Exercise and Health

Answers by Dr. Tim Allerton, Ph.D., RCEP, Exercise physiologist.

Being physically active decreases your likelihood of developing cardiovascular disease, type 2 diabetes and some forms of cancer (ex. Colon and breast cancers).

Consistent exercise lowers blood lipids, improves glucose and insulin sensitivity, lowers inflammation, lowers blood pressure, reduces visceral adipose tissue and is important for healthy body composition.

Exercise and physical activity also promote improved mental health and cognitive function, and are associated with lower rates of dementia and impaired cognition associated with the aging process.

The most current national recommendations for the total weekly amount of physical activity consist of a target of 150 to 300 minutes per week (30 to 60 minutes per day) of moderate to vigorous physical activity (MVPA).

Here are some updates based on the most recent evidence on how much physical activity is necessary to maintain health and prevent cardiometabolic disease:

For people who perform little to no MVPA, evidence shows that replacing sedentary time with some light physical activity will reduce the chances of developing cardiovascular disease and type 2 diabetes.

Regardless of sedentary time, adding moderate physical activity will reduce the health risks associated with sedentary behavior.

If you are already meeting the target range of 150 to 300 minutes per week of moderate to vigorous physical activity (MVPA), you can gain more benefits by doing more MVPA. The duration of MVPA bout time can be as brief as 10 minutes at a time to accumulate health benefits

References:

A large body of research shows that increasing physical activity and regular exercise will prevent the occurrence of early death due to cardiometabolic disease.

The total amount of years that someone will live (lifespan) is largely determined by genetics, physical activity level and avoidance of unhealthy activities such as poor diet, smoking and sedentary behavior. There is strong evidence that regular moderate to vigorous physical activity (MVPA) will improve healthy aging (healthspan). Those who regularly engage in aerobic and resistance training age with a healthier and more robust cardiovascular, musckuloskeletal and immune systems than those who do not remain active as they age.

A single bout of exercise has been shown to reduce insulin resistance. The beneficial effects of a single bout of exercise can last up to 72 hours. In sedentary people, even light exercise has been shown to improve insulin sensitivity. Exercise turns on metabolic pathways inside the skeletal muscle to increase sensitivity to insulin and lower blood glucose after a meal via a non-insulin related mechanism.

There is also substantial evidence that more regular vigorous exercise promotes greater insulin sensitivity. It is important to note that the effects of a single exercise bout are transient. Regularly engaging in exercise that reduces abdominal body fat (visceral adipose) has been shown to be one of the best ways to reduce insulin resistance.

When most people refer to “aerobic exercise”, what they mean is exercises that specifically challenge the heart and lungs via repetitive and rhythmic movements. Running, swimming, cycling and rowing are all examples of “aerobic” exercises.  These exercises, when done at the appropriate frequency, intensity and duration, are excellent to improve cardiovascular health, blood lipids and chronic inflammation.

The mechanisms of how aerobic exercise improves cardiovascular health have been studied extensively. Consistent aerobic exercise training improves the capacity of the heart to pump oxygen-rich blood by increasing the strength of heart muscle. The lungs adapt by increasing the capacity to extract oxygen from inhaled air and saturate the red blood cells. The skeletal muscle adapts by increasing mitochondrial capacity to be able to utilize a greater amount of oxygen.  These exercises will improve the maximal volume of oxygen one can consume (VO2max). Improving VO2max is one of the single best predictors of health and longevity.

Moderate intensity exercise corresponds to 64 to 76% of your maximum heart rate. Using the rating of perceived exertion scale (RPE), moderate intensity exercise would be classified as fairly light to somewhat difficult (12 to 13 on 6-20 RPE scale). Read more on how to calculate heart rate zones here.

Vigorous intensity aerobic exercise corresponds to 77-95% maximum heart rate. Vigorous intensity exercise should feel somewhat difficult to very difficult (RPE 14-17).

An easy way to calculate your maximum heart rate is to subtract your age from 220. Learn more here.

How fit are you really? Take the NTNU Fitness Calculator.

Cardiorespiratory Endurance Exercise Index
HRR = percent of your heart rate reserve. Your heart rate reserve is the difference between your resting heart rate and your maximum heart rate (HRmax – HRrest). For example, if training at 30% of your HRR, your target heart rate will be your resting heart rate plus 30 percent of the difference between your maximum heart rate and your resting heart rate, e.g. 30% (180 – 70) + 70 = 103. %HRmax = percent of miximum heart rate. %VO2max = percent of maximal oxygen uptake.

Muscle-building activity includes any exercise that places a load on a muscle or group of muscles that causes muscle fatigue or exhaustion. The current evidence-based findings generally recommend resistance training muscle strength activity that involves 2 to 3 days per week of 8 to 10 exercises (in a single bout or session) that incorporate all the major muscle groups. Novice to intermediate exercisers should perform resistance exercises at 60 to 70% of the maximum amount of weight they can lift (aka your 1 repetition maximum, or 1RM), or at a moderate to hard intensity.

Much like “aerobic” exercise, there is an inverse relationship between intensity and time for resistance activity. Resistance activities that are very intense, for example lifting heavy weights, cannot be performed frequently. On the other hand, very light weights can be moved many times. There is good evidence for the health benefits that come from either very intense resistance exercise performed infrequently, or light to moderate resistance exercise performed at a higher volume. A key research finding related to resistance exercise is that, to acquire the benefits of resistance training, the muscle group involved should be sufficiently fatigued regardless of the weight (heavy or light).

Performing resistance training and improving muscle strength and quality are critical to the healthy aging process. Maintaining and improving muscle strength is important to maintain posture and functional independence. Most importantly, improving muscle quality is essential to prevent the onset of frailty and disability.

Resources for exercise examples:

Similar to muscle-strengthening exercise, bone-strengthening exercises require the muscle and bone to be placed under a stress or “load” that causes fatigue. Engaging in regular resistance exercise is important to prevent or delay age-related bone loss.

Osteoporosis is a major concern for women age 40 and over. Load bearing exercises have been shown improve the bone mineral density of femoral neck (in the hip) and spine in premenopausal women. Ballistic exercising such a plyometric-type exercises (jumping, bounding, box jumps etc.) are frequently used to improve bone mineral density. Other examples of weight-bearing exercises include body weight push-ups, squats and lunges. Aerobic based exercises like running and jogging are also considered weight-bearing because the body weight is supported at all times throughout the movement. Pool-based exercises are not weight-bearing because the water relieves the pressure gravity on the bone and muscles. Other exercises such as yoga are considered weight bearing exercise, however, little is known about the capacity for yoga to increase bone density.

Exercise “connotes intentional physical activity for improving health and fitness”. Typically, exercise has goals set for time, duration and intensity.

Physical activity is defined as Any bodily movement produced by skeletal muscles that results in energy expenditure above resting levels”. Physical activity broadly encompasses exercise, sports and physical activities done as part of daily living, occupation, leisure and active transportation. All activity accumulated outside of structure “exercise” time is considered physical activity.

The desired outcome for exercise should be based on 1) current health status, 2) body weight, 3) physical abilities/limitations, and 4) functional goals. Generally, one should seek measurable improvements in cardiorespiratory fitness, muscular strength and endurance, flexibility, balance, agility, reaction time and power. Cardiorespiratory fitness would comprise the capacity for the heart and lungs to deliver oxygen-rich blood to the working muscle during exercise.  As one measure of cardiorespiratory fitness, your heart rate during exercise* and your resting heart rate can be easily measured during exercise with the help of wearable devices (fitbit, garmin, apple watch, etc.)

Lack of improvement in any of the components of physical fitness might suggest that your exercise amount or intensity are insufficient for your goals.

In some rare circumstances, excessive exercise can result in “overtraining”. Overtraining is associated with lethargy, excessive muscle soreness, frequent illness, insomnia and lack of desire to exercise.

*LifeOmic Note: Other measures your heart health and health benefits of exercise include your blood pressure, body mass, glucose levels, cholesterol and triglyceride levels, cortisol and inflammation markers such as c-reactive protein. These can be measured at your local pharmacy and through physician-ordered or direct-to-consumer blood tests such as those available through InsideTracker. You can see how your lifestyle and health behaviors such as exercise are impacting various biomarkers and measures of fitness, such as heart rate, with LifeOmic’s LIFE Extend app.

References:

There is no ideal physical activity within a given week. There is an enormous body of research to support the dose-response relationship between physical activity and health. The current recommendation for general health is a daily goal of at least 30 minutes per day of moderate to vigorous physical activity (MVPA).

For those who cannot attain this daily activity goal, the “weekend warrior” pattern of exercise where the majority of physical activity is accumulated over the course of couple of days during the week is a possible strategy. This pattern of physical activity has been shown to improve cardiorespiratory fitness for “weekend warriors” in a comparable way to those who engaged in more standard exercise patterns (3-5 days per week).

Note: The “weekend warrior” study referenced was done in healthy men with no cardiovascular risk factors. The safety of this exercise pattern should be considered if you have existing CVD or possess one more risk CVD risk factors. Learn more here.

For general health and in healthy people there is not likely a best time of day to engage in physical activity or exercise. Finding a time of day that you can consistently accomplish your exercise goals is best. Finding what works best for the individual maximizes adherence and resulting benefits.

However, in some clinical populations, the time of day appears to be an important consideration when managing outcomes.

*LifeOmic Note: Regular physical activity has consistently been associated with better sleep. Despite common beliefs, evening exercise is not consistently associated with decreased sleep quality in otherwise healthy individuals. However, you may want to avoid intense exercise within an hour of your bedtime due to heart rate changes.

There are no current recommendations for amount of time one should maintain peak heart rate. Since there is an inverse relationship between intensity and time, one would expect to not be able to maintain peak heart rate for very long. However, sprinting type exercises that elicit very high or peak heart rate have been shown to be effective at increasing mitochondrial content and VO2max.

Integrating sprints into a standard aerobic exercise routine is a good way to start experimenting with vigorous and maximal exercise.

Types of wearable of devices include:

  • Heart rate monitors
  • Accelerometers
  • Pedometers
  • Pulse Oximeters

These wearables attempt to estimate/measure:

  • Energy expenditure
  • Heart rate
  • Step Counts
  • Standing Time

For healthy people free of metabolic disease, exercise in the fasted state (up to 36 hours fasted) has been shown to be relatively safe when compared to exercise in the fed state. However, exercise performance can be diminished depending on the length of the fast and the type or intensity of exercise.

People with type 1 diabetes or insulin dependent type 2 diabetes should take special care when choosing to exercise in conjunction with fasting. Exercising in the fasted state without adjustment in insulin can increase the likelihood of developing hypoglycemia, which can be life threatening.

Exercise in either the fasted or fed state alters fuel (fat vs. carbohydrate) use during exercise and after a subsequent meal. Exercising in the fasted state significantly increases the use of fat as fuel. However, exercise after a meal (containing carbohydrates) will decrease fat use and increase carbohydrate use during exercise. There is no strong evidence that exercising in the fasted state leads to greater fat loss over a long period of time.

While there doesn’t appear to be a specific advantage to exercise or training in the fasted state in terms of performance, there are some interesting findings related to the impact on health. Exercising in the fasted state has been shown to reduce intramuscular triglycerides (implicated in insulin resistance) compared to fed exercise (Vieria et al 2016). Exercising in the fed state improves the blood glucose response to a subsequent meal (Edinburgh et al 2018).

Stress hormones such as epinephrine, norepinephrine, cortisol, etc. mobilize fuel, in the form of glucose, amino acids and free fatty acids, to increase their availability during the fight or flight response. Acute exercise raises the levels of stress hormones in the body in order to increase the availability of fuel (glucose, fat, and amino acids) to meet the demands of the working skeletal muscles. However, when exercise is preformed consistently, the hypothalamic pituitary adrenal axis (HPA) causes less stress hormones to be released to meet the demands of the body during exercise. This also manifests in lower HPA axis activity in the resting state. People that are physically fit typically have lower circulating stress hormones at rest.

Exercise Recommendations that Fit You

Answers by Dr. Tim Allerton, Ph.D., RCEP, Exercise physiologist.

Control of blood glucose is the primary goal in the management of type 2 diabetes. Since there is a demonstrated dose-response relationship between exercise and insulin sensitivity, people with T2D should exercise most days of the week, or avoid letting two days elapse between aerobic exercise sessions.

Resistance training in addition to consistent aerobic exercise will help improve long-term glycemic control.

Additionally, those with T2D should reduce sedentary time as much as possible. Losing weight (5-7% of one’s body weight) should also be emphasized as a part of a diet and exercise plan for someone with T2D.

There is generally strong evidence that physical activity reduces the risk of developing bladder, breast, colon, endometrium, esophagus, renal and gastric cancers. For example, high levels of physical activity are associated with a 24% lower risk of developing colon cancer in men and women. There are no current recommendations for specific forms of physical activity that would best impart protective effects against certain cancers.

For cancer patients and cancer survivors, the American College of Sports Medicine generally recommends the standard US Physical Activity Guideline for Americans (PAGA) of 150 minutes per week of MVPA and at least two days per week of resistance exercise.

Patients undergoing chemotherapy or recent surgery should take special care to allow adequate time for recovery and healing. However, patients undergoing treatment should attempt to avoid inactivity as much as possible.

LifeOmic Note: Exercise has been associated with a lower relative risk of cancer mortality and recurrence in patients with cancer, as well as fewer side effects of treatment. Maintenance of a healthy weight, a healthy diet and physical activity are also associated with reduced breast cancer risk.

A priority for aging populations is to avoid the development of frailty and disability. Strength and balance are important components of physical fitness and should be emphasized in order to reduce the incidence of falls in aging populations. Studies that have focused on strength and balance as an intervention in aging men and women reveal significant improvements in walking speed, balance and the ability to sit up from a chair and then walk immediately.

Incorporating exercises that mix aerobic and resistance activities, like dancing, yoga and games, are effective strategies for aging populations to maintain independence. Additionally, emphasizing resistance training and adequate protein intake to maintain or build muscle mass is an important strategy to avoid sarcopenia.

It is a common misconception that 10,000 steps per day is the necessary target for increased daily non-structured physical activity. Studies indicate that healthy adults can take between 4,000 to 18,000 steps per day. People taking less than 5,000 steps per day have been shown to have a higher prevalence of cardiometabolic risk factors that those taking a higher number of steps. However, when those people with low step counts increased their daily step counts, a variety of risk factors, including waist circumference, were improved.

A major limitation of step counting is that it does not tell you anything about the intensity of the activity at the time the steps were counted. Steps taken during a structured exercise bout may be more valuable in terms of improving health than those taken at leisure. For those individuals who are completely inactive or very sedentary throughout the day, a walking program is a great way to improve heart health and reduce the risks associated with physical inactivity. However, in order to gain greater benefits exercise, should proceed into moderate to vigorous intensity.

Some other considerations:

  • 10,000 steps per day might be a good target for people engaging in a low amount physical activity.
  • Steps should be taken over and above those taken in the course of habitual or incidental activities, in bouts of at least 10 minutes.
  • According to recent research, 7,000-8,000 steps is a reasonable threshold for (heart) health.

Most diets are compatible with a wide range of physical activities, exercises and sports as long as caloric needs are met. With any activity and diet, there is some trial and error in terms of amounts of carbohydrate, fat and protein necessary to achieve whatever goal is set (be it health, aesthetic appearance or performance).

The general metabolic needs of the activity (ex. Marathon training) and intention (competition vs. general exercise/fun) will dictate which diet is most appropriate. Training for endurance events typically requires high levels of muscle glycogen, which is replenished after training by consuming additional carbohydrates. However, athletes on a ketogenic diet have also demonstrated the ability to perform these tasks at a high level.

Some important considerations when matching physical activity to diet are:

  • Length of time on the diet. Some diets take time to adapt to and my make you feel lethargic during that time period, like the ketogenic diet.
  • Level of fitness/training or experience with diet. Are you an experienced athlete with several years of training or a novice exerciser? Have you been eating a certain way for a long time or is this diet change new?
  • Use a systematic approach. Don’t change too much at once.

For those with pulmonary issues and or exercise-induced asthma, training during periods of low temperature and or low humidity could exacerbate the symptoms (bronchostriction) of those conditions. Air pollution (motor traffic, industrial pollution, etc.), chlorine in swimming pools and ice rinks treated with chemicals can also increase trigger exercise-induced bronchoconstriction.

Identifying times of day when motor traffic is light will help to reduce the risk of developing exercise-induced bronchoconstriction. Identifying situations that induce symptoms is vital for those with pulmonary issues, as those circumstances appear to be very reproducible. Choosing exercises and intensities that can be completed with reduced or eliminated symptoms will help improve fitness and enjoyment of the activity.

Both aerobic and resistance training have been shown to be effective at reducing the symptoms associated with depression and anxiety when compared to stretching alone. While the mechanisms are not entirely understood, research suggests there are physiological (endorphins neurotransmitters, etc.) and psychological (self-efficacy, distraction, etc.) mechanisms at play.  Additionally, some mind-body practices, such as yoga and tai chi, have promise in this regard.

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