Effect of Ramadan fasting: Association with time of day on time-motion,technical aspect and psychophysiological response to simulated karate competition in young amateur competitors

Abstract

Ramadan is characterized by daily abstinence from food and fluid intake from dawn to sunset. The understanding of the Ramadan effects on the diurnal variations of athletic performance is crucial for practitioners, coach and researchers to prepare sport events and optimize performance. The aim of the present study was to reveal the effect of Ramadan on the performance aspect, heart rate and rating of perceived exertion during a karate match. In a randomized counterbalanced, 2 × 2 cross-over order, 22 male and female amateur karate athletes (age = 16.8 years, body mass = 59.1 kg, height = 168.3 cm) participated in simulated karate match at 8–10 a.m. and 5–7 p.m. on three different occasions: 1 week before Ramadan, the second week of Ramadan (during Ramadan), and 2 weeks after Ramadan. Performance aspects were analyzed, and heart rate and rating of perceived exertion were assessed before and immediately after the match at each visit. Our results demonstrated that Ramadan adversely affected time-motion variables (fighting time and preparatory time) and heart rate during simulated karate match (p < 0.05, all). However, heart rate pic response to karate match was higher during Ramadan when compared with before Ramadan and after Ramadan. However, rating of perceived exertion results did not show any variation during Ramadan phases. Concerning the interaction of Ramadan and time of day, fighting time and stoppage time were higher in the evening and in the morning before Ramadan and the inverse during Ramadan, respectively (p < 0.05). In conclusion, Ramadan altered the diurnal variation of performance aspect, in terms of fighting time and stoppage time, during simulated karate match.

Keywords

Circadian rhythm heart rate martial arts perceived exertion

Introduction

Karate is a high-intensity intermittent combat sport which is characterized by competitors’ (karate athletes) high levels of motivation, stress management, attention, physical fitness and complex technical–tactical ability.¹ The duration of a karate match is 3 min for senior males and 2 min for senior females in the upcoming 2020 Olympics. This comprises high-intensity efforts interspersed with periods of mild to moderate intensity work or resting, characterized by the athlete’s effort to maintain tactical superiority over his/her opponent.² It is well known that an effective training programme for the sport requires customization of components to the specific demands of karate.³

To understand the psychophysiological aspect of karate competition, numerous studies have employed different methods to quantify the internal and external loads.^1,4 Performance analysis (time-motion and technical–tactical aspects) is one of the most relevant internal-workload quantification methods.^1,4 In this context, combat sports scientists have used time-motion analysis to provide broader insight into the technical, tactical and physiological demands of the kumite (free non-contact fight) in karate athletes.^5–7 Along these lines, Beneke et al.⁸ reported that the effort–pause ratio (E:P) was 2:1 during simulated senior male karate competition. Moreover, Chaabène et al.⁶ showed that the E:P was 1:1.5 and the high-intensity action to rest ratio was 1:10. Other study found that karate athletes performed 17 ± 7 high-intensity actions per fight ranging from < 1 to 5 s each. In addition, Tabben et al.⁷ examined the effect of gender, match outcome and weight categories on performance analysis during the 2012 World Karate Championship and reported that the referee’s decisions caused an E:P of 1:1.5 with a significant difference between weight categories. Furthermore, the later study identified that the mean fighting activity, breaking activity and preparatory activity were higher in males than in females although no significant differences between winners and losers were noted. With regards to the technical aspects during karate competitions, upper-limb techniques were predominant⁶; specifically, kizami-zuki and kyakuzuki-jodan were the most used techniques during official karate competitions.^6,7

A number of studies have previously demonstrated the match demands of karate and the external factors that may affect karate performance.^5–7,9 However, there are many dietary factors, such as time, quantity and quality of food and fluid intake either before, during or after training or competition which might had an effect on karate performance.⁹

In this context, previous investigations examined the effect of food and fluid abstinence or “Ramadan fasting” and/or maximal exercise on neuromuscular performance and reaction times in young trained competitors.^10,11 Those authors reported that Ramadan fasting impaired reaction times.^10,11

This may be explained in part by the fact that in scheduling annual events many sports organizations do not consider religious observances for Muslim elite athletes. For example, the 2012 Olympics in London took place during Ramadan, the holy lunar month for Muslims in which healthy Muslim adults are expected to abstain from food, drink and smoking daily between dawn and sunset.

On the other hand, the effect of ‘time of day’ is an important factor that might alter technical aspects and psychophysiological responses in sports performance.¹² Otherwise, previous studies showed contradiction on the effect of Ramadan fasting on technical and psychophysiological responses in combat sport.^11,13,14 Thus, it is crucial to evaluate the effect of time of day during Ramadan.

In this context, recent studies revealed that Ramadan intermittent fasting (RIF) decreased aerobic and anaerobic performance, while others failed to identify a significant decrement of physical performance during RIF.¹³ This contradiction may be due to the time of day during which the exercise testing was performed. Recently, Chtourou et al.¹⁵ and Aloui et al.¹⁶ examined the effect of Ramadan on the diurnal variations of anaerobic and repeated-sprint performance. The authors reported that peak power (PP) and mean power (MP) during the Wingate test decreased in the evening during Ramadan.¹⁵

To the best of our knowledge no study has examined the effect of Ramadan on the diurnal variations of performance during a karate competition. Therefore, in light of the above considerations, the aim of this study was to determine the possible effect of Ramadan on physical performance, heart rate (HR) and rating of perceived exertion (RPE) during simulated karate matches.

Methods

Procedure

The current investigation was a randomized counterbalanced, 2 × 2 cross-over design conducted before and during the month of Ramadan in 2018, which began on 17 May 2018 and ended on 14 June 2018. All participants visited our laboratory (temperature range 17°C–22°C) on four separate occasions. During the first visit, which was scheduled 1 week before the first simulated competition, the participants were familiarized with the testing procedures. The second, third and fourth visits were 1 week before Ramadan, during Ramadan, and 2 weeks after Ramadan (see Figure 1). At each visit, participants engaged in a simulated karate competition, with a recovery period of at least 48 hours between, at two times of day (morning (8–10 a.m.), and afternoon (5–7 p.m.)). HR and RPE were assessed before and immediately after the specific match at each visit (see Figure 1).

Figure 1.

Schematic representing the study design.

Participants

Twenty-two male (n = 14) and female (n = 8) amateur karate athletes (n = 22; age = 16.8 ± 2.1 years, body mass = 59.1 ± 9.5 kg, height = 168.3 ± 9.9 cm) volunteered to participate in this study. They trained regularly three times a week for an average of 75 min per session and participated in regional and national level competitions.

To be eligible to participate in the study, participants were required to meet the following criteria: (a) they were fasting during Ramadan, (b) had been regularly eating and sleeping before, during and after Ramadan, (c) regularly performed training before, during and after Ramadan, and (d) had abstinence from strenuous exercise in the 48 h before simulated competition (see below).

The experimental protocol was approved by the local ethics committee of the University of Bizerte (Tunisia), which was conducted in accordance with the 1964 Helsinki declaration and its subsequent amendments. Written informed consent was obtained from the participants and their parents following a verbal description of all the experimental details, and prior to the start of experimental data collection.

Performance-analysis measurements

All simulated karate matches were recorded by using two Sony cameras (model DCR PC 108E, CCD 1,000,000 pixels, SSC 1/4000 per-s, Tokyo, Japan).

The video analysis software program (Dartfish Edition MPT34M Pro 5.5, Lausanne, Switzerland) was used to analyze the footage frame by frame (interval 0.016 s). A total of 66 karate combat sessions were analyzed. According to the procedure of previous studies,^6,7 the activity profile was analyzed and classified into three activities: preparatory activity (PT), fighting time (FT) and stoppage time (ST); for further details see Tabben et al.⁷ The effort (i.e. PT + FT)-to-pause (ST) ratio (E:P) was also calculated.

Two qualified experts in karate competitions analyzed the matches twice with a 1-week interval between. Of note, the level of agreement between the two analyses, which is assessed using the Cohen kappa statistic as suggested by Landis and Koch,¹⁷ was 0.87. Student t-test showed no significant difference in PT (t = 1.1, p = 0.22), FT (t = –1.65, p = 0.14) and ST (t = –0.18, p = 0.92) activities during the two observations from the two expert analyzers.

Heart rate

HR was monitored at 5 s intervals before and immediately after each karate match using a wireless chest HR transmitter and a wrist monitor recorder (Polar Electro, Finland). Resting HR was assessed before matches following 10 min supine rest.

Rate of perceived exertion

As described by Yousfi et al.¹⁸ the RPE scale allows participants to give a subjective exertion rating for the physical task. The validated French version of the category ratio-10 scale¹⁹ was used to assess before and immediately after the match at each visit. The scale has 10 points ranging from nothing at all (0) to extreme (10) exertion.

Statistical analysis

All statistical tests were performed using the commercial software “Statistical Package for the Social Sciences” (version 20.0; SPSS, Inc., Chicago, IL, USA). The Kolmogorov–Smirnov test was used to determine data’s normal distribution. Descriptive data are presented as mean and standard deviation for continuous data and with median with the first and third quartiles for frequency data.

A two-way repeated measures analysis of variance with Bonferroni post-hoc tests was used to compare continuous data by moments of days and of Ramadan fasting. The Eta squared (η²) was calculated and classified as 0.02 > 0.13 = small, 0.13 > 0.26 = medium and <0.26 = large effect size (ES). For frequency data, paired analyses were performed using negative binomial generalized model. The incidence rate ratio (IRR) was used to verify effect size. A significance level of p ≤ 0.05 was used for all analysis.

Results

Figure 2 shows the descriptive analysis of time-motion analysis by each relative phase for the simulated matches.

Figure 2.

Time-motion analyses in relative fighting, preparatory and stoppage phases, separated by moments of the day (morning and evening) and of Ramadan (before, during and after), presented by seconds. Significant difference when compared with EBR and EAR (p<0.05); significant difference when compared with after Ramadan (p<0.05); significant difference when compared with evening and morning after Ramadan (p<0.05).

For FT, the highest value was achieved in the evening before Ramadan, while the lowest value was reported in the evening during Ramadan. Both time of day (F = 4.34, small ES, η²=0.03, p = 0.039) and Ramadan (F = 21.05, medium ES, η²=0.25, p < 0.0001) had a significant effect, as well as the interaction of time of day × Ramadan (F = 7.60, medium ES, η²=0.11, p = 0.001). More specifically, FT assessed during the morning did not significantly differ between before, during and after Ramadan (1.46 ± 0.39 [95%CI 1.32 to 1.61], 1.25 ± 0.34 [95%CI 1.11 to 1.40], and 1.35 ± 0.33 [95%CI 1.21 to 1.49], respectively, p > 0.05), while FT assessed during the evening was higher before Ramadan and lower during Ramadan (1.75 ± 0.34 [95%CI 1.61 to 1.89] and 1.05 ± 0.34 [95%CI 0.91 to 1.19], respectively, p < 0.05) (see Figure 2).

With regard to PT, the highest value was achieved in the morning after Ramadan, whereas the lowest value was in the evening during Ramadan. The effects of time of day (F = 11.02, medium ES, η²=0.08, p = 0.001) and of Ramadan (F = 3.64, medium ES, η²=0.06, p = 0.029) were significant, while the interaction of time of day × Ramadan (F = 0.14, null ES, η²=0.00, p = 0.870) was not. Concerning the Ramadan effect, only the difference between during and after Ramadan was significantly different (mean difference –1.36 [95%CI –2.60 to –0.11], p = 0.029). While the differences between before and during Ramadan (mean difference 0.94 [95%CI –0.31 to 2.18], p = 0.213) and between before and after Ramadan (mean difference –0.42 [95%CI –1.67 to 0.83], p = 1.000) were not significant. Morning (9.63 ± 2.52 [95%CI 8.61 to 10.65], 8.52 ± 2.49 [95%CI 7.50 to 9.54], 10.15 ± 2.60 [95%CI 9.13 to 11.16], p > 0.05) and evening (8.19 ± 2.28 [95%CI 7.17 to 9.20], 7.42 ± 2.32 [95%CI 6.40 to 8.44], 8.51 ± 2.23 [95%CI 7.49 to 9.53], p > 0.05) times did not statistically differ between before, during and after Ramadan.

For ST, the time was greater in the evening during Ramadan, and least in the evening before Ramadan. Overall, time of day (F = 2.46, negligible ES, η²=0.02, p = 0.119) and Ramadan (F = 2.77, small ES, η²=0.04, p = 0.066) had no significant affect. Only the interaction time of day × Ramadan was significant (F = 17.80, medium ES, η²=0.22, p < 0.0001). In the morning, ST was different between during and after Ramadan (12.45 ± 2.55 [95%CI 11.30 to 13.61] versus 15.03 ± 3.04 [95%CI 13.87 to 16.19], p < 0.05), while in the evening there were differences between before and during Ramadan (11.40 ± 2.63 [95%CI 10.24 to 12.56] and 15.74 ± 2.55 [95% 14.58 to 16.89], respectively, p < 0.05) and between during and after Ramadan (15.74 ± 2.55 [95% 14.58 to 16.89] and 12.17 ± 2.64 [95%CI 11.01 to 13.33], respectively, p < 0.05) (see Figure 2).

Table 1 shows the descriptive analytical results of the technical analysis for each combat.

Table 1.

Technical analysis separated by moments of the day (morning and evening) and of Ramadan (before, during and after), presented by frequency during combats.

Variables	MBR	EBR	MDR	EDR	MAR	EAR
Variables	M(1Q;3Q)	M(1Q;3Q)	M(1Q;3Q)	M(1Q;3Q)	M(1Q;3Q)	M(1Q;3Q)
GyakuZuki-jodan	10.0 (7.5;12.3)	11.0 (8.8;13.0)	7.5 (5.0;9.0)	5.5 (3.0;7.0)	9.0 (5.5;10.3)	9.0 (8.0;12.0)
Kizami-zuki	13.0 (8.0;15.3)	15.5 (13.8;17.3)	9.0 (6.0;11.3)	8.0 (6.5;9.3)	12.0 (6.8;14.0)	14.0 (11.8;16.0)
Total Upper Limbs Attacks	24.0 (12.8;26.3)	26.0 (22.0;28.5)	16.5 (12.8;21.0)	14.0 (9.5;17.0)	22.0 (10.8;23.3)	23.0 (19.8;26.5)
Kizami Mawashi-geri-chudan	6.5 (0.8;11.0)	8.0 (6.8;9.0)	7.0 (6.0;9.0)	4.0 (1.8;7.0)	6.5 (0.8;11.0)	7.0 (5.8;8.3)
Mawashi-geri-jodan	0.5 (0.0;3.0)	0.0 (0.0;1.0)	1.0 (0.0;1.3)	1.0 (0.0;2.0)	0.5 (0.0;3.0)	0.5 (0.0;1.0)
Mawashi-geri-chudan	14.0 (8.5;15.0)	15.0 (12.0;17.0)	11.5 (10.0;13.3)	8.0 (7.0;10.0)	14.0 (8.5;15.0)	14.0 (11.0;15.0)
Total Lower Limbs Attacks	20.0 (14.5;23.3)	24.0 (20.5;26.3)	20.0 (18.5;21.5)	13.0 (11.0;17.3)	20.5 (14.5;23.8)	21.0 (17.8;24.0)

Note: Ura-mawashi-geri demonstrated 0.0 as median, first and third quartiles for all moments. No significant effects were observed (p > 0.05 for all comparisons).

1Q: first quartile; 3Q: third quartile; EAR: evening after Ramadan; EBR: evening before Ramadan; EDR: evening during Ramadan; M: median; MAR: morning after Ramadan; MBR: morning before Ramadan; MDR: morning during Ramadan.

The number of total upper limb attacks was the highest before Ramadan during the evening and the lowest during Ramadan, in the evening. Similar trends existed for the number of total lower limbs attacks (Table 1).

First, the upper limb attacks, for time of day (Wald χ² = 0.18, IRR = 0.80, p = 0.669), Ramadan (Wald χ² = 5.20, IRR = 0.63, p = 0.074) and interaction time of day × Ramadan (Wald χ² = 1.22, IRR = 1.53, p = 0.542), there was no statistical significance. Both in the morning and evening, no differences could be detected among the phases of Ramadan either (p > 0.05) (Table 1).

Moving to the lower limb attacks, for time of day (Wald χ² = 0.02, IRR = 0.92, p = 0.900), Ramadan (Wald χ² = 1.20, IRR = 0.76, p = 0.550) and interaction time of day × Ramadan (Wald χ² = 1.81, IRR = 0.72, p = 0.404), there was no statistical significance. Both in the morning and evening, no differences could be found between before, during and after Ramadan (p > 0.05) (Table 1).

Concerning the single technique GyakuZuki-jodan, time of day (Wald χ² = 0.01, IRR = 0.86, p = 0.931) and the interaction time of day × Ramadan (Wald χ² = 1.45, IRR = 1.95, p = 0.484), no statistical significance existed. The effect of Ramadan (Wald χ² = 5.19, IRR = 0.60, p = 0.075) was also not statistically significant.

Regarding Kizami Zuki, time of day (Wald χ² = 0.61, IRR = 0.77, p = 0.434) and the interaction time of day × Ramadan (Wald χ² = 0.97, IRR = 1.44, p = 0.615) were not significant, whereas Ramadan (Wald χ² = 4.76, IRR = 0.64, p = 0.092) only trended towards a significant affect (Table 1).

Concerning Kizami Mawashi gerichudan, the effects of time of day (Wald χ² = 0.65, IRR = 1.09, p = 0.421), Ramadan (Wald χ² = 1.13, IRR = 0.82, p = 0.570) and their interaction (Wald χ² = 1.32, IRR = 1.24, p = 0.516) were not significant.

Regarding Mawashi gerijodan, the impact of time of day (Wald χ² = 0.76, IRR = 1.88, p = 0.383), Ramadan (Wald χ² = 0.78, IRR = 1.23, p = 0.678), and interaction time of day × Ramadan (Wald χ² = 4.44, IRR = 0.33, p = 0.109) did not achieve the significance threshold (Table 1).

Concerning Mawashi gerichudan, the effect of time of day (Wald χ² = 0.00, IRR = 0.92, p = 0.952), Ramadan (Wald χ² = 2.07, IRR = 0.72, p = 0.355), and their interaction (Wald χ² = 1.40, IRR = 1.32, p = 0.496) were not statistically significant (Table 1).

Table 2 shows the descriptive analysis of HR analysis before and after match.

Table 2.

Heart rate analysis in fighting before and after match, separated by moments of the day (morning and evening) and of Ramadan (before, during and after).

Variables	MBR	EBR	MDR	EDR	MAR	EAR
Variables	X(SD)	X(SD)	X(SD)	X(SD)	X(SD)	X(SD)
Before match	84.7 (19.6)	84.1 (12.8)	72.2 (10.2)	79.9 (10.0)	70.7 (6.1)	87.3 (9.9)
After match	196.2 (8.9)	188.7 (12.6)	200.0 (7.2)*	198.6 (5.8)^*	192.3 (8.99)	189.7 (9.6)

*Significant difference when compared with the same time of day before and after Ramadan (p < 0.05).

EAR: evening after Ramadan; EBR: evening before Ramadan; EDR: evening during Ramadan; M: median; MAR: morning after Ramadan; MBR: morning before Ramadan; MDR: morning during Ramadan; SD: standard deviation; X: mean.

Regardless of time of day and the effect of Ramadan, HR increased post-match when compared with pre-match (p < 0.0001) (Table 2). With regards to pre- and post-match, pre-match HR was lower in the morning after Ramadan and higher in the evening after Ramadan, while post-match HR was lower in the evening before Ramadan and higher in the morning during Ramadan. Furthermore, overall, time of day had a significant effect on HR (F = 20.14, ES medium, η²=14, p < 0.0001), as well as the phase of Ramadan (F = 12.11, ES medium, η²=16, p < 0.0001). The interaction time of day × Ramadan, however, was not statistically significant (F = 2.07, ES small, η²=0.03, p = 0.130). HR significantly differed between before and during Ramadan (mean difference –15.23 [95%CI –23.02 to –7.43], p < 0.0001), as well as between during and after Ramadan (mean difference 11.30 [95%CI 3.50 to 19.09], p = 0.002). HR did not significantly differ between before and after Ramadan (mean difference –3.93 [95%CI –11.73 to 3.86], p = 0.670). In the morning, HR before Ramadan significantly differed between during and after Ramadan (111.55 ± 23.55 [95%CI 105.19 to 117.90], 127.82 ± 10.59 [95%CI 121.46 to 134.18], 121.59 ± 10.68 [95%CI 115.23 to 127.95], respectively, p < 0.05). In the evening, HR significantly differed between before and during Ramadan (104.55 ± 17.64 [95%CI 98.19 to 110.90] versus 118.73 ± 8.81 [95%CI 112.37 to 125.09], p < 0.05) and between during and after Ramadan (118.73 ± 8.81 [95%CI 112.37 to 125.09] versus 102.36 ± 13.88 [95%CI 96.01 to 108.72], p < 0.05) (Table 2).

Table 3 shows the responses and analysis of the RPE data. Regardless of the time of day and the effect of Ramadan, the simulated karate match induced an increase in RPE (p < 0.0001) (Table 3). With regards to pre- and post-match, pre-match, the highest value was in the evening during Ramadan and the lowest after Ramadan in the morning. Post-match, the highest value was achieved before Ramadan in the evening and the lowest after Ramadan in the morning. Time of day (Wald χ² = 0.00, IRR = 0.90, p = 0.978) and Ramadan (Wald χ² = 2.27, IRR = 1.73, p = 0.321), as well as the interaction time of day × Ramadan (Wald χ² = 0.04, IRR = 1.20, p = 0.837), revealed no statistically significant change. Differences between before and during Ramadan (p = 0.653), between before and after Ramadan (p = 0.466) and between during and after Ramadan (p = 0.124) were also not statistically significant. Finally, both in morning and evening, no differences could be detected among the phases of Ramadan (p > 0.05) (Table 3).

Table 3.

RPE analysis in fighting before and after match, separated by moments of the day (morning and evening) and of Ramadan (before, during and after).

Variables	MBR	EBR	MDR	EDR	MAR	EAR
Variables	X	X	X	X	X	X
Before match	0.5	0.3	0.4	0.6	0.1	1.0
After match	3.3	5.4	3.1	4.1	2.7	4.0

Note: No significant effects were observed (p > 0.05 for all comparisons).

Discussion

To our knowledge, this is the first study investigating the effect of Ramadan, time of day and their interaction on time-motion, technical analysis and psychophysiological response during simulated karate matches. Our findings showed significant reduction of FT and PT during Ramadan and an increase in HR response during Ramadan. Furthermore, a significant time of day effect was observed for time-motion variables (i.e. FT and PT) and HR during simulated karate match.

Time-motion analysis, technical aspect and psychophysiological response

The current study identified an overall E:P ratio of ∼1:1.5. Accordingly, Chaabène et al.⁶ and Tabben et al.⁷ reported an E:P ratio of ∼1:1.5 in official karate matches, with a higher E:P ratio in middle weight category than in light and heavy weight categories,⁷ although the mean FT in the present study was lower than the results reported in the study of Chaabène et al.⁶ This difference may be explained by the competitive level and contest type involved in each study.

However, regarding the technical aspect during simulated karate competition, the present study reported that amateur competitors used more upper limb techniques than lower limb. This finding is in accordance with previous studies, which may be explained by the shorter time taken by punches for their execution, as well as their lower energy requirement, compared with kicks.^4,20

Regardless of Ramadan and time of day effects, the HR and RPE increased immediately post-match when compared with pre-match values. Accordingly, Iide et al.²¹ reported that simulated karate sparring matches induced elevation of HR and RPE. The elevation of HR after a karate match may be due to the increase of catecholamine and adrenaline during match play and the decrease of insulin plasma rates,¹² which in turn increases the concentration of free fatty acids progressively and therefore, increased HR response.^5,22,23

Effect of time of day

The present study found that FT was higher in the evening than in the morning before Ramadan. These findings are in agreement with previous studies, which reported that peak aerobic and anaerobic performances were observed in the evening. Along these lines, Ryan et al.²⁴ studied the effect of time of day on physical performance during Australian Football League competition. The authors reported greater total distance covered and relative high-speed running distance in the evening than in the morning and afternoon match kick-off time. To explain this, it has been reported that peak physical performance depends on the time at which the body temperature is at its circadian peak.²⁵ For instance, Hammouda et al.²⁶ reported that body temperature was higher in the evening than the morning, which in turn increased the activity of some enzymes such as phosphofructokinase and lactate dehydrogenase.²⁷ In addition, some other biochemical markers, such as the higher uric acid, total bilirubin,²⁶ total antioxidant capacity,^26,28 activities of some antioxidant enzymes²⁹ and rate of lipid peroxidation in the evening^30,31 may be altered and lead to optimal performance at this time point.

In the same way, regarding the effect of time of day on HR response to a karate match, our data reported a significant difference between evening and morning. Accordingly, previous studies reported that HR reached the highest values after exercises in the evening.^32,33 Furthermore, Chtourou et al.²⁵ reported that diurnal variation does not affect RPE, with no significant difference between 09:00 a.m., 12:30 p.m. and 16:00 p.m., which is in agreement with our study data.

Effect of Ramadan

The current study revealed that Ramadan adversely affected time-motion variables (i.e. FT and PT) and HR during simulated karate matches. Likewise, Aziz et al.³⁴ reported that Ramadan fasting has negative effect of performance during soccer matches. More specifically, the distances covered in the moderate and high-speed zones throughout the match were lower during the Ramadan fasted-state than the non-fasted state. Total distance covered and relative speed throughout the match were also reduced during Ramadan than during the control match condition.³⁴ The reduction of physical performance during Ramadan may be explained by its effect on behavioural changes, which in turn modify the rhythm of performance.³⁵ In this context, Ramadan might directly affect the circadian rhythm of performance by (a) inducing a phase advance or delay in the rhythm or (b) reducing the amplitude of the rhythm of anaerobic power development,³⁶ and (c) reducing the athletes’ mood and motivation.³⁷

In addition, conflicting results have been reported in the literature regarding the effect of Ramadan on athletic performance. These discrepancies could be, in part, explained by the time of day of testing. Previous studies reported that athletic performance was adversely affected during Ramadan in the afternoon, just before sunset,^16,38 and in the evening only.¹⁵ The reduction of performance in the evening during Ramadan could be related to the higher muscle fatigue at this time of day due to a lack of energy stores availability.¹⁵

Regarding the effect of Ramadan on HR and RPE, the present study reported higher HR response to karate match during Ramadan when compared with before and after Ramadan, while RPE does not differ between phases of Ramadan. This might be explained by the hydrosodic restriction, the cumulative effect of fluid and electrolyte losses not being restored.^39,40 However, Güvenç⁴¹ reported similar HR and RPE values before and during Ramadan, which is not in accordance, in part, with our study findings. This divergence finding might be due to the fitness level of the participants and/or the difference in the exercise protocols used in the studies. Further investigations are warranted in that prospect.

Concerning the interaction of Ramadan and time of day, FT and ST were higher in the evening and in the morning before Ramadan and the inverse during Ramadan, respectively. According to Chtourou et al.,²⁵ PP and MP during the Wingate test were greater in the evening and morning before and during Ramadan, respectively.

Conclusions

The present study showed that Ramadan modifies the diurnal variation of performance aspects, in terms of FT and ST, during simulated karate match. Practitioners and coaches should take into account the effect of Ramadan on diurnal variation of performance aspect during a karate match.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

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

ORCID iD

Hassane Zouhal

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