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- Volume 16, Issue 3, 2004
South African Journal of Sports Medicine - Volume 16, Issue 3, 2004
Volumes & issues
Volume 16, Issue 3, 2004
Source: South African Journal of Sports Medicine 16, pp 1 –5 (2004)More Less
The recent development of portable blood lactate analysers has made it relatively easy to test blood lactate concentration in the field. This paper discusses the validity and accuracy of measuring blood lactate concentration as a marker of training status or exercise intensity and examines the assumptions upon which the above practice is based. <br>The mechanisms responsible for blood lactate accumulation according to different theories are discussed, followed by a review of the literature regarding the measurement, tracking and interpretation of blood lactate concentration. <br>The use of blood lactate concentration to monitor either training status or intensity is complicated by the inaccuracy of portable lactate analysers, multiple confounding factors affecting blood lactate concentration such as carbohydrate depletion, mode of exercise, ambient temperature, muscle damage and overtraining and difficulty in interpreting the results. The relationship between changes in blood lactate concentration following training and subsequent performance in competition has not been convincingly established. Therefore it may be concluded that changes in blood lactate concentration should be interpreted with caution as the changes do not track training status or exercise intensity with sufficient precision to have a practical application.
Message from the President of the South African Sports Medicine Association, Dr Demitri Constantinou : editorialAuthor Demitri ConstantinouSource: South African Journal of Sports Medicine 16 (2004)More Less
Extracted from text ... It gives me great pleasure to address the subscribers and readers of the South African Journal of Sports Medicine. I believe that the quality of the Journal and its relevance to its readers has gained enormous strength over the last two to three years. Papers submitted for publication are ever increasing in scientific strength. The Editor-in-Chief, Professor Mike Lambert, together with the Senior Associate Editor, Professor Maurice Mars, the Editorial Board and all the reviewers have worked tirelessly in ensuring that the Journal is something to proudly represent the Association. I urge all those who have manuscripts that could ..
Author E.M. PetersSource: South African Journal of Sports Medicine 16, pp 8 –13 (2004)More Less
Recent evidence supports multifaceted functions of interleukin- 6 (IL-6). While this cytokine was originally known for its pro-inflammatory function in diseases such as rheumatoid arthritis, today it is recognised for its important antagonistic, anti-inflammatory role in regulating immune processes. Released from skeletal muscle, abdominal adipose and hypothalamic tissue during exercise, it also has 'endocrine-like' metabolic regulatory action that has been linked to energy expenditure, glycogenolysis, and fat oxidation during acute exercise exposure. The quantity and timing of exercise-induced IL- 6 production is dependent on exercise duration, intensity and mode. Eccentric exercise that results in damage to contractile muscle tissue and/or the muscle cytoskeleton, is associated with an increase that peaks approximately 2 hours after cessation of exercise. In contrast, concentric exercise, which is not accompanied by an inflammatory response, induces an increment in IL-6 during exercise. During concentric exercise intramuscular IL-6 production is stimulated by complex signalling cascades which are initiated by elevated intramuscular calcium concentrations. With prolongation of the exercise IL-6 has been shown to act as a 'sensor' regulating blood glucose homeostasis and lipolysis in white adipose tissue. Activation of the IL-6 gene in skeletal muscle is substrate-regulated and greatest when muscle glycogen stores are low. The therapeutic potential of IL-6 in treating obesity has been established in both rodents and humans. While a deficiency of IL-6 has been associated with greater fat mass and lower metabolic rate during exercise, elevated circulating IL-6 concentrations have been shown to inhibit the production of tumour necrosis factor-alpha. This may provide a mechanism to explain how exercise attenuates metabolic disorders associated with low-grade inflammation such as type-2 diabetes, artherosclerosis and possibly autoimmune diseases.
Knowledge and perceptions of elite South African athletes on doping and doping control, 1998 v. 2002 : original research articleSource: South African Journal of Sports Medicine 16, pp 14 –18 (2004)More Less
<I>Objective :</I> To ascertain the knowledge, awareness and perceptions of elite South African sportspersons chosen for the Commonwealth Games in Manchester in 2002 with regard to doping, doping control, and the South African Institute for Drug-Free Sport (SAIDS). The study also sought to assess the changes in such parameters that may have occurred since the previous survey of 1998, conducted at the Kuala Lumpur Games. <br><I>Design :</I> The study was a questionnaire survey, administered to members of the South African team participating in the 2002 Commonwealth Games. The questionnaire was based on the United States National Collegiate Athletic Association (NCAA) Questionnaire. <br><I>Analysis :</I> The study is a descriptive study, with small sample size and response categories limiting the usefulness of statistical analysis. <br><I>Results :</I> The study revealed that more sportspersons were aware of the existence of SAIDS in 2002 than in 1998, with an increased number of athletes sourcing information from SAIDS (28% v. 7%). There was, however, no difference in knowledge between the groups with regard to the International Olympic classification of prohibited substances. Eighty-three per cent of athletes in the current study were of the opinion that doping control does serve as a useful deterrent, compared with 68% in the previous study. However athletes reported a significant increase in usage of amphetamines, ephedrine and marijuana compared with 1998. The majority of respondents denied use of prohibited drugs to enhance performance, largely because of a concern about their negative health effects. <br><I>Conclusions :</I> The advocacy, education and doping control programmes of SAIDS have noticeably increased from 1997 to the present. It is reasonable to infer that this has played a role in influencing attitudes and behaviour, as noted in the results of this survey.
Home ground advantage - fact or fallacy? A comment on the 2004 Super 12 rugby competition : original research articleSource: South African Journal of Sports Medicine 16, pp 19 –21 (2004)More Less
<I>Objective :</I> The aim of this study was to determine whether there was an advantage to playing at home in the 2004 Rugby Union Super 12 competition. The question was relevant because this unusual competition involved travelling across time zones during the competition, potentially negating any home ground advantage caused by fatigue from travel and changing time zones. <br><I>Main outcome measure :</I> The mean points difference (points for the team minus points against the team) for 'home' and 'away' fixtures was calculated for each team before the semi-final stage of the competition. <br><I>Result :</I> Combined results for all 12 teams showed that the points difference was positive and significantly greater at 'home' than 'away' fixtures (7.4 <u>+</u> 6.9 points v. -7.4 <u>+</u> 7.9 points, home v. away) (p < 0.05). <br><I>Conclusions :</I> The combined mean positive points difference at home indicates a home ground advantage, and that on average teams scored more points than their opposition when playing at home. This has implications for the 'fairness' of the competition as 6 teams had 6 home matches whereas the other 6 teams had 5 home matches in the 2004 Super 12 competition.
Prevalence of rugby injuries among elite high school and elite junior club players : original research articleSource: South African Journal of Sports Medicine 16, pp 22 –25 (2004)More Less
<I>Objective :</I> To investigate the prevalence of rugby injuries among 59 elite high school and 74 junior club players (ages 15 - 20 years). <br><I>Design and settings :</I> A standardised questionnaire was completed by the players to obtain information on injuries sustained during the 2002 season. In particular, information was obtained about player position, anatomical region injured and type of injury. <br><I>Results :</I> The 20-year-old elite club players had the highest injury prevalence. Most injuries occurred among forwards, particularly loose forwards. The lower limb was the most commonly injured anatomical region. The most common injuries were sprains and strains. <br><I>Conclusion :</I> Coaches and medical staff should use preventive methods to decrease the number of injuries in rugby.