The genetic and physical make up of humans has not changed significantly since those days, but our levels of physical activity have. In addition, with each subsequent generation, levels of physical activity have reduced - the highest participation in physical activity occurs among school-aged children and adolescents, but this tends to decrease with age. A study of 1032 participants, found that after age nine, physical activity decreased by 38 minutes per year, while weekend physical activity decreased by 41 minutes per year. Additionally, at around 13.1 years in girls and 14.7 years of age in boys, the level of physical activity went below the recommended 60 minutes of physical activity per day (1).
In addition, with each subsequent generation, levels of physical activity have reduced
In Australia, conservatively more than 8000 deaths occur annually due to lack of physical activity, costing not only lives and suffering, but also millions of dollars to the health care system. Increased physical activity has been associated with increased life expectancy, as well as reduced risk of heart disease, stroke, hypertension, obesity, diabetes, cognitive decline and Alzheimer's disease (2,3) and much more. The single biggest killer in Australia today is cardiovascular disease (CVD) and an individual who undertakes regular physical activity is half as likely as his sedentary counterpart to contract CVD (4,5,6).
A large number of studies have reported that physical activity not only reduces the risk of, but also protects against coronary heart disease (7,8,9). Additionally, in a cohort study of 743,498 men, aerobic fitness in late adolescence was a good predictor of a heart attack later in life. However, obese men with high aerobic fitness had a higher risk of heart attack than lean men with low aerobic fitness.
Therefore, it is important to be physically active and maintain a healthy weight to keep the risk of heart attack at its lowest (10).
High Blood pressure, or hypertension, is characterised as any blood pressure over 140/90, with the optimal being 120/80. Exercise resulting in weight loss, has been shown to have significant benefits in reducing blood pressure. Numerous large population-based studies (11,12,13) have demonstrated an inverse relationship between physical activity and blood pressure. In addition, interventional studies where individuals were trained to do more physical activity, demonstrated that increased exercise works to lower blood pressure (14,15). Furthermore, a randomised, controlled trial, found exercise training is effective in lowering blood pressure in overweight, sedentary patients with high-normal or mildly elevated blood pressure, and that weight loss is of added benefit when combined with aerobic training (16).
Physical activity has been shown to decrease mortality and increase life expectancy. In a study of 252,925 men and women, those doing moderate activity (at least 30 minutes on most days of the week) decreased mortality risk by 27%, whereas those who met recommendations for vigorous activity, at least 20 minutes, three times per week - not much if you really think about it - had a 32% reduction of mortality risk (17), a finding consistent with many other studies (18,19,20). And it is not too late to start now no matter how old you are. In a 4.9-year longitudinal study of 9,777 men, it was discovered that those who improved from unfit to fit, reduced their all-cause mortality risk by 44% and cardiovascular mortality by 52%, compared to those who remained unfit (21).
Inflammation and triglycerides
Inflammation is the underlying condition in many chronic illnesses, including CVD and cancer. Physical activity decreases inflammation and, additionally, those with higher cardio fitness levels have lower circulating levels of inflammation markers such as of IL-6, CRP and fibrinogen (22). Physical activity and fitness are also associated with improved plasma lipid (fat) profiles, including the ratio of high-density lipoproteins (HDLs) to low-density lipoproteins (LDLs), and plasma triglycerides. Triglycerides decrease by 24%, while HDLs increase by about 8%, in response to regular physical activity (23,24). Studies have also shown similarly favourable findings in diabetes (25).
Low levels of physical activity and cardio-respiratory fitness are associated with the development of metabolic syndrome and type 2 diabetes. In one study, older men and women, who were in the lowest third of cardio-respiratory fitness, had a 10-fold higher risk of developing metabolic syndrome than those who were in the highest third. There was a strong inverse association between fitness and metabolic syndrome, as well as a significant relationship to all the components of metabolic syndrome (26).
Additionally, a low fitness level has been found to be an important risk factor for incidence of type 2 diabetes - men with the lowest 25% of fitness had a relative risk of diabetes that was four times higher compared to those in the highest 25% (27). It seems that both physical activity and fitness are separately and independently associated with metabolic risk profile (28) i.e., they are both contributing factors to reducing the risk of metabolic syndrome.
Just as important as the amount of exercise for diabetes is the timing
Incorporating more exercise to the day-to-day routine is crucial for sufferers of type 2 diabetes. In type 2 diabetes, insulin is in short supply, or is difficult for the body to utilise; exercise has been shown to improve the body's sensitivity to insulin. Not only does exercise help improve the diabetic condition, it can also help reduce the risk of developing type 2 diabetes altogether. A Harvard University study examining the exercise habits of more than 70,000 women, showed that a 40 minute walk every day reduced type 2 diabetes risk by 40%, and with a longer walk the risk could be decreased by an even larger percentage.
Exercise also helps to increase blood flow, which is important to help reduce the risk of neuropathy, a common neurological disorder associated with type 2 diabetes. In addition, studies have shown that a short-term reduction in daily physical activity negatively affects insulin sensitivity.
One small step for diabetes. Just as important as the amount of exercise for diabetes is the timing. Much of the damage done in diabetes is done by the circulating sugar and/or high insulin levels causing oxidation, inflammation and acidosis.
Going for a walk 10 or so minutes after eating, particularly after a large dinner can have a direct and rapid impact on lowering blood sugar and subsequently the amount of insulin required to control the sugar.
It is very important to bear in mind that this small change to a day's routine can make a big difference in managing diabetes.
Effect on immune system
The immune system may be enhanced or depleted, depending on the intensity of physical activity (29) - both too little and too much exercise is proven to be detrimental to the immune system. For example, there is a high incidence of upper respiratory tract infections (URTI) in professional athletes (50-70% getting an infection in the two weeks following a marathon), which suggest that too much exercise can act as an immunosuppressant. Similarly, longitudinal studies have shown that moderate exercisers can overcome URTIs in half the time that an elite athlete does. Studies have also demonstrated similar findings with a decrease in mucosal (salivary etc) immunity with excessive exercise (30).
While excessive exercise may have a detrimental effect on the immune system, research has suggested that moderate levels of exercise can be beneficial to the immune system. Blood lymphocyte concentrations of a sedentary person are comparable to that of a high performance athlete, whereas the lymphocyte count is higher in a person who undertakes regular moderate exercise. Research suggests that regular, but not excessive exercise, improves the immune system (31,32).
Osteoarthritis (OA) is the second most common cause of disability in the developed countries and Rheumatoid Arthritis (RA), has also become a major health concern (33,34). Both are degenerative diseases of the joints, which can be improved with the implementation of moderate aerobic and weight bearing exercise. Research shows that short term gains of muscle strength, and a range of movement can increase the functionality of patients suffering from OA or RA. In addition, improved fitness levels have been shown to reduce the risk of gout, another form of arthritis, in physically active men (35).
Research suggests that regular, but not excessive exercise, improves the immune system (31,32).
Different forms of activity have been shown to have important impacts on our hormones and endocrine system. In the period prior to, during and after exercise, the endocrine system reacts in order for the body to function effectively and at optimum levels. Simultaneously, hormones governing the body's regulation, such as epinephrine and norepinephrine, are produced in greater quantities to assist the body in operating efficiently.
Additionally, physical activity has demonstrated positive effects on mental health, and has been shown to be more effective than drug therapy without any deadly side effects and works well alongside counselling therapy for depression and anxiety. It has been shown to improve individuals' mood, reduce anxiety and stress, and increase self esteem. Physical activity has been demonstrated to bring about positive structural brain changes and plasticity, as well as alter the production of neurotransmitters including Gamma-Aminobutyric acid (GABA). If you want to be smarter make sure you get enough exercise.
Drugs reduce exercise benefits
On the other side of the equation a number of medications can have a negative impact on the level of physical activity. For example, the most prescribed drugs worldwide, statins, which are used to lower cholesterol, reduce the effectiveness of exercise. A recent study found the statin previously sold under the brand name "Zocor," hindered the positive effects of exercise for obese and overweight adults by 85%. The study also found that this statin decreased the effectiveness of the mitochondria (power house) in the muscles.
...statins, which are used to lower cholesterol, reduce the effectiveness of exercise.
It seems that statins block the ability of exercise to improve the fitness levels of the individual who takes them. Participants in the exercise-only group increased their cardio-respiratory fitness by an average of 10% compared to a 1.5% increase among participants also prescribed statins. Additionally, skeletal muscle mitochondrial content, the site where muscle cells turn oxygen into energy, decreased by 4.5 percent in the group taking statins while the exercise-only group had a 13 percent increase, a normal response following exercise training.
With the new year upon us it is time to get serious about our physical activity. There are just far too many benefits. It doesn't have to be much - just a little bit every day is enough to get you started on a better health journey.
DISCLAIMER: Dr Peter Dingle is a researcher, educator and public health advocate. He has a PhD in the field of environmental toxicology and is not a medical doctor.
Dr Peter Dingle (PhD) has spent the past 30 years as a researcher, educator, author and advocate for a common sense approach to health and wellbeing. He has a PhD in the field of environmental toxicology and is not a medical doctor. He is Australia’s leading motivational health speaker and has 14 books in publication.