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Exercise for Health

1. Exercise and Blood Pressure

2. Osteoporosis

Exercise and Blood Pressure

High blood pressure affects approximately 20% of the human population at some point during their lives.  A person is considered to have high blood pressure when their systolic blood pressure is greater than 140mm Hg and their diastolic blood pressure is greater than 90mm Hg. 

High blood pressure is associated with many health problems including heart attacks and stroke.  High blood pressure causes the heart to work harder.  This can lead to enlargement of the left side of the heart and may eventually cause heart failure.  There is also an increased rate of arteriosclerosis (hardening of artery walls) and risk of blood clots associated with high blood pressure.  Therefore, if left untreated, high blood pressure re-presents a considerable risk to the individual. 

Traditionally, patients suffering with high blood pressure have been prescribed medication such as beta-blockers, in order to control, or reduce, their blood pressure.  These work by decreasing heart rate and the force of the hearts contraction.  However, in 1983 the World Health Organization recommended the use of non-pharmacological approaches as a primary and adjunctive treatment for high blood pressure (World Health Organization, 1983).   Of the non-pharmacological approaches, exercise is considered to be one of the most promising (Wallace, 2003).  The role of exercise in the treatment of high blood pressure is supported by The American College of Sports Medicine (ACSM) and the American Heart Association.  To have a positive effect on blood pressure the preferred exercise type is cardiovascular exercise (i.e. cycling, walking, swimming).  This involves continuous exercise performed at moderate exercise intensity (60-70% of maximum heart rate) for prolonged periods of time (normally more than 20 minutes duration).

Following exercise, individuals suffering with high blood pressure can expect to see a 5-25mm Hg reduction in systolic blood pressure and a 3-25mm Hg reduction in diastolic blood pressure (Tipton, 1991).  In fact even individuals with normal blood pressure can expect to see and average decrease of 3mm Hg for both systolic and diastolic blood pressure (Fagard 1994).

The current ACSM exercise recommendation for individuals with high blood pressure is dynamic cardiovascular exercise (walking, cycling etc) for 20-60minutes, at a moderate intensity (40-70% of maximal heart rate), on 3-5 days a week.

The reduction in blood pressure following training is believed to be primarily due to: 1) increased numbers of the tiny blood vessels (capillaries) that transport blood to muscles and organs such as the skin; 2) Opening of the capillaries at rest causing improved blood flow; 3) a drop in heart rate at rest and at low/moderate work loads; 4) a reduction in resistance to blood flow in the peripheral blood vessels – due primarily to a relaxation of the blood vessels at rest; and, 5) a reduction in the levels of catecholamines (stress hormones) in the blood – although stress hormones have many negative effects perhaps the most important one with regard to blood pressure is the constrictive effect they have on blood vessels.

Resistance training has often been overlooked as a treatment for hypertension, primarily because it is known to elevate diastolic blood pressure during the resistance exercise (Fardy, 1981).  However, a recent review found that resistance training does not raise blood pressure levels significantly (Kelley and Kelley 2000).  This review also reported that circuit training, rather than the traditional repetition strength training, led to greater reductions in blood pressure.  This was likely to be due to the greater number of repetitions, and reduced recovery, utilised with circuit training, compared with traditional resistance training.  Therefore, there is likely to be a greater cardiovascular component to circuit training than there is with traditional resistance training.  Recent research (Delagardelle et al., 2002) found that the positive effects of combined strength and endurance training on left ventricular (the main pumping chamber of the heart) function and peak oxygen uptake were significantly better than endurance training alone.  The authors speculated that the improvement in muscular strength was the major reason for the improvement in heart function.  Resistance training, through increasing the strength of specific muscles, is likely to allow the individuals to exercise at higher levels when performing cardiovascular exercise.  Several reviews of the effects of resistance training on endurance performance have shown this to be the case (Hickson et al., 1988; Marcinik et al., 1991).  This would lead to improved gains in cardiovascular fitness, improved exercise performance, and ultimately greater reductions in blood pressure.  Therefore, although cardiovascular exercise should be the primary exercise treatment of individuals with high blob pressure, resistance training – when combined with cardiovascular exercise – could also prove to be beneficial.

Exercise frequency and blood pressure:

Although exercise frequencies of 1 or 2 days per may result in small reductions in blood pressure, a frequency of 3 days per week is generally considered the minimal frequency for eliciting a benefit in blood pressure reduction (ACSM 1993).  However, greater frequencies result in greater reductions in blood pressure.

Exercise duration and blood pressure:

The minimum exercise duration to elicit a reduction in blood pressure is generally considered to be 10 minutes, however with greater exercise duration (45mins) there is a more significant reduction blood pressure (Inbar et al., 1991). 

Exercise intensity and blood pressure:

It is believed that lower exercise intensities (<70%VO2max ~ 65-70% HRmax) work better at reducing blood pressure than higher intensities (Hagberg et al., 2000).

Effect of Bodyweight on blood pressure:

Excess body fat is often associated with increased blood pressure, and as such weight loss is often recommended as a means of decreasing blood pressure.  However, the reduction in blood pressure that occurs following exercise treatment is not associated with reductions in bodyweight (ACSM 1993) and therefore exercise does not reduce blood pressure through reductions in bodyweight.

Interaction of blood pressure medication and exercise:

Some commonly pre-scribed blood pressure medications such as β-blockers are known to have a negative effect on exercise performance.  This is due primarily to a reduction in cardiac output due to decreased heart rate and force of contraction following β-blocker prescription.  β-blockers may also reduce the level of thermoregulation as well as reduce the effectiveness of exercise to lower blood lipid levels.  For these reasons β-blockers are not normally the medication of choice for combining exercise with blood pressure medication.  ACE inhibitors, calcium channel blockers and central α-agonists have the least negative effects on exercise (Chick et al., 1988).

Exercise recommendations for reducing/controlling blood pressure levels:

1. Use dynamic exercise specifically: walking, jogging, cycling and swimming
2. Exercise for at least 20minutes at a time. For optimum benefits gradually try to increase this to around 40-60minutes.
3. Exercise should be performed at moderate level (60-70% of maximum HR)
4. Exercise on at least 3 days a week. For optimum effects aim to exercise 4-5 days a week.

Osteoporosis

Bones consist of bone cells and an extracellular bone matrix which is made by the bone cells.  Bones are constantly in a process of removal of old bone and building new bone.  Old, worn-out bone is broken down and removed by cells called osteoclasts. The old bone is replaced with new bone by cells called osteoblasts.  The process of building new bone is called ossification.

Osteoporosis, also known as porous bone, occurs when there is a reduction in the overall quantity of bone tissue.  This occurs when the rate of bone reabsorption by the osteoclasts exceeds the new-formation of bone by osteoblasts.  As bone mass decreases the bones become more porous (contain more holes) and become weakened.  This may eventually lead to bone deformity and increased risk of bone fractures.  The occurrence of osteoporosis increases with age.  In both men and women bone mass reaches a peak at around the age of 25-30.  After the age of 30 bone mass slowly starts to decline slowly with age.  This decline in bone density continues with age with some women eventually loosing up to half their cancellous bone density.  The loss of bone density is slightly less in men but some men may loose up to 25% of their cancellous bone density.  Although both men and women are susceptible to osteoporosis, it is 2.5 times more commen in women.

The risk of osteoporosis in women is at its greatest following the menopause.  This is due to decreased production of the female hormone oestrogen after the menopause.  Oestrogen plays an important role in normal bone maintenance by having a stimulatory effect on osteoclast activity.  Other causes of osteoporosis in women include: removal of ovaries before the menopause; amenorrhea (lack of menstrual cycle) caused by extreme exercise or dieting; excessive drinking or smoking.

In men the primary cause of osteoporosis is decreasing testosterone levels.  Testosterone levels don’t usually drop significantly until the age of 60, hence, the way men tend to develop osteoporosis later in life than women.  One of the reasons men are less likely to suffer with osteoporosis is due to males having a denser bone mass to begin with.  Because men have a denser bone mass to begin with, a small loss of bone has less of an effect.

Osteoporosis in also associated with an inadequate intake of calcium, Vitamin C, Vitamin D and Magnesium.  Adults should consume 800-1000mg of calcium, 400mg of magnesium, 400IU of Vitamin D, and 60mg of vitamin C per day.  Of these vitamins and minerals, calcium is the most important.  Adults who are at risk of osteoporosis can increase their intake of calcium to 1000-1500mg per day.  Calcium rich foods include: dairy products (particularly milk), leafy vegetables (brocholli, kale, cabbage etc.), and many fish (tuna, salmon, sardines and haddock)

An individuals level of physical activity also has a major impact on bone density and hence the risk of osteoporosis.  Following 8 weeks of immobilization there is a significant reduction in bone mass.  Therefore, the risk of osteoporosis can be reduced by increasing activity levels.  Bones need regular weight bearing exercise to maintain their bone mass.  Regular weight bearing exercise causes muscles to stretch and contract which stimulates bones to strengthen by increasing osteoblast activity levels.  Good bone building exercises include: running, brisk walking, skipping and weight training.

Other considerations:

You should look to reduce caffeine intake as this has a negative effect on the absorption of calcium.  Intake of Fizzy (carbonated) drinks should also be reduced as this also has negative effects on calcium levels in the body.  The carbon dioxide in the fizzy drinks is acidic.  The body tries to neutralize this with calcium, thereby wasting valuable calcium.  High levels of alcohol consumption will also have a negative effect – moderate levels are said to be beneficial for bone health.

References

American College of Sports Medicine (1993) Position standards: physical activity, physical fitness and hypertension. Medicine and Science in Sports and Exercise. 25, i-X.

American Heart Association (1990) Medical statements, exercise standards: a statement for health professionals from the American Heart association. Circulation. 82, 2286-2322.

Chick, T. W., Halperin, A. K. and Gacek, E. M. (1988) Effect of antihypertensive medications on exercise performance: a review.  Medicine and Science in Sports and Exercise. 20, 447-454.

Delagardelle, G., Feiereisen, P., autier, P., Shita, R., Krecke, R. and Beissel, J. (2002) Strength/endurance training versus endurance training in congestive heart failure. Medicine and Science in Sports and Exercise. 34 (12), 1868-1872.

Fardy, P. S. (1981) Isometric exercise and the cardiovascular system. Physician and Sportsmedicine. 9, 43-53.

Hagberg, J. M., Park, J. J. and Brown, M. D. (2000) The role of exercise training in the treatment of hypertension: an update. Sports Medicine. 30 (3), 193-206.

Hickson, R.C., Dvorak, B.A. and Gorostiaga, E.M.(1988). Pottential for strength and endurance training to amplify endurance performance. Journal of Applied Physiology, 65 (5), 2285-2290.

Inbar, G., Wallace, J. P. and Jastremski, C. (1991) Interaction of intensity and duration on acute postexercise blood pressure reduction. [Abstract]. Journal of Cardiopulmonary Rehabilatation. 11, 320.

Kelley, G. A. and Kelley, K. S. (2000) Progressive resistance exercise and resting blood pressure: a meta-analysis of randomised controlled trials. Hypertension. 35 (3), 838-843.

Marcinik, E.J., Potts, J. and Schlabach, G. (1991). Effects of strength training on lactate threshold and endurance performance. Medicine of Science in Sports and Exercise, 23 (6), 739-743.

Tipton, C. M. (1991) Exercise training and hypertension: an update. In: Holloszy, J. O. Editor. Exercise and Sport Science Reviews. Williams and Wilkins. Baltimore (MD). 447-506.

Wallace, J. P. (2003) Exercise in Hypertension: A Clinical Review. Sports Medicine. 33 (8), 585-598.

World Health organization (1983) Primary prevention of essential hypertension. World Health Organization Technical Report Series 686. Geneva: World Health Organization.

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