to early 50s who are generally healthy but
have elevated blood pressure. The GPs
refer these patients so we can prescribe
evidence-based exercise to help them
improve their resting blood pressure without
the need for medication. Regrettably,
some of these individuals will not adhere
to the recommended dose (i.e. frequency,
intensity, duration) of aerobic and resistance
training exercise and subsequently will
require medication to normalise their
resting blood pressure. It should be noted
that these same individuals also usually
have unfavourable cholesterol levels (i.e.
high total cholesterol, high low-density
lipoproteins, high triglycerides and low high-
density lipoproteins – the latter being good
cholesterol) which is another risk factor
for cardiovascular and cerebrovascular
disease, and which has also been shown to
improve with exercise. These same patients
therefore end up on yet another prescribed
medication (usually a statin) to help reduce
this risk factor for cardiovascular and
cerebrovascular disease.
There is substantial research which
illustrates the benefits of regular exercise
training on resting systolic and diastolic
blood pressure. However, most individuals
do not realise that there is a benefit seen
in both acute (immediately following an
exercise session) and chronic (i.e. 10 weeks
or more) exercise training.
Dr Cutler and his colleagues, as part of
his PhD, conducted a very interesting study
which has recently attracted worldwide
attention. They are aware that post-exercise
hypotension (i.e. blood pressure lowering)
occurs in both healthy and hypertensive
individuals following an aerobic exercise
session. The mechanism for acute post-
exercise blood pressure lowering is still not
fully understood, but in brief, it is believed
that post-exercise hypotension has an effect
on nitric oxide. Nitric oxide causes blood
vessels to relax and dilate, and this lowers
blood pressure. For example, Houston and
Hays (2014) gave hypertensive individuals
oral lozenges that generated nitric oxide in
the mouth, and this resulted in a significant
decrease in resting blood pressure (4mmHg
systolic and 5 mmHg diastolic).
What is unique about Dr Cutler’s study
is that the researchers postulated that
normal antibacterial mouthwash has nitrate-
reducing properties on the oral bacteria in the
mouth, and that simply washing the mouth
out with an antibacterial mouthwash would
negate the blood pressure-lowering benefits
of the exercise session. A fascinating and
important research question.
The researchers recruited 23 healthy
individuals who were non-smokers, not
obese (BMI not > 30kg/m 2 ) and had normal
blood pressure. Participants completed
2 treadmill workouts at 65% (moderate
intensity) of their maximal aerobic capacity
(VO 2 max). The subjects completed four
sets of seven minutes running on the
treadmills, with a three-minute rest period
between each exercise bout. The subjects
were randomised such that prior to one
treadmill run they rinsed their mouth
with an antibacterial mouthwash (0.2%
chlorhexidine) and prior to the other with
a placebo (mint flavoured) one. They were
unaware of which they were using in each
instance. Blood pressure and nitric oxide
was measured before the treadmill exercise,
one hour post-exercise and two hours after.
Results: The average systolic blood
pressure was significantly lower at one hour
post-exercise (-5.2mmHg) and at two hours
post-exercise (-3.8mmHg) as compared to
the baseline resting measurement. However,
when the antibacterial mouthwash was
used, the systolic blood pressure response
post-exercise was reduced by 61% (i.e. the
systolic blood pressure only decreased by
2.0mmHg) at the one hour post-exercise
time period and 100% reduced at the two
hours post-exercise period.
Dr Cutler concluded that it appears that
oral bacteria are the key to opening up the
blood vessels, which is itself key to seeing
blood pressure decrease. If the bacteria
in the mouth are removed with the use of
antibacterial mouthwash, nitrite cannot be
produced and the blood vessels remain
in their current state (i.e. they do not relax
and vasodilate after exercise). He further
added that existing studies show that,
exercise aside, antibacterial mouthwash can
actually raise blood pressure under resting
conditions.
Pros: This was a very interesting study. We
have seen a number of gut-related health
and fitness research articles in the past two
years. It is becoming apparent that the oral
and gut microbiomes are far more important
to our health and wellbeing (and fitness) than
was previously suspected.
Cons: It would be beneficial for researchers
to conduct the study with individuals who
were hypertensive, elevated, stage 1 and
stage 2. This would be a good avenue for
future research.
THE QUICK READ
• There is substantial research which
illustrates the benefits of regular
exercise training on resting systolic
and diastolic blood pressure
• Researchers investigated whether
using antibacterial mouthwash
could negate the blood pressure-
lowering benefits of exercise by
reducing the nitrate-enabling
activity of oral bacteria
• Study subjects who rinsed their
mouths
with
antibacterial
mouthwash after an exercise
session had a significantly reduced
systolic blood pressure response
• The researchers suggested that
oral bacteria are the key to opening
up the blood vessels, which is
essential for blood pressure to
decrease.
REFERENCES
Cutler, C., Kiernan, M., Willis, JR., et al., (2019).
Post-exercise hypotension and skeletal muscle
oxygenation is regulated by nitrate-reducing
activity of oral bacteria. Free Radical Biology and
Medicine. 143:252-259.
Houston, M., & Hays, L. (2014). Acute effects of
an oral nitric oxide supplement on blood pressure,
endothelial function, and vascular compliance
in hypertensive patients. Journal of Clinical
Hypertension. 16(7): 524-529.
Dr Mike Climstein, PhD FASMF
FACSM FAAESS AEP
Dr Climstein is one of
Australia’s leading Accredited
Exercise Physiologists. He is a
faculty member in Clinical
Exercise Physiology, Sport &
Exercise Science at Southern
Cross University (Gold Coast).
Dr Joe Walsh, PhD
Joe is an exercise science
researcher. He has worked
in a number of large
international research teams
with study findings presented
around the world. In addition
to working in the university
sector, he is a director of
Fitness Clinic Five Dock and
Sport Science Institute.
NETWORK SUMMER 2019 | 59