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Introduction, aims

As you learned in the General Reading Strategies section the introduction of a research article usually consists of the following aspects;

  • the topic
  • the general background to the topic
  • a summary (and critical evaluation) of previous ideas / research / theories
  • the aim or purpose of the research
  • the outline indicating the (sub) sections of the text.
Here are the stages of the introduction to Hadjicharalambous, M., Georgiades, E., Kilduff, L. P., Turner, A. P., Tsofliou, F. and Pitsiladis, Y. P. (2006) Influence of caffeine on perception of effort, metabolism and exercise performance following a high-fat meal, Journal of Sports Sciences, 24:8,875-887.

Click on the question mark buttonicons to reveal some critical questions you could ask about each section of this introduction. You will need to click on the icon more than once to reveal all the critical questions.

Stage and purpose of stage Stage of the introduction Critical questions

1. ESTABLISHING THE FIELD

- asserting importance of the topic


- stating current knowledge (generally)

Caffeine has been reported to increase exercise performance by enhancing fat oxidation and, therefore, sparing glycogen (e.g. Costill, Dalsky, & Fink, 1978; Essig, Costill, & Van Handel, 1980), particularly during the early stages of prolonged high intensity exercise (Spriet et al., 1992). Several mechanisms have been proposed to explain this caffeine-induced sparing of muscle glycogen: (1) caffeine may reduce muscle glycogenolytic rate by inhibiting glycogen phosphorylase activity, the fluxgenerating step for muscle glycogenolysis (Rush & Spriet, 2001); (2) caffeine can enhance free fatty acid (FFA) mobilization by stimulating the release of epinephrine and, hence, increase the potential for fat oxidation (Spriet et al., 1992); and (3) caffeine may indirectly promote fat oxidation and carbohydrate sparing by inhibiting adenosine receptors in adipose tissue, which otherwise inhibit free fatty acid mobilization from adipocytes (Spriet, 1995).

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2. SUMMARISING PREVIOUS RESEARCH

- from the perspective of this research

A significant number of studies, however, suggest an increase in exercise performance without supporting the carbohydrate sparing effect of caffeine (e.g. Cox et al., 2002; Graham & Spriet, 1991; Greer, Friars, & Graham, 2000; Laurent et al., 2000). Improved high-intensity exercise performance has also been demonstrated following caffeine ingestion (e.g. Flinn, Gregory, McNaughton, Trstram, & Davies, 1990; Jackman, Wendling, Friars, & Graham, 1996; McNaughton, 1986), where muscle glycogen depletion is clearly not the primary cause of fatigue.

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3. PREPARING FOR PRESENT RESEARCH

- indicating a gap

- raising a question

It is likely, therefore, that caffeine may enhance endurance performance, not by sparing muscle glycogen but through other effect(s). For example, caffeine has been reported to: (a) reduce perception of effort (RPE) (e.g. Cole et al., 1996); (b) attenuate ‘‘central fatigue’’ by reducing brain serotonin turnover, through an inhibition of the enzyme tryptophan hydroxylase (Lim et al., 2001); and (c) inhibit central adenosine receptor activation, thereby attenuating ‘‘central fatigue’’ by increasing the dopamine:serotonin ratio in the brain (Davis et al., 2003). Alternatively, caffeine or one of its byproducts could directly affect skeletal muscle and/or influence the propagation of neural signals in regions between the brain and neuromuscular junction (for a review, see Spriet, 1995). The contradictions reported in the literature may be due to the multiple sites of action of caffeine, within both the central nervous system (CNS) and peripheral tissues (e.g. Fredholm, Battig, Holmen, Nehlig, & Zvartau, 1999). Therefore, an alternative approach, which attempts to distinguish primary from secondary effects of caffeine, is required.

An acute increase in plasma [FFA] similar to that reported following caffeine ingestion can be induced by giving participants a high fat meal (e.g. Whitley et al., 1998) with consequent increases in the rate of fat utilization (e.g. Hawley et al., 2000) and, therefore, an improvement in exercise performance (Hickson, Rennie, Conlee, Winder, & Holloszy, 1977; Pitsiladis, Smith, & Maughan, 1999).

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4. INTRODUCING PRESENT RESEARCH AND/OR ARTICLE

 - stating purpose and aims

Consequently, the aim of the present study was to examine the effects of caffeine ingestion, following acute elevation of plasma [FFA] induced by a high fat meal, on perceptual and metabolic responses during constant-load submaximal exercise, and on incremental and endurance exercise performance. It was hypothesized that co-ingestion of caffeine with a high fat meal could differentiate between putative altered substrate utilization effects of caffeine and other influences such as its action on the CNS.

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