By Dr Lim Chiw Yeh, Consultant, Department of Cardiology
Exercise has both short-term and long-term benefits in people with high blood sugar or Type 2 diabetes (T2D). During an exercise workout, the exercising muscle takes up sugar from the blood circulation. After exercising, the blood sugar level will tend to be lower. Reduction in blood sugar is closely associated with individual’s physical activity duration and intensity. When one exercises, the body becomes more sensitive to insulin (that is the hormone that allows cells in the body to use blood sugar for energy). The effect of increased insulin sensitivity after any physical activity can last from two to 72 hours. In the long term, exercise improves glycaemic control in adults with T2D. Exercise reduces glycated haemoglobin (Hba1c) values by approximately 0.5 to 0.7 percentage points.
If you have been diagnosed with pre-diabetes (higher-than-normal blood sugar level and at risk of developing T2D), lifestyle changes coupled with moderate-intensity exercise and modest weight loss, are greatly beneficial and may even reverse the condition.
Exercise can be broadly split into low, moderate and high (vigorous) intensity categories. Exercise intensity refers to how hard the body is working or the amount of physical energy used when exercising. In low-intensity exercise, there is a steady heart rate without a noticeable change in breathing, for example, you can chat and sing while exercising without running out of breath. At moderate intensity, there may be an increase in heart rate, breathing rate, and body temperature, for example, you are able to hold a short conversation while exercising, but probably not able to sing without getting out of breath. In a highintensity exercise, you will not be able to say a few words without catching a breath.Ideally, most individuals are recommended to:
Flexibility exercise (also refers to stretching) enhances joint flexibility and is highly beneficial for health and well-being, especially in older adults. They generally do not improve glycaemic control unless combined with another type of physical activity or other forms of exercise. Flexibility exercise is generally a low-intensity exercise and is easy to perform, thereby easier for older adults or those who are less fit to start off and adopt into their lifestyle.Aerobic exercise such as brisk walking, jogging, cycling or swimming, is the best type of exercise for heart health. Brisk walking is the safest form of exercise to start if you are uncertain of the level of intensity. Inactive adults should start gradually, with light intensity at a shorter duration (less than 10 minutes), and gradually progress to longer duration and more intensive exercise. Adults with T2D should do no more than two consecutive days of exercise due to the transient nature of exercise-induced improvements in insulin action. Older adults with T2D should aim to get as much aerobic exercise as their physical and mental health allows.Resistance exercise such as weight lifting, using resistance bands, push-ups, and sit-ups, typically results in 10% to 15% improvements in strength, bone mineral density, blood pressure, lipid profiles, skeletal muscle mass, and insulin sensitivity. Balance exercise such as lower body and core resistance exercises, yoga, and tai chi may reduce the risk of falls as it improves muscle strength and balance coordination of the lower limbs. This form of exercise has shown to have benefitted adults with diabetes with affected nerves issues. For the majority who plan to participate in low- to moderate-intensity exercise, it is not necessary to have pre-exercise medical evaluation. However, it is advisable to seek advice from your doctor prior to starting any exercise programme if you are:
Individuals with high blood pressure are advised to participate in at least 30 minutes of moderate-intensity exercise for five to seven days per week. This is associated with a reduction in systolic blood pressure of 5 to 7mmHg. These reductions would translate to a reduced risk of cardiovascular disease of 20 to 30%. Additional resistance training is highly effective in reducing blood pressure further. In the event that high blood pressure is poorly controlled (that is, resting systolic blood pressure surpasses 200 mmHg, and diastolic blood pressure surpasses 110mmHg), one should stop exercising till blood pressure returns to normal level.Resistance exercise that involves straining to lift, push or pull very heavy object, tends to hold one’s breath during muscle contraction and can result in extremely high blood pressure. This is called Valsalva manoeuvre, which is forcefully breathing out against a closed windpipe. It is best to avoid Valsalva manoeuvre during resistance exercise such as intensive heavy weightlifting.Some blood pressure medications may lead to sudden excessive reductions in post-exercise blood pressure. Hence, if you are taking blood pressure medications, do not stop or end an exercise suddenly, but do cool-down exercises before gradually ending your exercise.
Hyperlipidaemia (high cholesterol) means your blood has too much lipids (or fats), such as cholesterol and triglycerides. Physical activity can reduce triglycerides by up to 50% and increase good cholesterol (HDL) by 5 to 10%. Exercise may reduce bad cholesterol (LDL) by up to 5%. These improvements can be achieved through three and a half to seven hours of moderate- to high-intensity exercise per week. Low-intensity exercise rarely reduces bad cholesterol (LDL) to normal or near normal values. Medication, particularly with statins, coupled with exercise and lifestyle intervention, will greatly help in reducing bad cholesterol (LDL) and improving prognosis.
Exercise is important in the prevention of obesity. Maintaining adequate physical activity reduces the risk of weight gain.For weight loss, the goal is to increase energy expenditure by 1,000 to 1,200 calories per week, or slightly more than 150 calories per day. The amount of energy expended depends upon the duration and intensity of the exercise and your initial weight. For example, at 70kg, walking slowly for 60 minutes will burn around 147 calories. Whereas, at 100kg, same activity and duration will burn around 206 calories. Non- weight-bearing exercises such as cycling or swimming help to prevent obese individuals from musculoskeletal injuries. Obese individuals should limit high-volume weight-bearing exercises on a hard surface (such as jogging) to less than two hours a day until a considerable weight reduction is achieved. When weight loss is the desired goal, a diet should be combined with physical activity and the activity gradually increased over time as tolerated. For many individuals, more than 60 minutes per day of activity may be required to prevent weight regain following a significant weight loss.
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Kanaley JA, Colberg SR, Corcoran MH, et al. Exercise/Physical Activity in Individuals with Type 2 Diabetes: A Consensus Statement from the American College of Sports Medicine. Medicine and Science in Sports and Exercise. 2022 Feb;54(2):353-368. DOI: 10.1249/mss.0000000000002800. PMID: 35029593.2020 ESC Guidelines on Sports Cardiology and Exercise in Patients With Cardiovascular Disease: The Task Force on Sports Cardiology and Exercise in Patients With Cardiovascular Disease of the European Society of Cardiology (ESC). Eur Heart J 2020;Aug 29
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