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.

Thesis (M.S.), Wellness Management--University of Central Oklahoma, 2008. / Includes bibliographical references (leaves 51-56).

Thesis (M.S.)--Eastern Illinois University, 1994. / Includes bibliographical references (leaves 39-41).

The purpose of this thesis was to extend our understanding of the assessment and interpretation of aerobic exercise function of paediatric patients with cystic fibrosis (CF). The first investigation sought to establish (1) the validity of traditional criteria to verify maximal oxygen (V ̇O2max) during a maximal cardiopulmonary exercise test (CPET); and (2) the utility of supramaximal verification (Smax) to confirm V ̇O2max. Traditional criteria significantly underreported V ̇O2max, whilst Smax was shown to provide a valid measurement in this patient group. The reproducibility of this CPET protocol, over the short- (48 h) and medium- (4-6 weeks) term, was then established in study two. V ̇O2max was repeatedly determined with no learning effect over 48 h (typical error (TE): ∆150 mL; ∆9.3%) and 4-6 weeks (TE: ∆160 mL; ∆13.3%). Supplementary maximal and submaximal CPET parameters should be incorporated for a comprehensive evaluation of a patient, however they are characterised by greater variability over time. The influence of mild-to-moderate CF on aerobic exercise function and the matching of muscle O2 delivery-to-O2 utilisation during ramp incremental exercise to exhaustion were then examined in study three. Aerobic function was impaired in CF, indicated by very likely reduced fat-free mass normalised V ̇O2max (mean difference, ±90% CI: -7.9 mL∙kg-1∙min-1, ±6.1), very likely lower V ̇O2 gain (-1.44 mL∙min-1∙W-1, ±1.12) and a likely slower V ̇O2 mean response time (MRT) (11 s, ±13). Arterial oxygen saturation was lower in CF, supporting the notion that centrally mediated O2 delivery may be impaired during ramp incremental exercise. Although a faster rate of fractional O2 extraction would be expected in the face of reduced O2 delivery, this was not observed, suggesting additional impairment in O2 extraction and utilisation at the periphery in CF. The fourth study then demonstrated the clinical utility of CPET to assess the response to 12 weeks treatment with Ivacaftor, using a case-based design. Whilst one patient with relatively mild disease demonstrated no meaningful change in V ̇O2max, the second demonstrated a 30% improvement in V ̇O2max, due to increased O2 delivery and extraction. Furthermore, changes in aerobic function were detected earlier than spirometric indices of pulmonary function. This study demonstrated that CPET represents an important and comprehensive clinical assessment tool and its use as an outcome measure in the functional assessment of patients is encouraged. Study five investigated the V ̇O2 kinetics in this patient group. During moderate intensity cycling, the phase II V ̇O2 time constant (τ) (p = 0.84, effect size (ES) = 0.11) and overall MRT (p = 0.52, ES=0.33) were not slower in CF. However, both were slowed during very heavy intensity cycling (p = 0.02, ES = 1.28 and p = 0.01, ES = 1.40, respectively) in CF. Cardiac output and muscle deoxygenation dynamics were unaltered in CF, however, the arterial-venous O2 content difference (C(a-v ̅)O2) was reduced (p=0.03) during VH and ∆C(a-v ̅)O2 correlated with the phase II τ (r= -0.85; p=0.02) and MRT (r = -0.79; p=0.03) in CF. This study showed that impaired oxidative muscle metabolism in this group is exercise intensity-dependent and mechanistically linked to an intrinsic intramuscular impairment, which limits O2 extraction and utilisation. In conclusion, this thesis has provided guidelines for a valid and reproducible CPET protocol for children and adolescents with mild-to-moderate CF, demonstrated the utility of CPET as clinical outcome measure and furthered our understanding of the factors responsible for impaired aerobic exercise function in this patient group.

La société calédonienne a subi de profonds changements au cours de ces trente dernières années avec une rapide mutation de l’environnement et du mode de vie des populations. Ces changements ont un rôle déterminant dans l’évolution de la composition corporelle et de la condition physique des adultes mais aussi des adolescents et plus particulièrement des adolescents kanak. En effet, les jeunes Kanak vivent pour certains, dans un environnement rural en tribu et pour d’autres dans un environnement urbain. Ceci implique des comportements différents en fonction de leur lieu de vie. Ainsi, nous avons orienté nos travaux en direction de cette jeunesse (de 11 à 30 ans) en nous intéressant à la composition corporelle (données anthropométriques) et aux variables physiologiques (qualités physiques et activité physique) en milieu sportif et scolaire. L'ensemble des travaux réalisés a permis de conclure que: 1) les jeunes sportifs kanak sont de plus petite taille, sont plus agiles et explosifs et ont une meilleure capacité à répéter des sprints avec et sans changement de direction en comparaison avec les jeunes sportifs non- kanak. 2) Ces jeunes sportifs kanak sont capables de produire des efforts à des intensités élevées avec une capacité importante de récupération sans incidence sur leur bien-être durant une compétition de haut niveau. 3) Concernant les adolescents de 11 à 16 ans, le milieu rural est propice à une activité physique élevée et une bonne condition physique, notamment chez les garçons. Toutefois, une accumulation importante de masse grasse chez les filles vivant en milieu rural et urbain, tout comme pour les garçons vivant en milieu urbain, a été observée suggérant un changement dans les comportements des adolescents. Les conclusions de ces travaux soulignent l’importance d’un développement d’une politique d’éducation à la santé visant les changements de comportements au sein du mode de vie (alimentation, activité physique et temps passé à être inactif) chez les jeunes kanak. / The New Caledonian people have undergone profound changes over the last thirty years with a quick changing environment and population lifestyle. These changes have a determining role in the evolution of the body composition evolution and physical condition for adults but also for adolescents and especially kanak adolescents. Indeed, young Kanak live, for some, in a rural environment in tribes and, for others, in an urban environment. This implies different behaviours depending on their living place. Thus, we focused our work on this youth (aged 11 to 30) by studying the body composition (anthropometric data) and the physiological variables (physical fitness and physical activity) in federal sports and schools. The studies led us to the conclusion that: 1) kanak athletes are shorter, more agile and explosive, and are better at repeating sprints with and without change of direction compared to young non-Kanak athletes. 2) These young kanak athletes are able to practice in high intensity efforts with a significant capacity for recovery, without affecting their well-being during a high level competition. 3) For adolescents aged 11 to 16, the rural environment is suitable for high physical activity and physical fitness, particularly among boys. However, a significant fat mass accumulation among girls living in rural and urban areas as well as urban boys has been observed. These data suggest a change in adolescent behaviors. The work findings highlight the importance in developing a health education policy aimed at behavioral changes in lifestyle (diet, physical activity and time spent inactive) among the kanak youth.

This thesis is concerned with the role of iron in modulating right ventricular (RV) afterload during exercise in healthy people aged between 50 and 80 years. This is predicated on the requirement of the hypoxia-inducible factor (HIF) pathway for ferrous iron. A secondary objective is to examine the reactive oxygen species (ROS) hypothesis in human hypoxic pulmonary vasoconstriction (HPV) using exposure to hyperoxia. Chapters 3 and 4 describe basal relationships that may affect the HIF pathway and exercise capacity during ageing. These were explored in 113 participants using blood tests and exercise tests. Age and inflammatory factors, C-reactive protein, and ferritin were associated with impaired exercise capacity. In addition, ageing did not significantly affect haematological variables or iron status indicators. Chapters 5 and 6 describe the effect of a single intravenous iron infusion on the haematological variables in 32 participants in a randomised, placebo-controlled and double-blinded study. The effects of iron infusion on RV afterload during light exercise, and exercise capacity during heavy exercise, were examined in these participants. With iron infusion, erythropoietin production, and the increase in RV afterload during light exercise were blunted, potentially indicating involvement of the HIF pathway. However, blunting of RV afterload neither influenced the cardiac output during light exercise nor exercise capacity. Chapter 7 describes a study of 11 healthy volunteers, which investigated the ROS hypothesis in HPV using acute isocapnic hypoxia following an 8-hour exposure to hyperoxia. This sustained hyperoxic exposure did not influence the hypoxic behavior of the pulmonary vasculature. This thesis demonstrates the complex relationship between iron status and exercise capacity in older adults. It shows that the decrease in RV afterload during exercise caused by intravenous iron supplementation does not lead to an augmented cardiac output or exercise capacity. Finally, it calls into question the role of ROS in HPV.

This study addresses the effects of the changing workforce and the physiological and psychological benefits of fitness. The purpose of this experiment is to test the relationship between situational stressors, perceived fitness, exercise locus of control, self-control, and perceived stress.