Answer
Sylvia is not a great athlete and she wants to get fit rapidly . She thinks the way to do this is to exercise as vigorously as possible and make her heart beat as fast as possible during exercise. This, is not a prudent course of action for the reasons given below.
During physical activity, if the heart rate is too fast the ventricles do not have enough time to fill maximally. A cascade of harmful consequences follow from this:
The stroke volume decreases
The volume of the cardiac output (CO) declines
Blood pressures falls
There is insufficient blood supply/oxygen to the tissues.
When nervous tissues (CNS) are starved of oxygen, several unpleasant consequences might follow:
lightheadedness, palpitation, chest pain, shortness of breath(SOB) and loss of consciousness (LOC).
Work Step by Step
Sylvia would do well to build up her body physique slowly. The following information regarding heart rate and exercise should be useful:
Most people have a normal heart rate of 60-100 bpm, but this varies with age sex and physical condition. Resting heart rate is usually best measured just when one gets awake and before starting any physical tasks.
For a young woman of Sylvia's age and in her physical condition (poor), the normal heart rate would be about 79-84 bpm
If she becomes a good athlete, she might expect her heart rate (HR) to fall to around 54-60 bpm
In calculating their maximal heart rates athletes usually employ the formula 220 bpm- persons age
If we assume that Sylvia is 20 years old, her maximum rate at which her heart should be allowed to beat is 220 bpm-her age
i.e. 220-20 = 200 bpm
For moderate exercise her recommended target rate for a good workout would be 50-70% of 200 bpm = 100-140 bpm
For vigorous exercise the recommended target range would be 70-85% of 200 bpm =140-170 bpm
These are just sample calculations and not health recommendations. They just represent an example of the careful planning that Sylvia should do before starting her exercise program. This way she would not run the risk of damaging her health by poorly informed overzealousness.
