Does Ramadan fasting affect the diurnal variations in metabolic responses and total antioxidant capacity during exercise in young soccer players? Omar Hammouda, Hamdi Chtourou, Asma Aloui, Mohamed Arbi Mejri, Henda Chahed, Abdelhedi Miled, Karim Chamari, Anis Chaouachi, et al. Sport Sciences for Health Founded by the Faculty of Exercise Science - University of Milan, official journal of the Italian Society of Exercise and Sport Sciences ISSN 1824-7490 Sport Sci Health DOI 10.1007/s11332-014-0179-8
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Author's personal copy Sport Sci Health DOI 10.1007/s11332-014-0179-8
ORIGINAL ARTICLE
Does Ramadan fasting affect the diurnal variations in metabolic responses and total antioxidant capacity during exercise in young soccer players? Omar Hammouda • Hamdi Chtourou • Asma Aloui • Mohamed Arbi Mejri • Henda Chahed • Abdelhedi Miled Karim Chamari • Anis Chaouachi • Nizar Souissi
•
Received: 25 November 2013 / Accepted: 4 March 2014 Ó Springer-Verlag Italia 2014
Abstract The aim of this study was to investigate the effects of Ramadan fasting and time-of-day on biochemical responses to an intermittent exercise [Yo–Yo test level 1, (YYIRT)]. Twenty male soccer players (17.52 ± 0.2 years, 177.4 ± 2.9 cm) completed the YYIRT at 0700 and 1700 hours on three occasions: 1 week before Ramadan (BR), the second week of Ramadan (SWRR2), and the fourth week of Ramadan (ERR4). The total distance covered during the YYIRT (TD) was recorded. Moreover, blood samples were obtained before and after the YYIRT for biochemical measurements. TD was higher BR than during Ramadan in the evening (P \ 0.05), but not in the morning. However, there was no significant difference between BR and Ramadan in the morning. While postexercise values of blood lactate (Lac), glucose (GLC), and markers of muscle injury were greater higher in the
evening, resting total antioxidant status (TAS) and uric acid (UA) levels were higher in the morning as compared with the evening BR. These diurnal variations were hidden during Ramadan due to a significant decrease in Lac (P \ 0.01), GLC (P \ 0.05) and cellular damage (P \ 0.05) and an increase in TAS and UA (P \ 0.05) values in the evening. No significant difference in biochemical responses was observed in the morning during SWRR2 and ERR4 as compared with BR. In summary, the present study indicates that YYIRT performance was affected by Ramadan fasting only in the evening in young soccer players. The modified diurnal pattern of biochemical responses could explain this performance decrement.
O. Hammouda (&) H. Chtourou A. Aloui M. A. Mejri A. Chaouachi N. Souissi Research Laboratory ‘‘Sport Performance Optimization’’, National Center of Medicine and Sciences in Sport (CNMSS), Bp 326, Ave Med Ali Akid, El Menzah, 1004 Tunis, Tunisia e-mail:
[email protected]
Introduction
O. Hammouda H. Chtourou High Institute of Sport and Physical Education of Sfax, Sfax University, Sfax, Tunisia H. Chahed A. Miled Laboratoire de Biochimie, CHU Farhat Hached, Sousse, Tunisia K. Chamari Research and Education Center, Aspetar, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar N. Souissi High Institute of Sport and Physical Education of Ksar-Saı¨d, Manouba University, Manouba, Tunisia
Keywords Fasting Sport performance Transaminases Chronobiology Soccer Antioxidant
Muslim athletes may have to train or compete during the holy month of Ramadan. This religious tenet implies a total abstinence from food and fluid intake from dawn to sunset. Currently, there is little information regarding the effects of Ramadan fasting (RF) on physiological responses in well trained athletes [1–4]. Research suggested that Muslim athletes are likely to experience a myriad of biochemical adjustments that may lead to alterations in the hormonal, immune, and antioxidant systems during Ramadan [3–6]. Despite this, there is no clear evidence of a major increase in physiological stress or chronic systemic inflammation throughout the fasting month [3, 4, 6]. Moreover, most of the studies focused on resting levels of biochemical parameters, and data exhibiting changes in biochemical responses to exercise during Ramadan in trained subjects are lacking. In
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this context, Bouhlel et al. [1] observed that blood glucose (GLC) values did not change after exercise; however, haemoglobin concentrations and haematocrit were significantly higher at the end of Ramadan compared with before Ramadan. Recently, Aziz et al. [7] found that blood GLC levels measured at rest were lower during Ramadan than before Ramadan, while GLC and lactate (Lac) levels measured after an intermittent exercise were not significantly different between the two testing phases. Also, a decrease in urea concentrations was observed after a submaximal exercise performed during Ramadan, suggesting that there was no increase in endogenous protein metabolism to compensate the decreased protein intake [8, 9]. Furthermore, Chennaoui et al. [5] showed that salivary cortisol concentrations measured after a maximal endurance exercise were higher in the first week of Ramadan compared with before Ramadan, but dropped by the end of the fasting month. On the other hand, endurance training in a fasted state has been shown to increase muscle oxidative capacity [10] and enhance exercise-induced net intramyocellular lipid degradation [11]. The discrepancies between studies regarding the metabolic effects of RF are possibly linked to differences between protocols, the time of blood sampling, and the selection of the sampling day during Ramadan [12]. Likewise, it has been shown that RF affected the circadian pattern of body temperature, cortisol, melatonin, and biochemical measures [e.g., glycemia, transaminases, creatine kinase (CPK)], but does not affect lipid, carbohydrate, or protein metabolism, and mean daily serum hormone levels [12–16]. Also, Waterhouse et al. [17] reported a decrease in Lac concentrations during a submaximal exercise performed in the evening without a change in morning measures during Ramadan. The lower evening Lac levels [17] could be explained by a higher use of lipids as fuel at this time-of-day [16, 18, 19]. The determination of the circadian patterns of biochemical parameters during Ramadan may provide an explanation for the modified circadian pattern of sport performance during this month. In a previous research, we found that biochemical responses to the Yo–Yo intermittent recovery test level 1 (YYIRT) were time-of-day dependant [20]. In the present study, we aimed to examine the effect of RF on the diurnal variations in some biochemical parameters in response to the YYIRT.
Methods Participants Twelve male professional soccer players (age 17.52 ± 0.2 years, height 177.4 ± 2.9 cm) volunteered to
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participate in this study. They were affiliated with the same club competing in the Tunisian first professional league [20] and had a minimum of 5 years of training experience. The participants trained at least four evening sessions per week with an average of 2 h per session in addition to the weekend match. During Ramadan, the training program consisted of high intensity short-duration intermittent exercises. Goalkeepers and players who experienced injuries were excluded to have an homogeneous group in terms of physical characteristics (e.g., strength, anaerobic power and capacity, endurance). Participants were considered to be healthy on the basis of a medical examination. Also, they were non-smokers and did not consume caffeine or alcoholic beverages. To be included in the study, each participant was requested to keep standard times for eating (breakfast at 0700, lunch at 1200 hours, and dinner at 2000 hours) and sleeping habits (sleeping between 2300 and 0700 ± 1 h) before Ramadan. Moreover, participants were either of a ‘‘moderately morning type’’ (n = 4) or ‘‘neither type’’ (n = 8) based on their ¨ stberg self-assessment quesresponses to the Horne and O tionnaire [21]. The experimental design was approved by the Clinical Research Ethics Committee of the National Center of Medicine and Sciences in Sport of Tunis and met the ethical standards of the Declaration of Helsinki. The study was conducted in Sfax (southeast of Tunisia, altitude *7 m) in the summer of 2010 when the elapsed time from dawn to sunset was from 0402 to 1910 hours at the beginning and from 0431 to 1833 hours at the end of Ramadan. During this period, the participants abstained from food and drinks *16 h/day. Experimental design The experimental design consisted of three testing periods: 1 week before Ramadan (BR), the second week of Ramadan (R2), and the fourth week of Ramadan (R4). Body mass (BM) and fat mass (FM) were measured at each testing phase with an electronic balance (Tanita TBF300WA, Tokyo, Japan). Furthermore, at each period, the participants performed two test sessions at two times of day (i.e., 0700 and 1700 hours), with a recovery period C36 h in-between. Test sessions were completed in a counterbalanced design. Each one commenced with oral temperature measurement with a digital clinical thermometer (Omron, Paris, France; accuracy ±0.05 °C). Then, the soccer players performed an endurance specific test (YYIRT). Heart rate was recorded during the YYIRT using a Polar heart rate monitor (Polar Electro Oy, T61coded, Finland). Throughout the experimental period, participants were requested to maintain their habitual physical activities and to avoid strenuous activities *24 h before each test session.
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Dietary records
Antioxidants in the added sample cause suppression of this colour production in proportion to their concentrations. The detection limit for the TAS kit was 0.21 lmol/L.
A seven consecutive day dietary record was completed. Dietary records were done in the same weeks as test sessions (BR, R2, and R4). Participants received a detailed verbal explanation and written instructions on data collection procedures. They were asked to continue their usual dietary habits during the period of diet recording and to be as accurate as possible in recording the amount and types of food and fluids consumed. A list of common household measures (e.g., cups and tablespoons) and specific information about the quantity of each measure (grams, etc.) were given to each participant. Each individual’s diet was calculated using the Bilnut 4 software package (SCDA Nutrisoft, Cerelles, France) and the food composition tables published by the Tunisian National Institute of Statistics in 1978.
As described previously [20], the test consisted of 20-m shuttle runs performed at increasing velocities with 10 s of active recovery between runs until exhaustion. The end of the test was considered when the participant twice failed to reach the front line in time (objective evaluation) or he felt unable to complete another shuttle at the dictated speed (subjective evaluation). The total distance (TD) covered during the YYIRT (including the last incomplete shuttle) was considered as the test score. All players were already familiar with the test as it was part of their usual fitness assessment program.
Blood sampling and analysis
Statistical analyses
Fasting blood samples were collected from a forearm vein after 5 min of rest in a seated position and 3 min after the YYIRT. Samples were immediately placed into an ice bath and then centrifuged for 10 min at 2,5009g and 4 °C. Aliquots of the resulting plasma were stored at -80 °C until analyzed. To eliminate inter-assay variance, all samples were analyzed in the same assay run. All assays were performed in duplicate in the same laboratory with simultaneous use of a control serum from Randox Laboratories, Ltd. (Crumlin, Co., Antrim, UK). Also, all reagents employed in biochemical tests were obtained from Randox. Aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) activities were determined by an enzymatic rate method. Blood GLC levels were measured with the glucose oxidase method and Lac concentrations were assessed by the lactate oxidase peroxidase method. CPK activity was determined spectrophotometrically by measuring NADPH formed by hexokinase and the D-glucose-6-phosphate dehydrogenase coupled enzymatic system. Lactate dehydrogenase (LDH) activity was determined by measuring NADH consumption using reagent kits. Uric acid (UA) concentrations were determined by an enzymatic method at 550 nm using a Randox kit and protein concentrations (Pro) were determined by the Biuret method. Total antioxidant status (TAS) was measured using a kit purchased from Randox. In this assay, metmyoglobin reacts with H2O2 to form the radical species ferrylmyoglobin. A chromogen [2,20 -azinodi-(ethylbenzthiazoline sulfonate); ABTS] is incubated with the ferrylmyoglobin to produce the radical cation species ABTS?. This has a relatively stable blue-green colour measured at 600 nm.
All statistical tests were processed using STATISTICA Software (StatSoft, France). Mean and standard deviation (SD) were calculated for each variable. The Shapiro–Wilk W test of normality revealed that the data were normally distributed. Once the assumption of normality was confirmed, parametric tests were performed. Oral temperature, TD, and peak heart rate (HRpeak) data were analyzed using a two-way analysis of variance (ANOVA) [3 (Ramadan) 9 2 (time-of-day)]. Also, a three-way ANOVA [3 (Ramadan) 9 2 (time-of-day) 9 2 (blood samples)] with repeated measures was performed for the biochemical measurements. When appropriate, significant differences between means were tested using the Tukey post hoc test. A probability level of 0.05 was selected as the criterion for statistical significance.
The Yo–Yo intermittent recovery test level-1 (YYIRT)
Results Body composition and dietary intake BM and FM data are shown in Table 1. Statistical analyses indicated that BM (P \ 0.001) and FM (P \ 0.01) were lower during R4 than BR. Compared with BR, the estimated daily energy intake was substantially reduced during R4 (3,302 ± 709.8 vs. 2,693 ± 517.13 kcal/day respectively, P \ 0.01) (Table 1). This change was associated with a decrease in fat intake during R4 (P \ 0.05), while carbohydrate and protein intakes did not differ between Ramadan and BR (Table 1). Moreover, vitamin A, vitamin C, and vitamin E intakes were unchanged throughout the study (Table 1).
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Author's personal copy Sport Sci Health Table 1 Body mass, fat mass, and dietary intakes recorded before Ramadan (BR), during the second week of Ramadan (R2), and during the fourth week of Ramadan (R4) BR Body mass (kg) Fat mass (kg)
66.9 ± 13.4
R2
R4
65.02 ± 10.7**
64.13 ± 11.9***
16.4 ± 6.6
16.1 ± 9.5
15.3 ± 4.4**
Daily energy intake (kcal/day)
3,256 ± 660.1
2,875.7 ± 654*
2,705 ± 612.2**
Carbohydrates (g)
412.3 ± 135.1
401.2 ± 87.1
Proteins (g) Fats (g) Vitamin C (mg/day) Vitamin E (mg/day) Vitamin A (ER)
409.3 ± 86.4
95.9 ± 33
97.2 ± 40.2
96.6 ± 28.4
109.4 ± 64.2
104.3 ± 27.1
100.9 ± 36.4*
45.9 ± 29 4.23 ± 1.9
44.8 ± 38 5.1 ± 4.1
43.6 ± 49.8 4.6 ± 2.4
1,980.4 ± 2.6
1,815.5 ± 1.4
1,726.5 ± 2.3
Data are mean ± SD * Significantly different compared with BR value at P \ 0.05 ** Significantly different compared with BR value at P \ 0.01 *** Significantly different compared with BR value at P \ 0.001
1700 hours. Also, HRpeak decreased during R2 and R4 compared with BR in the evening (P \ 0.05; Table 2). Biochemical measurements
Fig. 1 Oral temperature (°C) measured at 0700 and 1700 hours before Ramadan (BR), during the second week of Ramadan (R2), and during the fourth week of Ramadan (R4). Data are mean ± SD. Asterisk significantly different from BR value at the same time-of-day (P \ 0.05). Triple hash symbol significantly different from 0700 hours value for the same period (P \ 0.001)
Temperature and YYIRT Performance Oral temperature was higher in the evening compared with the morning before and during Ramadan (P \ 0.001) (Fig. 1). This increase was higher BR (?0.71 ± 0.32 °C) than during R2 (?0.40 ± 0.28 °C) and R4 (?0.41 ± 0.32 °C). Oral temperature was not affected in the morning; however, there was a significant decrease in oral temperature during R4 compared with BR in the evening (P \ 0.05). The TD covered during the YYIRT was higher in the evening than the morning BR (P \ 0.05) (Table 2). However, these diurnal variations were not found during Ramadan. Moreover, the TD decreased significantly during R2 (P \ 0.01) and R4 (P \ 0.001) compared with BR at
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The biochemical parameters measured before and after the YYIRT, in the morning and in the evening, during the three testing phases, are displayed in Table 3. BR, the values of the measured biochemical parameters were higher after the exercise than resting levels in the morning and in the evening (P \ 0.001). Moreover, except for Lac, CPK (P \ 0.001), LDH (P \ 0.01), GLC (P \ 0.001), ASAT (P \ 0.01), and ALAT (P \ 0.001) values measured at rest were higher in the evening compared with the morning. These diurnal variations were maintained after the YYIRT. However, UA (P \ 0.01), TAS (P \ 0.001), and Pro (P \ 0.001) values measured at rest were higher in the morning than the evening. These diurnal variations were not found after the exercise. For R2, all parameters had higher values after the exercise compared with resting levels in the morning and in the evening (P \ 0.001). Similarly to BR, CPK (P \ 0.001), LDH (P \ 0.05), GLC (P \ 0.001), ASAT (P \ 0.05), and ALAT (P \ 0.05) values were higher in the evening than the morning during R2. These diurnal variations were maintained after the exercise. Nevertheless, UA (P \ 0.05), TAS (P \ 0.05), and Pro (P \ 0.05) values were lower in the evening compared with the morning. Except for Pro, these diurnal variations were not observed after the YYIRT. During R4, the levels of all parameters were higher after the YYIRT compared with resting values in the morning and in the evening (P \ 0.001). However, no diurnal variation was observed in resting values of the selected biochemical parameters at this testing period. After the
Author's personal copy Sport Sci Health Table 2 Total distance covered during the YYIRT (TD) and peak heart rate during the YYIRT (HRpeak) measured at the two times of day before Ramadan (BR), during the second week of Ramadan (R2), and during the fourth week of Ramadan (R4) BR
TD (m) HRpeak (beats/min)
R2
R4
0700 hours
1700 hours
0700 hours
1700 hours
0700 hours
1700 hours
1,746.53 ± 527.36#
1,947.64 ± 458
1,717 ± 554.35
1,798.47 ± 410.13**
1,722.43 ± 497.3
1,658.17 ± 522.13***
189 ± 3.1*
187.7 ± 3.5
191.4 ± 5.3
193 ± 5.9
189.4 ± 5.5
187.6 ± 2.8*
Data are mean ± SD * Significantly different from BR value at the same time-of-day (P \ 0.05) ** Significantly different from BR value at the same-time-of day (P \ 0.01) *** Significantly different from BR value at the same time-of-day (P \ 0.001) #
Significantly different from 1700 hours value for the same period (P \ 0.05)
exercise, only LDH values were significantly higher in the evening compared with the morning (P \ 0.01). Regarding the Ramadan effect, CPK, ASAT, and ALAT values measured before and after the YYIRT were lower during R4 compared with BR in the evening (P \ 0.001). Likewise, compared with BR, LDH values were lower during R2 after the exercise (P \ 0.01) and during R4 both before (P \ 0.001) and after (P \ 0.01) the exercise in the evening hours. GLC values were lower during R2 and R4 compared with BR in the evening (P \ 0.001 for before and after the exercise). Also, Lac values measured after the YYIRT were lower during R2 and R4 than BR in the evening (P \ 0.05). Compared with BR, UA values were higher during R2 before the exercise (P \ 0.05) and during R4 both before (P \ 0.05) and after (P \ 0.05) the exercise in the evening. Furthermore, resting values of TAS were higher during R4 than BR in the evening (P \ 0.01), while post-exercise values were not significantly different between the two testing phases at this time-of-day. Pro values measured before and after the YYIRT were higher during R2 and R4 compared with BR in the evening (P \ 0.05).
Discussion This study aimed to investigate the effects of RF on the diurnal variations in metabolic responses to an intermittent exercise in Tunisian soccer players. The present study’s results confirmed that RF affects endurance performance measured in the evening, but not in the morning. Moreover, RF modified the diurnal pattern of resting and post-exercise values of the studied biochemical parameters. The present study’s findings indicated that BM and FM were lower during R4 compared with BR. These results are in agreement with previous research [2, 22], and could be related to an increased use of lipids [1, 23] and a decrease in fat intake during Ramadan. Nevertheless, the findings of
a recent well controlled study indicated that RF didn’t ameliorate the oxidation during submaximal exercise [24]. As previously shown [25], this study demonstrated that the TD covered during the YYIRT was unaffected in the morning, but reduced in the evening during Ramadan. To date, few studies have examined the effect of RF on the diurnal variations in sport performance [25, 26]. The modified diurnal pattern of body temperature during Ramadan could explain the present results. Indeed, a circadian analysis, where values were obtained every 2 h, showed a delay in the acrophase, a decrease in the amplitude, and no variation in rectal temperature during Ramadan [27]. Concerning biochemical measures, and similarly to our recent findings [28–30], the present results indicated that resting and post-exercise levels of CPK, LDH, and ASAT showed higher evening values BR. These findings could explain, at least in part, the diurnal pattern of endurance performance [20]. During R4, resting and post-exercise levels of these parameters decreased in the evening. These modifications suppressed the diurnal pattern of resting values and reduced the amplitude of post-exercise levels. Also, Haouari-Oukerro et al. [13] observed a decrease in the amplitude and a shift in the acrophase of hepatic and myocellular enzymes (i.e., gamma-glutamyltransferase, alkaline phosphatase, CPK, and glutamic transaminase) during Ramadan. Moreover, recent findings demonstrated that RF did not adversely affect cellular damage [31]. In this context, it has been shown that oxidative stress [31] and inflammatory status (i.e., IL-6, C-reactive protein) [32] were reduced during Ramadan in healthy participants. The decrease in muscle damage observed during Ramadan could be, in part, explained by the caloric restriction observed in the present study (reduction in daily energy intake). Consistent with our recent findings [20, 28–30], resting and post-exercise levels of GLC and Lac were higher at 1700 hours as compared with 0700 hours BR. The morning to evening difference in Lac response to exercise might be
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Author's personal copy Sport Sci Health Table 3 Biochemical parameters measured before and after the YYIRT, at the two times of day, before Ramadan (BR), during the second week of Ramadan (R2), and during the fourth week of Ramadan (R4)
Before exercise
After exercise
0700 hours
1700 hours
0700 hours
1700 hours
156.09 ± 43.97
179.91 ± 57.67$
177 ± 51.62*
350.65 ± 40.74
$
*
BR CPK (IU/L) LDH (IU/L) GLC (mmol/L) Lac (mmol/L) UA (lmoL/L) TAS (lmol/L) Pro (g/L)
410.83 ± 35.78
4.36 ± 0.09
4.7 ± 0.4
1 ± 0.23 $
$
77.09 ± 8.29
243.56 ± 42.72 67.09 ± 4.13
24.8 ± 4.26
ALAT (IU/L)
19.78 ± 2.11
22.78 ± 4.27$
145.27 ± 29.42
168.09 ± 46.74$
359.56 ± 69.37
$
LDH (IU/L) GLC (mmol/L)
31 ± 4.69
4.26 ± 0.22
4.48 ± 0.3
Lac (mmol/L)
0.96 ± 0.13
UA (lmoL/L)
276.95 ± 22.36$
TAS (lmoL/L) Pro (g/L) ASAT (IU/L) ALAT (IU/L)
1.27 ± 0.08
$,#
$
76.18 ± 10.49
72 ± 4.94
194.27 ± 49.16$,*
*
504.95 ± 44.09$,*,#
456.24 ± 77
*
5.56 ± 0.67$,*,#
*
80.09 ± 9.62
$
25.9 ± 2.42
164.73 ± 31.42*
1.38 ± 0.07
#
30.1 ± 3.57
$
72.82 ± 6.71* 29.78 ± 3.56$,*
11.01 ± 0.4$,*,#
308.12 ± 35.05*
1.18 ± 0.09 $
1.3 ± 0.14*
$,*
26.11 ± 4.34*
10.16 ± 0.6
262.02 ± 37.5#
295.93 ± 38.35*
37.2 ± 6.68$,*
5.06 ± 0.57
0.98 ± 0.12
*
*
31.4 ± 5.91
401.55 ± 47.66
12.03 ± 0.37$,*
307.39 ± 46.48 81 ± 9.97
$
557.45 ± 111.51$,* 5.6 ± 0.29$,*
*
1.36 ± 0.15
ASAT (IU/L) R2 CPK (IU/L)
*
11.14 ± 0.59*
1.09 ± 0.15 $
420.27 ± 40.05 5.12 ± 0.08
1.09 ± 0.16
265.88 ± 38.64 1.23 ± 0.2
$
204.55 ± 67.37$,*
*
297.73 ± 39.52* 1.32 ± 0.07*
$,*
75.45 ± 5.91#
35.7 ± 3.89
*
40.4 ± 2.84$,*
24.56 ± 4.95
*
26.67 ± 5.15$,*
18.56 ± 3.24
20.89 ± 3.69
142.91 ± 25.07
150.36 ± 28.27#
161.45 ± 40.93*
182.36 ± 52.09$,*,#
350.47 ± 27.78
#
*
494.06 ± 37.15$,*,#
R4 CPK (IU/L) Data are mean ± SD $
Significant difference between the morning and the evening * Significant difference between before and after the exercise
#
Significant difference compared with before Ramadan
LDH (IU/L) GLC (mmol/L)
4.38 ± 0.33
436.71 ± 43.44
#
5.03 ± 0.39
*
5.12 ± 0.39*,#
*
10.63 ± 0.28*,#
4.48 ± 0.25
Lac (mmol/L)
0.96 ± 0.2
1.02 ± 0.09
10.53 ± 0.55
UA (lmoL/L)
281.7 ± 17.16
270.2 ± 16.66#
313.86 ± 23.15*
#
*
311.83 ± 28.06*,# 1.35 ± 0.1* 77.36 ± 7.19#
TAS (lmoL/L) Pro (g/L)
1.24 ± 0.07 77 ± 9.6
1.2 ± 0.04 75.09 ± 3.59#
1.38 ± 0.12 80.64 ± 7.78*
ASAT (IU/L)
25.9 ± 3.81
26.4 ± 3.69#
36 ± 3.74*
33.8 ± 3.19*,#
#
*
26.67 ± 2.18*,#
ALAT (IU/L)
17.89 ± 2.8
explained by the increase in catecholamine levels [33] and/ or the circadian variation in core temperature [34]. However, there was no diurnal variation in GLC and Lac levels measured at rest or after the YYIRT during R4 because of the decrease in evening values. Similarly, previous studies showed that resting GLC levels increased at 02:30 and 0800 hours and decreased at 17:30 hours during Ramadan [14, 35]. Concerning the exercise effect, recent research found that Lac levels decreased after a submaximal exercise performed during R4 in the evening [17]. However, a more recent research concluded that while Lac values remained unchanged, GLC levels were reduced during evening submaximal exercise [24]. These results could be explained by the modified circadian distribution of GLC levels during Ramadan [14]. Moreover, the lower Lac values reported during R4 in the evening could be attributed to a greater use of lipids as fuel at this time [16, 18,
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373.13 ± 30.83
18.89 ± 2.42
25.89 ± 2.42
19]. This fact was not confirmed in the study of Aziz et al. [24] which concluded that Ramadan fasting didn’t ameliorate fat burn during evening exercise despite a decrease in GLC levels. Furthermore, Hargreaves [36] showed that low endogenous concentrations of muscle glycogen and hypo-hydration are possible factors leading to lower blood GLC and blood Lac concentrations during Ramadan. However, a recent study indicated that only resting GLC levels decreased, while post-exercise values of Lac and GLC did not significantly change after an endurance exercise performed during Ramadan [7, 37]. Despite a decrease in carbohydrate intake during Ramadan, morning GLC levels did not change, which may be due to an upregulation of gluconeogenesis. Regarding protein metabolism, and similarly to previous research [35], Pro values measured before and after the YYIRT were higher during R2 and R4 compared with BR in
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the evening. Moreover, consistent with our recent findings [20, 28–30], the present results showed that resting and post-exercise levels of UA, the end product of purine breakdown, displayed higher morning values BR. Moreover, resting and post-exercise levels of UA increased significantly during Ramadan. The results of the wellcontrolled studies in athletes suggested that there is an increased rate of protein breakdown and fat oxidation during Ramadan [1, 2, 4]. Besides, the increased UA concentrations observed during Ramadan could be linked to dehydration [1, 2, 38] and an excessive breakdown of RNA tissue [39]. Furthermore, in the present study, the morning to evening difference in UA concentrations was reduced during R2 and was not observed during R4 by an increase in evening values. This may indicate a better antioxidant status at this time-of-day during R4. In addition, resting TAS values increased during R4 in the evening, while postexercise levels were unchanged throughout the study. The increase in TAS could be due to the caloric restriction induced by RF. To date, few studies have examined the effects of RF on oxidative stress biomarkers. Ibrahim et al. [31] observed a reduction in malondialdehyde, without a significant change in carbonylated proteins, glutathione, as well as glutathione peroxidase and catalase activities. However, a more recent study showed that 15-F2t-isoprostane, an urinary marker of oxidative stress, increased at the end of Ramadan proportionally to BM and FM [40]. The timing of food availability and intake exerted a powerful effect on the temporal characteristics of biochemical rhythmic phenomena [41]. In this context, chronobiological studies have shown that RF affects the circadian distribution of body temperature, cortisol, melatonin, and glycemia; but does not affect the metabolism of lipids, carbohydrates, or proteins, or mean daily serum hormone levels [15, 16]. In this context, Cerizza et al. [42] concluded that a proper lifestyle, in terms of dietary and physical habits and in terms of psychological motivations for eating, avoids young people becoming overweight and obese. One limitation of this study was the relatively small sample size and the lack of an untrained control group. Moreover, blood sampling was done only before and after the YYIRT. Further studies should investigate a delayed blood sample to check peak values.
Conclusion In summary, the present study’s results indicate that RF modifies the diurnal pattern of resting and post-exercise levels of the studied biochemical parameters. The concomitant decrease in the levels of biochemical markers of muscle damage, Lac, and GLC at 1700 hours could explain the modified diurnal pattern of endurance performance in
soccer players. It seems that the caloric restriction that characterizes RF could influence the biochemical responses and their diurnal pattern. Acknowledgments This study was supported by the Ministry of Higher Education and Scientific Research, Tunisia. We are grateful to all the players who have so willingly participated in the study. Conflict of interest The authors O. Hammouda, H. Chtourou, A. Aloui, M.A. Mejri, H. Chahed, A. Miled, K. Chamari, A. Chaouachi and N. Souissi declare that they have no conflicts of interest.
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