According to the American Heart Association, leading a healthy lifestyle through proper nutrition, regular exercise, stress management and sufficient sleep is imperative to control blood pressure. Maintaining normal blood pressure is essential in reducing your risk for coronary heart disease. In addition to preventing cardiovascular disease, a healthy blood pressure plays a role in regulating blood flow during daily activities and physical exercise.
The Function of Blood Pressure
Blood pressure is defined as the pressure exerted by the blood on the vessel walls, measured in millimeters of mercury, or mmHg, by a sphygmomanometer. The two components that make up blood pressure are the systolic blood pressure, or SBP, and the diastolic blood pressure, or DBP. The SBP is the pressure against the arteries when the left ventricle of the heart is fully contracted. The DBP is the pressure against the arteries when the left ventricle of the heart is relaxed or in between beats. Blood pressure is dependent on the balance between cardiac output, the amount of blood pumped out of the heart in one minute, and total peripheral resistance, the resistance of blood vessels on blood flow. The resistance to blood flow is altered by the constriction of dilation of blood vessels called arterioles. This concept is represented by the formula Blood Pressure = Cardiac Output X Total Peripheral Resistance.
Blood pressure is sensed by baroreceptors in the aorta of the heart and in the carotid arteries in the neck. When there is a change in blood pressure, the baroreceptors send a signal to the cardiovascular control center of the brain to alter cardiac output or the diameter of the arterioles. During exercise, a dilation of arterioles occurs in the active muscle to increase blood flow and meet metabolic demands.
Assessment of Blood Pressure
A sphygmomanometer is a blood pressure measurement system made up of an inflatable bladder to indicate the applied pressure, an inflatable bulb to create pressure, and a valve to release pressure. The cuff is placed around the upper arm and pumped up to block blood to the artery. The cuff should be 20 percent wider than the diameter of the limb for proper fitting. A stethoscope is used to listen for the sounds of the pulses. As the pressure is released, the first sound heard is the SBP or upper number. The last sound heard is the DBP or lower number. Blood pressure is recorded as a fraction. For example, healthy normal blood pressure for men is 120/80mmHg. For women, it's 110/75mmHg.
Blood Pressure Response During Cardio Exercise
During cardiovascular exercise such as running, swimming and cycling, normal blood pressure responds with an increase in SBP and no change or slight decrease in DBP. Blood pressure response is proportional to the overall exercise intensity. In other words, as exercise intensity gradually increases, SBP gradually increases. However, if there is a drop in SBP greater than 10 millimeters of mercury from baseline, despite increases in cardio exercise intensity, this is considered an abnormal response. Exercise-induced decreases in SBP may occur in people with cardiovascular disease. Although maximal heart rates are comparable for men and women during maximal exercise, men generally have a higher SBP.
Blood Pressure Response During Resistance Exercise
In contrast to cardio exercise, there is a disproportionately high blood pressure response to resistance training. During isometric exercise, where the muscle is contracted but there is no change in muscle length, both SBP and DBP can increase substantially even at only 30percent maximal effort. An example of an isometric muscle contraction is a sustained handgrip or a sustained pull-up arm hang. Isometric exercises aren't recommended for those with heart conditions. In addition, heavy resistance exercises involving movement of the muscle can cause extreme blood pressure responses. A study measuring arterial blood pressure response to heavy resistance in bodybuilders reported blood pressure responses for 95 percent to 100 percent maximal effort during a biceps curl, single leg press and a double leg press. Both SBP and DBP elevated, with average values exceeding 320/250mmHg for the double leg press. The elevation in pressure was believed to be due to the compression of the arteries by the muscles, a reflex response, and holding the breath. Researchers recommend that the length of the lifting set is the main factor in affecting blood pressure response. Therefore, optimal weight training modality for blood pressure health is three sets of 10 repetitions at 75 percent of maximal effort, with 90 seconds' rest between sets.
The Effects of Medication
Certain medications can affect blood pressure response during exercise. If you're taking vasodilators, calcium channel blockers and angiotensin-converting enzyme inhibitors, the blood pressure response to exercise is variably attenuated and can't be accurately predicted.
References
- The American Heart Association: Prevention & Treatment of High Blood Pressure
- The Journal of Applied Physiology: Arterial blood pressure response to heavy resistance exercise
- European Journal of Cardiovascular Prevention & Rehabilitation: Acute cardiovascular response to resistance training during cardiac rehabilitation: effect of repetition speed and rest periods
