The results of previous studies in untrained subjects have indicated that food and fluid intake frequency and quantity (Leiper, 2003; despite Husain, 1987), nocturnal sleep duration (Roky, 2004; Margolis, 2004) and daily physical activity (Waterhouse, 2008; Afifi, 1997) are reduced during the month of Ramadan. Furthermore, dehydration (Roky, 2004; Leiper, 2003), variation in hormone levels (Bogdan, 2001), impairment in muscular performances (Bigard, 1998), increase in lipid oxidation (Ramadan, 1999) and decrease in resting metabolic rate and VO2max (Sweileh, 1992) are some of the other changes observed during RF. It has been suggested that energy restriction, dehydration, sleep deprivation and circadian rhythm perturbation are possible factors influencing physical performance during Ramadan (Chaouachi, 2009b; Reilly, 2007).
Since the sporting calendar is not adapted for religious observances, and Muslim athletes continue to compete and train during the Ramadan month, it is important to determine whether this religious fast has any detrimental impact on athletic performance. However, to date, there are only a few studies concerning the effects of RF on physical performance in competitive athletes (Chaouachi, 2009a; Chennaoui, 2009; Kirkendall, 2008; Meckel, 2008; Karli, 2007; Zerguini, 2007). Many coaches and athletes still believe that athletic performance is adversely affected by RF (Chaouachi, 2009b; Leiper, 2008). But at present, there is some evidence to suggest that anaerobic exercise performance (power, speed, agility) is not negatively affected by RF in elite athletes who maintain their normal training regimen during the period of Ramadan (Chaouachi, 2009a; Kirkendall, 2008; Meckel, 2008; Karli, 2007).
There are conflicting reports, however, regarding the influence of RF on aerobic exercise performance in trained athletes. A marked reduction has been reported in some studies (Chennaoui, 2009; Meckel, 2008; Zerguini, 2007), while others have found either no significant change or an increase (Chaouachi, 2009a; Kirkendall, 2008; Karli, 2007) in aerobic exercise performance during the month of Ramadan. For example, in a recent study with elite athletes, Chaouachi et al. (2009a) observed no changes either in maximal aerobic velocity or in VO2max estimated from the shuttle run test during Ramadan. In another study carried out with elite soccer players, Kirkendall et al.
(2008) found that the running distance during the shuttle run test improved significantly by Batimastat the fourth week of Ramadan. However, in contrast to these reports, Zerguini et al. (2007) studied a group of professional soccer players and observed a marked reduction in 12-min run performance at the end of Ramadan. Inconsistent findings have also been reported with regard to the impact of RF on body composition (Chaouachi, 2009a; Chennaoui, 2009; Meckel, 2008; Maughan, 2008; Karli, 2007; Bouhlel, 2006).