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The COVID-19 pandemic and physical activity during intermittent fasting, is it safe? A call for action

Intermittent fasting (IF) has recently gained popularity, and has been used for centuries in many religious practices. The Ramadan fasting is a mandatory form of IF practiced by millions of healthy adult Muslims globally for a whole lunar month every year. In Islam, the “Sunna” also encourages Muslims to practice IF all along the year (e.g.; two days a week). The 2019-Coronavirus disease (COVID-19) pandemic in the context of Ramadan has raised the question whether fasting is safe practice during the COVID-19 pandemic health crisis, and what would be the healthy lifestyle behaviors while fasting that would minimize the risk of infection. As COVID-19 lacks a specific therapy, IF and physical activity could help promote human immunity and be part of holistic preventive strategy against COVID-19. In this commentary, the authors focus on this dilemma and provide recommendations to the fasting communities for safely practicing physical activity in time of COVID-19 pandemic.


INTRODUCTION
outcomes in case of infection [9]. Accordingly, it seems that performing PA during the COVID-19 pandemic is safe and crucial for immunity and can decrease the risk of COVID-19 infection and many other diseases [8,22,23]. The need to develop effective strategies to maintain an optimal level of PA during Ramadan is of high importance [10]; COVID-19 control protocols, by itself, dramatically impacted humans' life patterns (e.g., PA, sedentary time), recreational PA, diet, sleep, weight, and wellbeing [24,25], especially in the countries that have received the most impact from COVID-19 [26].
Moreover, individuals who fast are less inclined to exercise during Ramadan, which worsens PA levels during this month [27]. Therefore, Ramadan IF and PA could be a potential strategy amid this outbreak to support the immune system. In 2021, Aspetar provided clinical guidelines related to Ramadan IF and exercise for healthy individuals [17]. For athletes, and according to Aspetar guidelines [17], training times during Ramadan can be carried out during two maintime points: i) 1-2 hours before "Iftar": light to moderate technical/ tactical sessions with low to moderate cardiovascular load, or, intensive resistance training sessions of relatively short duration; and ii) Starting ~3 hours after "Iftar": high intensity and/or long duration training sessions. For non-athlete healthy individuals, exercising while fasting during COVID-19 lockdown should ideally be performed during two main-time points: just before "Iftar" and/or 2-3 hours after "Iftar". We recommend low to moderate intensity exercise, as a possible safe and feasible activity, such as home-based free weight, bodyweight training, brisk walks, stretching, yoga, and gardening [4,8,28,29]. These activities should be of moderate duration during Ramadan IF, especially at the beginning of the fasting month, when the body is adapting to the new dietary pattern. Subsequently, fasters can gradually increase the intensity and duration of PA. It should be noted that significant health benefits can be gained with adopting PA behaviors below the aforementioned ideal recommendations and, as such, individuals should be encouraged to move more and sit less through any possible means [30].
Exercising while fasting during the day can lead to increase water losses in sweat and from the lungs, which can cause headaches, tiredness, and difficulty of concentration. Thus, fasters should recover their hydration status during Ramadan by increased drinking during the night, in order to prevent the individuals from becoming chronically hypohydrated/dehydrated [18]. In addition, fasters should not skip "Suhoor". They should consume various foods, including many fruits and vegetables (water and fiber-rich foods), which can help prevent constipation while promoting immunity. Consuming low glycemic index foods at "Iftar", especially when they want to exercise after "Iftar" will prevent potential hypoglycemia during intensive exercise [32].
Sleep has been reported to be negatively affected by Ramadan IF [33]. Although sleep is known by its role in promoting immunity, prevalence of sleep disorders could be aggravated during the month Given that COVID-19 lockdowns primarily promote a more sedentary and passive lifestyle and could have a deleterious effects in older adults [8], patient populations [9], athletes [10], and other specific groups including prisoners, refugees, and asylum seekers [11], the COVID-19 pandemic in the context Ramadan has raised the question whether IF is safe during this health crisis, and what would be the healthy lifestyle behaviors during Ramadan IF that would potentially minimize the risk of infection from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Importantly, Islam's "Sunna" strongly encourages healthy adult Muslims to intermittently fast out of Ramadan. Throughout the year, hundreds of opportunities to fast are there, e.g. two days a week, and/or three consecutive days of IF in the middle of the lunar cycle (full moon, white nights). Ramadan IF is not a cause for concern for healthy people who adopt a healthy diet and drink plenty of fluids during the dark hours, have adequate sleep, and perform regular physical activity (PA). As COVID-19 lacks a specific therapy and home confinement may induce negative impairment in sleep patterns and PA levels [12], Ramadan IF and PA could help sustain humans' immunity and may become part of holistic preventive strategies against COVID-19.
Therefore, the present commentary focuses on this possibility and provides recommendations to the different community individuals.
Ramadan fasting is a safe dietary pattern similar to IF (e.g., 16/8 hours) where dietary intake is limited to a short window during the day. Ramadan IF has been suggested not to be an appropriate dietary approach for some individuals, including patients with reactive hypoglycemia, kidney pathologies, children, pregnant women, and people performing heavy physical work [4,[13][14][15][16]. In addition, Ramadan IF can in certain extreme cases hamper the athlete's ability to train and compete, and discourage the general community to exercise [17]. Although Ramadan IF can lead to health issues such as fatigue, dizziness, sleep deprivation, irritability, and headaches [18], IF may confer cardiac protection, even after a cardiovascular event and optimize circadian rhythms and ketogenesis [19].
Patients with ischemic cardiomyopathy [20] and hemodialysis or peritoneal dialysis [21] should not be encouraged to fast only after consultation with their physician. Therefore, further studies are needed to investigate the safety of this dietary pattern in these patient populations and any ill person shall seek their physician before practicing IF to make appropriate adjustment to the medication dosage [4].
Patients may require further testing and risk assessment before performing regular exercise.

Practical recommendation during Ramadan and COVID-19 pandemic
Research on the impact of regular PA and fasting during the pandemic is still not available. An overwhelming evidence demonstrates that PA plays a positive role in the primary and secondary prevention of several chronic medical conditions. In that regard, a recent study including more than 48,000 participants reported that adults meeting PA guidelines had reduced risk for developing severe COVID-19 Biology of Sport, Vol. 38 No4, 2021 731 Intermittent Fasting, Physical Activity, and COVID-19 Pandemic of Ramadan due to the stressful COVID-19 lockdowns. Some recommendations that can improve sleep quality include the following actions: afternoon napping, avoiding/minimizing screen viewing at least one hour before bedtime; avoiding prolonged, vigorous-intensity PA before sleep; and preparing a good sleep environment (comfortable, quite, dark and cool room) [34].
Finally, and most importantly, fasters who want to exercise during the COVID-19 pandemic should follow general healthy practices [35].
Sport and fitness equipment should be cleaned before and after use.
Fasters should exercise in well ventilated rooms, use their own towel and supplies and avoid touching their eyes, nose, and mouth.
Fasters should avoid exercising in groups to minimize human-tohuman contact, maintain physical distance in-between individuals if exercise is performed in groups, and wearing masks in crowded places. Although the transmission risk of SARS-CoV-2 infection appears low in professional team players [36,37], it is advisable to maintain more than two-meters distance between individuals because close running or cycling can increase the risk to be infected with COVID-19 [38,39]. Thus, maintaining more extensive distances up to 10 meters is necessary when exercising inside indoor environment [39] even if face masks are used. Although the contradictory results to whether wearing face mask affects exercise performance, wearing face masks while exercising is recommended and can be used to slow the spread of SARS-CoV-2 infection. Face mask use seems safe and might be essential during aerobic activity such as running or cycling because it has been reported that small droplets can spread as far as five meters while walking at a pace of four km/h and 10 meters when running at 14.4 km/h [40]. Heart rate, respiratory rate, blood pressure, oxyhemoglobin saturation and time of exhaustion are not significantly affected by wearing a surgical mask or N95 respirator during moderate to strenuous aerobic physical activity in healthy non-smoking volunteers [40]. People with lung or heart diseases should consult a physician before attempting physical activity with any mask [40]. In that regard, it has been shown that ventilation, cardiopulmonary exercise capacity and comfort are reduced by surgical masks and highly impaired by FFP2/N95 face masks in healthy individuals [41].

Conflict of interests
The authors declare that this commentary in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.