WHEN we compare the lifestyle of today’s adult population with that of 50 to 100 years ago, one of the most striking differences is how sedentary our lifestyle has become. Unfortunately, this change in lifestyle is an important contributor to the epidemic of chronic lifestyle diseases that plague our population.

This week we will take a look at the importance of exercise in improving our health. Epidemiologic surveys have suggested that, as a population, Jamaicans do not get enough exercise. The Jamaica Health and Lifestyles Survey III (2016-2017) found that 82 per cent of the population had low physical activity defined as not meeting the recommendations for exercise of the World Health Organization. This low level of activity has important consequences for our health as a country.

What are the dangers of a sedentary lifestyle?

If we were to look at 24 hours of the day and breakdown our physical activity during this time period, we would find that activity can be separated into four levels of exertion — sleep, sedentary activities, low-level activity, and moderate-/high-level activity. Sedentary activity can be thought of as low-level physical activity while sitting, lying, or reclining. Examples would include working at a desk, watching television, or lying on the couch using devices. Data from adults in the United States suggest that we spend approximately seven to eight hours each day sleeping, being sedentary or performing low levels of activity. For the average adult in the United States only 0.2 hours each day is spent doing activities at a moderate or vigorous level of exertion. There is a relationship between the amount of time that is spenteach day in sedentary activity, the risk of dying from cardiovascular causes, and the risk of death overall. Increases in the amount of time that is spent sedentary has also been associated with the risk of Type 2 diabetes, cardiovascular, disease and potentially some types of cancer. Given these associations, it has been suggested that we should try to spend less time in sedentary states. Aside from decreasing the amount of time in sedentary states, there are suggestions that increasing the amount of time spent in moderate to vigorous physical activity can improve some of the risk of our modern sedentary lifestyle.

What types of exercise are there?

There are different forms of exercise. These would include aerobic exercise (running, swimming, riding a bicycle, playing football), resistance exercises (weightlifting, bodyweight exercises), bone strengthening exercises (impact sports such as running, weightlifting), balance exercises, and flexibility exercises. The research linking exercise with improved cardiovascular and other health outcomes has primarily been done with aerobic exercise. When considering the efficacy of exercise, we think not only of the type of exercise, but also the intensity and duration for which it is done. Resistance exercise has also been proven to have some benefits for cardiac risk factors. The remaining types of exercise have been shown to improve muscle strength, to have positive effects on the activities of daily living, to reduce fall risk, and to improve bone health. Some forms of exercise, such as yoga, can combine light aerobic exercise, resistance, balance, and flexibility

What are the benefits of exercise?

Most of the research looking at the benefits of exercise on improving clinical outcomes has been done using moderate or vigorous intensities of aerobic exercise. Data from resistance training has also shown some promise in improving clinical outcomes. The proven benefits from regular aerobic exercise are myriad and include reduction in mortality; reduction in atherosclerotic cardiovascular disease; reduction in risk of Type 2 diabetes; reduction in risk of stroke, reduced risk of lung, breast and colon cancer; reduced risk of hypertension; reduced risk of dementia and Alzheimer’s disease; improved cognition; improved mood; improved sexual health; better sleep; less weight gain; and reduced symptoms of anxiety and depression.

In patients who have already been diagnosed with coronary artery disease and congestive heart failure, aerobic exercise has been shown to improve outcomes, patient functioning, and patient well-being. It is interesting to note that, although most of the benefits from exercise are derived over the long term, positive benefits can be noted after just one session with improved mood, reduced anxiety, and improved sleep and cognitive function being seen. While the benefits of exercise are greatest in those who have a lifetime of regular aerobic exercise, it has been proven that starting exercise at any age results in significant benefits. Resistance training does not have as much data, particularly in terms of reducing cardiovascular risk, but has been shown to help prevent age-related loss of muscle mass, to aid in physical functioning, to improve glucose control, improve bone health, and reduce the risk of falls. There does not appear to be good evidence that resistance training will reduce atherosclerotic disease, although there is some question as to whether it may produce some benefit in blood pressure control.

How much exercise do I need to do?

Currently it is suggested that, for cardiovascular benefit all adults should do moderate or vigorous aerobic exercise. The difference between the two types is a question of intensity. Moderate exercise includes brisk walking, dancing, gardening, slow cycling (less than 10 miles per hour) or doubles tennis. If moderate exercise is the sole means of exercise, then it is recommended that adults do 150 minutes per week. Vigorous exercise includes running, hiking uphill, heavy gardening (continuous digging), swimming laps, singles tennis. If vigorous exercise is the sole means of exercise, then the recommendation is for 75 minutes per week. It is important to note that, although we traditionally will tell patients to do 30 minutes of moderate exercises five days per week to achieve 150 minutes, research has found that the total amount of exercise in the week is the important thing. So, a patient who has limited time during the week may decide to do one hour on Saturdays and Sundays and 30 minutes mid-week. Another patient may feel more comfortable doing 10 minutes three times daily as opposed to 30 minutes at one time. More recently, studies have been done looking at what is termed high-intensity interval training. In this form of exercise repeated short intense efforts of aerobic exercise are done. The duration of the intense efforts varies from as low as a few seconds to several minutes. A rest period follows each intense effort, and periods of exertion and rest are alternated for the exercise period. The major advantage of high- intensity training is it’s time efficiency. It does appear to increase fitness and exercise ability like more traditional forms of exercise. There does remain the question as to whether the long- term benefits noted with longer duration exercise are present and this remains an area of active study. In terms of other forms of exercise aside from aerobic, the American Heart Association suggests that adults do resistance exercise two days per week for the benefits described above. The inclusion of balance and flexibility exercises, although not formally recommended, are likely of benefit.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Correspondence to info@caribbeanheart.com or call 876-906-2107