Disrupting Mating Behavior of Diaphorina citri (Liviidae).

Severe economic damage from citrus greening disease, caused by 'Candidatus Liberibacter asiaticus' bacteria, has stimulated development of methods to reduce mating and reproduction in populations of its insect vector, Diaphorina citri (Hemiptera: Liviidae). Male D. citri find mating partners by walking on host plants, intermittently producing vibrational calls that stimulate duetting replies by receptive females. The replies provide orientational feedback, assisting the search process. To test a hypothesis that D. citri mating can be disrupted using vibrational signals that compete with and/or mask female replies, courtship bioassays were conducted in citrus trees with or without interference from female reply mimics produced by a vibrating buzzer. Statistically significant reductions occurred in the rates and proportions of mating when the buzzer produced reply mimics within 0.4 s after male courtship calls compared with undisturbed controls. Observations of courtship behaviors in the two bioassays revealed activity patterns that likely contributed to the reductions. In both disruption and control tests, males reciprocated frequently between structural bifurcations and other transition points where signal amplitudes changed. Males in the disruption bioassay had to select among vibrational signals combined from the buzzer and the female at each transition point. They often turned towards the buzzer instead of the female. There was a statistically significant reduction in the proportion of males mating if they contacted the buzzer, possibly due to its higher vibration amplitude and duration in comparison with female replies. Potential applications of D. citri mating disruption technology in citrus groves are discussed.

Testing the activitystat hypothesis: a randomised controlled trial.

BACKGROUND: It has been hypothesised that an 'activitystat' may biologically regulate energy expenditure or physical activity levels, thereby limiting the effectiveness of physical activity interventions. Using a randomised controlled trial design, the aim of this study was to investigate the effect of a six-week exercise stimulus on energy expenditure and physical activity, in order to empirically test this hypothesis. METHODS: Previously inactive adults (n = 129) [age (mean ± SD) 41 ± 11 year; body mass index 26.1 ± 5.2 kg/m(2)] were randomly allocated to a Control group (n = 43) or a 6-week Moderate (150 min/week) (n = 43) or Extensive (300 min/week) (n = 43) exercise intervention group. Energy expenditure and physical activity were measured using a combination of accelerometry (total counts, minutes spent in moderate to vigorous physical activity) and detailed time use recalls using the Multimedia Activity Recall for Children and Adults (total daily energy expenditure, minutes spent in moderate to vigorous physical activity) at baseline, mid- and end-intervention and 3- and 6-month follow up. Resting metabolic rate was measured at baseline and end-intervention using indirect calorimetry. Analysis was conducted using random effects mixed modeling. RESULTS: At end-intervention, there were statistically significant increases in all energy expenditure and physical activity variables according to both accelerometry and time use recalls (p < 0.001) in the Moderate and Extensive groups, relative to Controls. There was no significant change in resting metabolic rate (p = 0.78). CONCLUSION: Taken together, these results show no evidence of an "activitystat" effect. In the current study, imposed exercise stimuli of 150-300 min/week resulted in commensurate increases in overall energy expenditure and physical activity, with no sign of compensation in either of these constructs. TRIAL REGISTRATION NUMBER: ACTRN12610000248066  (registered prospectively 24 March 2010).

Rapid Holocene thinning of an East Antarctic outlet glacier driven by marine ice sheet instability.

Outlet glaciers grounded on a bed that deepens inland and extends below sea level are potentially vulnerable to 'marine ice sheet instability'. This instability, which may lead to runaway ice loss, has been simulated in models, but its consequences have not been directly observed in geological records. Here we provide new surface-exposure ages from an outlet of the East Antarctic Ice Sheet that reveal rapid glacier thinning occurred approximately 7,000 years ago, in the absence of large environmental changes. Glacier thinning persisted for more than two and a half centuries, resulting in hundreds of metres of ice loss. Numerical simulations indicate that ice surface drawdown accelerated when the otherwise steadily retreating glacier encountered a bedrock trough. Together, the geological reconstruction and numerical simulations suggest that centennial-scale glacier thinning arose from unstable grounding line retreat. Capturing these instability processes in ice sheet models is important for predicting Antarctica's future contribution to sea level change.

Spatial and temporal variability of Alexandrium cyst fluxes in the Gulf of Maine: Relationship to seasonal particle export and resuspension.

Quantification of Alexandrium cyst fluxes through the Gulf of Maine water column is central to understanding the linkage between the source and fate of annual Alexandrium blooms in the offshore waters. These blooms often lead to paralytic shellfish poisoning (PSP) and extensive closures of shellfish beds. We report here on time-series sediment trap deployments completed at four offshore locations in the gulf between 2005 and 2010 as components of two ECOHAB-GOM field programs. Data presented documents the substantial spatial and temporal fluctuations in Alexandrium fundyense cyst fluxes in the gulf. Cyst delivery out of the euphotic zone peaked primarily between July and August following annual spring-summer Alexandrium blooms and was greatest in the western gulf. At all sites, cyst flux maxima to the subsurface waters were rarely coincident with seasonal peaks in the total mass export of particulate material indicating that cyst delivery was primarily via individually sinking cysts. Where persistent benthic nepheloid layers (BNLs) exist, significant sediment resuspension input of cysts to the near-bottom water column was evidenced by deep cyst fluxes that were up to several orders of magnitude greater than that measured above the BNL. The largest cyst fluxes in the BNL were observed in the eastern gulf, suggesting greater resuspension energy and BNL cyst inventories in this region. Temporal similarities between peak cyst export out of the upper ocean and peak cyst fluxes in the BNL were observed and document the contribution of seasonal, newly formed cysts to the BNL. The data however also suggest that many Alexandrium cells comprising the massive, short-lived blooms do not transition into cysts. Time-series flow measurements and a simple 1D model demonstrate that the BNL cyst fluxes reflect the combined effects of tidal energy-maintained resuspension, deposition, and input of cysts from the overlying water column.

No change in hemoglobin mass after 40 days of physical activity in previously untrained adults.

A high hemoglobin mass (Hb(mass)) is associated with a high maximum aerobic power (VO(2max)), however, the extent to which Hb(mass) is influenced by training is currently unclear. Accordingly, this study monitored changes in Hb(mass) and VO(2max) in 12 previously untrained adults (aged 18-25 years) following 40 days of regular physical activity. Hb(mass) and VO(2max) were assessed at the start and end of a 40-day physical activity program, which comprised of approximately 40 min of daily, moderate-intensity physical activity. Relative VO(2max) increased by 11.3%, yet there was no significant change in relative Hb(mass) (1.7%) and body mass (0.2%) during the 40-day period. There was a significant correlation between Hb(mass) and VO(2max) at the start of the study (r=0.58, P=0.05), but not between the change in relative VO(2max) and the change in relative Hb(mass) (r=-0.07, P=0.83). Our results support the concept of relative stability in Hb(mass) with approximately 1 month of moderate-intensity physical activity suggesting that Hb(mass) may be used for talent identification and possibly for anti-doping purposes.

Assessment of the pharmacological effects of inotropic drugs on left ventricular pressure and contractility: an evaluation of the QA interval as an indirect indicator of cardiac inotropism.

INTRODUCTION: The ICH S7A and S7B guidelines require that effects of test substances on the cardiovascular system be assessed with respect to blood pressure, heart rate and electrocardiogram intervals. Where adverse effects are identified additional supplemental studies, including ventricular contractility, should be conducted as deemed appropriate. However, there is an absence of definitive guidance regarding when to pursue supplementary studies, in part due to ill-defined criteria of what constitutes an adverse effect and to surgical/technical monitoring limitations of study designs. However with advances in technology it is now feasible to develop models for assessing LVP and contractility in conjunction with standard assessments. The objectives of this study were to 1) develop a model for chronic evaluation of LVP and contractility, 2) illustrate changes in LV contractility without concurrent proportional changes in heart rate and/or systemic blood pressure and 3) determine if the QA interval, the time between the Q on the ECG and the beginning of the upstroke on the arterial blood pressure, can be used as a indicator of altered LV contractility. METHODS: Dogs (N=4) were implanted with a telemetry transmitter. LVP, contractility, ECG and BP were assessed prior to and up to 24 h following administration of Atenolol (10 mg/kg) and Pimobendan (0.45 mg/kg). RESULTS: Atenolol caused an approximately 30% decrease in HR, followed by a sustained decrease in maximum left ventricular contractility (+dP/dt mmHg/s). No effects were noted on blood pressure. Pimobendan caused a 100% increase in contractility (+dP/dt mmHg/s) which remained elevated for approximately 4 h. No effects were noted on blood pressure. Heart rate was highly variable initial decreasing, followed by a highly variable increase until 4 h postdose. Following administration of both compounds changes in maximum left ventricular contractility correlated with reverse changes in QA interval duration. DISCUSSION: This model demonstrates that evaluation of LV contractility complements measurements of heart rate and blood pressure as part of a more complete cardiovascular safety assessment strategy. Furthermore, we demonstrate an apparent correlation between dP/dt and QA interval and concluded that QA interval can be utilized as an indicator of a potential inotropic effect. However further confirmation should be assessed through additional in-vivo measurements of LVP and contractility.

Olympic lightweight and open-class rowers possess distinctive physical and proportionality characteristics.

Rowers competing at the 2000 Olympic Games were measured for 38 anthropometric dimensions. The aim was to identify common physical characteristics that could provide a competitive advantage. The participants included 140 male open-class rowers, 69 female open-class rowers, 50 male lightweight rowers, and 14 female lightweight rowers. Body mass, stature, and sitting height were different (P < 0.01) between the open-class and lightweight rowers, as well as a comparison group of healthy young adults ("non-rowers", 42 males, 71 females), for both sexes. After scaling for stature, the open-class rowers remained proportionally heavier than the non-rowers, with greater proportional chest, waist, and thigh dimensions (P < 0.01). Rowers across all categories possessed a proportionally smaller hip girth than the non-rowers (P < 0.01), which suggested the equipment places some constraints on this dimension. Top-ranked male open-class rowers were significantly taller and heavier and had a greater sitting height (P < 0.01) than their lower-ranked counterparts. They were also more muscular in the upper body, as indicated by a larger relaxed arm girth and forearm girth (P < 0.01). For the male lightweight rowers, only proportional thigh length was greater in the best competitors (P < 0.01). In the female open-class rowers, skinfold thicknesses were lower in the more highly placed competitors (P < 0.01). In conclusion, the rowers in this sample demonstrated distinctive physical characteristics that distinguish them from non-rowers and other sports performers.

Profile of movement demands of national football players in Australia.

Descriptive data on game movement demands of contemporary players in the Australian National Soccer League (NSL, now the A League) are lacking. The purpose of this study was to profile movement demands of NSL games and specifically analyse distance covered, time in various speed categories (e.g., walking, jogging, striding, etc.), number of sprint speed efforts and overall mean player speed. Video tapes of 45 players from the 2002 to 2003 NSL season were analysed for whole- and half-game movement patterns and game statistics using Trak Performance software. Bivariate and ANOVA statistics were used for between game halves and positional comparisons. Results showed no changes to the frequency and speed of high intensity demands in both halves of the game. However, a 14% slower overall speed in the second half of the game when compared with the first half was attributed to fewer observations of the low intensity movements (9.0% less walking and 12.4% less jogging) and more stationary periods. Engagement in game events such as kicking and passing was also 11.2% less frequent in the second versus first half of games. Position-specific results of higher movement speeds of midfield players (7.2kmh(-1)), compared with defenders (6.1kmh(-1)), agree with previous results from international professional leagues. The results provide position-specific directions for future conditioning drills and benchmark fitness requirements in high level soccer players. The results also highlight the challenge to ensure consistency of second-half performances for elite level soccer players in Australia.

Comparison of global positioning and computer-based tracking systems for measuring player movement distance during Australian football.

Sports scientists require a thorough understanding of the energy demands of sports and physical activities so that optimal training strategies and game simulations can be constructed. A range of techniques has been used to both directly assess and estimate the physiological and biochemical changes during competition. A fundamental approach to understanding the contribution of the energy systems in physical activity has involved the use of time-motion studies. A number of tools have been used from simple pen and paper methods, the use of video recordings, to sophisticated electronic tracking devices. Depending on the sport, there may be difficulties in using electronic tracking devices because of concerns of player safety. This paper assesses two methods currently used to measure player movement patterns during competition: (1) global positioning technology (GPS) and (2) a computer-based tracking (CBT) system that relies on a calibrated miniaturised playing field and mechanical movements of the tracker. A range of ways was used to determine the validity and reliability of these methods for tracking Australian footballers for distance covered during games. Comparisons were also made between these methods. The results indicate distances measured using CBT overestimated the actual values (measured with a calibrated trundle wheel) by an average of about 5.8%. The GPS system overestimated the actual values by about 4.8%. Distances measured using CBT in experienced hands were as accurate as the GPS technology. Both systems showed relatively small errors in true distances.

Evidence for secular trends in children's physical activity behaviour.

It is not clear whether the global increase in weight problems in children is the result of excessive energy intake or decreasing energy expenditure. Methodological limitations have made it difficult to analyse. There is evidence that at least part of the problem may lie with increasing energy consumption, but it is important to examine the other side of the energy equation also. However, it is not possible to conclusively describe physical activity trends because of the absence of suitable baseline data. One solution is to summate all available evidence in as many areas of daily activities as possible and then draw tentative conclusions. This review summarises available trend data on direct representations of physical activity in a range of contexts, together with indirect measures such as sedentariness, fitness, and attitudes. The conclusions drawn are: physical activity in clearly defined contexts such as active transport, school physical education, and organised sports is declining in many countries; young people would like to be active but are often constrained by external factors such as school policy or curricula, parental rules in relation to safety and convenience, and physical environmental factors.

A comparison of patients relapsing to addictive drug use with non-relapsing patients following residential addiction treatment in Antigua.

The outcome of a 29-day residential addiction treatment programme for persons from Antigua and Barbuda with addiction to drugs or alcohol was assessed. All 100 patients entering the drug and alcohol treatment programme at Crossroads Centre Antigua between November 1998 and October 2002 were included. All patients were assessed with regards to drug or alcohol use or abstinence in November 2002 using telephone and mail follow-up as well as informal follow-up with families and other community contacts. Crossroads Centre Antigua is a 35 bed, 29-day residential treatment centre for drug and alcohol addiction serving patients from developed countries (85%) and from the Caribbean region (15%). Patients records were also reviewed to obtain age, gender, ethnicity, drug of choice, years of problematic use, completion of the 29 day programme, family member participation at Crossroads Centre Antigua (a four-day programme) and acceptance of halfway house placement. Of the 100 Antiguan patients admitted, 46 (46%) were abstinent (non-relapsers) at average 20.7+/-14.7 months after treatment. Abstinence did not have to be continuous. Forty-nine were known to be using drug or alcohol (49%) and five (5%) were lost to follow-up and considered to be using drugs (relapsers). Age (37.5 vs 41.1 years), gender (28% vs 22% female), ethnicity (87% vs 87% Afro-Caribbean), years of harmful use (12.7 vs 12.5 years) did not differ significantly between relapsers and non-relapsers. Crack cocaine use (67% vs 65%) and alcohol use (26% vs 31%) as primary addiction did not differ significantly between relapsers and non-relapsers. Relapsers were significantly less likely to complete the 29- day programme (81% vs 100%, p < 0.01), have family members participate at Crossroads (32% vs 54%, p < 0.05) or accept halfway house placement (4% vs 54%, p < 0.001). In conclusion, abstinence was achieved in 46% of those entering treatment, in 51% completing treatment, in 60% whose families participated and in 92% of those accepting halfway house placement.

A comparison of patients relapsing to addictive drug use with non-relapsing patients following residential addiction treatment in Antigua / Una Comparación de Pacientes que Recayeron en el uso Adictivo de Drogas, con Pacientes que no Experimentaron Recaída Tras Seguir un Tratamiento Residencial de la Adicción en Antigua

The outcome of a 29-day residential addiction treatment programme for persons from Antigua and Barbuda with addiction to drugs or alcohol was assessed. All 100 patients entering the drug and alcohol treatment programme at Crossroads Centre Antigua between November 1998 and October 2002 were included. All patients were assessed with regards to drug or alcohol use or abstinence in November 2002 using telephone and mail follow-up as well as informal follow-up with families and other community contacts. Crossroads Centre Antigua is a 35 bed, 29-day residential treatment centre for drug and alcohol addiction serving patients from developed countries (85%) and from the Caribbean region (15%). Patients records were also reviewed to obtain age, gender, ethnicity, drug of choice, years of problematic use, completion of the 29 day programme, family member participation at Crossroads Centre Antigua (a four-day programme) and acceptance of halfway house placement. Of the 100 Antiguan patients admitted, 46 (46%) were abstinent (non-relapsers) at average 20.7+/-14.7 months after treatment. Abstinence did not have to be continuous. Forty-nine were known to be using drug or alcohol (49%) and five (5%) were lost to follow-up and considered to be using drugs (relapsers). Age (37.5 vs 41.1 years), gender (28% vs 22% female), ethnicity (87% vs 87% Afro-Caribbean), years of harmful use (12.7 vs 12.5 years) did not differ significantly between relapsers and non-relapsers. Crack cocaine use (67% vs 65%) and alcohol use (26% vs 31%) as primary addiction did not differ significantly between relapsers and non-relapsers. Relapsers were significantly less likely to complete the 29- day programme (81% vs 100%, p < 0.01), have family members participate at Crossroads (32% vs 54%, p < 0.05) or accept halfway house placement (4% vs 54%, p < 0.001). In conclusion, abstinence was achieved in 46% of those entering treatment, in 51% completing treatment, in 60% whose families participated and in 92% of those accepting halfway house placement

Se evaluó el resultado de un programa de 29 días de tratamiento residencial de la adicción para personas de Antigua y Barbuda adictas a drogas o alcohol. Fueron incluidos todos los pacientes de un total de 100 que entraron a formar parte del programa de tratamiento contra las drogas y el alcohol en el Crossroads Centre Antigua entre noviembre de 1998 y octubre de 2002. Todos los pacientes fueron evaluados en relación con el uso o la abstinencia de drogas o alcohol en noviembre 2002, mediante un seguimiento por vía telefónica o correo, así como a través de un seguimiento informal con familiares u otros contactos en la comunidad. El Crossroads Centre Antigua es un centro de 35 camas para el tratamiento residencial por 29 días de la adicción a las drogas o el alcohol. El centro presta servicios a pacientes de los países desarrollados (85%) y de la región del Caribe (15%). También se revisaron los récords médicos de los pacientes para obtener datos sobre edad, sexo, etnicidad, droga de elección, años de uso problemático, cumplimiento del programa de 29 días, participación de miembros de la familia en el Crossroads Centre Antigua (un programa de cuatro días) y aceptación de su inclusión en una "casa de medio camino." De los 100 pacientes antigüenses admitidos, 46 (46%) eran abstinentes (no recayentes) en un momento determinado, ubicado como promedio 20.7 ± 14.7 meses después del tratamiento. La abstinencia no tenía que ser continua. Se sabía que 49 (49%) estaban usando drogas o alcohol, y cinco (5%) fueron dados por perdidos del seguimiento y de regreso al uso de las drogas (recayentes). La edad (37.5 vs 41.1 años), sexo (28% varones vs 22% hembra), etnicidad (87% vs 87% Afrocaribeños), y los años de consumo perjudicial (12.7 vs 12.5 años) no presentaron diferencias significativas entre los recayentes y los no recayentes. El uso de la cocaína-crack (67% vs 65%) y el uso del alcohol (26% vs.31%) como adicción primaria, no mostró diferencias significativas entre los recayentes y los no recayentes. Los recayentes mostraron una probabilidad significativamente menor en cuanto a completar el programa de 29 días (81% vs 100%, p < 0.01), hacer que miembros de su familia participaran en Crossroads (32% vs 54%, p < 0.05) o aceptar su inclusión en la casa de medio camino (4% vs 54%, p < 0.001). En conclusión, se logró abstinencia en el 46% de los que adoptaron el tratamiento, el 51% de los que completaron el tratamiento, el 60% de aquellos cuyas familias participaron, y el 92% de quienes aceptaron ser ubicados en la casa de medio camino.

A decrease in the association between the physical activity patterns of Australian parents and their children; 1985-1997.

The present study investigated the interactions between parents' and children's physical activity levels by examining whether or not parents who exercise have children who participate in sport. Of primary interest was an investigation of trends in these interactions over time. Information was collected from 10-13 y old children in 1985 (n = 2463) and then again in 1997-99 (n = 1469), about their sports participation and their perceptions of parents' exercise habits. Boys' participation in at least one sport declined from 87% in 1985 to 76% in 1997/1999 while, among girls, participation fell from 80% to 71%. According to their children's perceptions, mothers exercising regularly fell from 36% to 31% between surveys, while fathers exercising regularly fell from 39% to 32%. Interactions between parents' and children's exercise and sports behaviours were examined employing chi-square analysis techniques. Results showed gender-specific relationships for the 1985 sample, such that active fathers were associated with increased participation in sports by boys, and inactive mothers were associated with less participation in sports by girls. These interactions seemed to diminish over time. It is possible that changes in social structures during this time may be affecting familial behaviour relationships, such as the role modelling of active behaviours.

Client-centred assessment and the identification of meaningful treatment goals for individuals with a spinal cord injury.

STUDY DESIGN: Retrospective analysis. OBJECTIVES: (1) Describe the self-care, productivity and leisure problems identified by individuals with a spinal cord injury (SCI) during rehabilitation, (2) describe the perceived level of satisfaction and performance with self-care, productivity and leisure activities following an SCI, (3) quantify the relationship between the Canadian occupational performance measure (COPM), a client-centred, individualized measure of function, and the functional independence measure (FIM). SETTING: Tertiary rehabilitation centre, spinal cord injury unit, GF Strong Rehabilitation Centre, Vancouver, Canada. METHODS: Health records from 41 individuals with an SCI admitted between 2000 and 2002 were reviewed. Information was obtained from assessments performed on admission and discharge. Self-care, productivity and leisure problems identified by individuals with an SCI were described and their perceived level of performance and satisfaction was calculated. The relationship between the COPM and the FIM was measured by the Pearson product correlation. RESULTS: Self-care goals were identified most frequently (79%) followed by productivity (12%) and leisure (9%) goals. The top three problems identified by individuals with an SCI were functional mobility (including transfers and wheelchair use), dressing and grooming. A fair relationship was found between the COPM and the FIM (r between 0.351 and 0.514, P<0.05). CONCLUSIONS: The results highlight the importance of including a client-centred outcome measure in the assessment of individuals with an SCI. Initial support is provided for use of the COPM in individuals with an SCI.

Evidence for the aetiology of injuries in Australian football.

OBJECTIVES: To determine in Australian football (a) the influence of ground hardness and playing grade (level) on game speed and structure, and (b) player movement patterns throughout the game and across levels. METHODS: The design consisted of several studies. Seventeen games played on grounds of different hardness in 2000 were used to determine game speed and structure. Four first grade and four second grade grand final games (1994, 1996, 1997, 1999) were used to determine the game speed and structure on the same ground but at different levels. Fifty one players (44 first grade and seven second grade) were used to measure movement patterns within games and across levels during the 2000 season. RESULTS: There was a significant relation between ground hardness and game speed, which could lead to higher injury rates when the ground is harder. There was a 6.7% difference in game speed between the first and second grade levels reflecting differences in injury incidence. The first grade games were also characterised by a greater number of shorter, high intensity play periods and longer stop periods than the second grade games. Midfield players in the first grade games covered about 24% greater distance than their second grade counterparts, and there was a significant difference in their playing speeds. CONCLUSIONS: Over the past 40 years, the game speed in the top level of Australian football has approximately doubled. Over the same time, the number of collisions and the estimated injury incidence have also doubled. This study provides additional support to the suggestion that these variables are strongly linked. Factors such as ground hardness, playing level, and time during the game influence game speed and are therefore important in injury development in Australian football.

Morphological evolution of athletes over the 20th century: causes and consequences.

Over the course of the past century it has become increasingly difficult to find athletes of the size and shape required to compete successfully at the highest level. Sport is Darwinian in that only the 'fittest' reach the highest level of participation. Not every physical characteristic could be expected to play a role in this selection process, but two that are important and for which substantial data assemblies exist, are height and mass. Measurements of elite athlete sizes were obtained from a variety of sources as far back as records allowed. We charted the shift in these anthropometric characteristics of elite sportspeople over time, against a backdrop of secular changes in the general population. Athletes in many sports have been getting taller and more massive over time; the rates of rise outstripping those of the secular trend. In open-ended sports, more massive players have an advantage. Larger players average longer careers and obtain greater financial rewards. In some sports it is equally difficult to find athletes small enough to compete. In contrast, there are sports that demand a narrow range of morphological characteristics. In these sports the size of the most successful athletes over the century has remained constant, despite the drift in the population characteristics from which they are drawn. A number of social factors both drive and are driven by the search for athletes of increasingly rare morphology. These include globalisation and international recruitment, greater financial and social incentives, and the use of special training methods and artificial growth stimuli. In many sports the demand for a specific range in body size reinforces the need to adopt questionable and illegal behaviours to reach the required size and shape to compete at the top level. Future scenarios also include 'gene-farming' through assortative mating and athlete gamete banks.

Increases in intramuscular pressure raise arterial blood pressure during dynamic exercise.

This investigation was designed to determine the role of intramuscular pressure-sensitive mechanoreceptors and chemically sensitive metaboreceptors in affecting the blood pressure response to dynamic exercise in humans. Sixteen subjects performed incremental (20 W/min) cycle exercise to fatigue under four conditions: control, exercise with thigh cuff occlusion of 90 Torr (Cuff occlusion), exercise with lower body positive pressure (LBPP) of 45 Torr, and a combination of thigh cuff occlusion and LBPP (combination). Indexes of central command (heart rate, oxygen uptake, ratings of perceived exertion, and electromyographic activity), cardiac output, stroke volume, and total peripheral resistance were not significantly different between the four conditions. Mechanical stimulation during LBPP and combination conditions resulted in significant elevations in intramuscular pressure and mean arterial pressure from control at rest and throughout the incremental exercise protocol (P < 0.05). Conversely, there existed no significant changes in mean arterial pressure when the metaboreflex was stimulated by cuff occlusion. These findings suggest that under normal conditions the mechanoreflex is tonically active and is the primary mediator of exercise pressor reflex-induced alterations in arterial blood pressure during submaximal dynamic exercise in humans.