CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
AFRICA
259
groups. An alpha level of less than 5% (
p
≤
0.05) was considered
statistically significant. All data are presented as means
±
SE.
Results
There was no significant baseline difference between the groups
in terms of age, body mass, BMI, FIT index, waist-to-hip ratio,
resting heart rate, aerobic capacity, SBP and DBP. However,
there were significant differences between the treatment and
control groups for maximal voluntary contraction pre- and post-
intervention (Table 1).
For SBP, there was no interaction effect between the treatment
and control groups (
p
=
0.17), however there was a significant
time effect (
p
=
0.036), with SBP being lower post-intervention.
The treatment group showed a reduction from 123
±
9.1 to 120.6
±
7.3 mmHg, while the control group showed a reduction from
130.6
±
6.4 to 120.3
±
4.8 mmHg (Fig. 1). There was, however,
no significant difference in the percentage change in SBP
between the two groups (
p
=
0.26) (Fig. 1).
For DBP, there was no interaction effect between the treat-
ment and control groups (
p
=
0.25), however there was a very
significant time effect (
p
=
0.0079) with DBP being lower post-
intervention. The treatment group showed a reduction from 78
±
5.1 to 75.5
±
4.9 mmHg, while the control group showed a
reduction from 83.88
±
4.1 to 78.3
±
4.2 mmHg (Fig. 2). There
was, however, no significant difference in the percentage change
in DBP between the two groups (
p
=
0.31) (Fig. 2).
Discussion
The main finding of this study was that the middle-aged women
experienced a significant reduction in resting systolic and
diastolic blood pressure in response to five consecutive days
of laboratory monitoring, regardless of which group they were
in (control or treatment). The findings are contrary to previous
studies, which reported the hypotensive effects of isometric
handgrip training, although in most previous studies, a control
group was not used. Since both groups experienced reductions
in BP, the hypothesised hypotensive mechanisms of isometric
handgrip exercise may not apply to the short-term isometric
handgrip-training protocol used in the present study.
A unique finding of the study was that sitting quietly for 15
minutes a day for five consecutive days, whether performing
isometric handgrip training or not, had a lowering effect on rest-
ing blood pressure. Numerous studies have focused on the effects
of relaxation techniques on BP. A study performed by Peters
et
al
. (1977) found that relaxation techniques, as well as ‘sitting
quietly’ (when performed twice daily for 15 minutes each), elic-
ited BP reductions.
18
Individuals who were taught the relaxation
techniques, however, had greater BP reductions.
18
In addition,
the relaxation-technique group had greater reductions over time
(over a 12-week period).
18
Possible reasons for these reductions
may have been related to a decreased activation of the hypotha-
lamic–pituitary–adrenal axis and/or the sympathetic nervous
system associated with the relaxation technique.
19,20
McGrady
et al
. (1987) investigated the relationship between
cortisol, the relaxation response and high BP. The author found
a significant effect of relaxation training on lowering hypotha-
lamic–pituitary–adrenal axis activation, which was associated
with a reduction in BP levels.
20
Albright
et al.
(1991) examined
the effect of a stress-management programme on BP levels
and found that baseline measures of systolic and diastolic
blood pressure decreased significantly after participation in the
Fig. 1. SBP time responses (mean
±
SE) and percent-
age changes of the control (
n
=
9) and treatment (
n
=
9)
groups. *Time effect,
p
=
0.036.
160
140
120
100
80
60
Pre
Post
SBP (mmHg)
Control
Experiment
Time
0
–5
–10
–15
Control
Experiment
% Change SBP
Fig. 2. DBP time responses (mean
±
SE) and percent-
age changes of the control (
n
=
9) and treatment (
n
=
9)
groups. *Time effect,
p
=
0.0079.
0
–2
–4
–6
–8
–10
Control
Experiment
% Change DBP
Control
Treatment
100
80
60
40
DBP (mmHg)
Pre
Post
Time
