CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
258
AFRICA
Elevations in BP occur in both men and women with increas-
ing age, however such increases seem to be greater among post-
menopausal women. None of the above studies have investigated
the effects of isometric handgrip training on BP levels in middle-
aged females (40–60 years old). These studies have also lacked
a control group that does not perform any isometric handgrip
training.
The purpose of this study was, therefore, to (1) determine
the effects of short-term isometric handgrip training on BP in
middle-aged females, and (2) compare these results to a control
group who would not be performing any isometric contractions.
Based on past research showing general BP decreases following
isometric handgrip training, it was hypothesised that perform-
ing isometric handgrip contractions for 180 seconds a day, for
five consecutive days, at 30% of maximal voluntary contraction
would reduce the resting BP levels of middle-aged women.
Methods
Eighteen middle-aged women who were untrained yet physically
active were recruited telephonically (Table 1). Physical activity
status was determined using the FIT index of Kasari.
15
This index
requires that points are allocated depending on the frequency,
intensity and time spent performing physical activity per week,
with scores ranging from one (minimum activity) to 100 (train-
ing at a high intensity every day of the week). Individuals were
included in the study if their FIT index ranged from 8 to 10. This
would describe individuals who perform a few days of moderate-
intensity physical activity per month, with the duration of physi-
cal activity ranging from 20 to 30 minutes per session.
Participation was voluntary, and written informed consent
was obtained from all participants. The Institution’s Faculty
of Health Sciences Ethics Committee approved this study.
Participants were excluded from the study if they were receiv-
ing pharmacological treatment for hypertension, or tricyclic
anti-depressant medication, if they had heart and/or metabolic
disease (congestive heart failure, diabetes), or had an exagger-
ated BP response to exercise (
≥
40 mmHg systolic, and/or
≥
20
mmHg diastolic following performance of an isometric handgrip
maximal contraction).
The study included initial screening of the participants. They
were asked to complete a medical history form (including demo-
graphic information, information relating to their hypertension,
and reproduction, menstrual and family history). Participants
were also asked to continue with their normal daily routines for
the duration of the study. The pre- and post-testing as well as the
intervention were performed in a human performance laboratory.
The laboratory temperature (20–22°C) and humidity (50–60%)
were kept constant throughout the study.
Pre-testing took place on a Thursday morning between 08:30
and 11:30. Testing involved baseline measures of height, body
mass, and waist and hip circumference. Body mass index (BMI)
and the waist-to-hip ratio (WHR) were then calculated from
these measures. After five minutes of rest, seated resting BP
(ausculatory method, using a calibrated aneroid sphygmoma-
nometer), and seated resting heart rate (HR) (using a Suunto
T6 heart rate monitor) were recorded. Blood pressure measure-
ment was performed according to the recommendations of the
American Heart Association.
16
Following resting BP and HR measurement, a maximal
voluntary contraction (grip strength) test was performed using
each hand (right and left). This value was used to determine
the appropriate magnitude of contraction (set at 30% maxi-
mal voluntary contraction) required during the intervention. A
sub-maximal treadmill test was then performed (single-stage
treadmill test) to estimate each participant’s aerobic capacity.
17
Participants were randomly assigned to either the isometric
handgrip training group (
n
=
9) or the control group (
n
=
9).
The intervention was performed on five consecutive days of
the week (Monday to Friday) (session duration ~15 minutes/
session) for both groups. The treatment group had their seated
resting HR and BP measured after five minutes of rest. They
were then required to perform an isometric handgrip contrac-
tion with one hand for 45 seconds at 30% of maximal voluntary
contraction. A period of one minute followed this to act as a
rest period. An isometric contraction using the other hand was
then performed (at 30% maximal voluntary contraction) for 45
seconds. A one-minute rest period followed, and this procedure
was repeated, resulting in four isometric contractions held for 45
seconds (two contractions per hand). This made the total dura-
tion of exercise 180 seconds (three minutes) per session. Five
sessions made the total exercise duration of the treatment group
for the entire study 15 minutes.
BP and HR measurements were recorded immediately before
the first 45-second contraction, and immediately after the fourth
45-second contraction. This indicated the acute response to
the treatment. After sitting for three minutes, HR and BP were
measured again.
Upon arrival at the human performance laboratory, the control
group was required to sit for five minutes. Their resting BP and
HR were then recorded, followed by an additional five minutes
of sitting, and subsequent recording of BP and HR. The control
group did not perform any isometric contractions.
Post-testing was performed on the Monday morning (08:30
and 11:30) following the last intervention session (Friday). All
pre-test measurements were repeated in the post-testing session.
Statistical analysis
Data were analysed using a two-factor (group
x
time) ANOVA
with a Tukey
post-hoc
test to determine specific differences. A
t
-test was used to compare the demographic characteristics of the
TABLE 1. PARTICIPANT CHARACTERISTICS (MEAN
±
SE)
AND
P
-VALUE FOR TREATMENTVERSUS CONTROL
Variables
Treatment (
n
=
9) Control (
n
=
9)
p
-value
Age
47.88
±
1.8
49.88
±
1.4
0.47
Body mass
63.91
±
3.6
71.80
±
5.3
0.32
Body mass index
24.92
±
1.3
27.26
±
0.8
0.15
Waist–hip ratio
0.76
±
0.02
0.77
±
0.02
0.89
Resting HR
67.75
±
4.5
74.50
±
3.5
0.25
SBP: pre-
123.0
±
9.1
130.6
±
6.4
0.50
DBP: pre-
78.00
±
5.1
83.88
±
4.1
0.39
Aerobic capacity
33.93
±
2.30
34.27
±
1.30
0.90
FIT index
32.63
±
8.43
28.88
±
8.20
0.94
MVC (right): pre-
23.38
±
1.24
29.25
±
1.72
0.02*
MVC (left): pre-
23.00
±
1.38
27.50
±
1.64
0.05*
MVC (right): post-
25.63
±
1.10
30.63
±
2.17
0.06
MVC (left): post-
24.13
±
1.50
29.38
±
1.88
0.05*
MVC: maximal voluntary contraction.
