Blood Pressure Classifications and Associated Health Risks
Blood pressure is the pressure exerted by the blood on the walls of blood vessels. This is useful information because it tells us how well the heart is pumping blood, how healthy the blood vessels are, and whether there are restrictions in the vascular system that are impeding blood flow.
The usual readings refer to resting blood pressure in the brachial artery, measured by placing a cuff around the upper arm. Blood pressure fluctuates with each beat of the heart; the maximum pressure occurs when the heart beats and blood is ejected into the arterial system (systole) and the minimum pressure occurs when the heart relaxes between beats (diastole).
The table that follows outlines the blood pressure classifications and their associated health risks.
|Low blood pressure (hypotension)||<90||<60||Not considered a health risk, but may be indicative of related issues|
|Normal blood pressure||90 – 120||60 – 80||No health risk|
|Pre- high blood pressure||120 – 140||80 – 90||Increasing risk of cardiovascular disease|
|High blood pressure (hypertension)||>140||>90||hypertension is a health risk in terms of cardiovascular disease (Stroke/CHD), kidney dysfunction and certain types of dementia|
Effects of Exercise on Blood Pressure
Short-term:In order to meet the extra demands for blood flow during moderate sustained cardiovascular exercise, the systolic pressure typically increases to around 140 – 160mmHg. In other words, the heart is contracting more forcefully. However, the diastolic blood pressure stays the same (McArdle, Katch, & Katch, 2006). Diastolic pressure is indicative of the resistance to flow in the blood vessels between beats and this does not vary much with moderate exercise. During the recovery period after moderate exercise there is a decrease in systolic blood pressure temporarily below pre-exercise levels for up to 12 hours.
However, during heavy resistance training involving sustained muscle contractions, compression of the blood vessels can occur. This compression restricts the blood flow causing both systolic and diastolic pressures to increase.
If the breath is held whilst straining to lift a heavy weight, then pressure on the vena cava can temporarily reduce blood flow back to the heart. When the lift ends and the breath is released, this can cause a rebound effect and a ‘surge’ of blood flowing into the heart, which briefly, but significantly, increases blood pressure. This is known as the ‘valsalva effect’. Therefore clients with hypertension or coronary heart disease should avoid strenuous, high intensity resistance training because of the strain it places on the heart. In particular, they should avoid holding the breath as they lift.
Long-term:With regular cardiovascular training, resting blood pressure is reduced by as much as 10mmHg in those who already have mild to moderate hypertension. In addition, the duration of diastole increases, which improves coronary blood flow and decreases the overall stress on the heart.
The Benefits and Risks of Cardiovascular Training
There are numerous proven health benefits to be gained as a result of cardiovascular training. At the same time these benefits should be weighed against potential health risks. This helps to decide upon the safest and most effective programmes for your clients. The table that follows summarises those benefits and risks.
|Health Benefits||Potential Health risks|
|Improvements in everyday function, such as walking, stair climbing, shopping and gardening. Increased bone density in specific areas of the skeleton placed under load (particularly from high-impact exercise modalities) Decreased risk of CHD and other chronic degenerative conditions Modest reductions in high blood pressure Improved blood cholesterol profile Reduction of body fat/maintenance of body fat levels within a healthy range Improved control of blood sugar which is crucial for regulating diabetes Decreased stress and anxiety||Increased risk of injuries such as: Muscle strains Joint sprains Muscle imbalances through participation in certain modes of exercise Increased workload on the heart Increased amount of carbon dioxide produced Increased amount of lactic acid produced Decreased body fat to below recommended levels in some athletes|
(Central YMCA Qualifications, 2010)