PubMed Health⌕ Search

Biomedical subjects

S Lawrence

Publications and source records attributed to S Lawrence.

At least 19 recordsLinked to original sources
PubMed2005

Time-motion analysis of elite field hockey during several games in succession: a tournament scenario.

International field hockey tournaments may require teams to play three games within a period of four days. Therefore, there is potential for residual fatigue to affect the movement patterns of players during subsequent games. The purpose of this study was to document changes in time-motion analysis of 14 elite male field hockey players during three games within a period of four days during an international tournament. In addition, the nature of and any changes in repeated-sprint activity were investigated using a criteria of a minimum of three sprints with a mean recovery duration between sprints of < 21 s. The percent of total game time spent standing significantly increased across all three games (7.4+/-.2, 11.2+/-2.7 and 15.6+/-5.6%, respectively, P<0.05). Conversely, the percent time spent jogging significantly decreased from game 1 to game 2 and from game 1 to game 3 (40.5+/-7.3, 34.8+/-7.4 and 29.4+/-5.7%, respectively, P<0.05). Furthermore, the percent time in striding significantly increased from game 1 to game 3 and from game 2 to game 3 (4.1+/-1.3, 5.1+/-0.9 and 5.8+/-1.4%, respectively. P<0.05). Changes in mean motion frequency and duration were recorded across games for the motions of standing, striding and sprinting. The frequency of exercise bouts that met the criteria for 'repeated-sprint' decreased across the three games (17, 11 and 8, respectively). In summary, the results suggest that when elite field hockey players play three games within four days there are significant changes in time-motion analysis.

Adult↗
PubMed2004

Longitudinal assessment of the effects of field-hockey training on repeated sprint ability.

Repeated-sprint ability is thought to be an important fitness component of team sports. However, little is known about the effect sport-specific training has on this fitness component. Therefore, the purpose of this study was to investigate the effects of field-hockey specific training on repeated-sprint ability, plasma hypoxanthine (Hx) concentration and other blood parameters in 18 elite female field-hockey players. All subjects performed a repeated-sprint ability test on a cycle ergometer (5 x 6-sec maximal sprints every 30 secs) before and after seven weeks of training, designed to improve repeated-sprint ability. Following training, there was a significant (P< 0.05) increase in absolute total work (20.73+/-2.00 to 21.15+/-2.07 kJ, mean+/-SD). However, there was no significant change in total work when expressed per kg of body mass (341.3+/-16.4 to 345.5+/-18.8 J x kg(-1)). In addition, training resulted in a significant (P< 0.05) decrease in change values (peak-rest values) for Hx (8.2+/-3.8 to 5.5+/-2.7 micromol x L(-1)) and hydrogen ion concentration (22.8+/-5.2 to 19.1+/-5.1 nmol x L(-1)). The significant increase in absolute total work following seven weeks of field-hockey specific training was most likely due to an increase in lean muscle mass. The significant decrease in plasma Hx concentration (post-test minus rest values) following seven weeks of field hockey-specific training provides evidence that Hx production and/or efflux from the muscle are reduced. Therefore, one adaptation of sport-specific repeated-sprint training may be to conserve the purine nucleotide pool.

Adaptation, Physiological↗
PubMed2004

Competing with kreteks: transnational tobacco companies, globalisation, and Indonesia.

OBJECTIVE: To examine the strategies employed by transnational tobacco companies (TTCs) to compete more effectively compete with the dominant kretek manufacturers in Indonesia, and to consider implications of their failure. METHODS: Systematic analysis of corporate documents obtained from British American Tobacco's (BAT's) Guildford depository and from industry and tobacco control websites document collections. RESULTS: The limited progress of the TTCs in Indonesia is best explained by the distinctive political economy of its tobacco industry. Though effective when collaborating on regulatory issues of mutual interest, TTCs have been less able than kretek manufacturers to exercise political influence where their interests conflict. Global strategies of TTCs have undergone significant local adaptation in attempting to compete in this distinctive environment. While maintaining uniformity in core brand attributes, TTCs have sought to reconcile international imagery with local norms, particularly to appeal to women. BAT unsuccessfully attempted to develop clove based products that imitated the appeal of kreteks, withdrawn following concerns about exposing the company to charges of operating double standards. CONCLUSIONS: The documents presented highlight the complexity of the global tobacco industry. Tobacco control efforts need to address more effectively the ongoing impact of kreteks while recognising the distinctive threats posed by TTCs.

Culture↗
PubMed2004

Complicity in contraband: British American Tobacco and cigarette smuggling in Asia.

OBJECTIVES: To examine the complicity of British American Tobacco (BAT) in cigarette smuggling in Asia, and to assess the centrality of illicit trade to regional corporate strategy. METHODS: Analysis of previously confidential documents from BAT's Guildford depository. An iterative strategy combined searches based on geography, organisational structure, and key personnel, while corporate euphemisms for contraband were identified by triangulation. RESULTS: BAT documents demonstrate the strategic importance of smuggling across global, regional, national, and local levels. Particularly important in Asia, contraband enabled access to closed markets, created pressure for market opening, and was highly profitable. Documents demonstrate BAT's detailed oversight of illicit trade, seeking to reconcile the conflicting demands of control and deniability. CONCLUSIONS: BAT documents demonstrate that smuggling has been driven by corporate objectives, indicate national measures by which the problem can be addressed, and highlight the importance of a coordinated global response via WHO's Framework Convention on Tobacco Control.

Asia↗
PubMed2003

Assessing technician effects when extracting quantities from microscope images.

Consider an experiment where the response is based on an image; e.g., an image captured to a computer file by a digital camera mounted on a microscope. Suppose relevant quantitative measures are extracted from the images so that results can be analyzed by conventional statistical methods. The steps involved in extracting the measures may require that the technicians, who are processing the images, perform some subjective manipulations. In this case, it is important to determine the bias and variability, if any, attributable to the technicians' decisions. This paper describes the experimental design and statistical analyses that are useful for those determinations. The design and analysis are illustrated by application to two biofilm research projects that involved quantitative image analysis. In one investigation, the technician was required to choose a threshold level, then the image analysis program automatically extracted relevant measures from the resulting black and white image. In the other investigation, the technician was required to choose fiducial points in each of two images collected on different microscopes; then the image analysis program registered the images by stretching, rotating, and overlaying them, so that their quantitative features could be correlated. These investigations elucidated the effects of the technicians' decisions, thereby helping us to assess properly the statistical uncertainties in the conclusions for the primary experiments.

Analysis of Variance↗
PubMed2003

Predictors of repeated-sprint ability in elite female hockey players.

The ability to maintain maximal power over a series of sprints may depend, in part, on the resynthesis of PCr and the buffering of hydrogen ions (H+). As a result, repeated-sprint ability may be related to VO2peak and changes in plasma pH. Fourteen elite female field-hockey players (Mean +/- SD body mass: 61.1 +/- 5.9 kg and VO2pea: 55.7 +/- 3.2 mL x kg(-1) x min(-1)) participated in this investigation. Tests consisted of a repeated-sprint ability test (5 x 6-s all-out sprints every 30 s) and a VO2peak test. Capillary and venous blood was sampled before and after the 5 x 6-s cycle test for the determination of lactate concentration and pH. There were no significant correlations between VO2peak (mL x kg(-1) x min(-1)) and total work (J.kg(-1); r = 0.35), or power decrement (r = 0.30) during the repeated-sprint ability test. There was, however, a significant correlation between power decrement and change in plasma [H+] (r = 0.66; P < 0.05). The results of this study show that in a homogenous group of elite, team-sport athletes, VO2peak (mL x kg(-1) x min(-1)) is not a strong predictor of repeated-sprint ability. However, in this group, there is a significant correlation between change in plasma [H+] and repeated-sprint ability.

Adult↗
PubMed2003

Effect of wearing an ice cooling jacket on repeat sprint performance in warm/humid conditions.

OBJECTIVE: To examine the effect of cooling the skin with an ice jacket before and between exercise bouts (to simulate quarter and half time breaks) on prolonged repeat sprint exercise performance in warm/humid conditions. METHODS: After an initial familiarisation session, seven trained male hockey players performed two testing sessions (seven days apart), comprising an 80 minute intermittent, repeat sprint cycling exercise protocol inside a climate chamber set at 30 degrees C and 60% relative humidity. On one occasion a skin cooling procedure was implemented (in random counterbalanced order), with subjects wearing an ice cooling jacket both before (for five minutes) and in the recovery periods (2 x 5 min and 1 x 10 min) during the test. Measures of performance (work done and power output on each sprint), heart rates, blood lactate concentrations, core (rectal) and skin temperatures, sweat loss, perceived exertion, and ratings of thirst, thermal discomfort, and fatigue were obtained in both trials. RESULTS: In the cooling condition, chest (torso) skin temperature, thermal discomfort, and rating of thirst were all significantly lower (p<0.05), but no significant difference (p>0.05) was observed between conditions for measures of work done, power output, heart rate, blood lactate concentration, core or mean skin temperature, perceived exertion, sweat loss, or ratings of fatigue. However, high effect sizes indicated trends to lowered lactate concentrations, sweat loss, and mean skin temperatures in the cooling condition. CONCLUSIONS: The intermittent use of an ice cooling jacket, both before and during a repeat sprint cycling protocol in warm/humid conditions, did not improve physical performance, although the perception of thermal load was reduced. Longer periods of cooling both before and during exercise (to lower mean skin temperature by a greater degree than observed here) may be necessary to produce such a change.

Adult↗
PubMed2002

Nicotinic receptors in the putamen of patients with dementia with Lewy bodies and Parkinson's disease: relation to changes in alpha-synuclein expression.

A reduction in nicotinic receptor (nAChR) binding has previously been observed in putamen in Parkinson's disease (PD) and dementia with Lewy bodies (DLB). The present study demonstrates no concommitant reduction in the expression of alpha2-alpha7, beta2 and beta3 nAChR subunit proteins. Alphasynuclein, which can interfere with membrane protein function and is a key constituent of PD and DLB pathology, was increased (insoluble fraction) in both disorders, although nAChR binding loss did not correlate with alpha-synuclein expression within patient groups. The results point to a possible abnormality of striatal nicotinic receptor assembly in PD and DLB.

Aged↗
PubMed2002

Pre-exercise oral creatine ingestion does not improve prolonged intermittent sprint exercise in humans.

BACKGROUND: This investigation determined whether pre-exercise oral Cr ingestion could enhance prolonged intermittent sprint exercise performance. METHODS EXPERIMENTAL DESIGN: a randomised, double-blind crossover design was employed. SETTING: testing was performed at the Western Australian Institute of Sport and participants were monitored and treated by both scientific and medical personnel. PARTICIPANTS: eight active, but not well-trained males with a background in multiple-sprint based sports acted as subjects for this investigation. INTERVENTIONS: subjects ingested either 15 g Cr.H2O or placebo 120 min and 60 min prior to the start of an 80-min maximal sprint cycling task (10 sets of multiple 6-sec sprints with varying active recoveries). Subjects were retested 14 days later, being required to ingest the alternate supplement and repeat the exercise test. MEASURES: performance variables (work done and peak power) were obtained throughout the exercise challenge. Muscle biopsies (vastus lateralis) were raised to a peak of 2348+/-223 micromol x l(-1) prior to the commencement of exercise after Cr ingestion. There were no significant changes in any cycling performance parameters following Cr ingestion, although blood La- was significantly lower (p<0.05) than placebo at all time points during were taken preexercise as well as immediately and 3 min post-exercise in order to determine concentrations of ATP, PCr, Cr, La- and glycogen. Venous blood was drawn prior to and on four occasions during the exercise test, and analysed for Cr, NH3+, La- and pH. RESULTS: Serum Cr concentrations exercise, and plasma NH3+ accumulation was also significantly reduced (p<0.05) in the Cr condition, but only in the second half of the 80-min exercise test. Muscle ATP and TCr levels as well as postexercise PCr replenishment were unaffected following Cr administration. CONCLUSIONS: The data suggest that although the pre-exercise ingestion of a large Cr dose was shown to have some impact on blood borne metabolites, it does not improve maximal prolonged intermittent sprint exercise performance, possibly due to an insufficient time allowed for uptake of serum Cr by skeletal muscle to occur. Therefore, this form of loading does not provide an alternative method of Cr supplementation to the traditional five-day supplementation regimes established by previous research.

Adult↗
PubMed2001

The validity of a repeated sprint ability test.

Many team sports require participants to repeatedly produce maximal or near maximal sprints of short duration (1-7s) with brief recovery periods, over an extended period of time (60-90 min). Therefore, an important fitness component for these sports is what is often termed repeated sprint ability (RSA). A variety of tests have been devised to assess RSA. However, while the reliability of some of these tests has been reported, there has been no published attempt to assess the validity of RSA tests. The purpose of the present paper was to assess the validity of a popular RSA test--the 5 x 6 s cycle test. Ten moderately-trained males (Mean+/-SD age: 23.6+/-3.0 yrs, mass: 71.8+/-7.4 kg, peak VO2: 46.32+/-4.16 ml.kg(-1)min(-1)) participated in the investigation. Following familiarisation, subjects reported to the laboratory at the same time of day, on three occasions, each separated by at least 48 hours. Testing consisted of a 5 x 6 s cycle test (5 x 6 s maximal sprints every 30 s), a graded exercise test (GXT) and a simulated game (3 x 15 min periods separated by five min). The simulated game consisted of a 1-min circuit that was repeated 15 times in each period. The circuit replicated typical movement patterns observed during motion analysis of field hockey games. Each circuit commenced with a 15-m maximum sprint through timing gates. Time to run 5, 10 and 15 m was recorded. Oxygen consumption was measured during both the GXT and the simulated game with a portable gas analysis system (Cosmed K4 b2, Italy). Correlation coefficients between dependent variables were calculated using Pearson's Product Moment (r). There was a significant correlation between power decrement during the 5 x 6 s cycle test and decrement in 15-m time across the three periods (r = 0.76, P<0.05), but not decrement in 10-m time (r = 0.54) or 5-m time (r = 0.42). These results suggest that the 5 x 6 s cycle test is valid for assessing the decrement in 15-m time, but not the decrement in 5 or 10m time. Thus, one measure of RSA (sprint decrement) appears to be specific to the test protocol, rather than a general quality. The most likely explanation is that the energy requirements of the 5 x 6 s cycle test more closely match those required to repeatedly run 15 m (mean time = 2.74 s) than to repeatedly run 10 m (mean time = 1.97 s) or 5 m (mean time = 1.13 s). It is therefore suggested that, while the 5 x 6 s cycle test is often used to assess RSA ability in a wide range of sports, it may need to be modified to reflect the common sprint distances found in specific sports.

Adult↗
PubMed2001

Understanding the careers of physician educators in family medicine.

PURPOSE: Little is known about what contributes to the career decisions of physician educators in family medicine. This study sought to understand the variables that influence these decisions and to identify key sources of vitality for physician educators in family medicine. METHOD: A national sample of randomly selected physician educators in family medicine responded to a postcard survey regarding their contribution(s) to education and career satisfaction. A series of exclusion criteria were applied to 399 useable responses, yielding 24 physician educators who participated in a semi-structured telephone interview focusing on their careers. Using qualitative research methods, themes were identified and categorized from the transcribed interviews and investigators' field notes. RESULTS: The career decisions and actions of physician educators in family medicine emanated from an underlying set of values and beliefs associated with "making the world better." Participants sought challenging, diverse, and stimulating positions from which they could have an impact in ways that were consistent with their values. Three major sources of vitality (learners, colleagues, and patients) complemented the desire for challenging positions. Physician educators in family medicine, however, continually struggled to balance their personal and professional lives. CONCLUSION: The study results highlight the key variables that draw faculty into education and sustain their vitality, and the professional and personal challenges that can derail or support their careers. This information can be used to recruit, develop, and retain successful and productive physician educators in family medicine.

Adaptation, Psychological↗
PubMed2001

Effect of creatine loading on long-term sprint exercise performance and metabolism.

PURPOSE: This study examined whether creatine (Cr) supplementation could enhance long-term repeated-sprint exercise performance of approximately 80 min in duration. METHODS: Fourteen active, but not well-trained, male subjects initially performed 10 sets of either 5 or 6 x 6 s maximal bike sprints, with varying recoveries (24, 54, or 84 s between sprints) over a period of 80 min. Work done (kJ) and peak power (W) were recorded for each sprint, and venous blood was collected preexercise and on four occasions during the exercise challenge. Muscle biopsies (vastus lateralis) were obtained preexercise as well as 0 min and 3 min postexercise. Subjects were then administered either 20 g.d-1 Cr.H2O (N = 7) or placebo (N = 7) for 5 d. Urine samples were collected for each 24 h of the supplementation period. Subjects were then retested using the same procedures as in test 1. RESULTS: Total work done increased significantly (P < 0.05) from 251.7 +/- 18.4 kJ presupplementation to 266.9 +/- 19.3 kJ (6% increase) after Cr ingestion. No change was observed for the placebo group (254.0 +/- 10.4 kJ to 252.3 +/- 9.3 kJ). Work done also improved significantly (P < 0.05) during 6 x 6 s sets with 54-s and 84-s recoveries and approached significance (P = 0.052) in 5 x 6 s sets with 24-s recovery in the Cr condition. Peak power was significantly increased (P < 0.05) in all types of exercise sets after Cr loading. No differences were observed for any performance variables in the placebo group. Resting muscle Cr and PCr concentrations were significantly elevated (P < 0.05) after 5 d of Cr supplementation (Cr: 48.9%; PCr: 12.5%). Phosphocreatine levels were also significantly higher (P < 0.05) immediately and 3 min after the completion of exercise in the Cr condition. CONCLUSION: The results of this study indicate that Cr ingestion (20 g.day-1 x 5 d) improved exercise performance during 80 min of repeated-sprint exercise, possibly due to an increased TCr store and improved PCr replenishment rate.

Administration, Oral↗
PubMed2001

New Zealand pathologists: a case study in occupational control.

This paper examines the progressive exertion of external managerial control over New Zealand pathologists as the country's New Public Management health reforms were implemented during the 1990s. Perspectives on professionalism, and its role in the effective use of resources, are discussed as part of the examination of this shift in decision-making power from pathologists to external management. Our analysis, based on a range of archived and interview data collected over the period 1997-2000, suggests that publicly unacceptable compromises in pathology service quality were risked by the pursuit of tight bureaucratic and free market controls over pathology practice. The paper concludes with suggestions for a health professional control model facilitative of maximal health gain.

Decision Making, Organizational↗
PubMed2001

Expecting dirt but saying dart: the creation of a blend memory.

During a naming task, time pressure and a manipulation of the proportion of related prime-target pairs were used to induce subjects to generate an expectation to the prime. On some trials, the presented target was orthographically and generally phonologically similar to the expected target. The expectancy manipulation was barely detectable in the priming data but was clearly evident on a final recognition test. In addition, the recognition data showed that the nearly simultaneous activation of an expectation and sensory information derived from the orthographically and phonologically similar target produced a false memory. It is argued that this represents a blend memory.

Humans↗
PubMed2000

The health of mothers of children with cutaneous neonatal lupus erythematosus differs from that of mothers of children with congenital heart block.

PURPOSE: Neonatal lupus erythematosus is caused by the transplacental passage of maternal autoantibodies. The aim of this study was to determine the risk of connective tissue disorders in mothers of children with cutaneous neonatal lupus erythematosus, as compared with the risk in mothers of children with congenital heart block, which is also often caused by maternal autoantibodies. SUBJECTS AND METHODS: We prospectively studied all mothers of children with cutaneous neonatal lupus erythematosus during a 14-year period at the Hospital for Sick Children, Toronto, Ontario, Canada. We identified 28 mothers, of whom 24 were eligible for study. The health and antibody status of the mothers were determined at the birth of the child and at followup. RESULTS: All mothers had anti-Ro antibodies at the time of birth. Initially 10 mothers were healthy and 14 mothers had either a defined (n = 9) or an undifferentiated (n = 5) autoimmune disorder. At a mean follow-up of 7 years, 13 (1 of whom had died) had a defined connective tissue disease, and 5 had an undifferentiated autoimmune disorder. Only 6 (25%) remained asymptomatic. By comparison, 36 (56%) of 64 mothers of children with congenital heart block were asymptomatic at follow-up (P <0.005). CONCLUSIONS: The majority of mothers of children with cutaneous neonatal lupus erythematosus had a defined or undifferentiated autoimmune disorder at the time of the child's birth, and others developed these conditions during follow-up. The health of these mothers appears to differ from that of mothers of children with congenital heart block.

Adult↗