For much of history, high levels of intense daily exercise was probably a necessary requirement for human survival . However, in most industrialized countries the necessity for physical activity to sustain life is declining. As a result, we are seeing a decline in physical fitness in many of these populations.
The purpose of this article is to explore the scientific literature to uncover the role that physical activity plays in the maintenance of good health and the avoidance of chronic disease. We will also discuss what sorts of exercise are best, and why, for some people, exercise may not be a great option.
What is Exercise?
Physical exercise refers to any bodily activity that enhances or maintains physical fitness, health, and wellbeing .
The idea that physical activity is important for health and disease prevention is not a new concept but has been appreciated for millennia. Indeed, Hippocrates (∼450 BC) stated that the body falls sick when exercise is deficient.
The Global Burden of Disease Study carried out by the World Health Organization included physical inactivity as one of the most important risk factors threatening global health .
In fact, research from the U.S. Centers for Disease and Prevention has attributed 23.3% of U.S. deaths to no regular exercise.
It’s important to note that weekly exercise doesn’t have to be that long to obtain these benefits.
Health Benefits of Exercise
1) Enhances Brain Health
Studies show that physically inactive children perform worse academically than their active counterparts .
Indeed, aerobically fit children outperform unfit children in tests for decision-making power.
Exercise also increases IGF-1. IGF-1 promotes neuronal growth, survival, and differentiation and improves cognitive performance.
Exercise enhances Klotho, the anti-aging and brain-boosting protein.
One study found that three 60 minute sessions of moderate physical activity per week increased memory. This was possibly due to increased blood flow to certain parts of the brain (hippocampi) .
Even in old people, aerobic exercise can increase cognition, brain size, and power .
Studies have shown that without a regular exercise regime the brain deteriorates and loses cognitive power much faster .
In fact, one study found that elderly people who engage in aerobic exercise had bigger brains . Non-aerobic yoga or toning exercises did not produce the same effect.
One study found that, in obese children, physical activity caused improved executive function and mathematics test scores .
By strengthening neurogenesis, metabolism, and vascular function, exercise promotes brain plasticity .
Moderate physical activity increases neurotrophins, proteins that support brain plasticity (ability to change). As such, exercise is probably even more important for the young (<25), developing brain .
Exercise also promotes brain plasticity by strengthening neurogenesis, metabolism, and vascular function .
Swimming training improves cognitive functions in rats and lowers the accumulation of damaged proteins .
By regulating growth factors, exercise increases brain function .
2) Increases Heart Health
Many studies have shown that regular physical activity is associated with a reduced risk of cardiovascular disease .
One long-term study looked at the effects of regular exercise on men and women over the age of 73. It found that total exercise, exercise intensity, and leisure time intensity were all associated with a lower risk of heart attack .
For women, the beneficial effects of exercise on the heart requires just 1 hour of walking per week .
Furthermore, the benefits of exercise extend to those who already have heart disease. Several studies have shown that exercise can reverse existing heart disease.
Low-intensity exercise (<45% of max intensity) improves the health of people with heart disease .
A very recent study confirmed that regular walking is the best form of physical activity for heart health .
3) Limits Diabetes and Metabolic Syndrome
In one study, every extra 500kcal burned per week through exercise decreased the risk of diabetes by 6% .
Exercise increases insulin sensitivity .
40 minutes of intense exercise per week reduced the risk of diabetes in middle-aged men .
Weight loss via exercise can reduce the risk of diabetes by 40-60% among overweight individuals .
Moderate physical activity for >150 minutes per week was found to be more effective than the drug metformin .
Regular exercise is also an important tool for treating existing diabetic conditions. For example, one study showed that diabetics who walked at least two hours per week had 39-54% less chance of dying .
Resistance training (e.g. weights) might help regulate blood sugars more than aerobic exercise .
4) Reduces Stress, Anxiety & Depression
People who engage in regular physical activity experience less depressive and anxious symptoms .
Both aerobic (e.g swimming) and anaerobic (e.g. weight training) exercise effectively lowers depression and enhances mood .
Exercise may be as effective as anti-depressant medications for reducing depression .
Individuals who maintain a reasonable level of aerobic fitness are less likely to relapse into depression .
High levels of physical activity are associated with improved heart rate variability scores (stress resilience marker) .
One study found that college students who exercised regularly experienced less stress and hassle than those who didn’t .
Participation in Hatha Yoga classes was found to significantly reduce perceived stress .
Another study found that regular physical activity buffered the stressful effects of widowhood in elderly subjects .
In one study, both African dance (rigorous exercise) and yoga caused significant improvements in stress levels .
As well as reducing mental stress, some forms of exercise are very effective at reducing cellular stress. For example, yoga has been shown to improve antioxidant status and limit oxidative damage .
5) Improves Sleep Quality
The idea that exercise helps sleep has existed for thousands of years .
People who work out on a treadmill at 7:00 am sleep longer, experience deeper sleep cycles, and spend 75 percent more time in the most reparative stages of slumber than those who exercise at later times that day.
Similarly, people who exercise regularly may have improved thermoregulation. This means they can cool down more efficiently before sleep (important for deep sleep cycles) .
Exercise may improve sleep quality by improving your circadian rhythm. Many studies have shown that routine exercise can shift the circadian system towards a healthy light-dark cycle [55, 56, 57, 58].
Exercise can also help sleep by boosting BDNF and metabolism in the day time, both of which help sleep at night.
Individuals undergoing cancer treatment often suffer from impaired sleep quality. A suitable exercise regime can help these people sleep better, possibly by affecting sleep-influencing cytokines, such as IL-6 .
The most positive effects on sleep quality occur when exercise is completed 4-8 hours before bedtime .
Evidence suggests that exercise does not need to be intense to elicit a positive effect on sleepwalking intensity is fine .
Exercise is a great option for insomniacs looking to avoid the negative side effects of sleeping pills .
For sleep, the best times to exercise are in the morning or at about 4-5PM.
If you exercise in the morning, it will help sleep because of increased BDNF and metabolism in the daytime (which helps you sleep at night).
If you exercise at about 4-5PM, it will help you sleep because exercise raises your body’s temperature for about four to five hours; after that, your core temperature decreases, which signals your body to start shifting into sleep mode.
Aerobic exercise is better for sleep because you want to increase your body temperature as much as possible since that benefits slow wave sleep.
6) Boosts Longevity
A large number of population studies over the last 50 years have shown that low physical activity is associated with increased total mortality .
In one experiment, people who went from unfit to fit in 5 years had 44% less chance of dying than those that stayed unfit .
Another study found that the physical fitness of healthy middle-aged men is a strong predictor of death. Just small increases in physical fitness are associated with a significantly lowered risk of death .
Men who hold or improve their levels of physical fitness are less likely to die from all causes than persistently unfit men .
The older you are, the greater the impact physical activity will have on your life expectancy .
These longevity benefits can be achieved by relatively small amounts of activity .
7) Helps Prevent Brain Degeneration
Individuals who exercise regularly have lower rates of age-related memory and cognitive decline than sedentary people .
In fact, one study showed that women who exercise the most have a 20% lower risk of developing cognitive impairment .
Resistance training exercises can improve the memory of elderly individuals with prior memory problems .
One study found that individuals older than 65 had much less chance of dementia if they exercised at least 3 times per week .
Regular physical activity, especially resistance training, can protect against the development of Alzheimer’s disease .
Exercise may protect against Alzheimer’s disease by reducing homocysteine levels .
8) May Prevent and Treat Cancer
In fact, a very recent study found that exercise can reduce the chances of getting 13 different types of cancers .
Physically active individuals have 30-40% less risk of colon cancer than those that are inactive.
One study demonstrated that moderate physical activity (e.g. mowing lawn) is more protective than low-intensity (e.g. walking) .
Intense exercise and walking both reduce the risk of breast cancer .
9) Increases Bone Health
Bone density can be increased with regular physical activity, especially resistance training.
This is why the National Institute for Health recommends weight-bearing exercises, which force you to work against gravity, for good bone health . Examples include weight training, hiking and stair climbing.
Resistance training is better than traditional pharmacological and nutritional approaches for improving bone health. This is because it influences other risk factors for osteoporosis, such as strength, balance, and muscle mass .
One study looked at schoolgirls who engaged in three sessions of high-impact exercise per week. After two years the girls had experienced a “substantial bone mineral accrual advantage” .
Similarly, both Tai Chi and resistance training prevent bone density loss in elderly women .
Regular weight-bearing activities are especially important in preventing loss of bone density and osteoporosis in postmenopausal women (87).
Improved bone health from resistance training is achievable with light weights. For example, one study found that low weight, high repetition resistance training increased bone density by 8% in adults .
10) Increases Metabolism and Fat Loss
One study found that 45 minutes of hard exercise increased post-exercise energy expenditure. This revved up metabolism lasted for 14 hours .
As mentioned above, exercise can increase muscle mass. Higher amounts of muscle mass increase metabolism. This helps you burn more calories, even at rest, meaning you can eat more and stay lean [93, 94, 95].
Regular physical activity can mitigate the risks associated with being overweight or obese .
11) Increases Muscular Strength
Exercise increases functional strength and, thus, can make everyday activities easier, especially for the elderly .
One study instructed forty individuals with a bone disease to complete a 3-month supervised resistance exercise program. The participants had an increase in lean body mass (muscle) and reported improved quality of life .
In elderly individuals, resistance training can limit muscle loss associated with old age .
12) Reduces Back Pain
The science suggests that most forms of exercise are equally effective at treating back pain .
In one study, 2.5 years of aerobic exercise was enough for sufferers of lower back pain to significantly lower their intake of pain medication .
13) Increases Libido and Sexual Energy
Exercise frequency and physical fitness enhance attractivity and increase energy levels. Both of these make people feel better about themselves. Increased self-worth leads to greater sexual desires and performance [105, 106].
Men who engage in regular physical activity are less likely to experience erectile dysfunction (107).
14) Helps With Arthritis
One study found that arthritic subjects who engaged in a water exercise program experienced improvements in physical function and less pain .
For arthritis sufferers, regular exercise can increase functional ability (e.g ability to climb stairs) and range of motion .
15) Increases Growth Hormone and Testosterone
The type of exercise you decide to engage in will depend on your specific health goals. For example, I personally choose to do yoga because it improves stress resilience more than other exercises .
Regardless of the type of exercise you decide to engage in, there are four basic principles of an effective exercise program:
- Overload – you should engage in an activity that is harder than your normal or habitual baseline. Essentially, this means that you must push past your comfort zone at each training session .
- Progression – Over time, you should steadily and safely increase the amount of effort .
- Adaptation – Using the principles of overload and progression effectively, your body will adapt to function at the new performance level with comfort .
- Specificity – Benefits from physical activity and exercise are specific to the tissues and organs subjected to progressive overload. Thus, you should train in a way that strengthens your weakest areas to create a healthy, balanced body .
What’s most important is that you avoid being inactive. In a way, it’s more important to avoid inactivity than engage in intense exercise. This is why I recommend standing desks or treadmill desks.
Couple this type of continuous, low-intensity activity with just 60 minutes of moderate-intensity aerobic activity per week and you will be far healthier than your inactive counterpart.
Start slowly. Cardiac events, such as a heart attack, are rare during physical activity. But the risk certainly does increase when someone suddenly becomes much more active than usual.
If you have a long-term health condition, such as arthritis, diabetes, or heart disease, then it might be best to speak with your doctor first to find out how exercise might affect you.
Pregnant women should avoid overly intense physical activity.