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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 6, November/December 2020
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AFRICA
mean seven-day awake METs in female teachers in the light-PA
group was found. The weak relationship between PA and CIMT
was also observed in a somewhat similar study.
45
PA was measured using a combined accelerometer and heart
rate monitor, the ActiHeart. One of the main observations of
the study was the high level of sedentary behaviour in adults,
which is in agreement with other studies.
8,9,46
The participants’
occupation might explain the high percentage of teachers being
classified as physically inactive or lightly physically active, as
most of their working time is spent standing, sitting or walking
slowly, which are all forms of sedentary or light energy cost
activity.
39
Physical inactivity may lead to the development of
cardiovascular disease risk factors, such as overweight and
obesity,
47
and this was evident in the present study. The observed
high prevalence of overweight and obesity found in this sample
of teachers is consistent with the statistics for South Africa noted
in the World Health Organisation’s 2017 Overweight and Obesity
report.
48
The inverse relationship between CIMT and PA in the
sedentary group of teachers is similar to the study by Parsons
et al.
23
in older males (age 78 years), and the study of Gomez-
Marcos
et al.
as assessed by accelerometer and seven-day
physical activity recall (PAR)
49
in healthy adults (56 years).
The potential beneficial effect of PA and therefore increased
energy expenditure on lowering subclinical atherosclerosis levels
is apparent.
12
Contrastingly, Ascenso
et al.
50
indicated that the
effect of PA was not observed in sedentary obese adolescents but
was present in individuals who were classed as lightly physically
active. Conflicting results from Kozàkovà
et al.
24
indicated a
significant positive relationship with a sedentary or light-PA
ratio and CIMT in a healthy adult population (44 years).
The relationship between CIMT and PA has not been
well established; different studies have reported controversial
results about the relationship between CIMT and PA. This
controversy may be explained by several influential factors
in the relationship, such as age, gender, previous disease,
measurement instruments and methods, and PA intensity.
49
Huynh
et al.
51
indicated that sedentary behaviour and low levels
of PA were not associated with carotid distensibility. However,
in a systematic review, Kadoglou and colleagues
52
suggested that
although the influence of PA on CIMT was inconsistent among
healthy individuals, physical inactivity was associated with an
increased CIMT.
The association between PAL and CIMT in our cohort may
be significant due to the levels of TEE and REE in the equation,
taking into account not only the energy expenditure due to
AEE and the TEE but also the REE. We can speculate that
the observed prevalence of overweight and obesity might be a
contributor to the lack of a significant relationship between AEE
and CIMT, in the sense that obese individuals’ average daily
metabolic rate, not non-basal energy expenditure, is positively
related to body size.
53
Westerterp
53
stated that AEE is the energy expenditure
associated with muscular contractions involved in performing
body postures and movements. We may assume that our
study participants with mean BMIs almost equal to 30 kg/m
2
regardless of their PA levels might have struggled to achieve
a five- to 20-fold increase in metabolic rate compared with
non-obese individuals.
54
Westerterp
53
argued that the ratio of
energy cost for low:moderate:high-intensity activity is 1:2:4, and
the contribution of high-intensity activity to AEE is about 25%.
Most teachers move around or walk when teaching sessions take
place,
55
but this might not be enough to reach an AEE equal to
or above 25%.
Unfortunately, in our study, only one participant (0.9%), who
was not included in the analyses, participated at moderate-to-
high intensity, and that could also be a reason for not finding a
significant relationship between AEE and CIMT. It should also
be noted that sedentary behaviour that is measured at one time
point to capture a participant’s typical weekly PA might have
contributed to the observed associations.
56
The mean WC values for male and female teachers in our
study were above the measurements classified as ‘at risk of
disease’, according to the ACSM (males ≥ 102 cm; females ≥
88 cm).
36
The non-significant relationship between CIMT and
WC in this study is congruent with the findings of one study
conducted in apparently healthy adults.
21
Contradictory evidence
from Ascenso
et al.
50
indicates no correlation between sedentary
time and WC; however, their study was conducted in obese
adolescents, which may explain the reason for the disparity.
In our study, we also found significant gender differences in
CIMT, with male teachers in both the sedentary and light-PA
groups having higher CIMT than female teachers. This can
be explained by risk-factor classification, with males at higher
risk of developing CVD at an earlier age.
36
The results can be
affirmed by similar studies in young populations; Ried-Larsen
et al.
57
also found significantly higher CIMT in Danish boys
than in girls. Furthermore, Ascenso
et al.
50
stated similar gender
differences in CIMT; however, the results were not significant.
This result was similar to Jain
et al.
,
58
who found that males had
a significantly higher burden of subclinical disease, measured by
non-invasive imaging.
An unexplained significant negative relationship observed in
our study between CIMT and TEE was also shown by Walker
et al.
56
in males who were classified in a sedentary group. The
findings might in part be explained by the 56% of participants
classified as light PA who presented with overweight and obesity
in our study. This finding was inconsistent with findings in
obese children and adolescents in other studies; however, they
did not focus on adults or teachers and revealed insignificant
correlations between sedentary behaviour and CIMT. However,
light PA was positively correlated with CIMT.
50
In a study by Kozàkovà
et al.
24
among Caucasian males
and females, a positive association existed between CIMT
and time spent sedentary, whereas an inverse relationship was
found between light PA and CIMT. Conversely, Ried-Larsen
and colleagues,
25
studying Danish adolescents, reported no
associations between CIMT and moderate-to-vigorous PA or
vigorous PA. Studies in British adults and young Indian adults
have reported inverse associations between CIMT and PA;
23,59
while Ebrahim
et al.
60
reported no relationship in British adults.
Inconsistent findings were most likely due to considerable
variation in PA measurement protocols and variability of the
study populations, using arbitrary cut-off values.
52,56
In our study, male teachers had higher AEE, mean seven-day
awake METs and PAL than female teachers in the sedentary
group, as well as higher TEE than females in the light-PA group.
The results are comparable to those of Guthold and colleagues,
9
who reported a higher prevalence of physical inactivity among
South African females compared with males. Additionally,