Physical activity and diabetes prevention.

Diabetes has reached epidemic proportions worldwide and is associated with a large economic burden, increased risk of cardiovascular disease, and premature mortality. Hyperglycemia is the hallmark clinical manifestation of diabetes and evolves through a multifactorial etiology of genetic, environmental, and behavioral enablers. Approximately 90% of diabetes cases are the non-insulin-dependent phenotype, which is characterized by a progressive deterioration in insulin-mediated glucose disposal, particularly by peripheral tissues. Our hypothesis is that the most proximal behavioral cause of insulin resistance is physical inactivity. Indeed, several streams of scientific research have demonstrated a role for physical activity in the etiology and prevention of diabetes and its related morbidity. In this review we will discuss some of the key observational and experimental studies that have examined associations among physical activity, cardiorespiratory fitness, and non-insulin-dependent diabetes.     

Physical activity and the healthy mind.

Physicians should seek to enhance the quality rather than the quantity of human life. Physical activity programs can increase life satisfaction through an immediate increase of arousal and a long-term enhancement of self-esteem and body image. In the young child competition can cause excessive arousal, but long-term adverse effects are rare. In the adult a reduction of anxiety and stress and a general feeling of well-being reduce the frequency of minor medical complaints, generating important economic benefits. Physical activity programs also help to correct the reactive depression that accompanies conditions such as myocardial infarction. Interest in physical activity should be stimulated from the earliest years of primary school. The allocation of curricular time to physical education does not hamper academic achievement. Rather, through its impact on psychomotor learning, it enhances the total process of intellectual and psychomotor development.     

Physical activity, skeletal health and fractures in a long term perspective

Exercise during adolescence, especially during the pre-pubertal years, builds a skeleton with a high bone mineral density (BMD) and possibly a larger skeleton with a different skeletal architecture. This would lead to a stronger skeleton more resistant to trauma. These changes could be of biological significance for fracture reduction, if they were maintained into old age where fragility fractures exponentially rise. The Achilles heel of exercise is its cessation. Most BMD benefits achieved by exercise appear to be eroded with cessation of exercise. Reduced exercise intensity after a period of high activity, may maintain some residual BMD benefits into old age. A decreased fracture rate in the population could perhaps be achieved by promoting a physically active life style with lifelong high activity. But what happens if the activity in former athletes is reduced to the same level as in individuals who never exercised? The null hypothesis that exercise has no effect on fracture rates in old age cannot be rejected on the basis of any published, randomised, prospective data. Instead we have to rely on retrospective observational and case control studies, all hypothesis-generating, not hypothesis-testing. Existing data suggest that there could be a reduced fracture risk in former athletes. This notion may be correct, but consistently replicated sampling bias may produce the same observation and any biological explanation for this fracture reduction is unclear. Residual structural skeletal benefits, improved muscle strength, coordination and balance are all traits possibly maintained in former athletes after their active career. These traits may possibly reduce the number of fractures in later life.     

Physical activity and stroke in British middle aged men.

OBJECTIVES--To assess the relation between physical activity and stroke and to determine the overall benefit of physical activity for all major cardiovascular events. DESIGN--Prospective study of a cohort of men followed up for 9.5 years. SETTING--General practices in 24 towns in England, Wales, and Scotland (British regional heart study). SUBJECTS--7735 men aged 40-59 at screening, selected at random from one general practice in each of 24 towns. MAIN OUTCOME MEASURES--Fatal and non-fatal strokes and heart attacks. RESULTS--128 major strokes (fatal and non-fatal) occurred. Physical activity was inversely associated with risk of stroke independent of coronary risk factors, heavy drinking, and pre-existing ischaemic heart disease or stroke (relative risk 1.0 for inactivity, 0.6 moderate activity, and 0.3 vigorous activity; test for trend p = 0.008). The association remained after excluding men reporting regular sporting (vigorous) activity. However, vigorous physical activity was associated with a marginally significant increased risk of heart attack compared with moderate or moderately vigorous activity in men with no pre-existing ischaemic heart disease or stroke (relative risk 1.6%; 95% confidence interval 0.96 to 2.8). In men with symptomatic ischaemic heart disease or stroke those doing moderately vigorous or vigorous activity had a risk of heart attack slightly higher than that in inactive men (relative risk = 1.6; 0.8 to 3.3). CONCLUSIONS--Moderate physical activity significantly reduces the risk of stroke and heart attacks in men both with and without pre-existing ischaemic heart disease. More vigorous activity did not confer any further protection. Moderate activity, such as frequent walking and recreational activity or weekly sporting activity, should be encouraged without restriction.     

Physical activity and energy expenditure in lean and obese adult human subjects.

We compared the physical activity of 11 lean and 11 obese men and women over a 7-day period. There were no significant differences in either the amount of movement recorded with an accelerometer (9.5 (SD 3.9) vs 9.9 (SD 2.6) kcounts.day-1), or in the energy expenditure due to physical activity reflected by the difference between the average daily metabolic rate measured by the doubly labelled water technique and the sleeping metabolic rate measured in a respiration chamber and adjusted for fat-free mass: 112 (SD 33) vs 118 (SD 22) kJ.kg-1.day-1. The obese showed a non-significant loss of body mass of 0.5 (SD 1.1) kg, probably due to reduced intake during the 7-day intake recording period.     

Blood and vein-wall fibrinolytic activity in health and vascular disease.

The resting blood fibrinolytic activity of 120 normal subjects and 294 patients with various forms of vascular disease was assessed by measuring the dilute blood clot lysis time and fibrin plate lysis area before and after 10 minutes of venous congestion. The tissue fibrinolytic activity of several of these subjects was assessed in vein biopsy specimens. The results suggested that there was a correlation between blood and tissue fibrinolytic activity and that certain venous diseases, particularly recurrent superficial thrombophlebitis and venous liposclerosis, were associated with a deficiency of blood and tissue fibrinolytic activity.