blood pressure and heart rate chapter 3. what is blood pressure the force exerted by the blood on...
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Blood Pressure and Heart Rate
Chapter 3
What is Blood Pressure
• The force exerted by the blood on the walls of the arteries (and veins) as the blood is pumped around the circulation.
• Measured in units of mmHg.
• Most common methods of measuring BP is by ascultation (listening for sounds).
Components of Blood Pressure
• Systolic pressure– The highest pressure in the arteries due to the
ejection of blood from the heart into the aorta.
• Diastolic pressure– The lowest pressure in the arteries occurring during
the relaxation phase of the heart– Should measure both 4th and 5th phase.
• Pulse Pressure– Difference in systolic and diastolic pressure; it is the
driving force that propels the blood in the arteries
Resting Blood Pressure
• Optimal – Systolic is < 120 mmHg– Diastolic is < 80 mmHg
• Hypertension– Stage 1: 140-159/90-99– Stage 2: ≥160/≥100
Exercise Blood Pressure
• Varies with age and gender• Fitter individuals usually have lower
exercise blood pressure.• Normal Response to incremental Exercise
– Systolic increases linearly until approaching maximal at which time it begins to plateau. Increases approx. 10-15 mmHg per Met or per 150 - 300 kgm.min-1.
– Diastolic does not significantly change.
Blood Pressure and Heart Rate Response to Exercise
0
20
40
60
80
100
120
140
160
180
200
Rest 150 300 450 600 750 900
Power Output (kgm .min-1)
Blo
od
Pre
ssu
re (
mm
Hg
)
0
20
40
60
80
100
120
140
160
180
200
Hea
rt R
ate
(bp
m)
SBP
4th Phase
5th Phase
HR
Heart Rate
• Number of ventricular contractions per minute
• Usually the same as pulse rate
Palpating Heart Rate
• Heart rates measured at a steady-state (constant power output) should be measured for as long as feasible up to 60 seconds. Minimum time is 15 seconds.
• Heat rates measured after the exercise is stopped but you want to know the HR during the exercise should be measured for 6, 10 or 15 seconds, the shorter the better but must maintain accuracy.
Resting Heart Rate
• Determined by genetics and fitness level• Although lower resting HRs are not always
indicative of higher fitness when comparing across individuals, the general pattern is that more fit individuals have lower resting HRs.
• Within a healthy individual, a decrease in resting HR is indicative if increased CV fitness.
Exercise Hear Rate
• Heart rate increases linearly with increasing power output until approaching maximum at which time it begins to plateau.
• Amount of increase related to fitness
• CR fitness decreases submaximal HR at any power output.
Maximal Heart Rate
• Maximal HR is primarily a function of age
• Fitness, gender, body mass do not affect maximal HR.
• Estimation of Maximal HR– Traditional equation: (220 – age)– Best equation: [208-(0.7 x age)]– SEE for predicting maximal HR is 10-12 bpm.
General Indications for Stopping an Exercise Test in Low-Risk Adults
• Onset of angina-like symptoms• A drop of 20 mmHg or more during steady-state
exercise in systolic BP or a failure of the SBP to rise with an increase in exercise intensity
• Excessive rise in blood pressure:– SBP > 260 mmHg– DBP >115 mmHg
• Failure of HR to increase with increasing power
Power Output on the Bicycle Ergometer
• Power = (Force X Distance)/ Time
• Force = kilograms of resistance applied
• Distance = distance the flywheel travels per pedal revolution (6 meters)
• RPM = number of pedal revolutions per minute
• Units of power = kgm.min-1
• Alternative is watts (1 watt = 6 kgm.min-1)
