CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
AFRICA
257
Effect of short-term isometric handgrip training on blood
pressure in middle-aged females
JOLENE MORTIMER, ANDREW J MCKUNE
Summary
Objective:
To determine the effect of isometric handgrip
training on blood pressure (BP) in middle-aged women
(47.88
±
1.8 years).
Methods:
Isometric handgrip training was performed over
five consecutive days. In each session, the treatment group
(
n
=
9) performed four isometric contractions of 45 seconds
each at 30% of their maximal grip strength. The control
group (
n
=
9) sat for 15 minutes without exercising, for five
consecutive days. Resting systolic (SBP) and diastolic blood
pressure (DBP) were measured pre- and post-intervention.
Data were analysed using a two-factor ANOVA (
p
≤
0.05).
Results:
Blood pressure readings were reduced in both
groups (SBP:
p
=
0.036; DBP:
p
=
0.0079), however there was
no interaction effect for SBP or DBP.
Conclusions:
The findings suggest that 15 minutes of sitting
per day for five consecutive days is just as effective as isomet-
ric handgrip training for reducing BP levels. Future research
is required to investigate the optimal isometric handgrip
training stimulus required to reduce resting BP levels.
Keywords:
isometric exercise, blood pressure, females, middle-
aged
Submitted 26/11/09, accepted 26/11/10
Published online 15/12/10
Cardiovasc J Afr
2011;
22
: 257–260
DOI: 10.5830/CVJA-2010-090
Hypertension is defined as having a systolic blood pressure
(SBP) of 140 mmHg or more, and/or a diastolic blood pressure
(DBP) of 90 mmHg or more.
1
Thirty per cent of the global popu-
lation is believed to suffer from hypertension.
2
It is also believed
to be the cause of 7.1 million deaths per year, and hypertension
is expected to have an increased prevalence of 60% by the year
2025.
3
In South Africa, research has found that about six million
South Africans have hypertension.
4
Even mild stages of hypertension have been shown to increase
the risk of developing more severe hypertension and cardio-
vascular disease.
5
Increases in BP of 20/10 mmHg double the
risk of cardiovascular disease, while reducing SBP by 3 mmHg
decreases the risk of coronary heart disease by 5–9%, and stroke
by 8–14%.
6
The Framingham Heart Study revealed that reducing
DBP by 2 mmHg reduced coronary heart disease by 9% and
stroke incidents by 15%. A 7.5-mmHg decrease in DBP reduced
coronary heart disease by 29% and stroke incidents by 48%.
6
This clearly indicates the benefit of reducing BP levels.
Traditional treatment of hypertension follows the use of phar-
macological agents and lifestyle changes (aerobic exercise, diet,
stopping smoking, losing weight, managing stress, and reducing
and limiting the amount of sodium and alcohol consumed).
6
It
has been found that the use of pharmacological agents as treat-
ment for hypertension is successful in only about 53% of cases
in the USA.
2
Aerobic exercise (e.g. walking, running, cycling and
swimming) has previously been recommended by the American
College of Sports Medicine as the primary exercise intervention
to prevent and treat hypertension, supplementing this with resist-
ance exercise.
6
In addition to aerobic and resistance training, static (isomet-
ric) exercise has been suggested as an alternative exercise inter-
vention to treat hypertension.
2
However, the American College of
Sports Medicine has not provided any guidelines with regard to
isometric training and hypertension.
6
Previous studies on the hypotensive effects of isometric
exercise found that whole-body isometric contractions (using
the arms and legs) chronically reduced BP levels.
7,8
Subsequent
studies have revealed decreases in BP following participation
of hypertensives in isometric handgrip exercise programmes,
and return to pre-exercise BP levels following cessation of
such programmes.
9,10
Further studies have been performed on
medicated hypertensives, on unmedicated hypertensives, and on
young normotensive patients.
1,2,11
Recently, Millar and associates assessed the effects of isomet-
ric handgrip training (using programmed digital hand dyna-
mometers) on medicated hypertensives and determined whether
inexpensive spring-loaded handgrips elicited the same response.
2
These studies found decreases in both SBP and DBP when indi-
viduals participated in an isometric handgrip exercise regime.
The extent of the decrease differed depending on the intervention
variables, including: force of contraction, frequency of exercise
(three, four or five days per week), and duration of intervention
(five, six or eight weeks).
2
The greatest average decrease in SBP (156
±
9.4 to 137
±
7.8
mmHg,
p
<
0.0005) was recorded by Taylor
et al.
(2003) who
had medicated hypertensives perform four two-minute isometric
handgrip contractions with one-minute rest periods in between,
three days per week for 10 weeks.
9
The greatest average reduc-
tion in DBP (86.5
±
2.01 to 71.6
±
3.50 mmHg,
p
<
0.0001) was
observed by Wiley
et al.
(1992) who had the participants (with
high-normal DBP) perform four two-minute isometric handgrip
contractions at 30% of maximal voluntary contraction, three
days a week for eight weeks (24 sessions), with three-minute rest
periods in between contractions.
10
Studies investigating the health benefits of short-term exer-
cise protocols (
≤
10 days of exercise training) are becoming more
popular.
12-14
There are, however, no studies that have investigated
the effect of a short-term (e.g. a five-day) isometric handgrip
training protocol on BP levels.
Discipline of Sports Science, School of Physiotherapy,
Sports Science and Optometry, Faculty of Health Sciences,
University of KwaZulu-Natal, Durban, South Africa
JOLENE MORTIMER, BSps Hons, Biokinetics
ANDREW J MCKUNE, Dtech,
