CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
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AFRICA
programme.
19
In addition, reactivity to a psychological stressor
(oral quiz) was significantly lower, as revealed by reduced
systolic and diastolic pressure. A reduction in sympathetic nerv-
ous system activity was postulated as a possible mechanism for
the changes observed.
19
Further research is required to examine
the association between resting BP measurements and alterations
in the hypothalamic–pituitary–adrenal axis and/or sympathetic
nervous system in middle-aged women.
The participants’ familiarity with the laboratory environment
may have accounted for the reductions in BP in the present
study, however, research has found that familiarity does not play
a major part in BP reductions in long-term follow-up studies of
hypertensives.
21
Short-term follow-up studies (such as this study)
have not been investigated in terms of familiarity.
In white-coat hypertension, blood pressure is usually persis-
tently elevated in the presence of a healthcare worker, particu-
larly a physician, however, when measured elsewhere, including
while at work, the blood pressure is not elevated.
16
Although it
can occur at any age, this is more common in older men and
women.
16
It is possible that white-coat hypertension may have
caused pre-testing BP values to be higher in our study.
22
The
combination of this, followed by increased familiarity with the
laboratory environment may have caused the reductions seen in
the present study.
An important practical recommendation based on the find-
ings is that future studies aiming to investigate BP should include
a minimum of five days of BP monitoring, so as to (1) maximise
the effect of familiarity on BP readings once the study commenc-
es; (2) minimise the effects of white-coat hypertension on BP
readings upon commencement of the study; and (3) allow for any
other effects to take their course before the study commences.
This would help eliminate bias that may be ‘injected’ into the
study through such effects.
Conclusion
This was a short-term study, which may have accounted for the
similar magnitude of reductions in BP in the two groups. The
effect of isometric handgrip training may possibly only occur
over longer time periods (as supported by previous literature).
Future research should therefore investigate the effect of isomet-
ric handgrip training over extended time periods using a non-
exercise control group. Future studies should also investigate
such an effect on hypertensive individuals (stage I hypertension,
for example), as any changes in BP with training could be rela-
tive to the initial resting BP level.
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