Chronotype, sleep, and perceived exertion during intermittent fasting in young athletes

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

Abstract

During intermittent fasting of Ramadan, research has shown a modification in athletes’ sleep habits and lifestyle. As a result, these changes might affect a range of chronobiological and psychological parameters. Thus, the present study explores the effect of intermittent fasting during Ramadan and circadian preference on sleep patterns and perception after aerobic exercise. This study included ninety-six active students (16.94 ± 1.09 years, BMI: 21.59 ± 3.52kg/m²). We identified the circadian preferences by exploiting Morningness-Eveningness Questionnaire (MEQ). Then we assess the perceived exertion at three-point times by using Rating of perceived exertion scale (RPE) after an aerobic exercise. At the end of Ramadan, we assess the sleep quality by using The Pittsburgh Sleep Quality Index (PSQI). Our analysis revealed that perceived exertion increased significantly during the three-time points, but sleep quality and maximal oxygen uptake decreased. Also, the results showed a significant association between chronotype and perceived exertion during Ramadan. Moreover, a meaningful prediction was detected of maximal oxygen uptake from BMI and perceived exertion. The main conclusion is that intermittent fasting affects sleep patterns, perceived exertion, and aerobic performance.

Résumé

Pendant le jeûne intermittent du Ramadan, les études ont montré une modification des habitudes de sommeil et du mode de vie des athlètes. En conséquence, ces changements pourraient affecter une série de paramètres chronobiologiques et psychologiques. Notre étude explore donc l’effet du jeûne intermittent lors du Ramadan et de la préférence circadienne sur les habitudes de sommeil et la perception d’effort après un exercice aérobie. Cette étude a porté sur 96 étudiants actifs (16.94 ± 1.09 ans, IMC: 21.59 ± 3.52 kg/m²). Nous avons identifié les préférences circadiennes à l’aide du Morningness-Eveningness Questionnaire (MEQ). Nous avons ensuite évalué l’effort perçu en trois moments à l’aide de l’échelle de perception de l’effort de Borg après un exercice aérobie. À la fin du Ramadan, nous avons évalué la qualité du sommeil à l’aide de l’indice de qualité du sommeil de Pittsburgh (PSQI). Notre analyse a révélé que l’effort perçu augmentait de manière significative au cours des trois périodes, tandis que la qualité du sommeil et la consommation maximale d’oxygène diminuaient. Les résultats ont également montré une association significative entre le chronotype et l’effort perçu pendant le Ramadan. En outre, une prédiction significative de la consommation maximale d’oxygène a été détectée à partir de l’IMC et de l’effort perçu. La principale conclusion est que le jeûne intermittent affecte les habitudes de sommeil, la perception de l’effort et la performance aérobie.

Mots-clés: circadien, perception, qualité du sommeil, VO_2max, Ramadan

Introduction

Ramadan intermittent fasting (RIF) is a religious rite in Islam during which healthy Muslims abstain from food, drink, smoking, and certain other habits from sunrise to sunset for 29–30 days. This eating pattern and length between two meals lead to changes in lifestyle rhythms. Some of the alterations related to RIF may alter sleep habits and the biological clock during that period [1]. Evidence about alternations of circadian rhythm and sleeping patterns during RIF has inspired various researchers to investigate the influence of this month on athletes’ performance [2], although the results remain slightly unstable. Other studies concluded that RIF has no impact on performance tests among fasting athletes [3], particularly strength, endurance, and jump height [4]. However, other research suggested negative effects on tests such as speed, agility, endurance [5], and aerobic capacity [6]. Other research reported that the perception of fatigue after a physical exercise is similar before and during Ramadan [7]. However, other studies showed a negative impact arguing by restricting food intake [8]. Nevertheless, to our knowledge, no previous research has studied the potential effects of chronotype and sleep patterns on the physical perception among young athletes during RIF.
Thus, the first purpose of the present study was to check if RIF has any potential effects on aerobic performance, sleep quality and rating of perceived exertion. The second aim is to verify if the chronotype influence perceived exertion during RIF. The present study hypothesized that RIF impacts sleep quality, aerobic performance and perceived exertion. Also, we speculated that chronotype is associated to perceived exertion and sleep quality, but not with aerobic performance.

Methods

1. Study Design and Setting

This is a quasi-experimental design (Fig. 1) that has been done with pre-and post-test. The study was carried out between Mars/Mai 2022. The length of the fasting period and beyond was similar for evaluating athletes. The Ramadan observance officially started on April 3 and finished on
Mai 2. Where the duration of each fasting day was around 13–14 hours in length on average. The ENS-C Research and Ethics Committee conducted and approved the study, and the recommendations of Human Ethics in Research were followed according to the Helsinki Declaration.

2. Participants

Ninety-six active students (16.94 ± 1.09 years, BMI: 21.59 ± 3.52 kg/m²) voluntarily participated in this study (male=32, female=64). All subjects were non-smokers, non-drinkers, without sleep disorders, and declared that they regularly practiced at least five hours per week. Before starting, we described the circumstances of the protocol, including possible benefits/risks. Then, researchers obtained consent from all participants in the study project.

3. Assessment

The Morningness–Eveningness questionnaire (MEQ)
The chronotype was identified using the MEQ [9]. It is a questionnaire with 19 items about individuals’ preferences for performing various activities. Each question has a set of closed answer choices, which is supposed to calculate a total score from 16 to 86. Based on the global MEQ scores and the classification adopted by Taillard et al. [10], the researchers divided the participants into M, N, and E types that corresponded with the morningness–eveningness scale: 16–41 = E types; 42–58 = N types; 59–86 = M types.

The Pittsburgh Sleep Quality Index (PSQI)
The study used the Arabic version of PSQI [11], with 19 questions with seven subdimensions (sleep duration, latency, disruptions, quality, efficiency, daytime dysfunction, and use of sleep medication). The global score varied from “0” to “21” (“no difficulty” to “severe difficulties”). A score above five is suggested as evidence of a possible risk of sleep problems (poor sleeper). Actuality PSQI could be used to screen individuals for substantial sleep disturbance.

20-m shuttle run test (20MSR)
The 20-m shuttle run [12], or “Multistage fitness test”, was used to evaluate cardiorespiratory fitness. It was administered in the school gymnasium. The 20MSR test consists of running progressively to exhaustion between two lines set
20 m apart, following signals played from a pre-recorded soundtrack (beep). The initial speed was 8.5 km^-1, increasing by 0.5 km^-1 every minute. The end of the test occurs when the participant stops or fails to reach the lines in time on two consecutive occasions. Then, the peak oxygen uptake (VO_2peak measured in ml·kg-1min^-1) was estimated based on the 20MSR table.

Rating of perceived exertion scale (RPE)
The RPE scale is reliable for measuring perceived exertion or exercise intensity. In this study, we used the Arabic version validated by Sallam et al. [13]. Immediately after completing the 20-m shuttle run test, the participant assesses his feeling of exertion. The RPE is a visual rating scale, including comments that describe exertion levels by adopting a 20-point Borg scale.

4. Statistical Analyses

All Data was analyzed with the statistical software IBM SPSS Version 25 (IBM, Armonk, NY, USA) and presented as the mean ± standard deviation (SD). The data was explored by t-tests and mixed variance analysis (ANOVA) with repeated measurement for dependent samples. Significant differences between means were checked using the Bonferroni post hoc test whenever applicable. Effect sizes were estimated as partial eta-squared for the ANOVA analysis to identify the magnitude of the change. We examine the correlation between all variables by computing Spearman’s rank correlation coefficient. Significance was assumed for all analyses at the threshold of p <0.05.

Results

A paired samples t-test was performed to compare the sleep quality of before and during RIF. The analysis showed a significant difference between PSQI_BR and PSQI_DR [t (95) = -9.34, p <0.001], with medium effect size (d=0.90). Thus, the sleep quality decreases with Ramadan (Tab. 1). To verify the association between chronotype, gender, and BMI, we computed Chi-Square (x²). The result showed no significant connection respectively, [x² = 1.34, p = 0.509], [x² = 9.02, p = 0.172].
A repeated-measures ANOVA was performed and revealed a considerable impact of RIF on VO_2peak, F (1.57, 146.18) = 20.30, p<0 .001. The post hoc pairwise comparison revealed that VO_2peak decreased between the initial assessment and 1st week of RIF (p = 0.007). Also, the VO_{2peak DR2} reached a significant decrease compared to VO_{2peak BR}. In addition, VO_2peakDR2 showed a significant decrease compared to VO_{2peak DR1.} Consequently, we may assume that RIF significantly affects aerobic capacity as assessed by the 20-shuttle test during Ramadan.
The ANOVA with repeated measurements showed a significant effect of RIF on RPE, F (2, 186) = 12.17, p<0.001, and the post hoc pairwise comparison revealed that RPE increased between the initial assessment and the second, and it was statistically significant (p = 0.016). Also, the RPE_DR2 did reach a significant increase compared to RPE_BR. In addition, RPE_DR2 is significantly higher when compared to RPE_DR2. As a result, we can state that ANOVA findings show a significant influence of RIF on perception as measured by the RPE_DR.
To identify whether the perception is impacted by sleep quality or chronotype, mixed ANOVA repeated measures were conducted and showed no significant interaction for sleep quality F (2,188) = 0.64, p = 0.539. Nonetheless, a significant association was established between chronotype and RPE_DR2 F (2,93) = 7.51, p = 0.001. The multiple comparison showed that M-type reported low score compared to N-type. The correlation did not identify any meaningful relationship between RPE and PSQI score (Tab. 2).
A stepwise multiple regression was applied to predict VO_{2peak DR2} from BMI and RPE_BR, which showed that these factors statistically could predict the VO_2peak, F (2, 93) = 5.84, p = 0.004, R² = 0.112. Each variable considerably increased the predicted significantly, p < 0.05. The summary form of the equation to predict VO_{2peak DR2} is: VO_{2peak DR2} predicted= 38.66-(0.86*RPE_BR) +(0.61*BMI).

Discussion

The study aimed to investigate the effect of RIF on high-intensity long-term maximal performance, sleep quality, and rating of perceived exertion. Also, we investigated the chronotype’s influence on RPE during RIF. The third objective was to assess the interaction of VO_2peak with chronotype and sleep quality during RIF.
Our findings revealed that sleep quality measured by the PSQI was affected by RIF; this supports the results of Baklouti et al. [14] who reported that subjective sleep quality was negatively affected at the end of Ramadan compared to before. In contrast to our study, other researchers showed no significant difference in PSQI comparing before to during RIF [15]. According to some researchers, possible explanation is related to the large amount of food consumed only overnight and other bad intake habits [16].
The results of our analysis reveal that VO_2peak decrease with Ramadan. Our results are consistent with those of previous research that showed a negative effect of RIF on intense aerobic performance [17]. These results also align with previous research that confirmed this reduction even if the training charge was maintained during Ramadan [18]. In contrast to our result, other researchers failed to observe substantial performance decrements during the month of Ramadan [15], and this is reported for athletes and physically active men [18]. Our results can be explained by alterations in eating, drinking, and sleeping habits during RIF [19]. Also, it has been shown that negative mood and mental activity may be the main reasons for the decline in performance during Ramadan [20].
The outcomes of our study suggest that the perception of exertion increased during Ramadan. These findings support the conclusions of other studies that showed RPE scores were higher during RIF in comparison with before [21]. Moreover, our finding is consistent with other investigations that showed an increase in subjective feelings of fatigue, illness, lethargy, and mood during high-intensity exercise among Muslims athletes [22]. But These findings are not consistent with those of several other studies that have shown no significant difference in RPE scores between time measures [23]. Generally, this outcome can be explained by muscle fatigue during RIF [24]. Also, we can suggest other explanations such as decline mood [20] and in hypohydration, especially when exercise is done in the late afternoon [25].
Our study extends previous research by demonstrating a significant association between chronotype and RPE_DR2. This result supports the conclusions drawn by previous research that reported a significant link between circadian preferences and RPE measured using a 20-point Borg scale [26]. Another study found that M-type swimmers felt less exertion in the morning when performing a 200-meter swim test than in the evening. However, no significant changes were found for N and E-type [27]. Research in this area is still limited, with only a few studies being conducted thus far. More research is required to look into the impact of chronotype on stimulus perception during different time points in Ramadan’s day.
The results of our study highlight the possibility of using RPE and BMI to predict the VO_2peak during third week of Ramadan. Indeed, these results match those shown in an earlier study that VO_2peak can be estimated using a submaximal graded exercise test when extrapolated to RPE [28]. Our finding is consistent with prior research that suggested an acceptable estimate of VO_2peak from RPE in young to middle-aged sedentary males [29]. To develop a complete picture of this prediction, additional studies will be needed to verify if chronotype can be one of the most effective predictors estimates of VO_2peak during Ramadan.
It is worth noting that the need for more reporting of the nutritional information of participants during Ramadan limits our study. Also, we needed to assess the level of motivation to ensure that all participants were producing maximal effort during the physical test. Finally, another limitation is that RPE was assessed directly after the 20MSR. The perception may change if we delay the RPE for 30 minutes after the physical exercise.
The main conclusion from the present study is that PSQI total score and RPE increased significantly during three-time points, and VO2peak decreased. In addition to a significant association between chronotype and RPE. And finally, a significant prediction of VO_2peakDR2 from BMI and RPE_BR.

Practical implications

Our findings suggest that RIF affect circadian patterns and athletes’ perceptions. We recommend athletes to regulate sleep time during RIF. Also we advise athletes to avoid competitions that requires maximum physical activity, because the physiological conditions are not optimized for this purpose.

Acknowledgement

We are grateful to the students of AL Anouar High school (Sidi Taibi- Morocco) for their participation in the study. Also, we would like to thank AHMED BEN LHADJ, MUSTAFA BOUKRICHA, HIND KABCH, IKRAM LEMFEDAL and education Staff who enthusiastically supported the study by allowing access to system data for the intervention.

Declaration of Interest

The authors report no declaration of interest. The authors alone are responsible for the content and writing of paper.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Corresponding author

Anas El-Jaziz
Hassan II University of Casablanca, Normal Higher School (ENS-C),
BP 50069, Ghandi, Morocco
Tel: +212690959414
Email: anas.eljaziz@enscasa.ma

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