The use of CAF by athletes' is mainly driven by its reported ability to improve exercise performance, and is therefore commonly used by endurance athletes in competitions since its removal from the World Anti-Doping Agency list in 2004. However, the specific mechanism explaining its ergogenic effects, and its effect on top trained endurance athletes is lacking scientific research.
Place: Norges Idrettshøgskole
Caffeine and Endurance Performance in Athletes
The aim of the thesis was therefore to examine the effects of caffeine ingestion on factors considered determining for endurance sport performance and fatigue.
The doctoral thesis consisted of Five scientific studies. In total 65 male sub-elite and elite endurance athletes volunteered to participate, with twelve subjects participating in more than one study. All subjects included were trained endurance athletes with a O2max in the range of 67.2 to 90.5 (mL·kg-1·min-1). All studies included in the dissertation were performed in a randomized, double-blinded, placebo-controlled, crossover design at the Norwegian School of Sports Sciences in the Department of Physical Performance, between 2012 and 2016. Specifically the studies investigated the effects of caffeine's ingestion on: O2max, Fractional Utilization of O2max, accumulated O2-deficit, work economy (O2-cost), pacing strategy, PRE and pain tested in relation to exercise performance during different mode (time until voluntary exhaustion vs TT), duration (10-120min), muscular usage (double poling vs running), or condition (sea level vs altitude)
Collectively the results from the five studies of the thesis demonstrate that CAF ingestion of 3-6 mg·kg-1 is an effectiveaid for improving endurance performance in top athletes. Improvements were greater during time until voluntary exhaustion (~8-20%) trials compared to time trial (TT) testing (~1-5%). Improvements are observed independent of mode (time until voluntary exhaustion vs TT), duration (10-120min), muscular usage (double poling vs running), or condition (sea level vs altitude) where approximately 75% of test subjects improved their performance following CAF ingestion. The reduction in both pain and RPE following CAF ingestion seem important for explaining exercise improvements. Novel results from the thesis are the observations that CAF ingestion increased aerobic power (O2max), fractional utilization ofO2max and anaerobic power (O2-deficit), thus increasing energy availability (ATP turnover). No difference in work economy, pacing strategy or substrate utilization was however evident following CAF ingestion.
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