Specific aspects of contemporary triathlon: implications for physiological analysis and performance

Triathlon competitions are performed over markedly different distances and under a variety of technical constraints. In 'standard-distance' triathlons involving 1.5km swim, 40km cycling and 10km running, a World Cup series as well as a World Championship race is available for 'elite' competitors. In contrast, 'age-group' triathletes may compete in 5-year age categories at a World Championship level, but not against the elite competitors. The difference between elite and age-group races is that during the cycle stage elite competitors may 'draft' or cycle in a sheltered position; age-group athletes complete the cycle stage as an individual time trial. Within triathlons there are a number of specific aspects that make the physiological demands different from the individual sports of swimming, cycling and running. The physiological demands of the cycle stage in elite races may also differ compared with the age-group format. This in turn may influence performance during the cycle leg and subsequent running stage. Wetsuit use and drafting during swimming (in both elite and age-group races) result in improved buoyancy and a reduction in frontal resistance, respectively. Both of these factors will result in improved performance and efficiency relative to normal pool-based swimming efforts. Overall cycling performance after swimming in a triathlon is not typically affected. However, it is possible that during the initial stages of the cycle leg the ability of an athlete to generate the high power outputs necessary for tactical position changes may be impeded. Drafting during cycling results in a reduction in frontal resistance and reduced energy cost at a given submaximal intensity. The reduced energy expenditure during the cycle stage results in an improvement in running, so an athlete may exercise at a higher percentage of maximal oxygen uptake. In elite triathlon races, the cycle courses offer specific physiological demands that may result in different fatigue responses when compared with standard time-trial courses. Furthermore, it is possible that different physical and physiological characteristics may make some athletes more suited to races where the cycle course is either flat or has undulating sections. An athlete's ability to perform running activity after cycling, during a triathlon, may be influenced by the pedalling frequency and also the physiological demands of the cycle stage. The technical features of elite and age-group triathlons together with the physiological demands of longer distance events should be considered in experimental design, training practice and also performance diagnosis of triathletes.     

Pedigree Selection and Tests of Linkage in a Hutterite Asthma Pedigree

We explored methods for kinship and linkage analysis in a Hutterite pedigree comprising 1,544 individuals, 72 of whom were diagnosed with asthma. Subpedigrees were selected by (a) identifying nuclear families containing asthmatics, (b) identifying couples with many asthmatic descendants in an ad hoc manner, and (c) finding the most recent common ancestors of all asthmatics. Markov chain Monte Carlo (MCMC) methods were used to estimate allele sharing in the larger subpedigrees and transmission/disequilibrium tests were performed on nuclear families. On chromosome 5q near the cytokine cluster, modest evidence for linkage to asthma was obtained. Using MCMC, we were able to evaluate the evidence for linkage in complex subpedigrees of several hundred individuals, and hence, incorporate some of the co‐ancestry of this founder population. © 2001 Wiley‐Liss, Inc.     

Inadvertent subclavian artery puncture in an intravenous drug abuser.

Arterial complications from inadvertent arterial puncture in intravenous drug abusers are well recognised. Most reports describe injury to the femoral artery with occasional reports of brachial and radial artery injury. A case of subclavian artery injury is described in this paper, and the pathophysiology and treatment of intraarterial drug injection discussed.     

Supplement use is associated with health status and health-related behaviors in the 1946 British birth cohort

Use of dietary supplements may be one of a number of health-related behaviors that cluster together. The current study investigated the underlying diet, health-related characteristics, and behaviors of users and nonusers of dietary supplements in a longitudinal study of health. Participants (n = 1776) completed a 5-d food diary including information on dietary supplement use (vitamins, minerals, and nutraceuticals) at age 53 y. Sociodemographic information and data on smoking, alcohol, and physical activity were obtained along with anthropometric measurements, blood pressure, and a blood sample (nonfasting subjects). A significantly greater percentage of women reported supplement use compared with men (45.1 vs. 25.2%). Supplement use was associated with lower BMI, lower waist circumference, higher plasma folate and plasma vitamin B-12 concentrations, nonsmoking, participation in physical activity, and nonmanual social class in women and with plasma folate concentrations and participation in physical activity in men. Nonsupplement users tended to be nonconsumers of breakfast cereals, fruit, fruit juice, yogurt, oily fish, and olive oil and had lower dietary intakes of potassium, magnesium, phosphorus, iron, and vitamin C even after adjustment for sociodemographic and behavioral factors. Overall, supplement users tended to differ from nonsupplement users on a range of health-related behaviors and health status indicators, although there were fewer significant associations in men. Similarly, dietary supplements users tended to have underlying diets that, were healthier and those taking supplements may be the least likely to need them. These results support the notion of a clustering of healthy behaviors and cardiovascular risk factors, particularly for women.     

Canadian physical therapists' interest in web-based and computer-assisted continuing education

BACKGROUND AND PURPOSE: Distance education via computer-assisted learning (CAL), including Web-based and CD-ROM learning, confers a number of advantages compared with traditional learning methods. The purposes of this study were (1) to determine the interest of Canadian physical therapists in participating in continuing education using CAL methods and (2) to determine whether interest in CAL was related to type of employment, area of practice, education, computer skill and access, and other demographic variables. SUBJECTS AND METHODS: A random sample of Canadian physical therapists and all members of cardiopulmonary interest groups were surveyed. RESULTS: Of 1,426 survey questionnaires mailed, 69 were returned (58 were unopened and 11 were duplicates). From the remaining 1,357 potential survey responses, 757 responses were received, for an overall response rate of 56%. Seventy-eight percent of the respondents indicated their interest in participating in CAL. Factors associated with interest in CAL included 2 or more hours of Internet access per week, Internet access at both home and work, computer skill, education level, practice area, and belonging to a cardiopulmonary interest group. DISCUSSION AND CONCLUSION: The findings indicate a large positive interest in CAL. Increasing CAL continuing education opportunities could increase options for physical therapists to meet professional expectations for continuing competency.     

Activation of hepatic guanylate cyclase by nitrosyl-heme complexes: Comparison of unpurified and partially purified enzyme

The objective of this study was to evaluate the effects of several agents on activation of both unpurified and partially purified hepatic soluble guanylate cyclase by performed NO (nitric oxide or nitrosyl)-heme complexes. Guanylate cyclase was activated by NO complexes of the heme compounds, hematin, hemoglobin, myoglobin, catalase and cytochrome c, and also by the reaction product of NO and ferredoxin, a non-heme, iron sulfur electron transfer protein. NO-lipoxygenase, which contains non-heme iron, did not activate guanylate cyclase. NO-heme complexes activated unpurified enzyme almost equally well in the presence of either Mg²⁺ or Mn²⁺. However, activation of purified (350- to 750-fold) guanylate cyclase was markedly greater with Mg²⁺ than with Mn²⁺. At concentrations that did not alter basal enzymatic activity, Ca²⁺ markedly inhibited guanylate cyclase activation in the presence of Mg²⁺ but not of Mn²⁺. Hemoproteins inhibited activation of unpurified and purified enzyme by NO-heme complexes, and increasing the concentrations of the latter overcame the inhibition. Gel filtration studies indicated that uncomplexed and NO-complexed hematin bind to common or adjacent sites on guanylate cyclase. Whereas dl-dithiothreitol enhanced activation, ferricyanide, cystine, o-iodosobenzoic acid and ethacrynic acid inhibited activation of guanylate cyclase by NO-heme complexes. The data indicate that the effects of these diverse agents on guanylate cyclase activation by preformed NO-heme are similar to their effects on enzyme activation by NO and nitroso compounds, both of which readily form NO-heme complexes. Therefore, the effects of these diverse agents may be on guanylate cyclase rather than on NO-heme formation.     

Long-term synaptic enhancement in hippocampus is not regulated by postsynaptic membrane potential

The contributions of membrane potential and postsynaptic discharge during afferent fibre tetanization to the generation of long-lasting synaptic enhancement was studied by intra- and extracellular recording in the CA1 region of hippocampal slices. Neither parameter affected the magnitude of intracellular synaptic enhancement. Thus, if postsynaptic integration is involved in the control of the enhancement process, the integration must be chemically rather than electrically mediated.     

Raman microspectroscopy and imaging provides insights into heme aggregation and denaturation within human erythrocytes

The oxygenation process of a human erythrocyte is monitored using a Raman microimaging technique. Raman images of the 1638 cm(-1) band are recorded in the oxygenated and deoxygenated state using only 120 s of laser exposure and approximately 1 mW of defocused laser power. The images show hemoglobin oxygenating and deoxygenating within the cell. Prolonged laser imaging exposure (<180 s) at low temperatures results in photoinduced and/or thermal degradation. The effect of thermal degradation is investigated by recording spectra of erythrocytes as a function of temperature between 4 and 52 degrees C. Five bands at 1396, 1365, 1248, 972, and 662 cm(-1) are identified as markers for heme aggregation. Raman images recorded of cells after prolonged laser exposure appear to show heme aggregation commencing in the middle and moving toward the periphery of the cell. UV-visible spectra of erythrocytes show the Soret band to be broader and red shifted (approximately 3 nm) at temperatures between 45 and 55 degrees indicative of excitonic interactions. It is postulated that the enhancement of the aggregation marker bands observed at 632.8-nm excitation results primarily from excitonic interactions between the aggregated hemes in response to protein denaturation. The results have important medical implications in detecting and monitoring heme aggregation associated with hemopathies such as sickle cell disease.