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.

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.

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.

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.

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.

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.

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.

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.

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)