EXERCISE

A PROSPECTIVE STUDY OF RECREATIONAL PHYSICAL ACTIVITY AND BREAST CANCER RISK

Increased physical activity has been hypothesised to prevent breast cancer, largely by reducing cumulative lifetime exposure to circulating ovarian hormones. However, epidemiologic findings are inconsistent, and there is no consensus on the best way to quantify physical activity. Therefore, a study was carried out to examine this issue in women in the Nurses’ Health study. In 1980 and on subsequent surveys, women were asked about the average number of hours per week spent in various moderate and vigorous recreational physical activity.

During 16 years of follow-up 3,137 cases of invasive breast cancer were identified. It was found that women who were more physically active in adulthood had a lower risk of breast cancer than those who were less physically active. Comparing those who reported engaging in moderate or vigorous physical activity for 7 or more hours per week with those who engaged in such activity for less than 1 hour per week, the relative risk was 0.82. These results, therefore, support the evidence suggesting that higher levels of adult physical activity afford modest protection against breast cancer.
Rockhill, B et al
ARCH. INT. MED. 1999, 159 (19) 2290-96

ECHINACEA PROTECTS ATHLETES

A double-blind, placebo controlled study was carried out to compare the effects of Echinacea, magnesium supplements, and placebo on the immune function of 42 male athletes undergoing an exhausting triathlon sprint.

The group taking Echinacea had significant decreases in interleukin 2R (IL-2R) in blood and urine, and increased IL-6, suggesting a protective effect of echinacea against exertion-induced immunosuppression.

During the training, 3 of the 13 athletes in the magnesium group and 4 of the13 in the placebo group developed colds, while none of those taking Echinacea developed colds.
Berg A, et al,
J. CLIN RES. 1998, 1, 367-380
Courtesy HERBALGRAM

DYNAMIC EXERCISE NORMALISES RESTING BLOOD PRESSURE IN MILDLY HYPERTENSIVE PREMENOPAUSAL WOMEN

Endurance exercise is advocated as adjuvant treatment for hypertension because participation in a dynamic exercise program lowers resting blood pressure. Recently, exercise has been shown to acutely and transiently reduce systolic blood pressure and/or diastolic blood pressure in hypertensive men, an effect that has been termed post-exercise hypotension (PEH). Therefore, a study was carried out on 18 premenopausal women (7 hypertensive and 11normotensive) to determine if PEH occurs in women and to elucidate possible haemodynamic and hormonal mechanisms. Participants wore an ambulatory blood pressure monitor throughout the day after 40 minutes of a rest sham session and 40 minutes of cycle exercise, of which 30 minutes was performed at 60% of maximal oxygen consumption. It was found that systolic, diastolic, and mean arterial blood pressure decreased in the hypertensive women by a mean of 9.5 ? 2.8 mm Hg, 6.7 ? 2.4 mm Hg, and 7.7 ? 2.4 mm Hg, respectively, for up to 7 hours after versus before exercise, whereas blood pressure was similar in the normotensive women.

After exercise, total systemic vascular resistance was lower, and cardiac output, catecholamines, and plasma renin activity were greater than before exercise in both groups of women. Thus, PEH was observed for up to 7 hours after exercise in mildly hypertensive women and was not explained by the haemodynamic and hormonal adjustments that occurred after exercise. The magnitude and duration of PEH may be sufficient to normalise the blood pressure of certain hypertensive women throughout most of the day.
Pescatello, L.S. et al
AM. HEART J. 1999, 138 (5 pt 1) 916-21

COMPARISON OF PAST VERSUS RECENT PHYSICAL ACTIVITY IN THE PREVENTION OF PREMATURE DEATH AND CORONARY ARTERY DISEASE

During the last four decades many studies have shown that people who are more active tend to live longer. Exercise has proven beneficial in many conditions, ranging from osteoporosis to depression to cerebrovascular disease. An important issue that has not been studied much is which is more important in decreasing total and cardiovascular mortality rates: physical activity that was done long ago or that which was done more recently? Therefore, researchers assessed activity levels in 5209 men and women in the Framingham Heart Study from 1956 to 1958 and again from 1969 to 1973. Cox proportional hazards regression was used to calculate the relative risk of being sedentary, both unadjusted and controlling for smoking, weight, systolic blood pressure, cholesterol, glucose intolerance, left ventricular hypertrophy, chronic obstructive pulmonary disease, and cancer. The overall 16-year mortality rate was 37% for men and 27% for women. When both distant and recent activity levels were included along with major cardiovascular risk factors, for recent activity the most active tertile had lower overall mortality rate than the least active tertile for men (risk ratio 0.58) and women (risk ratio 0.61). However, for distant activity there was no difference in overall mortality rate between the most and least active tertiles either for men or for women. Thus, the reduction in overall mortality rates is more associated with recent activity than distant activity and it appears that for sedentary patients, it may never be too late to begin exercising.
Sherman, S.E. et al
AM. HEART J. 1999, 138 (5 pt 1) 900-7

WALKING COMPARED WITH VIGOROUS PHYSICAL ACTIVITY AND RISK OF TYPE 2 DIABETES IN WOMEN

Strong epidemiologic evidence suggests that physical activity is associated with a reduced risk of type 2 diabetes. However, the role of moderate-intensity activity such as walking is not well understood. Therefore, a study was carried out to examine the relationship of total physical activity and incidence of type 2 diabetes in women and to compare the benefits of walking versus vigorous activity as predictors of subsequent risk of developing the disease. The study group consisted of 70,102 women aged 40 to 65 years who did not have diabetes, cardiovascular disease, or cancer at baseline. During 8 years of follow-up there were 1,419 incident cases of type 2 diabetes. After adjusting for age, smoking, alcohol use, history of hypertension, history of high cholesterol, and other covariates, the relative risks (RRs) of developing type 2 diabetes across quintiles of physical activity (least to most) were 1.0, 0.77, 0.75, 0.62, and 0.54. After adjusting for body mass index (BMI), RRs were 1.0, 0.84, 0.87, 0.77, and 0.74. Among women who did not perform vigorous activity, multivariate RRs of type 2 diabetes across quintiles of MET score for walking were 1.0, 0.91, 0.73, 0.69, and 0.58. After adjusting for BMI, the trend remained statistically significant. Faster walking pace was independently associated with decreased risk. Equivalent energy expenditures from walking and vigorous activity resulted in comparable magnitudes of risk reduction.
Hu, F.B. et al
J.A.M.A. 1999, 282 (15) 1433-39

AGEING OF THE CARDIOVASCULAR SYSTEM DURING 33 YEARS OF AEROBIC EXERCISE

With increasing age there is loss of aerobic capacity, which can result in poorer quality of life, reduced chance of survival in an emergency and greater potential for developing hypokinetic diseases. Therefore, a study was carried out to determine the effect of ageing on the circulatory system in middle-aged men during 33 years of physical training. The study group consisted of 15 men initially aged 45 years who took part in an exercise-training programme for 25-33 years. The aerobic training consisted of swimming, jogging, walking and cycling 3-4 times per week. Sessions were for 61-70 minutes at 77-84% of heart rate reserve.

There was no change in resting heart rate, blood pressure, percentage fat or body composition. Minimal cardiovascular losses at maximal work included 5.8-6.8% in minimal oxygen uptake per decade, 25 beats in maximum heart rate and 26 beats in heart rate reserve. Thus, exercise training has a favourable effect on ageing of the cardiovascular system in older men, resulting in minimal loss of oxygen uptake, no rise in resting blood pressure and no change in body composition.
KASCH, F.W. et al
AGE & AGEING 1999, 28 (6) 531-6

EFFECTS OF PHYSICAL ACTIVITY AND VENTILATORY FUNCTION ON RISK FOR STROKE IN MEN

Stroke is a major cause of illness, death, and health expenditures. Physical activity has been found to confer favourable changes on many cardiovascular risk factors and to reduce the risk for cardiovascular disease and cancer. Therefore, a study was carried out to examine the association of leisure-time physical activity and pulmonary function with risk for stroke.

Participants in the study were 4,484 men aged 45 to 80 years who were followed for a mean of 10.6 ?3.6 years. It was found that new stroke developed in 249 men (5.6%). Of these 44 (18%) were haemorrhagic and 205 (82%) ischemic. After controlling for known risk factors for cerebrovascular disease, leisure-time physical activity maintained after 40 years of age was associated with a reduced risk for stroke: relative risk, 0.69 for total stroke and 0.62 for ischemic stroke. Also, risk for stroke increased with diminishing ventilatory function: relative risk, 1.9 for the lowest compared with the highest quintile.

Thus, middle-aged men who participate in leisure-time physical activity and have good pulmonary function seem to have a lower risk for stroke than men who are not active or have diminished pulmonary function.
Agnarsson, U. et al,
ANN. INT. MED. 1999, 130 (12) 987-90

WALKING TO WORK AND THE RISK FOR HYPERTENSION IN MEN

There is good evidence that physical activity reduces the risk for cardiovascular disease, possibly by lowering blood pressure. However, it is not known whether mild physical activity, especially walking, reduces the risk for hypertension. Therefore, a study was carried out to investigate the association of the duration of the walk to work and leisure-time physical activity with the risk for hypertension.

The study group comprised 6,017 Japanese men aged 35 to 60 years with systolic blood pressure less than 140 mm Hg, diastolic blood pressure less than 90 mm Hg, normal glucose intolerance, and no history of hypertension or diabetes at baseline. During 59,784 person-years of follow-up, 626 cases of hypertension were confirmed. It was found that the duration of the walk to work was associated with a reduction in the risk for incident hypertension. The multivariate-adjusted relative risks were 1.00 for a walk of 10 minutes or less (reference category), 0.88 for an 11- to 20-minute walk, and 0.71 for a walk of 21 minutes or more.

It is therefore estimated that for every 26.3 men who walk more than 20 minutes to work, one case of hypertension will be prevented.
Hayashi, T. et al,
ANN. INTERN. MED. 1999, 130 (1) 21-6

EFFECTS OF LIFESTYLE ACTIVITY VS STRUCTURED AEROBIC EXERCISE IN OBESE WOMEN

Obesity is a serious and common health problem. Physical inactivity contributes to weight gain, but only 22% of Americans are regularly active. Therefore, a study was carried out to examine the short- and long-term changes in weight, body composition, and cardiovascular risk profiles produced by diet combined with either structured aerobic or moderate-intensity lifestyle activity. Such activity would include increasing the amount of walking in the daily routine, performing more yard work, and using the stairs when possible. Participants in the study were given a program of either structured aerobic exercise or moderate lifestyle activity and a low-fat diet of about 1200 kcal/d. Changes in body weight, body composition, cardiovascular risk profiles, and physical fitness were assessed at 16 weeks and at 1 year. Mean weight losses during the aerobic group and 7.9 kg for the lifestyle group. The aerobic group lost significantly less fat-free mass (0.5 kg) than the lifestyle group (1.4-kg).

During the 1-year follow-up, the aerobic group regained 1.6 kg, while the lifestyle group regained 0.08 kg. At week 16, serum triglyceride levels and total cholesterol levels were reduced significantly from baseline but did not differ significantly between groups. Thus a program of diet plus lifestyle activity may offer similar health benefits and be a suitable alternative to diet plus structured aerobic activity for obese women.
Anderson, R.E. et al,
J.A.M.A. 1999, 281 (4) 335-40

LEISURE-TIME PHYSICAL ACTIVITY AND THE RISK OF PRIMARY CARDIAC ARREST

It is now generally accepted that regular exercise is associated with an overall reduction in the risk of coronary heart disease, including sudden cardiac death. However, less understood is the exercise intensity required to achieve the cardiac benefit of regular exercise. Therefore, researchers used data from a population-based case-control study to assess the associations of regular high-intensity and moderate-intensity leisure-time physical activity with primary cardiac arrest.

It was found that, compared with subjects who performed none of the activities, the odds ratio for primary cardiac arrest from matched analyses was 0.34 among subjects who performed only gardening activities for more than 60 minutes per week; 0.27 among subjects who walked for exercise for more than 60 minutes per week; and 0.34 among subjects who engaged in any high-intensity activities, after adjustment for age, smoking, education, diabetes, hypertension, and health status. The results suggest, therefore, that regular participation in moderate-intensity activities such as walking and gardening are associated with a reduced risk of primary cardiac arrest.
Lemaitre, R.N. et al
ARCH.INTERN.MED. 1999, 159 (7) 686-90

PHYSICAL ACTIVITY AND BENIGN PROSTATIC HYPERPLASIA

Benign prostatic hyperplasia (BHP), a condition characterised by hyperplastic nodules in the periurethral region and transition zone of the prostate, overall prostatic enlargement, and lower urinary tract symptoms, is highly prevalent among middle-aged and elderly men. Sympathetic nervous system activity, which is decreased by physical activity, is associated with increased prostatic symptoms. Therefore a study was carried out to determine whether physical activity leads to fewer lower urinary tract symptoms. Men who were aged 40-75 years at baseline in 1986 were observed for subsequent incidence of surgery for BHP.

After controlling for age, race or ethnicity, alcohol consumption, and smoking, physical activity was inversely related with total BHP (Odds ratio, OR, 0.75), surgery for BHP (OR, 0.76), and symptomatic BHP (OR, 0.75). Walking, the most prevalent activity, was inversely related to BHP risk; men who walked 2-3 h/wk had a 25% lower risk of total BHP. Therefore, the results indicate that more physically active men have a lower frequency of urinary tract symptoms.
Platz, E.A. et al
ARCH. INT. MED. 1998, 158 (21) 2349-56

MANUAL LABOUR HELPS LOWER BREAST CANCER RISK

Researchers in the US have found that when women work hard physically it is the toil itself, not the lack of energy, that stops menstruation. The physical work causes progesterone levels to drop and ovulation to cease. Exercise is known to lower the risk of breast cancer, and this may be why the incidence of breast cancer is lower in the developing world.
NEW SCIENTIST, 17th Oct. 1999

EXERCISE PREVENTS STROKE AND IMPROVES RECOVERY FROM STROKE

A 13-year study of more than 11,000 men showed that those who took moderate exercise (equivalent to a hour’s brisk walk 5 days a week) had a 46% lower stroke risk than those who did little or no exercise. The biggest reduction in stroke risk was associated with an energy expenditure of 2000-2999 kcal/week. The US study showed that walking, stair climbing, dancing, cycling and gardening reduced the risk of stroke and that the lowest risk was associated with walking 20 km or more each week. Patients who had had a mild or moderate stroke were given three 1.5-hour intensive sessions every week for 8 weeks. These patients had greater improvement in lower extremity motor function and gait speed than control patients who received usual physician care only.
Bonn, D.
LANCET 1998, 352 (9135) 1201

ASSOCIATION OF PHYSICAL ACTIVITY AND HUMAN SLEEP DISORDERS

Symptoms of disturbed sleep are common in the general population, with overall prevalence rates of between 35% and 41%. A study was carried out to investigate the influence of moderate exercise or physical activity on self-reported sleep disorders among a randomly selected population of adults. Sleep disorders were classified as disorders in maintaining sleep, excessive daily sleepiness, nightmares, and any sleep disorder. The results showed that more women than men reported participating in a regular exercise program and having sleep symptoms of disorders in maintaining sleep and nightmares, and that more men than women did regular vigorous activity and walking at a brisk pace for more than 6 blocks per day. Both men and women had significantly reduced risk of disorders in maintaining sleep associated with regular activity at least once a week, participating regularly in an exercise program, and walking at a normal pace for more than 6 blocks per day. Therefore, the data supports the evidence that a program of regular exercise may be a useful therapeutic modality in the treatment of patients with sleep disorders.
Sherrill, D.L. et al
ARCH. INTERN. MED. 1998, 158 (17) 1894-98

EFFECT OF A LOW-IMPACT EXERCISE PROGRAM ON BONE MINERAL DENSITY IN CROHN'S DISEASE

Osteoporosis is a common complication of inflammatory bowel disease, and people with Crohn's disease are at particular risk. Since physical exercise increases bone mineral density (BMD) in healthy young adults and slows the rate of bone loss in later life, a randomised controlled trial was carried out to investigate the effect of exercise on BMD in patients with Crohn's'disease. Participants in the trial were randomised to a control group or a low-impact exercise program of increasing intensity. BMD was measured at baseline and 12 months at the hip and spine.

Nonsignificant gains in BMD occurred at the hip and spine in the exercise group compared with controls, but in fully compliant patients BMD increased by 3.54% at the femoral neck, 2.97% at the spine, 4.1% at Ward's triangle, and 7.77% at the greater trochanter. Increases in BMD were significantly related to the number of exercise sessions completed. Thus, progressive low-impact exercise is a potentially effective method of increasing BMD in Crohn's disease and, if sustained, the increases may reduce the risk of osteoporotic fracture.
Robinson, RJ. et al
GASTROENTEROL. 1998, 115 (1) 36-41

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