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Gross efficiency and cycling performance: a brief review
Simon A Jobson,James G Hopker,Thomas Korff,Louis Passfield
Journal of Science and Cycling , 2012,
Abstract: Efficiency, the ratio of work generated to the total metabolic energy cost, has been suggested to be a key determinant of endurance cycling performance. The purpose of this brief review is to evaluate the influence of gross efficiency on cycling power output and to consider whether or not gross efficiency can be modified. In a re-analysis of data from five separate studies, variation in gross efficiency explained ~30% of the variation in power output during cycling time-trials. Whilst other variables, notably VO2max and lactate threshold, have been shown to explain more of the variance in cycling power output, these results confirm the important influence of gross efficiency. Case study, cross-sectional, longitudinal, and intervention research designs have all been used to demonstrate that exercise training can enhance gross efficiency. Whilst improvements have been seen with a wide range of training types (endurance, strength, altitude), it would appear that high intensity training is the most potent stimulus for changes in gross efficiency. In addition to physiological adaptations, gross efficiency might also be improved through biomechanical adaptations. However, ‘intuitive’ technique and equipment adjustments may not always be effective. For example, whilst ‘pedalling in circles’ allows pedalling to become mechanically more effective, this technique does not result in short term improvements in gross efficiency.
EFFECT OF THE ROTOR CRANK SYSTEM ON CYCLING PERFORMANCE
Simon A. Jobson,James Hopker,Andrew Galbraith,Damian A. Coleman
Journal of Sports Science and Medicine , 2009,
Abstract: The aim of this study was to evaluate the impact of a novel crank system on laboratory time-trial cycling performance. The Rotor system makes each pedal independent from the other so that the cranks are no longer fixed at 180°. Twelve male competitive but non-elite cyclists (mean ± s: 35 ± 7 yr, Wmax = 363 ± 38 W, VO2peak = 4.5 ± 0.3 L·min-1) completed 6-weeks of their normal training using either a conventional (CON) or the novel Rotor (ROT) pedal system. All participants then completed two 40.23-km time-trials on an air-braked ergometer, one using CON and one using ROT. Mean performance speeds were not different between trials (CON = 41.7 km·h-1 vs. ROT = 41.6 km·h-1, P > 0.05). Indeed, the pedal system used during the time-trials had no impact on any of the measured variables (power output, cadence, heart rate, VO2, RER, gross efficiency). Furthermore, the ANOVA identified no significant interaction effect between main effects (Time-trial crank system*Training crank system, P > 0.05). To the authors' knowledge, this is the first study to examine the effects of the Rotor system on endurance performance rather than endurance capacity. These results suggest that the Rotor system has no measurable impact on time-trial performance. However, further studies should examine the importance of the Rotor 'regulation point' and the suggestion that the Rotor system has acute ergogenic effects if used infrequently
CYCLING EFFICIENCY IN TRAINED MALE AND FEMALE COMPETITIVE CYCLISTS
James Hopker,Simon Jobson,Helen Carter and Louis Passfield
Journal of Sports Science and Medicine , 2010,
Abstract: The aim of this study was to examine differences in cycling efficiency between competitive male and female cyclists. Thirteen trained male (mean ± SD: 34 ± 8 yr, 74.1 ± 6.0 kg, Maximum Aerobic Power (MAP) 414 ± 40 W, VO2max 61.3 ± 5.4 ml·kg-1·min-1) and 13 trained female (34 ± 9 yr, 60.1 ± 5.2 kg, MAP 293 ± 22 W, VO2max 48.9 ± 6.1 ml·kg-1·min-1) competitive cyclists completed a cycling test to ascertain their gross efficiency (GE). Leg and lean leg volume of all cyclists was also measured. Calculated GE was significantly higher in female cyclists at 150W (22.5 ± 2.1 vs 19.9 ± 1. 8%; p < 0.01) and 180W (22.3 ± 1.8 vs 20.4 ± 1.5%; p = 0.01). Cadence was not significantly different between the groups (88 ± 6 vs 91 ± 5 rev·min-1). Lean leg volume was significantly lower for female cyclists (4.04 ± 0.5 vs 5.51 ± 0.8 dm3; p < 0.01) and was inversely related to GE in both groups at 150 and 180W (r = -0.59 and -0.58; p < 0.05). Lean leg volume was shown to account for the differences in GE between the males and females. During an "unloaded" pedalling condition, male cyclists had a significantly higher O2 cost than female cyclists (1.0 ± 0.1 vs 0.7 ± 0.1 L·min-1; p < 0.01), indicative of a greater non-propulsive cost of cycling. These results suggest that differences in efficiency between trained male and female cyclists can be partly accounted for by sex-specific variation in lean leg volume
Placebo effect of an inert gel on experimentally induced leg muscle pain
James G Hopker, Abigail J Foad, Christopher J Beedie, et al
Open Access Journal of Sports Medicine , 2010, DOI: http://dx.doi.org/10.2147/OAJSM.S13564
Abstract: cebo effect of an inert gel on experimentally induced leg muscle pain Original Research (2820) Total Article Views Authors: James G Hopker, Abigail J Foad, Christopher J Beedie, et al Published Date November 2010 Volume 2010:1 Pages 215 - 221 DOI: http://dx.doi.org/10.2147/OAJSM.S13564 James G Hopker1, Abigail J Foad2, Christopher J Beedie2, Damian A Coleman2, Geoffrey Leach1 1Centre for Sports Studies, University of Kent, Chatham, Kent, UK; 2Department of Sports Science, Tourism and Leisure, Canterbury Christ Church University, Canterbury, Kent, UK Purpose: This study examined the therapeutic effects of an inert placebo gel on experimentally induced muscle pain in a sports therapy setting. It aimed to investigate the degree to which conditioned analgesia, coupled with an expectation of intervention, was a factor in subsequent analgesia. Methods: Participants were sixteen male and eight female sports therapy students at a UK University. With institutional ethics board approval and following informed consent procedures, each was exposed to pain stimulus in the lower leg in five conditions, ie, conditioning, prebaseline, experimental (two placebo gel applications), and postbaseline. In conditioning trials, participants identified a level of pain stimulus equivalent to a perceived pain rating of 6/10. An inert placebo gel was then applied to the site with the explicit instruction that it was an analgesic. Participants were re-exposed to the pain stimulus, the level of which, without their knowledge, had been decreased, creating the impression of an analgesic effect resulting from the gel. In experimental conditions, the placebo gel was applied and the level of pain stimulus required to elicit a pain rating of 6/10 recorded. Results: Following application of the placebo gel, the level of pain stimulus required to elicit a pain rating of 6/10 increased by 8.2%. Application of the placebo gel significantly decreased participant’s perceptions of muscle pain (P = 0.001). Conclusion: Subjects’ experience and expectation of pain reduction may be major factors in the therapeutic process. These factors should be considered in the sports therapeutic environment.
Placebo effect of an inert gel on experimentally induced leg muscle pain
James G Hopker,Abigail J Foad,Christopher J Beedie,et al
Open Access Journal of Sports Medicine , 2010,
Abstract: James G Hopker1, Abigail J Foad2, Christopher J Beedie2, Damian A Coleman2, Geoffrey Leach11Centre for Sports Studies, University of Kent, Chatham, Kent, UK; 2Department of Sports Science, Tourism and Leisure, Canterbury Christ Church University, Canterbury, Kent, UKPurpose: This study examined the therapeutic effects of an inert placebo gel on experimentally induced muscle pain in a sports therapy setting. It aimed to investigate the degree to which conditioned analgesia, coupled with an expectation of intervention, was a factor in subsequent analgesia.Methods: Participants were sixteen male and eight female sports therapy students at a UK University. With institutional ethics board approval and following informed consent procedures, each was exposed to pain stimulus in the lower leg in five conditions, ie, conditioning, prebaseline, experimental (two placebo gel applications), and postbaseline. In conditioning trials, participants identified a level of pain stimulus equivalent to a perceived pain rating of 6/10. An inert placebo gel was then applied to the site with the explicit instruction that it was an analgesic. Participants were re-exposed to the pain stimulus, the level of which, without their knowledge, had been decreased, creating the impression of an analgesic effect resulting from the gel. In experimental conditions, the placebo gel was applied and the level of pain stimulus required to elicit a pain rating of 6/10 recorded.Results: Following application of the placebo gel, the level of pain stimulus required to elicit a pain rating of 6/10 increased by 8.2%. Application of the placebo gel significantly decreased participant’s perceptions of muscle pain (P = 0.001).Conclusion: Subjects’ experience and expectation of pain reduction may be major factors in the therapeutic process. These factors should be considered in the sports therapeutic environment.Keywords: conditioning, expectation, perception, positive belief, sports therapy
FAMILIARISATION AND RELIABILITY OF SPRINT TEST INDICES DURING LABORATORY AND FIELD ASSESSMENT
James G. Hopker,Damian A. Coleman,Jonathan D. Wiles,Andrew Galbraith
Journal of Sports Science and Medicine , 2009,
Abstract: The aim of the study was to assess the reliability of sprint performance in both field and laboratory conditions. Twenty-one male (mean ± s: 19 ± 1 years, 1.79 ± 0.07 m, 77.6 ± 7.1 kg) and seventeen female team sport players (mean ± s: 21 ± 4 years, 1.68 ± 0. 07 m, 62.7 ± 4.7 kg) performed a maximal 20-metre sprint running test on eight separate occasions. Four trials were conducted on a non-motorised treadmill in the laboratory; the other four were conducted outdoors on a hard-court training surface with time recorded by single-beam photocells. Trials were conducted in random order with no familiarisation prior to testing. There was a significant difference between times recorded during outdoor field trials (OFT) and indoor laboratory trials (ILT) using a non-motorised treadmill (3.47 ± 0.53 vs. 6.06 ±1.17s; p < 0.001). The coefficient of variation (CV) for time was 2.55-4.22% for OFT and 5.1-7.2% for ILT. During ILT peak force (420.9 ± 87.7N), mean force (147.2 ± 24.7N), peak power (1376.8 ± 451.9W) and mean power (514.8 ± 164.4W), and were measured. The CV for all ILT variables was highest during trial 1-2 comparison. The CV (95% confidence interval) for the trial 3-4 comparison yielded: 9.4% (7.7-12. 1%), 7.9% (6.4-10.2%), 10.1% (8.2-13.1%) and 6.2% (5.1-8.0%) for PF, MF, PP and MP and respectively. The results indicate that reliable data can be derived for single maximal sprint measures, using fixed distance protocols. However, significant differences in time/speed over 20-m exist between field and laboratory conditions. This is primarily due to the frictional resistance in the non- motorised treadmill. Measures of force and power during ILT require at least 3 familiarisations to reduce variability in test scores
Bupivacaine and botulinum toxin to treat comitant strabismus
Hopker, Luisa Moreira;Zaupa, Priscila Fernandes;Lima Filho, Acácio Alves de Souza;Cronemberger, Monica Fialho;Tabuse, Marcia Keiko Uyeno;Nakanami, Célia Regina;Allemann, Norma;Mendon?a, Tomás Scalamandré;
Arquivos Brasileiros de Oftalmologia , 2012, DOI: 10.1590/S0004-27492012000200008
Abstract: purpose: to evaluate the change in ocular motility and muscle thickness measured with ultrasonography after intramuscular injection of bupivacaine and botulinum toxin a. methods: eight patients (five female) were enrolled to measure ocular motility prior and 1, 7, 30 and 180 days after one injection of 2 ml of 1.5% bupivacaine and 2.5 u of botulinum toxin a in agonist and antagonist muscles, respectively, of eight amblyopic eyes. muscle thickness was measured prior and on days 1, 7 and 30 after injection using 10-mhz ultrasonography (eyelid technique). results: mean change in alignment was 10 prism diopters after 180 days (n=6). an average increase of 1.01 mm in muscle thickness was observed after 30 days of bupivacaine injection and 0.28 mm increase was observed after botulinum toxin a injection, as measured by ultrasonography. lateral rectus muscles injected with bupivacaine had a mean increase of 1.5 mm in muscle thickness. conclusion: in this study, a change in ocular motility was observed after 180 days of intramuscular injection of bupivacaine and botulinum toxin in horizontal extraocular muscles. overall, there was an increase of muscle thickness in both botulinum toxinum a and bupivacaine injected muscles after 30 days of injection when measured by ultrasonography. this change was more pronounced on lateral rectus muscles after bupivacaine injection.
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