Browsing by Author "Clark B"

Now showing 1 - 4 of 4
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    A comparative analysis of critical power models in elite road cyclists
    (Elsevier B.V, 2021) Clark B; Macdermid PW
    The aims of this study were to compare four different critical power model's ability to ascertain critical power and W' in elite road cyclists, while making comparison to power output at respiratory compensation point, work rate (J·sec-1) at Wmax, and the work done above critical power during the Wmax test in relation to the W'. Ten male, elite endurance cyclists (V̇O2max ​= ​71.9 ​± ​5.9 ​ml ​kg-1·min-1) all familiar with critical power testing, participated in 3 testing sessions comprising 1. 15-s isokinetic (130 ​rpm) sprint, 1-min time trial, a ramp test to exhaustion, 2-3. a 4-min and/or 10-min self-paced maximal time trial separated by at least 24-h but limited to a 3-week period. The main findings show that all critical power models provided different W' (F(1.061,8.486) ​= ​39.07, p ​= ​0.0002) and critical powers (F(1.022,8.179) ​= ​32.31, p ​= ​0.0004), while there was no difference between each model's critical power and power output at respiratory compensation point (F(1.155, 9.243) ​= ​2.72, p ​= ​0.131). Differences between models or comparisons with respiratory compensation point were deemed not clinically useful in the provision of training prescription or performance monitoring if the aim is to equal work rate at compensation point. There was also no post-hoc difference between work completed at Wmax (kJ) (p ​= ​0.890) and W' using the nonlinear-3 model. Further research is required to investigate the physiological markers of intensity associated with respiratory compensation point and critical power work rate and the bioenergetic contribution to W'.
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    Evaluation of the effects of medium-term (57-day) omeprazole administration and of omeprazole discontinuation on serum gastrin and serum chromogranin A concentrations in the horse.
    (John Wiley and Sons, Inc., 2023-07-01) Clark B; Steel C; Vokes J; Shan JR; Gedye K; Lovett A; Sykes BW
    BACKGROUND: Rebound gastric hyperacidity (RGH) secondary to hypergastrinemia has been suggested to contribute to the rapid recurrence of equine squamous gastric disease (ESGD) in horses after discontinuation of omeprazole. HYPOTHESIS/OBJECTIVES: To evaluate changes in serum gastrin and chromogranin A (CgA) concentrations in response to medium-term (57-day) omeprazole treatment and after omeprazole discontinuation. ANIMALS: Fourteen mature Thoroughbred racehorses in simulated race training. METHODS: Horses received 2.28 g of oral omeprazole PO q24h for 57 days within a 61-day period, excluding a withholding period applied mid-protocol during which treatment was stopped as part of a concurrent study. Serum samples were collected on day 0 before omeprazole treatment, on day 1 of each week of the treatment period, and for an additional 5 weeks after discontinuation of treatment. Serum gastrin and CgA concentrations were analyzed using radioimmunoassay (RIA) and ELISA, respectively. RESULTS: Median serum gastrin concentrations increased 2.5-fold from baseline to day 7 (P < .001) but did not increase further during the omeprazole treatment period. Median serum gastrin concentrations returned to baseline within 2 to 4 days after administration of the last dose of omeprazole. No effect of treatment or discontinuation was seen in serum CgA concentrations. CONCLUSIONS AND CLINICAL IMPORTANCE: Serum gastrin concentrations increased in response to omeprazole treatment but returned to baseline within 2 to 4 days after the last dose of omeprazole. No effect of treatment or discontinuation was seen in serum CgA concentrations. Our results do not support the use of tapering protocols in horses.
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    The impact of childhood sexual abuse on psychological distress among women in New Zealand.
    (2012-02) Flett RA; Kazantzis N; Long NR; MacDonald C; Millar M; Clark B; Edwards H; Petrik AM
    PROBLEMS: In order to better understand the long-term impact of child sex abuse, this study examined the association between women's experience of abuse, health symptoms, and psychological distress in adulthood. There is limited information about child abuse outside the United States. METHODS: Nine hundred sixty-one women participated in a structured interview. RESULTS: Participants who had experienced abuse (13%) were significantly more vulnerable to psychological distress in adulthood if they were younger, less satisfied with their standard of living, and resided in urban areas. CONCLUSION: Dissemination and evaluation of therapies for the treatment of sex abuse in the New Zealand context is warranted.
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    VLamax Correlates Strongly With Glycolytic Performance
    (Taylor and Francis Group on behalf of SHAPE America, 2025-04-18) Clark B; Macdermid PW
    VLamax estimates an athlete’s maximal-glycolytic rate. This study aimed to determine the relationships between the VLamax and cycle ergometry efforts with a high-glycolytic energy contribution and the influence of VLamax and VO2max on respiratory compensation point. Eleven national-international endurance cyclists (VO2max = 70.7 ± 5.9 ml·kg−1·min−1) completed a 15-s isokinetic-test with pre- and postlactate measurements to determine VLamax, a 1-min maximal effort, and a ramp test to exhaustion in a single test session. The main findings showed strong relationships between VLamax and the mean absolute (r = 0.83, p =.002) and relative (r = 0.88, p =.0004) power during the lactic interval of the 15-s isokinetic-test. This relationship weakened when comparing VLamax with mean absolute (r = 0.52, p =.098) and relative (r = 0.29, p =.393) power during a 1-min maximal effort. Combining the VLamax and VO2max data through multiple regression resulted in a positive effect on the estimation of respiratory compensation point. It was concluded that the VLamax is a relevant indicator of maximal glycolytic rate. However, this metric currently lacks scientific validation as an accurate estimate of glycolytic rate and provides minimal extra information over using the power output from the isokinetic test alone. Practitioners may simply measure power over glycolytically demanding efforts to understand the maximal glycolytic rate of their athletes.