Analyzing track sprint cyclists' performances using position-specific maximal-torque and power-cadence relationships

Previous studies have demonstrated the importance of maximal Torque-Cadence (T-C) and Power-Cadence (P-C) relationships, for the performances of world class track sprint cyclists. If these relationships are affected by the function of the lower limb muscles, the ability of cyclists to generate torque and power at a given cadence may vary depending on their riding position. During sprint events (individual and team sprints and Keirin), cyclists alternate between standing and seated positions. The T-C and P-C relationships may change with the position adopted by the cyclists. PURPOSE: The aim of this study was to evaluate the necessity to define position specific maximal T-C and P-C relationships. METHODS: Eight junior elite track cyclists from the National Talent Identification squad undertook two inertial-load tests that consisted of four all-out sprints each. One test was undertaken at the velodrome in a standing position on a carbon fibre track bike, and the other test was completed in a seated position on an air-braked stationary ergometer. A calibrated SRM power meter interfaced to a custom instrumentation package was used for all mechanical measurements. Maximal T-C and P-C relationships were analysed to calculate maximal Torque (T0), maximal Power (Pmax) and optimal pedalling cadence (PCopt). RESULTS: All individual T-C and P-C relationships obtained for both body positions were fitted by linear regressions (r2=0.95 ± 0.02) and second order polynomials (r2=0.96 ± 0.01), respectively. T0 was higher (209 ± 2.2N.m vs. 177.0 ± 3.9N.m, p<0.05), PCopt was lower (112.5 ± 11.4rpm vs. 120.1 ± 6.7rpm, p<0.05), and Pmax was higher (1261 ± 235W vs. 1076 ± 183W, p<0.05) in standing position compared to seated position. CONCLUSION: Analysis of track sprint cyclists’ performances can be improved by the determination of position-specific maximal T-C and P-C relationships .

Cycling at 120 when compared to 80 rev/min increases the accumulated oxygen deficit but does not affect the precision of its calculation

The aim of the present study was to determine the influence of pedal rate on the precision and quantification of the accumulated oxygen deficit (AOD). Eight trained male triathletes completed a lactate threshold test, VO2 peak test, 10 x 3 min submaximal exercise bouts and a high-intensity exercise bout, all performed at 80 and 120 rev/min. For both pedal rates the intensities for the sub-maximal and high-intensity tests were relative to the lactate threshold and VO2 peak work rates. The VO2-power regressions were calculated using 5 intensities from above the lactate threshold combined with a y intercept value with VO2 measured after 3 min of exercise. For the 120 compared to the 80 rev/min tests, the lactate threshold work rate (255±13 versus 276±47 Watts) (p<0.01) and VO2 peak work rate (352±17 versus 382±20, Watts) (p<0.05) were lower at 120 rev/m. Conversely, the VO2 peak and the VO2 measured during the exhaustive exercise were the same for both pedal rates (p>0.05). Using linear regression modelling the slope of the VO2-power regression (0.0112 versus 0.010 L/Watt) (p<0.01), the estimated total energy demand (ETED) (5.13±0.75 versus 4.89±0.88 L/min) and the AOD (4.27±0.94 versus 3.66±1.25 L) (p<0.05) were greater at 120 rev/m. However, the 95% confidence interval for the ETED and the standard error of the predicted value were the same for both pedal rates (p>0.05). Our results demonstrate that pedal rate effects the size but not the precision of the calculated AOD and should therefore be considered when developing an AOD protocol.

Diabetes MILES - Australia (Management and Impact for Long-Term Empowerment and Success) : methods and sample characteristics of a national survey of the psychological aspects of living with type 1 or type 2 diabetes in Australian adults

Background Successful management of diabetes requires attention to the behavioural, psychological and social aspects of this progressive condition. The Diabetes MILES (Management and Impact for Long-term Empowerment and Success) Study is an international collaborative. Diabetes MILES-Australia, the first Diabetes MILES initiative to be undertaken, was a national survey of adults living with type 1 or type 2 diabetes in Australia. The aim of this study was to gather data that will provide insights into how Australians manage their diabetes, the support they receive and the impact of diabetes on their lives, as well as to use the data to validate new diabetes outcome measures.

Methods The survey was designed to include a core set of self-report measures, as well as modules specific to diabetes type or management regimens. Other measures or items were included in only half of the surveys. Cognitive debriefing interviews with 20 participants ensured the survey content was relevant and easily understood. In July 2011, the survey was posted to 15,000 adults (aged 18-70 years) with type 1 or type 2 diabetes selected randomly from the National Diabetes Services Scheme (NDSS) database. An online version of the survey was advertised nationally. A total of 3,338 eligible Australians took part; most (70.4%) completed the postal survey. Respondents of both diabetes types and genders, and of all ages, were adequately represented in both the postal and online survey sub-samples. More people with type 2 diabetes than type 1 diabetes took part in Diabetes MILES-Australia (58.8% versus 41.2%). Most respondents spoke English as their main language, were married/in a de facto relationship, had at least a high school education, were occupied in paid work, had an annual household income > $AUS40,000, and lived in metropolitan areas.

Discussion A potential limitation of the study is the under-representation of respondents from culturally and linguistically diverse backgrounds (including Aboriginal and Torres Strait Islander origin). Diabetes MILES-Australia represents a major achievement in the study of diabetes in Australia, where for the first time, the focus is on psychosocial and behavioural aspects of this condition at a national level.

Labeling of multiple HIV-1 proteins with the biarsenical-tetracysteine system

Due to its small size and versatility, the biarsenical-tetracysteine system is an attractive way to label viral proteins for live cell imaging. This study describes the genetic labeling of the human immunodeficiency virus type 1 (HIV-1) structural proteins (matrix, capsid and nucleocapsid), enzymes (protease, reverse transcriptase, RNAse H and integrase) and envelope glycoprotein 120 with a tetracysteine tag in the context of a full-length virus. We measure the impact of these modifications on the natural virus infection and, most importantly, present the first infectious HIV-1 construct containing a fluorescently-labeled nucleocapsid protein. Furthermore, due to the high background levels normally associated with the labeling of tetracysteine-tagged proteins we have also optimized a metabolic labeling system that produces infectious virus containing the natural envelope glycoproteins and specifically labeled tetracysteine-tagged proteins that can easily be detected after virus infection of T-lymphocytes. This approach can be adapted to other viral systems for the visualization of the interplay between virus and host cell during infection.

Intramuscular heat shock protein 72 and heme oxygenase-1 mRNA are reduced in patients with type 2 diabetes: evidence that insulin resistance is associated with a disturbed antioxidant defense mechanism

To examine whether genes associated with cellular defense against oxidative stress are associated with insulin sensitivity, patients with type 2 diabetes (n = 7) and age-matched (n = 5) and young (n = 9) control subjects underwent a euglycemic-hyperinsulinemic clamp for 120 min. Muscle samples were obtained before and after the clamp and analyzed for heat shock protein (HSP)72 and heme oxygenase (HO)-1 mRNA, intramuscular triglyceride content, and the maximal activities of β-hyroxyacyl-CoA dehydrogenase (β-HAD) and citrate synthase (CS). Basal expression of both HSP72 and HO-1 mRNA were lower (P < 0.05) by 33 and 55%, respectively, when comparing diabetic patients with age-matched and young control subjects, with no differences between the latter groups. Both basal HSP72 (r = 0.75, P < 0.001) and HO-1 (r = 0.50, P < 0.05) mRNA expression correlated with the glucose infusion rate during the clamp. Significant correlations were also observed between HSP72 mRNA and both β-HAD (r = 0.61, P < 0.01) and CS (r = 0.65, P < 0.01). HSP72 mRNA was induced (P < 0.05) by the clamp in all groups. Although HO-1 mRNA was unaffected by the clamp in both the young and age-matched control subjects, it was increased (P < 0.05) ∼70-fold in the diabetic patients after the clamp. These data demonstrate that genes involved in providing cellular protection against oxidative stress are defective in patients with type 2 diabetes and correlate with insulin-stimulated glucose disposal and markers of muscle oxidative capacity. The data provide new evidence that the pathogenesis of type 2 diabetes involves perturbations to the antioxidant defense mechanism within skeletal muscle.