Cardiovascular Journal of Africa: Vol 28 No 3 (May/June 2017)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 3, May/June 2017 AFRICA 179
RIF is not obligatory for pre-pubescent children, and many
observe it from early adolescence.12,26 However, even though
Islam requires such a practice only after puberty, it is a relatively
frequent practice that pre-pubescent children attempt to fast the
whole of Ramadan.12,26
Effect of RIF on HR
RIF seemed to have a significant effect on HR, determined
during the 6MWT. Our study showed that R-4 HR values
were lower than those of pre-R (second minute), R-2 (first and
second minutes), and post-R (first, second, fourth, fifth and sixth
minutes), with no significant difference between the four testing
phases in resting and third-minute HR values (Fig. 1). To our
knowledge, this study is the first to examine the impact of RIF
on the HR of healthy children.
Our results are in line with those observed in some studies
conducted on adults,19,24 but opposite to those of Zerguini et al.25
Husain et al.19 showed that resting HR in adults was markedly
lowered in sedentary fasting male subjects (aged 20–45 years)
during the month of Ramadan, while responses in females were
only slightly decreased. Ramadan and Barac-Nieto24 found a
small but significant HR reduction in response to sub-maximal
exercise during the month of Ramadan in sedentary males aged
35 ± 2 years. Zerguini et al.25 found that HR measured after a
12-minute run was higher during R-4 than pre-R in professional
soccer players aged 17–34 years. Karli et al.22 observed that peak
HR values determined after a 30-second Wingate test were not
significantly different between Ramadan and pre-R in elite
power athletes aged 20–40 years. Brisswalter et al.23 found that
maximal HR recorded after an incremental maximal running
test was not modified during R-4 (vs pre-R) in well-trained
runners aged 24 ± 3 years. Also, Güvenç21 found that HR at eight,
10, 11 and 12 km/h of a modified 20-m shuttle-run test and peak
HR after this exercise were unchanged during Ramadan in male
soccer players aged 17 ± 1 years. Finally, HR during a 60-minute
endurance treadmill running test,31 and a multi-stage fitness test20
remained unaffected during Ramadan in moderately trained
active men (mean age: 27 ± 7 years) and in elite judokas (mean
age: 18 ± 1 years), respectively.
There are three possible explanations as to how the decrease
in HR during RIF could be explained:
• significant reduction in endurance capacity during Ramadan. 12
In a previous study, it was shown that the 6MWD was lower
during R-4 compared to pre-R but returned to baseline
values post-R. Therefore, the RIF-induced attenuation of HR
during walking tests should be taken into consideration when
assessing human exercise capacity, applying the HR output
relationship.
• changes in lifestyle during Ramadan.12 This mainly impacts on
the schedule of food intake, which may affect HR.32 Indeed,
fasting lowers the metabolic rate due to the absence of diges-
tion, which increases HR for two or three hours during the day. 33
The possible role of plasma leptin and ghrelin concentrations
(i.e. satiety and hunger hormones, respectively, known to affect
cardiovascular activity34,35) as an explanation of HR reduction
was rejected by Zoladz et al.,36 who found no effect of the over-
night fast on pre- and during-exercise plasma leptin and ghrelin
concentrations. However, this may be due to the relatively short
duration of fasting in their study compared to RIF.37,38 This
possible explanation should be considered in future studies.
• reduced sympathetic tone during fasting.19 Zoladz et al .36
demonstrated a significant decrease in HR by about 10 bpm
after an overnight fast. Their most likely explanation was
the observed significant increase in plasma norepinephrine
concentration, leading to an increase in systemic vascular
resistance, loading of arterial baroreceptors, and causing
vagal stimulation.39,40
The validity of the above explanations, taken from studies done
in adults, should be demonstrated in children.
Effect of RIF on oxy-sat
RIF seemed to have a statistically significant effect on oxy-sat
determined during the third and fifth minutes of the 6MWT.
R-2 oxy-sat values were higher than those of pre-R (third
minute) and post-R (fifth minute), and post-R values were lower
than those of pre-R and R-4 (fifth minute). These significant
changes between phases were approximately five points (Fig.
2), and could not be considered clinically significant since that
requires a change of more than five points.17,18,27 Therefore RIF
slightly improved blood oxygenation and oxygen transport by
haemoglobin, suggesting that the haemoglobin affinity with
oxygen may have increased.41,42
Recently, a novel desaturation index (6MWD × oxy-sat) has
been proposed, with the objective of improving the information
obtained from the 6MWT.17,18 In our study, this index was lower
during R-4 compared to pre-R (Fig. 3). However, during the four
testing phases, the desaturation index was in the normal range
(minimum–maximum: 32 305–78 720). In chronic respiratory
dysfunction patients, a low 6MWD × oxy-sat product (e.g. 20 000
m) was related to a clearly increased hazard ratio for mortality, 43
and it predicted quality of life.44
The rationale for HR and oxy-sat measurements in
non-diseased children deals with children’s safety. For instance,
during school sports practice late in the afternoon, especially
when Ramadan occurs in summer, the length of the fast could
potentially be a concern with young fasting children. Moreover,
such information could help medical and educational authorities
to make rational decisions concerning banning/allowing the
practice of RIF on school grounds. It is of paramount importance
to note that banning of such a religious practice could trigger
sharp reactions from the concerned communities; therefore, any
potential banning has to be based on sound and powerful data.
Limitations
The main limitation of the present study, as observed in
previous ones on RIF effects on the physical capacities of
healthy children,11-14,26 was the absence of a non-fasting control
group. The inclusion of such a group may decrease the risk of
learning effects skewing the findings, and circumvent any hazard
to the internal strength of the results.12,26 This crucial point was
previously discussed.12,26 The second limitation was not measuring
the walked distance in each minute of the 6MWT. Therefore, the
correlation between HR and the 6MWD in each minute of the
6MWT was not studied. However, as recommended, the boys
were invited to walk as far as possible in six minutes along a flat
hallway.30 In addition, none of them needed to rest since they
knew how to pace themselves, based on pre-experiment tests. 12,30