A complex series of metabolic pathways are present in human muscle that break down substrates from nutritional sources to produce energy for different types of muscular activity. However, depending on the activity in which an individual is engaged, the body will make use of different energy systems that have been adapted for the particular activity. More specifically, utilization of bioenergetic substrates depends on the type, intensity, and duration of the exercise. The aerobic oxidative system is used for longer duration activities of low to moderate intensity, the anaerobic glycolytic system is used for short to moderate duration activities of higher intensity, and the high energy phosphagen system is used for short duration activities of high intensity. The efficiency and effectiveness of these pathways can be enhanced through physical activity and training. It is these bioenergetic pathways that are the focus of this review.

Physiological assessment of athletes is an important process for the characterization of the athlete, monitoring progress and the trained state or 'level of preparedness' of an athlete, as well as aiding the process of training program design. Interestingly, the majority of physiological assessments performed on athletes can also be performed on children with disease, and therefore clinicians can learn a great deal about physiology and assessment of patient populations through the examination of the physiological responses of elite athletes. This review describes typical physiological responses of elite athletes to tests of aerobic and anaerobic metabolism and provides a specific focus upon respiratory limitations to exercise performance. Typical responses of elite athletes are described to provide the scientist and clinician with a perspective of the upper range of physiological capacities of elite athletes.

Regular exercise and habitual physical activity are important for patients with cystic fibrosis (CF). Research has demonstrated the benefits of aerobic, anaerobic, and strength exercise training programs for health and quality of life, however, the CF patient is faced with unique barriers and challenges to participation. Recently, increased levels of habitual physical activity have been shown to slow the decline in lung function in patients with CF, and regular participation in a variety of activities may result in greater adherence in the long term. Research is now available to justify the incorporation of exercise into the routine care of patients with CF. This paper provides the background and rationale for the implementation of exercise and habitual physical activity recommendations by the health care team. Education of health care providers regarding the importance of exercise and habitual physical activity for patients with CF is needed in order for exercise and physical activity to be incorporated as key components of clinical practice and into the lives of patients with CF.

Golf is now a sport where physical training is an integral component of elite players' practice and contributes to the ability to play at a high level consistently and without injury. Relationships between physical conditioning and golf performance have not been reported. Therefore, the objective of this research was to identify physiological correlates of golf performance in elite golfers under laboratory (ball speed and distance) and tournament conditions (average score, greens in regulation, short game measures, and putting accuracy).The correlation analysis revealed significant associations between mass, height, body mass index, sit height, arm length, and predicted Vo2max and golf measures. Significant correlations were noted between anterior abdominal muscle endurance and driver carry distance (r = 0.38; P = 0.04) and average putt distance after a chip shot (r = -0.44; P = 0.03), between dominant side abdominal muscle endurance and average putt distance after a chip shot (r = -0.43; P = 0.03), and between nondominant-side abdominal muscle endurance and average putt distance after a sand shot (r = -0.59; P = 0.001). Further correlations were found among sit and reach and driver carry distance (r = -0.36; P = 0.04), 5-iron ball speed (r = - 0.41; P = 0.02), 5-iron carry distance (r = -0.44; P = 0.01), and score (r = 0.43; P = 0.03). Correlation analysis revealed significant associations among peripheral muscle test results, golf driver results, 5-iron ball measures, score, and putting efficacy.These results may be important for developing training programs based on sound physiological rationale and for the development of talent identification programs. Results suggest that core strength and stability, flexibility, balance, and peripheral muscle strength are correlated with golf performance and should be included in golf training programs.

RATIONALE: Cystic fibrosis (CF) leads to pathological changes in organs that express the cystic fibrosis transmembrane conductance regulator (CFTR), including secretory cells of the digestive tract and the pancreas. Maintaining nutritional sufficiency is challenging for CF patients and therefore accurate monitoring is important for their clinical management. PURPOSE: The objectives of this study were to evaluate the effectiveness of skinfold measurements as an accurate method for determining body composition (fat mass (FM) and lean body mass (LBM)) of this population, using dual-energy X-ray absorptiometry (DEXA) as a gold standard comparison and to determine the most accurate equation for this calculation in children with CF. METHODS: Fifty-five pediatric patients with CF participated in the study. FM and LBM calculated via four methods: Slaughter, Durnin, Durenberg (2-site and 4-site). The relationship between the methods and DEXA results were estimated by intraclass-correlation coefficient (ICC) and Bland and Altman analyses. RESULTS: The Slaughter method was the most accurate (ICC of 0.92 for FM and 0.99 for LBM) and displayed the least bias over the range of FM and LBM in CF patients. In addition, the results of Bland Altman analyses comparing each skinfold method to DEXA, revealed that the results were evenly distributed along the range of values for the Slaughter calculation, whereas the other three methods under and over estimated % fat results at the upper and lower ends of the range respectively. CONCLUSION: We therefore conclude that the Slaughter method may be used for body composition assessment of pediatric CF patients. This provides clinical teams with a simple, accurate and non-invasive method that can be used to monitor nutritional status in pediatric patients with CF. (c) 2008 Wiley-Liss, Inc.

Accurate measurements of arterial P(CO(2)) (P(a,CO(2))) currently require blood sampling because the end-tidal P(CO(2)) (P(ET,CO(2))) of the expired gas often does not accurately reflect the mean alveolar P(CO(2)) and P(a,CO(2)). Differences between P(ET,CO(2)) and P(a,CO(2)) result from regional inhomogeneities in perfusion and gas exchange. We hypothesized that breathing via a sequential gas delivery circuit would reduce these inhomogeneities sufficiently to allow accurate prediction of P(a,CO(2)) from P(ET,CO(2)). We tested this hypothesis in five healthy middle-aged men by comparing their P(ET,CO(2)) values with P(a,CO(2)) values at various combinations of P(ET,CO(2)) (between 35 and 50 mmHg), P(O(2)) (between 70 and 300 mmHg), and breathing frequencies (f; between 6 and 24 breaths min(-1)). Once each individual was in a steady state, P(a,CO(2)) was collected in duplicate by consecutive blood samples to assess its repeatability. The difference between P(ET,CO(2)) and average P(a,CO(2)) was 0.5 +/- 1.7 mmHg (P = 0.53; 95% CI -2.8, 3.8 mmHg) whereas the mean difference between the two measurements of P(a,CO(2)) was -0.1 +/- 1.6 mmHg (95% CI -3.7, 2.6 mmHg). Repeated measures ANOVAs revealed no significant differences between P(ET,CO(2)) and P(a,CO(2)) over the ranges of P(O(2)), f and target P(ET,CO(2)). We conclude that when breathing via a sequential gas delivery circuit, P(ET,CO(2)) provides as accurate a measurement of P(a,CO(2)) as the actual analysis of arterial blood.

Obesity and the related metabolic syndrome have become a worldwide epidemic. Inactivity appears to be a primary causative factor in the pathogenesis of this obesity and metabolic syndrome. There are two possible, perhaps not mutually exclusive, events that may lead to intramyocellular lipid accumulation and mitochondrial dysfunction in patients with obesity. First, obesity, with high intake-associated lipid accumulation in muscle may interfere with cellular mitochondrial function through generation of reactive oxygen species leading to lipid membrane peroxidative injury and disruption of mitochondrial membrane-dependent enzymes. This in turn leads to impaired oxidative metabolism. Secondly, a primary defect in mitochondrial oxidative metabolism may be responsible for a reduction in fatty acid oxidation leading to intramyocellular lipid accumulation as a secondary event. Non-invasive techniques such as proton (1H) and phosphorus (31P) magnetic resonance spectroscopy, coupled with specific magnetic resonance imaging techniques, may facilitate the investigation of the effects of various ergometric interventions on the pathophysiology of obesity and the metabolic syndrome. Exercise has positive effects on glucose metabolism, aerobic metabolism, mitochondrial density, and respiratory chain proteins in patients with metabolic syndrome, and we propose that this may be due to the exercise effects on AMP kinase, and a prospective physiological mechanism for this benefit is presented. A physiological model of the effect of intramyocellular lipid accumulation on oxidative metabolism and insulin mediated glucose uptake is proposed.

PURPOSE: To understand potential benefits of exercise in the cystic fibrosis (CF) population, there needs to be accurate methods to quantify it. The Habitual Activity Estimation Scale (HAES) questionnaire has been shown to be a feasible tool to measure physical activity however the reliability and validity have yet to be determined in the CF population. METHODS: Fourteen (seven male, seven female) patients aged 16.2 +/- 4.2 years with CF participated in this study. Participants were clinically stable at the time of the study and participating in their habitual physical activity. To assess reliability, patients completed the HAES and a validated 3-day activity diary, and wore an ActiGraph Accelerometer for two consecutive weeks. Validity was assessed by comparing the activity results of each of the three instruments over a single week time period. RESULTS: ICC estimates of reliability for the HAES, diary, and accelerometer were 0.72 (P < 0.0001), 0.76 (P < 0.0001), 0.63 (P < 0.0001), respectively. Validity analysis indicated that there were significant relationships between the participants' activity results as estimated by the HAES, diary and accelerometer. Further, significant relationships were detected between activity measures when broken into morning, afternoon, or evening periods, and between measures from weekday or weekend days. There were also significant relationships among the three instruments when recording different activity levels (somewhat inactive, somewhat active, and very active). CONCLUSION: The findings of this study suggest that the HAES questionnaire is a reliable and valid instrument that can be used to assess activities of varying intensity in patients with CF.

The current study's experiments tested the hypothesis that limb movement frequency is a significant determinant of exercise hyperpnoea. To this end, 19 healthy participants walked on a treadmill, where work was varied sinusiodally by alterations in either treadmill speed or grade. Measured responses were fitted with sine waves to determine their amplitudes and phase angles. Walking pace amplitude was greater during speed tests than grade tests, and phase lag relative to the treadmill smaller, as expected. Ventilation, carbon dioxide production, and oxygen uptake amplitudes were higher during speed tests than grade tests. Further, phase angle lags relative to the treadmill for these measures were shorter during speed tests than grade tests. We concluded that these findings demonstrate the presence of changes in breathing during exercise that can be attributed to changes in limb movement frequency.

The efficiency of the respiratory system presents significant limitations on the body's ability to perform exercise due to the effects of the increased work of breathing, respiratory muscle fatigue, and dyspnoea. Respiratory muscle training is an intervention that may be able to address these limitations, but the impact of respiratory muscle training on exercise performance remains controversial. Therefore, in this study we evaluated the effects of a 12-week (10 sessions week(-1)) concurrent inspiratory and expiratory muscle training (CRMT) program in 34 adolescent competitive swimmers. The CRMT program consisted of 6 weeks during which the experimental group (E, n = 17) performed CRMT and the sham group (S, n = 17) performed sham CRMT, followed by 6 weeks when the E and S groups performed CRMT of differing intensities. CRMT training resulted in a significant improvement in forced inspiratory volume in 1 s (FIV1.0) (P = 0.050) and forced expiratory volume in 1 s (FEV1.0) (P = 0.045) in the E group, which exceeded the S group's results. Significant improvements in pulmonary function, breathing power, and chemoreflex ventilation threshold were observed in both groups, and there was a trend toward an improvement in swimming critical speed after 12 weeks of training (P = 0.08). We concluded that although swim training results in attenuation of the ventilatory response to hypercapnia and in improvements in pulmonary function and sustainable breathing power, supplemental respiratory muscle training has no additional effect except on dynamic pulmonary function variables.