated in four experimental trials in a repeated crossover design. Isocaloric low GI-high protein (lentils), high GI-high protein (potato + egg whites), or high GI-low protein (potato) meals were consumed two hours before a 90-minute treadmill soccer match simulation. A fasted control condition was also employed. Blood and expired gas samples were collected before and during exercise to assess markers of carbohydrate and fat metabolism. The distance covered on five 1-minute sprints (separated by 2.5 minutes of recovery) performed during the last 15 minutes of the match was used to assess performance. Serum insulin concentration at the start of exercise was higher in the high GI-low protein condition compared to all other conditions (p<0.001). During exercise, the rate of carbohydrate oxidation was significantly higher and the rate of fat oxidation was significantly lower in the high GI-low protein condition compared to control (p<0.05). The distance covered on sprints 1 and 2 was significantly greater in the low GI-high protein condition compared to control (p<0.05). The distance covered on sprint 2 was significantly greater in the high GI-high protein condition compared to control (p<0.05). There were no significant differences between conditions for sprints 3-5. Ratings of perceived exertion (RPE) throughout exercise were significantly lower in the low GI-high protein condition compared to both control and high GI-low protein conditions (p<0.05). It is concluded that low GI-high protein and high GI-high protein pre-exercise meals result in small improvements in initial repeated sprint performance compared to fasted control. Performance was not improved following a high GI-low protein pre-exercise meal compared to control, indicating that the increased carbohydrate oxidation and decreased fat oxidation in this condition may have negated any potential performance advantage of carbohydrate consumption. The lower RPE throughout exercise in low GI-high protein compared to control and high GI-low protein indicates a possible beneficial effect of consuming a low GI meal prior to soccer-specific intermittent exercise.

The glycemic index (GI) of a pre-exercise meal has been shown to affect substrate oxidation during exercise and may influence exercise performance. Previous research in this area has focused on continuous, moderate intensity exercise. The purpose of this study was to examine the effects of low and high glycemic index (GI) pre-exercise meals on metabolism and performance during soccer-specific intermittent exercise. Thirteen trained male soccer players (22.3 ± 3.3 yrs) participated in four experimental trials in a repeated crossover design. Isocaloric low GI-high protein (lentils), high GI-high protein (potato + egg whites), or high GI-low protein (potato) meals were consumed two hours before a 90-minute treadmill soccer match simulation. A fasted control condition was also employed. Blood and expired gas samples were collected before and during exercise to assess markers of carbohydrate and fat metabolism. The distance covered on five 1-minute sprints (separated by 2.5 minutes of recovery) performed during the last 15 minutes of the match was used to assess performance. Serum insulin concentration at the start of exercise was higher in the high GI-low protein condition compared to all other conditions (p<0.001). During exercise, the rate of carbohydrate oxidation was significantly higher and the rate of fat oxidation was significantly lower in the high GI-low protein condition compared to control (p<0.05). The distance covered on sprints 1 and 2 was significantly greater in the low GI-high protein condition compared to control (p<0.05). The distance covered on sprint 2 was significantly greater in the high GI-high protein condition compared to control (p<0.05). There were no significant differences between conditions for sprints 3-5. Ratings of perceived exertion (RPE) throughout exercise were significantly lower in the low GI-high protein condition compared to both control and high GI-low protein conditions (p<0.05). It is concluded that low GI-high protein and high GI-high protein pre-exercise meals result in small improvements in initial repeated sprint performance compared to fasted control. Performance was not improved following a high GI-low protein pre-exercise meal compared to control, indicating that the increased carbohydrate oxidation and decreased fat oxidation in this condition may have negated any potential performance advantage of carbohydrate consumption. The lower RPE throughout exercise in low GI-high protein compared to control and high GI-low protein indicates a possible beneficial effect of consuming a low GI meal prior to soccer-specific intermittent exercise.

The purpose of this study was to investigate the effects of hydroxytyrosol (HT) supplementation on markers of mitochondrial biogenesis, aerobic capacity, and endurance exercise performance in recreationally active men. Sixty-one (n = 61) subjects (21.46 ± 0.22 yrs, 179.46 ± 0.79 cm, 78.91 ± 1.19 kg) consumed either a high dose (HI) HT supplement (150 mg HT), a low dose (LO) HT supplement (50 mg HT), or a placebo (PLA) every day for 6 weeks. Muscle biopsies from the vastus lateralis were obtained at baseline and after 6 weeks of supplement consumption and analyzed for markers of mitochondrial biogenesis: succinate dehydrogenase (SDH), citrate synthase (CS), and peroxisome proliferator-activated receptor ɣ coactivator (PGC)-1α. Subjects completed exercise testing on a bicycle ergometer at baseline and after 3 and 6 weeks of supplement consumption to measure changes in maximal aerobic power (VO2MAX), lactate threshold, respiratory exchange ratio (RER), substrate utilization, and endurance exercise performance on a 20 km time trial course. The primary findings were that HT supplementation increased muscle oxidative enzyme activity suggesting increased oxidative capacity. HT also increased time trial performance at midpoint and endpoint and this corresponded with an improvement in lactate threshold and a lower RER for the LO HT treatment. Time trial performance was also improved at endpoint for PLA, however, unlike LO an HI HT, this was accompanied by a significant increase in rating of perceived exercise (RPE) and not associated with improvements in muscle oxidative capacity. Our results indicate that HT ranging from 50 to 150 mg/day for 6 weeks can improve muscle oxidative capacity and aerobic performance, and suggests that HT may be used chronically to improve mitochondrial function. HT may be used as an effective means to increase mitochondria to improve exercise performance, and limit diseases associated with mitochondrial dysfunction such as cardiovascular disease, type II diabetes, and some cancers. / text