Chronotype, Aerobic Performance, and Sleep Quality of Young Athletes Before and During Ramadan Observance

Article information

Sleep Med Res. 2023;14(2):98-104

Publication date (electronic) : 2023 June 30

doi : https://doi.org/10.17241/smr.2023.01739

Anas El-Jaziz, PhD, Said Lotfi, PhD

Multidisciplinary Laboratory In Education Sciences and Training Engeneering (LMSEIF), Sport Science Assessment and Physical Activity Didactic, Normal Higher School (ENS-C), Hassan II University of Casablanca, Casablanca, Morocco

Corresponding Author Anas El-Jaziz, PhD Multidisciplinary Laboratory In Education Sciences and Training Engeneering (LMSEIF). Sport Science Assessment and Physical Activity Didactic. Normal Higher School (ENS-C), Hassan II University of Casablanca, BP 50069, Ghandi, Morocco Tel +212-690959414 Fax +212 5 22 23 58 14 E-mail anas.eljaziz@enscasa.ma

Received 2023 May 24; Revised 2023 June 4; Accepted 2023 June 19.

Abstract

INTRODUCTION

Fasting is a regular practice in several religions, including Christianity, Judaism, and Hinduism. Also, Muslims consider the month of Ramadan a holy month that requires fasting with high regard for faith. Indeed, fasting, as a form of intermittent fasting [1], starts at dawn to sunset during the whole month of Ramadan without interruption for 29 or 30 days [2]. The average fasting time varies according to the season and geographical location [3]. Nevertheless, in Morocco, it is around 12–18 hours. During that, people abstain from eating and drinking until dawn. Afterwards, they are free to eat until the next dawn.

The Ramadan intermittent fasting (RIF) makes some modifications, including altered eating schedules, sleep patterns, and exercise [4], that decrease the usual energy intake of the human body and alter the circadian rhythm [5]. Consequently, it puts the organism in a critical state. Notably psychological stability (e.g., motivation), physiological mechanisms, and biochemistry reactions could have detrimental effects on sports performance. Various aspects of human health and exercise performance can be affected. Moreover, the most significant repercussion is the decrease in physical activity [6]. Since most Muslim athletes continue to practice and participate in sporting competitions during the sacred month of Ramadan, young athletes should be fully aware of the potential effects of Ramadan rituals on their circadian rhythm and physical performance.

According to the available research, RIF has a negative effect on peak oxygen uptake (VO_2peak) and athletic performance. Indeed, this study was conducted with 32 professional medium-distance male runners in the summer of 2019. They performed the Cooper Test before and during Ramadan. As a result, they showed that the physical performance of athletes deteriorated during Ramadan [7]. In addition, a systematic review including meta-analysis explored 28 articles (up to December 2019) and found that RIF affects maximum oxygen uptake negatively (RIF; standardized mean difference = -2.20, p < 0.001) [8]. Nevertheless, other studies showed significant increases in VO_2peak in male athletes. The participants were asked to run on the track for 30 minutes on two separate occasions (before and during Ramadan). The mean result revealed that Ramadan fasting had a small but significant impact on endurance running performance [9]. By contrast, no significant effects of RIF on aerobic performance were found when meta-analyzing pre-post data of all RIF interventions, confirming that athletes can participate in a competition in a fasting state with little impact on physical performance [10].

Muslim athletes who train during Ramadan may also cause significant changes associated with sleep disturbances and changes in sleep patterns [11]. Indeed, during fasting, athletes prefer to train in the evenings or early mornings, which affects quality and sleep duration [12]. In addition, previous studies have shown that sleep disorders significantly impact post-exercise recovery [13], fatigue [14], and circadian rhythm [15]. The last systematic review in 2020 showed that training during RIF decreases the total sleep times in athletes. However, no significant effect on other sleep characteristics was found [16]. For Moroccan young athletes at secondary school, the arrival of Ramadan poses an annual challenge. The Moroccan Ministry of National Education, Preschool and Sport changes the class schedule yearly during Ramadan, so these young athletes need more time to train during the day. As a reaction, they delay it until the evening, mainly after the first meal of the day (fasting break) or after the night prayer (Taraweeh), which will impact their own personal training rhythm. Additionally, due to the Moroccan table’s nature (carbohydrates and lipids but low in water and vegetables), that usually consumed late at night, more troubles are emerging due to gastric troubles, which can influence athletes’ sleep quality and circadian rhythm.

For all these reasons and given the lack of literature on the effect of RIF and circadian rhythm on the performance and sleep quality of young Moroccan athletes, this study aimed to evaluate the relationship between sleep quality, circadian preferences, and aerobic fitness during the RIF. We hypothesized that fasting during the daytime in the holy month of Ramadan may affect the long-term maximal performance of Muslim athletes and their sleep patterns according to their circadian profile.

METHODS

Study Design and Setting

This experimental study with repeated measures in a non-random sample of volunteers was conducted during the month preceding and during Ramadan in 2022. It started on April 3 and finished on May 2. The temperature reached up to 21°. The minimum seasonal temperature is 14°. The average fasting duration was 15 hours 30 minutes. The study was conducted according to the Declaration of Helsinki and was approved by the Local Ethics Committee of Normal Higher School of Casablanca with the number No. 09-2021. All participants signed an informed consent agreeing to participate in the study. The sample performed a 20-m shuttle run test (SRT) [17] at three different time points: the first was before one week of Ramadan (BR), and the others were during the second (DR 1) and last week of Ramadan (DR 2). The Morningness-Eveningness Questionnaire (MEQ) [18] was completed just before Ramadan (BR), and the Pittsburgh Sleep Quality Index (PSQI) [19] was completed before and at the end of Ramadan (ER) (Fig. 1).

Fig. 1.

Schematic explanation of the experimental protocol. MEQ, Morningness-Eveningness Questionnaire; SRT, 20-m shuttle run test; PSQI, Pittsburgh Sleep Quality Index.

RESULTS

MEQ Outcomes

Based on the MEQ scores, 29 moderately morning types (24.8%: 13 males and 16 females), 7 moderately evening types (6%: 2 male and 5 females), and 81 neither types (69.2%: 30 males and 51 females) were identified (Table 1). The chi-square (χ²) tests showed no significant association between chronotype and sex (χ² = 0.855, p = 0.652). With one-way ANOVA, it was found that the MEQ does not vary significantly with the type of sport practiced (F = 0.72, p > 0.05) and with BMI (F = 1.07, p > 0.05). The correlation between the MEQ score and the VO_2peak before RIF was significant (r = 0.18, p < 0.05), but not for the other measure during RIF. Then, it was significant with PSQI global score before and at the end of Ramadan (PSQI_BR: r = -0.27, p < 0.05; PSQI_ER: r = -0.25, p < 0.05).

Table 1.

Descriptive statistics for all variables

SRT Outcomes

Repeated measures ANOVA shows a significant difference in the three measurements (F = 8.951, p = 0.001). Also, one-way MANOVA showed significant difference in VO_2peak based on the circadian profile (F(2, 224) = 2.90, p < 0.05; Wilk’s λ = 0.861, partial η² = 0.72). A Pearson correlation coefficient was computed to assess the linear relationship between VO_2peak and PSQI global score (Table 2). Also, there was a negative correlation between the PSQI ER and VO_{2peak BR} (r_BR = -0.194, p = 0.036), and no relationship with the other measures.

Table 2.

Correlations between variables

PSQI Outcomes

A one-way repeated measures ANOVA was performed to determine if the mean PSQI in athletes differed between two times (BR, ER). A t-test revealed that RIF led to statistically significant differences in PSQI global score (t = -10.12, p < 0.001) (Table 3). Also, one-way MANOVA showed significant difference in sleep quality based on the circadian profile (F(4, 226) = 3.43, p = 0.01; Wilk’s λ = 0.889, partial η² = 0.59). From the linear regression, it was found that the quality of sleep at the end of Ramadan causes a reduction in VO_2peak significantly (B = -0.95, beta = -0.19, t = -2.03, p = 0.044).

Table 3.

PSQI parameters recorded before and at the end of Ramadan

DISCUSSION

The present study aimed to investigate the impact of the circadian profile on aerobic physical performance and sleep quality in the young athletes’ Muslim community during RIF. The result showed that Vo2max and sleep quality declined during RIF. It also showed that the circadian profiles of athletes affect these variations. In addition, there was a negative correlation between the PSQI_ER and VO_{2peak BR}. Also, the positive correlation between chronotype and VO_{2max BR}.

The current study found that the sleep quality deteriorated during Ramadan. These results support previous research which links sleep patterns and RIF. Indeed, sleep quality is negatively impacted during Ramadan [20] and at the end of the Ramadan [21]. Other studies showed that while training was maintained at least twice weekly, only the overall amount of sleep was reduced during RIF [22]. Our result showed a negative correlation between the PSQI_ER and VO_{2peak BR}. The present findings disagree with earlier data showing that sleep deprivation does not affect anaerobic performance [23]. But, according to prior research, longer sleep duration and better sleep quality are associated with higher performance and competitive success in athletes [24]. One interesting finding is that aerobic performance was affected negatively by the RIF. Indeed, empirical studies suggest that Ramadan observance has little impact on aerobic function [25] and on the maximal oxygen intake of athletes [8]. One possible explanation for these findings is that the dehydration associated with Ramadan may lower blood volume, maximal cardiac output, and muscle glycogen reserves, which may impact maximal oxygen uptake [8]. However, our results differ from other studies that worked on short-term fasting (7 days). They found no effect on aerobic performance, walking efficiency, or maximum oxygen uptake [26]. A possible explanation might be that the body’s mechanisms can still support and adapt to this fast intermittent fasting. Moreover, an additional study is required to examine the relationship between Ramadan fasting and changes in aerobic exercise, using designs that control the daily uptake and the level of physical activity during RIF, to verify if the results are independent of it. In the current study, sex is not associated to the chronotype. Many previous studies involving adolescents did not find sex differences in the frequency of morning or evening types [27]. But other study showed that biological sex has significant interactions with circadian processes [28]. In particular, it reported that females tend to be “early birds” and have faster internal clocks than men [29]. One interesting finding is that the circadian profiles of athletes correlated positively with aerobic performance before but not during RIF. Our results seem consistent with other research, which failed to show any circadian or diurnal rhythmicity effect on long-duration exercise performance during Ramadan [30]. In contrast, other studies reported significant changes in aerobic performance for the full marathon [11], 2000-m rowing sprint [31], and 200-m swimming trial [32]; or when the exercise is done in the evening [33]. Furthermore, the E-type athletes had better values of VO_2peak [34]. Previous studies have indicated that high caloric consumption can alter the clock genes in the brain [35]. Given these considerations, the available scientific data appear to be equivocal. We need more research to define the effect of Ramadan on circadian typology during aerobic exercise to propose the best program training for young athletes and avoid the decline in performance in Ramadan fasting. The present findings suggest a significant difference of sleep quality based on chronotype. This result is inconsistent with other research, which showed that biological clock markers, daytime sleepiness, or sleep characteristics did not change across the whole diurnal intermittent fasting of Ramadan [36]. However, this result is consistent with other research, which showed that late-night-dinner eating and sleeping with a full stomach could negatively affect the circadian rhythm [36] and quality of sleep [37]. Indeed, it has been demonstrated repeatedly that Ramadan fasting is generally associated with changes in sleep, habitude intake [38], and mood states [39]. All this hypothesis may explain the sleep quality during Ramadan [20]. For this reason, our results need to be interpreted with caution. To other Arab nations, the changes cannot be generalized. Several of the reported changes also reflect regionally specific cultural and lifestyle changes.

The study presents some limitations. The anthropometric data were measured only before Ramadan, not during and after Ramadan. Since the study was limited to assessing the chronotype only during Ramadan, it was possible to find more changes in circadian rhythms during or after Ramadan. Thus, it is highly recommended to take more than one measure. It is unfortunate that the study did not include an objective method for the measurement of sleep and the circadian typology. The use of electronic devices is very recommended. The most important limitation lies in the fact that we cannot find a control group that did not observe Ramadan. Indeed, finding a sample that satisfied our inclusion criteria and that did not fast during Ramadan was a challenge. The only people who did not fast were athletes who were sick or women athletes who were on their menstrual period. Finally, the study did not check the motivation level of the participants during the physical test. It is possible that not all participants have the same preference for the endurance tests.

The main goal of the current study was to evaluate the effect of circadian preferences and sleep patterns on aerobic performance during the intermittent fasting of the holy month of Ramadan. We hypothesized that intermittent fasting may affect the long-term maximal performance and sleep quality but not the circadian type. The research showed that VO_2max and sleep quality declined during RIF. It also showed that the circadian profiles of athletes affect these variations. In addition, there was a negative correlation between the PSQI_ER and VO_{2peak BR}. Also, the positive correlation between chronotype and Vo2max BR. Given the above considerations, the choice of practice time during Ramadan should not be arbitrary. It is recommended to check the individual circadian preferences and other sleep patterns before suggesting the best training program. Further investigations are needed to reveal athletes’ strategies to cope with the negative effects of changing sleep habits and circadian rhythms during official athletic competitions.

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