Long-Chain Omega-3 Fatty Acid Intake Is Associated with Age but not Cognitive Performance in an Older Australian Sample.

BACKGROUND: Long-chain omega-3 polyunsaturated fatty acids (LCn-3 PUFA) are essential nutrients and may be capable of delaying age-related cognitive decline. However, previous studies indicate that Australians are not meeting recommendations for LCn-3 PUFA intake. The current study therefore examined LCn-3 PUFA intake in an older Australia sample, as well as associations between LCn-3 PUFA intake and cognitive function. METHODS: Cross-sectional data were collected from 90 adults aged 50 to 80 years. LCn-3 PUFA intake was assessed using a food frequency questionnaire and red blood cell fatty acid profiles were used to calculate the Omega-3 Index (RBC n-3 index). Cognitive function was measured using Addenbrooke's Cognitive Examination-III. RESULTS: Positive associations were observed between age and RBC n-3 index (b=0.06, 95% CI: 0.01 - 0.10, P=0.01), and age and LCn-3 PUFA intake from fish oil capsules (b=17.5, 95% CI: 2.4 - 32.5 mg/day, P=0.02). When adjusting for LCn-3 PUFA from fish oil capsules, the association between age and RBC n-3 index was no longer significant. No associations were observed between LCn-3 PUFA intake and cognitive function. CONCLUSION: LCn-3 PUFA and fish oil consumption increased with age in this sample of older Australians, particularly due to supplement intake. However, LCn-3 PUFA intake was not associated with cognitive function.

Relationships between older adults' use of time and cardio-respiratory fitness, obesity and cardio-metabolic risk: A compositional isotemporal substitution analysis.

OBJECTIVE: Older adults' health has been linked with time in moderate-to-vigorous physical activity (MVPA), and recent studies suggest time in sedentary behaviour may also be important. Time-use behaviours (MVPA, light physical activity, sedentary time and sleep) are co-dependent, and therefore their associations with health should be examined in an integrated manner. This is the first study to investigate the relationship between older adults' reallocation of time among these time-use behaviours and markers of cardio-respiratory fitness, obesity and cardio-metabolic risk. STUDY DESIGN: Cross-sectional study of 122 Australians (65 ±â€¯3 y, 61% female). MAIN OUTCOME MEASURES: Daily time use: average daily minutes spent in MVPA, light physical activity, sedentary time and sleep derived from 24-h, 7-day accelerometry, were conceptualised as a time-use composition. Cardio-respiratory fitness: graded submaximal cycle ergometer test. Obesity: objectively measured body mass index (BMI) and waist-to-hip ratio (WHR). Cardio-metabolic risk: sphygmomanometer-measured resting blood pressure and fingertip blood sampling for fasting total cholesterol and glucose. RESULTS: Time-use composition was significantly associated with obesity markers (BMI, p = 0.001; WHR, p < 0.001). The reallocation of 15 min to MVPA from any of the other behaviours was associated with approximately +1.1 (95% confidence interval 0.2; 1.9) ml/kg-1 min-1 VO2max, -0.7 (-1.0; -0.3) BMI units and -1.2 (-1.8; -0.7) WHR percentage points, while the opposite reallocation (15 min from MVPA to other behaviours) was associated with larger difference estimates of -1.8 (-3.2; -0.4) ml/kg-1 min-1 VO2max, +1.2 (0.5; 1.9) BMI units and +2.1 (1.2; 3.1) WHR percentage points. CONCLUSION: These findings reinforce the importance of MVPA for health among older adults. Interventions to maintain MVPA, even without increasing it, may be valuable.

Sleep duration or bedtime? Exploring the association between sleep timing behaviour, diet and BMI in children and adolescents.

OBJECTIVE: To determine whether sleep timing behaviour is associated with energy intake and diet quality in children and adolescents. DESIGN: Cross-sectional analysis of nationally representative survey data. SAMPLE: A total of 2200 participants of the 2007 Australian National Children's Nutrition and Physical Activity Survey aged 9-16 years with 2 days of food intake data, 4 days of use of time data and complete anthropometry. Participants were grouped into one of four sleep-wake behaviour categories: early bed-early rise (EE); early bed-late rise (EL); late bed-early rise (LE) and late bed-late rise (LL). The four categories were compared for body mass index (BMI) z-score, energy intake and diet quality assessed using the Dietary Guideline Index for Children and Adolescents. Analyses were adjusted for survey design, sociodemographic characteristics, sleep duration and physical activity level (PAL). RESULTS: In adjusted multivariate regression models with sleep timing behaviour group as the independent variable, the 'LL' category compared with the 'EE' category had a higher BMI z-score (ß=0.20, 95% confidence interval (CI) 0.06 to 0.34, P=0.007), and lower diet quality (ß=-4.0, 95% CI -5.7 to -2.3, P<0.001). Children and adolescents who went to bed late also had a higher intake of extra foods (that is, energy-dense, nutrient-poor foods) while those whom went to bed early consumed more fruit and vegetables. Energy intake was associated with sleep duration (ß=-4.5 kJ, 95% CI -6.7 to -2.4, P<0.001), but not sleep timing behaviour. CONCLUSION: Late bedtimes and late wake up times are associated with poorer diet quality, independent of sleep duration, PAL and child and sociodemographic characteristics.

Minutes, MET minutes, and METs: unpacking socio-economic gradients in physical activity in adolescents.

BACKGROUND: There is conflicting evidence regarding the relationship between socio-economic position (SEP) and physical activity in adolescents. The aim of this study was to investigate associations between SEP and characteristics of physical activity in Australian adolescents using a high-resolution use-of-time tool. METHOD: Use-of-time and pedometer data were collected on a random sample of 2071 9-16-year-old Australian children. Use-of-time was recorded using a computerised 24-h use-of-time recall, the Multimedia Activity Recall for Children and Adults. Reported household income was used as a marker of SEP. RESULTS: There were no differences in self-reported minutes of moderate to vigorous physical activity (MVPA) across the income bands and only very small differences in the number of daily steps. However, the mix of MVPA components varied across income bands, with adolescents from low-SEP families experiencing less sport but more active transport. Because the mean rate of energy expenditure was greater in sport than in other forms of MVPA (play, active transport or chores), there were significant differences in MVPA-related and total daily energy expenditure across income bands, with the lower bands having significantly lower values. Differences in total daily energy expenditure were almost entirely explained by differences in energy expenditure associated with sport. CONCLUSION: Physical activity patterns vary across SEP bands in Australian adolescents, with sport being the major locus of differences. Instruments which do not account for the energy costs of various activities may fail to detect important relationships.

Trends in the prevalence of childhood overweight and obesity in Australia between 1985 and 2008.

BACKGROUND: Popular media, health experts and researchers talk about a paediatric 'obesity epidemic' with exponentially increasing rates of obesity and overweight. However, some recent reports suggest that prevalence may have plateaued. This study examined trends in the prevalence of Australian childhood overweight and obesity since 1985. Specifically, it aimed to determine whether there have been (a) overall increases in average body mass index (BMI), (b) differential patterns of change within age groups and (c) increases in BMI within each weight-status category. METHOD: Forty-one Australian studies of childhood weight status conducted between 1985 and 2008 were reviewed. The studies included data on 264 905 Australians aged 2-18 years, with raw data being available on 70 758 children (27%). Children were classified as overweight or obese based on BMI using the criteria of Cole et al. (BMJ, 2000). The prevalence estimates were adjusted for age and sex, and plotted against measurement year using Lowess plots and two-linear-segment models. Where raw data were available, BMI z-scores (UK 1990 standard) were plotted against measurement year for all children and children in various age groups. Lowess plots and two-linear-segment models were used to assess secular trends in BMI z-scores pre- and post-1996 within age, gender and weight-status categories. RESULTS: There has been a plateau, or only slight increase, in the percentage of boys and girls classified as overweight or obese, with almost no change over the last 10 years. In boys and girls, prevalence rates have settled around 21-25% for overweight and obesity together, and 5-6% for obesity alone. Similar trends were found for BMI z-scores. These patterns were fairly consistent across the age span. Within each weight-status category, average BMI has not increased. CONCLUSIONS: Although levels of Australian paediatric overweight remain high, the prevalence of overweight and obesity seems to have flattened and has not followed the anticipated exponential trajectory.

One million skinfolds: secular trends in the fatness of young people 1951-2004.

BACKGROUND/OBJECTIVES: There are abundant data on secular trends in the body mass index (BMI) of children. However, BMI is an imperfect index of fatness, whereas skinfold thicknesses provide a more direct measure. This study aims to meta-analyse historical studies of triceps and subscapular skinfold thicknesses in young people aged 0-18 years in developed countries. SUBJECTS/METHODS: A total of 154 studies conducted between 1951 and 2003 were analysed, covering 2390 reports at the age x sex x country level, and more than 458,547 young people from 30 developed countries. Percentage body fat (% BF) was estimated using the Slaughter equations. The distribution of fat on the body was indexed by the triceps/subscapular (T/S) ratio. The skewness of skinfold distributions was operationalized by the coefficient of variation and the mean-median difference. RESULTS: There have been increases in triceps and subscapular skinfold thicknesses, at the rate of 0.4-0.5 mm per decade over the period 1951-2003. % BF has been increasing at the rate of 0.9% BF per decade. The distribution of fat on the body, as indexed by the triceps/subscapular (T/S) ratio, has become more central. There has been an increasing positive skew in the distribution of subcutaneous fat thickness in the population. CONCLUSIONS: These trends describe very unfavourable changes in the body composition of young people, foreshadowing a potential increase in the incidence of cardiovascular and metabolic disease.

Secular trends in the aerobic fitness test performance and body mass index of Korean children and adolescents (1968-2000).

There is increasing evidence that the aerobic fitness performance of children is declining, at least in developed countries. To see if there was evidence of similar trends in a non-Western country, this study analysed data on 6-18-year-old Koreans tested between 1968 and 2000 using distance runs ranging from 600 to 1200 m. All existing data on the results of children's aerobic fitness tests in Korea were collated. In addition to six individual studies, very large datasets were available from the Korean Ministries of Education, and the Ministry of Culture and Tourism. Data on a total of 22,127,265 6-18-year-old children were available in the form of group means and standard deviations. Data were collated for each age x sex x test group, and performances were expressed as percentages of the fitted values for the year 1992 to standardise across tests, ages and sexes. All age x sex x test groups were then combined, and curves were fitted using weighted regression. A two-linear segment model best described the pattern of change (r = 0.83, p < 0.001). There was a relatively slow decline (0.26 % per year) in the aerobic performance of Korean children between 1968 and 1984. After 1984, however, there was a steep decline in performance, averaging 0.80 % per year. The rate of decline was greater in boys, younger children and children from outside the capital Seoul. Changes in running performance showed a similar pattern to changes in estimated body mass index. Compared to other countries, there has been a sharp decline in Korean children's performance on tests of aerobic fitness, which has been concurrent with increases in estimated body mass index.

Scaling maximal oxygen uptake to predict cycling time-trial performance in the field: a non-linear approach.

The purpose of the present article is to identify the most appropriate method of scaling VO2max for differences in body mass when assessing the energy cost of time-trial cycling. The data from three time-trial cycling studies were analysed (N = 79) using a proportional power-function ANCOVA model. The maximum oxygen uptake-to-mass ratio found to predict cycling speed was VO2max(m)(-0.32) precisely the same as that derived by Swain for sub-maximal cycling speeds (10, 15 and 20 mph). The analysis was also able to confirm a proportional curvilinear association between cycling speed and energy cost, given by (VO2max(m)(-0.32))0.41. The model predicts, for example, that for a male cyclist (72 kg) to increase his average speed from 30 km h(-1) to 35 km h(-1), he would require an increase in VO2max from 2.36 l min(-1) to 3.44 l min(-1), an increase of 1.08 l min(-1). In contrast, for the cyclist to increase his mean speed from 40 km h(-1) to 45 km h(-1), he would require a greater increase in VO2max from 4.77 l min(-1) to 6.36 l min(-1), i.e. an increase of 1.59 l min(-1). The model is also able to accommodate other determinants of time-trial cycling, e.g. the benefit of cycling with a side wind (5% faster) compared with facing a predominately head/tail wind (P<0.05). Future research could explore whether the same scaling approach could be applied to, for example, alternative measures of recording power output to improve the prediction of time-trial cycling performance.

Secular trends in physical performance of Australian children. Evidence from the Talent Search program.

AIM: This study examined trends in aerobic fitness in 12-15-year-old South Australian schoolchildren in the years 1995-2000, based on data from the Australian Sports Commission's Talent Search program. METHODS: A total of 18,631 children were tested. The aerobic performance test used was the 20 m shuttle run test (20 mSRT). The 20 mSRT scores were expressed as completed laps, and converted to estimated VO(2)max values. RESULTS: There were significant declines (p=0.04-0.0001) across all age-gender slices, equivalent to 0.18 to 0.36 ml O(2) x kg(-1) x min(-1) x yr(-1), or about 0.4-0.8% of mean values per year. The rate of decline is consistent with several other Australian and overseas studies in the years 1980-2000, which have used a variety of aerobic tests across a wide range of age groups. In relation to children of similar age in 7 other countries, Australian children show poor to average aerobic fitness levels. CONCLUSION: It is possible that the decay in Australian children's aerobic fitness is in part due to reduced physical activity.

One hundred years of growth: the evolution of height, mass, and body composition in Australian children, 1899-1999.

This paper summarizes 41 reports on the height and mass of Australian children aged between 5.00 and 16.99 years between 1899 and 1999. In all, data on 644,613 children were collated, including individual data on 68,196 children. After primary data treatment to correct for methodological and statistical artifacts, regressions were calculated to quantify the rate of change of height and mass over time. Distributional analysis was used to probe for changes in skewness of mass values, indicative of differentially greater increases at higher percentiles. In addition, studies reporting skin fold measurements were analyzed to assess changes in subcutaneous adiposity since 1976. The results show that height has been increasing at a rate of about 1.02 cm.decade(-1), and mass at a rate of about 0.99 kg.decade(-1). The height and mass of children continue to increase, after a slowing down in the rate of increase between 1950 and 1980. Increases in mass at the higher percentiles have been much greater than at lower percentiles, particularly since the mid-1980s, suggesting that the incidence of obesity is increasing in Australian children. Furthermore, a steady linear increase in subcutaneous skin fold thicknesses since 1976 suggests that the overall level of fatness is increasing in Australian children. These findings indicate that Australian children are following trends becoming evident elsewhere in the developed world, and that we may see an increasingly large subset of increasingly obese children in the early years of the 21st century.

Reticulocyte parameters as potential discriminators of recombinant human erythropoietin abuse in elite athletes.

This study investigated using reticulocyte (retic) parameters as indirect markers of human recombinant erythropoietin (r-HuEPO) abuse in elite athletes. Absolute reticulocyte count (# retic), the per cell haemoglobin content of reticulocytes (CHr), reticulocyte haemoglobin mass per litre of blood (RetHb) and red blood cell:reticulocyte haemoglobin (RBCHb:RetHb) ratio were assessed using flow cytometry. Venous blood was drawn from 155 elite athletes from six sports during regular training to establish reference ranges (95% confidence interval) for these parameters. The reference ranges were compared with those of a non-athletic population (n = 23), four groups of athletes (n = 24) before and after exposure to simulated altitudes (2,500-3,000 m for 11-23 nights), two groups of elite cyclists (n = 13) before and after four weeks of training at natural altitude (1,780 and 2,690 m), and with those of non-athletic subjects from a separate study (n =24) before and 1-2 days after they were injected with 1,200 U x kg(-1) r-HuEPO over a 9-10 day period. Generally the changes induced by r-HuEPO injection exceeded by approximately 100% the magnitude of the changes associated with natural altitude exposure. Simulated altitude exposure did not significantly alter the reticulocyte parameters. From the sample of 155 non-users and 24 r-HuEPO users, the population mean and variance, as well as the 95% confidence limits for the population mean and population variance, were estimated. Relative to arbitrarily chosen cut-off levels, the confidence limits for the rate of true positives and rate of true negatives were also calculated. Based on the lowest rate of false positives and highest rate of true positives, the best discriminator between r-HuEPO users and non-users was # retic, marginally superior to RBCHb: RetHb ratio and RetHb. At a cut-off for # retic of 221 x 10(9)x L(-1) we could be 95% sure that we would find no more than 7 false positives in every 100,000 tests. We would expect to pick up 51.8% of users, and could be 95% sure of picking up at least 38% of current or recent users. This result highlights the potential power of retic parameters for detecting r-HuEPO abuse among athletes. However, the efficacy of these cut-offs for detecting r-HuEPO abuse is unknown if an athlete is a chronic user or stops using r-HuEPO several weeks before being tested.

Physiological correlates of bilateral symmetry in humans.

Departures from perfect bilateral symmetry are thought to mirror an organism's ability to maintain developmental homeostasis. There is evidence showing that symmetry is negatively correlated with evolutionary and physical fitness. The purpose of this study was to determine the relationship between symmetry and health-related physiological characteristics in males and females. Forty-six male and female subjects participated in this study. Both facial and anthropometric traits were investigated for deviations from perfect bilateral symmetry. After measurements were made the subjects were tested on a range of physiological variables. There was no pattern of consistent significant correlations between fluctuating asymmetry and the physiological variables across all traits, and poor inter-correlations between the fluctuating asymmetries measured at different sites. The study failed to confirm the hypothesis that symmetric individuals were physiologically fitter when compared to their asymmetric counterparts.

The evolution of Australian football.

Australian football has undergone considerable change over the past century. This evolution seems to have accelerated more recently since the introduction and major influence of the media, increased professionalism and the start of a national competition. In this study we have attempted to quantify the evolution in game 'style' by measuring events during elite football games (from video analysis) and gathering physical information on players involved at the highest level. These data are important to gain insight into the game demands so that player preparation may be enhanced and when predicting the nature of the game in the future. Understanding the patterns of play within the game may also be useful when assessing the possible impact of rule changes, for example, increasing the number of interchange players on the potential for injury. Four games were selected, one from each of the past 4 decades to determine the rate at which specific, measurable events occurred in the games. Height and mass data on players were also obtained from official records of registered players in the VFL/AFL competitions. The results indicate the 'speed' of the game has approximately doubled in the period 1961-1997. The proportion of the total game which involves 'play' time has been reduced significantly while breaks in play are more frequent and longer. Despite this pattern, however, the average game tempo has increased along with player height and mass and we present a case which suggests these are likely determinants of the increased incidence of player injuries and lost match time.

Infrared thermometry in the diagnosis and treatment of heat exhaustion.

Infrared (IR) thermometers (FirstTemp 2000A, Intelligent Medical Systems, California) were used to monitor tympanic temperature (Tty) in 12 collapsed fun-runners suspected of suffering exertion-induced heat exhaustion (EIHE). Rectal temperature (Tre) was monitored via digital clinical thermometers. Conditions during the fun-run and in the field treatment centre were cool (air temperature 16-18 degrees C, relative humidity 60-65%). On admission, Tty was (mean +/- SEM) 1.2 +/- 0.3 degrees C lower than Tre. For admission plus subsequent monitoring data pooled, although Tty correlated significantly with Tre (r = 0.86, p < 0.001), mean Tty (37.4 +/- 0.2 degrees C) was significantly lower (p < 0.01) than mean Tre (38.4 +/- 0.4 degrees C). Cotton wool ear pads, applied to 10 of the runners on admission to minimise environmental effects on Tty, did not significantly improve the IR monitoring. A Tty > or = 37.1 degrees C predicted a Tre > or = 38 degrees C (an established diagnostic criterion for EIHE) with a sensitivity of 0.93 and a specificity of 0.63. These data indicate that IR tympanic thermometry, when utilised in cool environments, can result in misdiagnosis of heat exhaustion. Although IR thermometry shows some promise as a rapid, non-invasive means of monitoring core temperature, it should not be used in the diagnosis and treatment of heat exhaustion unless further research validates the method.

Modeling road-cycling performance.

This paper presents a complete set of equations for a "first principles" mathematical model of road-cycling performance, including corrections for the effect of winds, tire pressure and wheel radius, altitude, relative humidity, rotational kinetic energy, drafting, and changed drag. The relevant physiological, biophysical, and environmental variables were measured in 41 experienced cyclists completing a 26-km road time trial. The correlation between actual and predicted times was 0.89 (P < or = 0.0001), with a mean difference of 0.74 min (1.73% of mean performance time) and a mean absolute difference of 1.65 min (3.87%). Multiple simulations were performed where model inputs were randomly varied using a normal distribution about the measured values with a SD equivalent to the estimated day-to-day variability or technical error of measurement in each of the inputs. This analysis yielded 95% confidence limits for the predicted times. The model suggests that the main physiological factors contributing to road-cycling performance are maximal O2 consumption, fractional utilization of maximal O2 consumption, mechanical efficiency, and projected frontal area. The model is then applied to some practical problems in road cycling: the effect of drafting, the advantage of using smaller front wheels, the effects of added mass, the importance of rotational kinetic energy, the effect of changes in drag due to changes in bicycle configuration, the normalization of performances under different conditions, and the limits of human performance.

Exercise stimulus increases ventilation from maximal to supramaximal intensity.

This study investigated the influence of an exercise stimulus on pulmonary ventilation (VE) during severe levels of exercise in a group of ten athletes. The altered ventilation was assessed in relation to its effect on blood gas status, in particular to the incidence and severity of exercise induced hypoxaemia. Direct measurements of arterial blood were made at rest and during the last 15 s of two intense periods of cycling; once at an intensity found to elicit maximal oxygen uptake (VO2max; MAX) and once at an intensity established to require 115% of VO2max (SMAX). Oxygen uptake (VO2) and ventilatory markers were continually recorded during the exercise and respiratory flow-volume loops were measured at rest and during the final 30 s of each minute for both exercise intensities. When compared to MAX exercise, the subjects had higher ventilation and partial pressure of arterial oxygen (PaO2) during the SMAX intensity. Regression analysis for both conditions indicated the levels of PaO2 and oxygen saturation of arterial blood (SaO2) were positively correlated with relative levels of ventilation during exercise. It was apparent that mechanical constraints to ventilate further were not present during the MAX test since the subjects were able to elevate VE during SMAX and attenuate the level of hypoxaemia. This was also confirmed by analysis of the flow volume recordings. These data support the conclusions firstly, that overwhelming mechanical constraints on VE were not present during the MAX exercise, secondly, the subjects exhibiting the most severe hypoxaemia had no consistent relationship with any measure of expiratory flow limitation, and thirdly, ventilatory patterns during intense exercise are strong predictors of blood gas status.

The effects of altered exercise distribution on lymphocyte subpopulations.

The effects of exercise distribution on lymphocyte count, lymphocyte subpopulations and plasma cortisol concentration in peripheral blood were assessed in 19 healthy subjects. The subjects were randomly divided into group A (n = 10) or group B (n = 9) according to exercise distribution. Both groups underwent a 10-week programme involving 5 x 2-week blocks: baseline (B), training period 1 (TP1), stabilisation 1 (S1), training period 2 (TP2), and stabilisation 2 (S2). During B, S1 and S2 normal training was undertaken. During TP1 and TP2 the subjects increased the amount of training by 50% in week 1 and by 100% in week 2. During TP1 subjects in group A exercised 6 days.week-1, while during TP2 these subjects exercised on 3 alternate days.week-1, but doubled the duration of each training session. The subjects in group B reversed this training order. Blood was collected 36-42 h following exercise period B, and at the end of periods TP1, S1, TP2 and S2, and also 12-18 h following completion of exercise at the end of TP1 and TP2. There were no significant differences (P > 0.05) between the 6 day.week-1 programme and the 3 alternate day.week-1 programme in total lymphocyte count, CD3+, CD4+, CD8+, CD16+, or CD19+ cells, the CD4:CD8 ratio, HLA-DR+ (activated) T cells or plasma cortisol concentrations. Following both TP1 and TP2 there was a nonsignificant decrease in lymphocyte subpopulations. However following both S1 and S2 (baseline training) there was a significant increase in total lymphocyte count, CD3+, CD4+ and CD8+ lymphocytes. The S2 variables statistically significant from B were: total lymphocyte count (P < 0.01), CD3+ T-cells and percentage of circulating lymphocytes (P < 0.01), CD4+ cells (P < or = 0.0001), CD8+ cells (P < 0.05), and HLA-DR+ (activated) T-cells (P < 0.05). The results indicated that provided the amount of exercise is constant for a given period, then exercise distribution is not a critical variable in the alteration of lymphocyte subpopulations that may occur in response to overload training. However 2 weeks of overload training followed by 2 weeks of active recovery (baseline) training may induce an increase in the lymphocyte count.

Mathematical model of cycling performance.

A model of cycling performance is presented. The model is based on equating two expressions for the total amount of work performed. One expression is deduced from biomechanical principles deriving energy requirements from total resistance. The other models the energy available from aerobic and anaerobic energy systems, including the effect of oxygen uptake kinetics at the onset of exercise. The equation can then be solved for any of the variables. Empirically derived field and laboratory data were used to assess the accuracy of the model. Model estimates of 4,000-m individual pursuit performance times showed a correlation of 0.803 (P < or = 0.0001) with times measured in 18 high-performance track cyclists, with a mean difference (predicted--measured) of 4.6 s (1.3% of mean performance time). The model enables estimates of the performance impact of alterations in physiological, biomechanical, anthropometric, and environmental parameters.

Aerobic and anaerobic indices contributing to track endurance cycling performance.

A group of 18 male high performance track endurance and sprint cyclists were assessed to provide a descriptive training season specific physiological profile, to examine the relationship between selected physiological and anthropometric variables and cycling performance in a 4000-m individual pursuit (IP4000) and to propose a functional model for predicting success in the IP4000. Anthropometric characteristics, absolute and relative measurements of maximal oxygen uptake (VO2max), blood lactate transition thresholds (Thla- and Th(an),i), VO2 kinetics, cycling economy and maximal accumulated oxygen deficit (MAOD) were assessed, with cyclists also performing a IP4000 under competition conditions. Peak post-competition blood lactate concentrations and acid-base values were measured. Although all corresponding indices of Thla- and Th(an),i occurred at significantly different intensities there were high intercorrelations between them (0.51-0.85). There was no significant difference in MAOD when assessed using a 2 or 5 min protocol (61.4 vs 60.2 ml.kg-1, respectively). The highest significant correlations were found among IP4000 and the following: VO2max (ml.kg-2/3.min-1; r = -0.79), power output at lactate threshold (Wthla) (W; r = -0.86), half time of VO2 response whilst cycling at 115% VO2max (s; r = 0.48) and MAOD when assessed using the 5 min protocol (ml.kg-1; r = -0.50). A stepwise multiple regression yielded the following equation, which had an r of 0.86 and a standard error of estimate of 5.7 s: IP4000 (s) = 462.9 - 0.366 x (Wthla) - 0.306 x (MAOD) - 0.438 x (VO2max) where Wthla is in W, MAOD is in ml.kg-1 and VO2max is in ml.kg-1 x min-1.(ABSTRACT TRUNCATED AT 250 WORDS)