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Item Metabolic flexibility and endurance performance : a thesis submitted for the degree of Doctor of Philosophy, School of Sport and Exercise, College of Health, Massey University(Massey University, 2017) O'Connor, William JamesThis thesis examined the sex-specific biochemical, physiological and physical performance responses of highly-trained endurance athletes to chronic moderate and low carbohydrate (CHO) training diets. In addition, a novel exogenous ketone supplement was studied to examine its effects on participants’ physiology and performance during the two contrasting diets. STUDY ONE: This study was designed to test whether adaptation to a low CHO diet affects physical capacity during prolonged exercise. Thirteen highly-trained endurance athletes (eight males, VO₂max = 66.0 ± 9.5 mL·kg⁻¹·min⁻¹ ; five females, VO₂max = 50.6 ± 8.4 mL·kg⁻¹·min⁻¹) consumed a moderate (>5 g CHO·kg⁻¹·day⁻¹) or low (<2 g CHO·kg⁻¹·day⁻¹) CHO training diet for four weeks, in a randomised cross-over design. Performance was measured, after a 24 h moderate CHO “loading” regime, through a self-paced time trial to complete a fixed workload, equivalent to five hours at a workload calculated to elicit 55% VO₂max. Although time-to-complete was not significantly different between diets, the average absolute (watts) and relative (W/kg) power outputs were significantly better on the low CHO diet (p = 0.03 and 0.02 respectively). Both sexes responded similarly in terms of performance, whilst only women significantly improved body composition when CHO was restricted (p = 0.02). It was concluded that when CHO is restricted during training, trained endurance athletes show improved ultra-endurance performance relative to their body mass. STUDY TWO: This study was designed to test the sex specific response to a low CHO diet during fasted endurance exercise. The participants and dietary restrictions were the same as outlined in Study One. Physiological measures were collected before, during and after a two-hour ride at a fixed power output, equivalent to 60 % VO₂max. The ride was undertaken after an overnight (>12 hours) fast and completed at three points throughout each dietary intervention (baseline, week two, week four). As expected there were a significant main effect of diet and time on substrate oxidation rates during fasted exercise (p < 0.05). The low CHO diet resulted in lower CHO oxidation and higher fat oxidation (FATox) in both sexes throughout the exercise. The degree of ‘adaptation’ to low CHO intake increased from baseline to week four, with significant interactions between trial and diet (p < 0.05). There was a sex specific negative correlation between the rate of CHO oxidation and perceived exertion (RPE) at the end of the fasted exercise (p = 0.001). Women consistently had a higher RPE at the end of the exercise (p = 0.04). These data show that both men and women can increase their rates of FATox, in a time-dependent manner, when CHO is restricted in the training diet. STUDY THREE: This study was designed to examine the differences in the blood metabolome of highly-trained male endurance athletes (VO₂max = 6.0 ± 9.5 mL·kg⁻¹·min⁻¹)who each underwent two contrasting dietary interventions, in a randomised crossover design as follows: four weeks moderate (> 5 g CHO·kg⁻¹·day⁻¹) or low (< 2 g CHO·kg⁻¹·day⁻¹) CHO. Exercise training was controlled during both conditions. Fasting venous blood samples were collected before and after exercise at 60% VO₂max and the plasma metabolome was analysed using 700 Hz H1 nuclear magnetic resonance (NMR) spectroscopy. Unsupervised (PCA) and supervised (PLSA-DA & OPLS-DA) multivariate statistical analysis models failed to statistically separate the sample groups in regards to the dietary intervention. However, both methods of supervised discriminant analysis (PLS-DA and OPLS-DA) could separate groups based on time (i.e. pre–post exercise). The variable influence on projection (VIP) was used to identify the individual metabolites causing the group separation within the discriminant analysis. Metabolites were analysed using two-way ANOVA and paired t-tests, with the only significant difference being the blood glucose response to exercise at the end of each dietary intervention (p = 0.006). In conclusion, neither the resting nor exercising metabolome is significantly influenced by the CHO content of the diet. This indicates that endurance-trained individuals possess the metabolic flexibility to counter changes in dietary CHO availability and maintain a normal circulating metabolic profile. STUDY FOUR: The aim of this case study was two-fold: to test the effectiveness of a proposed study, and to explore the validity of reports which have claimed that ingesting a ketone supplement can improve endurance performance. One highly-trained male triathlete (VO₂max = 73.0 mL·kg⁻¹·min⁻¹) completed four time-to-exhaustion (TTE) cycling bouts, each preceded by two hours of cycling at 60% VO₂max (power = 213 W). The exercise bouts were completed in a crossover design as follows: ketogenic diet (< 1.5 g CHO·kg⁻¹·day⁻¹) and regular (non-ketogenic) sports drink (K), ketogenic diet with ketone-containing drink (K+KS), high CHO diet (> 5 g CHO·kg⁻¹·day⁻¹) and regular sports drink (CHO), moderate CHO diet and ketone-containing drink (CHO+KS). Ketosis was confirmed with sustained resting blood β – hydroxybutyrate (β-HB) levels of >0.2 mM. Ketone supplementation was associated with better performance following both dietary interventions, with CHO+KS being better than K+KS (12:54 minutes vs 13:32 minutes, respectively). Ketone supplementation resulted in higher [β-HB] during exercise relative to the sports drink (0.63 & 0.78 mM vs 0.20 & 0.25 mM, respectively). VO₂ and blood lactate did not noticeably differ during the fixed intensity ride, but differed greatly during the TTE, with VO₂ beginning higher on the high CHO diet. The results from this study show the potential benefits of ingesting a ketone supplement on endurance performance and suggest that the moderate CHO status of the individual may have an additive effect. Based on these results, it was suggested that a full scientific study be carried out to further test the effectiveness of ketone supplementation on endurance performance. STUDY FIVE: The aim of this study was to test the effects of ingesting a ketone supplement on endurance performance in two different metabolic states, induced by dietary interventions. Six well-trained male endurance athletes (age: 29 ± 9 yrs, mass: 74.1 ± 7.7 kg, VO₂max: 64.1 ± 5.8 mL·kg⁻¹·min⁻¹) underwent a randomised, double-blinded, placebo-controlled protocol, consisting of two dietary interventions, completed as a cross-over design. Following each dietary intervention, a performance session was carried out, during which, participants drank either a ketone-containing (KS) or placebo (PLB) drink. Thus, the performance session was carried out a total of six times; habitual diet (BASE1, BASE2), moderate-CHO diet + PLB (PLB+CHO), moderate-CHO diet + KS (KS+CHO), ketogenic diet + PLB (PLB+K), ketogenic diet + KS (KS+K). Physiological measures were taken during each performance session, which consisted of a 40-minute fixed intensity ride, followed by a self-paced time trial (TT), to complete a fixed workload equivalent to 20 minutes at 75% VO₂ max. There were no main effects or interactions between diet and KS on TT performance or body mass. The KS significantly increased the beta-hydroxybutyrate concentration [β-HB] in the blood at rest and during exercise (peak = 1.1 mM) (p = 0.001). The KS caused an attenuated blood lactate response during the TT compared to baseline and PLB. The respiratory exchange ratio (RER) was significantly lower on the ketogenic diet at rest and throughout fixed intensity exercise but did not differ during the TT. It is concluded that the circulating [β-HB] attained were not high enough to significantly contribute to muscular energy provision via oxidative phosphorylation and that future research into ketone supplements and exercise performance should ensure that a minimum of 2 mM [β-HB] is obtained. Further, the CHO status of the individual can be largely ignored as supplementation appears to be equally effective irrespective of the CHO status.Item Dietary antioxidants and the efficiency of oxygen transport and uptake during endurance exercise : a thesis submitted for the degree of Doctor of Philosophy, School of Sport and Exercise, College of Health, Massey University(Massey University, 2018) Crum, Emma MayThis thesis aimed to determine whether various dietary antioxidant supplementation protocols could enhance the efficiency of oxygen (O2) transport during endurance cycling, and subsequently improve exercise performance. Two naturally-sourced supplements (keratin; KER and pomegranate extract; POMx) were selected for investigation, based on their rich content of either thiols (KER) or polyphenols (POMx). Study One was a crossover study which compared the effect of chronic KER intake compared to a sodium caseinate placebo (CAS) of equal protein content. Fifteen endurance-trained males consumed the supplement on six days per week, for a period of four weeks (0.8 g.kg-1d-1), while participating in endurance cycling training. Blood samples collected throughout each intervention period were unchanged by either supplement for any parameter measured (all p > 0.05). Likewise, neither the O2 consumption (VO2) required to sustain a given level of submaximal cycling exercise, nor the maximal VO2 attained during a graded exercise test to exhaustion were affected by KER or CAS (submaximal VO2, p = 0.13; VO2max, p = 0.25). Further, the maximal power output obtained in the VO2max test was not significantly different between treatments (p = 0.51). Consequently, KER was not recommended as an ergogenic aid for athletes. Study Two investigated the effects of acute POMx supplementation on VO2 during submaximal and maximal cycling exercise, in normoxic (sea-level; SEA) and hypoxic (1657m altitude; ALT) environments. In a randomized, double-blinded, crossover study design, eight highly-trained cyclists ingested 1000 mg of POMx or a placebo (PLAC), 2.5 hours prior to completing three stages of submaximal cycling at 50%, 65% and 80% of maximal O2 consumption (VO2max), followed by a time trial to exhaustion at a workload calculated to elicit 100%VO2max (TTE100%). The protocol was completed on four occasions: in SEA and ALT, with a POMx, and a PLAC trial in each environment. POMx did not alter VO2 during submaximal exercise in either environment (p = 0.67), or during the TTE100% in SEA (p = 0.46). However, its intake allowed maintenance of SEA VO2 values during intense exercise in hypoxic conditions, as indicated by the VO2 measured five minutes into the TTE100% (+3.8 ml.min-1kg-1, 95% CI, -5.7, 9.5, p = 0.001). However, despite this, POMx did not significantly affect TTE100% performance in either environment (p = 0.41), possibly due to the highly-trained nature of participants, who may have required a longer supplementation period for an ergogenic effect to be observed with POMx. Study Three was based on the above findings, and aimed to determine whether an 8-day supplementation period with POMx would be sufficient to alter VO2 and cycling performance at sea-level. Further, this study explored the benefits of combining thiol and polyphenol antioxidants to take advantage of their theoretically complementary effects on erythrocytes and nitric oxide (NO). Eight trained cyclists completed four supplementation protocols in a randomized, blinded, crossover designed study: placebo (stevia, PLAC), POMx only, N-acetylcysteine (NAC) only and POMx + NAC (BOTH) for eight days (15 mg.kg-1d-1). On the eighth day, 2.5 hours after the final dose, the participants completed a submaximal cycling protocol, as described for Study Two, followed by a five-minute time trial. As opposed to the acute supplementation protocol in the previous study, short-term POMx supplementation decreased the VO2 required to complete each stage of the submaximal part of the exercise test compared to all other supplement conditions (-2.1 ml.min-1kg-1, 95% CI, -2.8, -0.23, p < 0.04). In contrast, NAC significantly increased submaximal VO2 (+1.9 ml.min-1kg-1, 95% CI, 0.26, 3.6, p < 0.03), negating the POMx-lowering effects on POMx when the two were co-supplemented. Regardless, none of the treatments significantly altered performance in the subsequent time trial (p > 0.05). Thus, it is suggested that this test was too short for the increased VO2 efficiency to show any meaningful effects on performance. In conclusion, based on the lack of evidence for enhancement of performance, this thesis does not support the recommendation of the selected dietary antioxidant supplements for athletes, for performance-enhancing effects at least. However, because the primary outcome measure of this thesis, VO2, appears to be altered by POMx, the intake of polyphenol-rich products warrants further investigation. Based on the results of Chapters 6 and 7, it appears that the benefits of POMx become more significant as demands on O2 transport and utilization processes increase. Therefore, the suggested areas of future research would involve exercise of greater duration, and environmental conditions where O2 availability and/or limitations to the various transport parameters differ.Item The significance of CYP1A2 genotype on caffeine metabolism and exercise performance : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Human Nutrition at Massey University, Manawatu, New Zealand(Massey University, 2015) McGrath, Michelle ClareObjective: The objective of this study was to investigate whether a single nucleotide polymorphism (C to A transversion at position -163 downstream of the first transcribed nucleotide) in the enzyme that metabolizes caffeine (CYP1A2), would explain the variability seen in caffeine related responses in endurance exercise performance. In a double blind crossover trial, well trained male endurance athletes (n=11, mean VO2 max 69±4 mL.kg-1.min-1) ingested either caffeine (5 mg.kg-1) or a placebo 60 minutes prior to performing a lab based experimental protocol involving a two hour steady state cycle (70% VO2 max) followed by a 30 minute time trial to measure performance. The rate of caffeine metabolism over seven hours (inclusive of exercise period) was also determined by the HPLC analysis of plasma caffeine and its major metabolites, paraxanthine, theophylline and theobromine. Caffeine metabolism at rest over a similar seven hour period was also determined in the same manner. Results: Caffeine improved endurance performance by 7.1% (p=0.037) compared to a placebo. Caffeine also significantly elevated heart rate during the time trial (p=0.003); and RPE (p=0.010) and VO2 (p=0.047) during steady state exercise. There was no correlation between caffeine or paraxanthine concentrations at the start of the time trial and subsequent performance and the rate of caffeine metabolism was not significantly different between resting or exercising trials. Furthermore there was no significant interaction between caffeine treatment and CYP1A2 genotype on performance or any other variables measured. However there was a trend for carriers of the C allele showing faster metabolism than those homozygous A/A (p=0.097). Conclusions: Caffeine is ergogenic during endurance exercise, however individual responses were variable. In this study this variability could not be explained by CYP1A2 genotype. However the small sample size in this study especially when subjects were divided into genotype groups, makes drawing conclusions difficult.Item Effect of caffeine ingestion on aspects of endurance performance and cognition in CYP1A2 hetrozygous A/C male recreational athletes : a thesis presented in partial fulfilment for the requirements of a Master of Science in Sport and Exercise Science at Massey University, Albany, New Zealand(Massey University, 2016) Southward, KyleBackground: Globally, caffeine is the most widely accessible psychoactive drug and has been shown to improve endurance performance as well as aspects of cognition, mood and perceptual responses during exercise. However, the ergogenic effects of caffeine between individuals are variable, and the cause of this variability is unknown. The CYP1A2 gene is known to mediate caffeine metabolism and has been suggested as a contributor to the variability of the ergogenic effects of caffeine. Purpose: To investigate the effects of CYP1A2 genotype on exercise performance (10 km time trial), sleep, mood, cognition and perceptual responses following caffeine ingestion in adult male recreational athletes. Methods: 16 recreationally trained athletes (age = 26.9 ± 7.93 y; weight = 77.00 ± 9.04 kg) volunteered for this study. Participants completed a familiarisation session at least one week before the first trial and a saliva sample was collected for testing of the participants’ CYP1A2 genotype. Participants completed two trials one week apart in a randomised double-blind placebo-controlled cross-over design. Participants were asked to abstain from caffeine ingestion and keep a food diary for 24 h prior to the trial. Participants wore an actigraph, and completed a sleep diary and Leeds Sleep Evaluation Questionnaire (LSEQ) every day for the two week duration of the trials starting 3 days before the first trial and ending 3 days after the second trial. The main trial consisted of a set of pre- and post-ingestion measures which included leg power by vertical jump height (squat jump – SJ; countermovement jump – CMJ), leg strength by maximal voluntary concentric and eccentric contraction of the knee extensors (isokinetic dynamometer), perceptual (feeling scale – FS; felt arousal scale – FAS), mood (profile of mood states – POMS), cognition (digit vigilance – DV; Corsi blocks – CB; rapid visual information processing – RVIP) and heart rate. Pre- and post-ingestion urine, saliva and blood samples were also collected for analysis of caffeine metabolism and genotype. Following completion of pre-ingestion measures, participants consumed a capsule containing either anhydrous caffeine (6 mg∙kg-1) or placebo (maltodextrin) and were instructed to rest quietly for 50 min. Following post-ingestion measures, participants completed a 10-km time trial run. Perceptual measures (FS and FAS) including ratings of perceived exertion (RPE) were recorded every 2.5 km and heart rate was recorded every 1 km. A venous blood sample and saliva sample was collected at 5 km and 10 km. At completion of the 10-km time trial all post-ingestion measures were repeated, followed by another 50 min rest period. After the second 50 min rest period the participants completed the perceptual, mood and cognitive measures and further blood, urine and saliva samples were collected. Participants returned 24 and 48 h post-ingestion to repeat all post-ingestion measures and another blood, urine and saliva sample was collected. This protocol was then repeated 1 week later for the alternate treatment (placebo or caffeine). The effect of treatment (caffeine, placebo) and the interaction effect of treatment x time were assessed using a repeated measures ANOVA. A student’s t-test was used to measure differences between Leeds sleep evaluation questionnaire (LSEQ) and actigraph data. Results: Fourteen of sixteen participants were heterozygous A/C CYP1A2 for the CYP1A2 genotype and therefore results based on genotypes could not be compared as originally intended. Plasma caffeine, paraxanthine and theophylline concentrations were all elevated following caffeine ingestion (P < 0.05) peaking at 10-km, 1 hour after the 10-km run and 24 hours post caffeine ingestion respectively. Caffeine did not significantly improve 10-km run times. Eccentric leg strength but not concentric leg strength was improved following caffeine ingestion (P < 0.05). Squat jump height but not countermovement jump height was improved following caffeine ingestion (P < 0.05). Digit vigilance reaction times were decreased significantly following caffeine ingestion (P < 0.05) and a trend of decreased rapid visual information processing (RVIP) reaction times were seen (P < 0.1), however, no improvements in the accuracy during cognitive tests were seen following caffeine ingestion. A trend of increased heart rate (P < 0.1) during exercise was observed following caffeine ingestion, but no significant differences in heart rate before and after exercise were observed. Conclusions: While no overall, significant improvements in run time occurred following caffeine ingestion, 11 of 14 participants had a faster run time following caffeine ingestion compared to placebo. Caffeine, rather than the metabolites of caffeine, is likely the main cause of any observed ergogenic effects following caffeine ingestion as the improvements in reaction times, mood and endurance performance occurred when plasma caffeine concentration was elevated but plasma caffeine metabolite concentrations were low. It was found that caffeine ingestion improves endurance performance and reaction times during cognitive tasks. Taken together, the pharmacokinetics of the caffeine and caffeine metabolite peaks suggest that for athletes with the A/C CYP1A2 genotype ingestion of caffeine 1.5 – 2 h prior to an event may be more beneficial for endurance performance compared to the usual recommendations of taking caffeine 1 h prior to exercise. Keywords: caffeine, endurance exercise, CYP1A2, performance, genetics