It’s hard to know how much exercise you need given all the conflicting information. Some say that walking a mile or two a day is plenty while others believe you need to be doing marathons and triathlons. Fortunately, there are many studies showing the health benefits gained from exercise and the volume, duration and intensity need to realize these benefits. So, how much exercise do you need?
The Benefits of Exercise:
Physical activity has been shown to have a number of physiological and psychological benefits. Some benefits of physical activity include:
- Cardiovascular Disease: Physical activity has been shown to reduce the risk of developing cardiovascular disease by 35% (Macera & Hootman 2003).
- Cancer: There is strong evidence that physical activity reduces the risk of colon, breast, and endometrial cancers. There is weaker evidence that physical activity reduces the risk of ovarian, lung, and prostate cancers. There is either no or insufficient evidence for all other cancers (Friedenreich & Neilson 2010). To be specific, research has shown that physical activity can reduce the risk of colon cancer in men by 30% to 40%, and breast cancer in women by 20% to 30% (Lee 2003).
- Stroke: Highly active individuals have a 25% lower risk of stroke incidence or mortality than less active individuals (Lee & Folsom 2003).
- Type 2 Diabetes: Moderate physical activity was found to reduce the risk of diabetes in men by 40% (Jefferis & Whincup 2012). Additionally, those individuals with diabetes who walked for at least 120 minutes a week, had a 39% to 54% reduced risk of mortality (Gregg & Gerzoff 2003).
- Obesity: Physical activity has been shown to prevent weight gain, promote weight loss, and maintain weight loss (Donnelly & Blair 2009).
- Osteoporosis: Physical activity helps prevent osteoporosis (Nguyen & Center 2000).
- Depression: Physical activity has been shown to reduce the risk of becoming depressed (Teychenne & Ball 2008). Physical activity has also been shown to reduce the symptoms of depression (Dunn & Trivedi 2001).
- Alzheimer’s disease & Dementia: Physical activity has been shown to prevent or delay the onset of Alzheimer’s disease and dementia (Rockwood & Middleton 2007).
- Cognitive function: Physical activity has been shown to improve cognitive function in children (Ellemberg & St-Louis-Deschenes 2010) and adults (Kramer & Erickson 2007).
- Stress: Physical activity has been shown to reduce stress (Smits & Tart 2011).
- Mood: Physical activity has been shown to improve mood (Reed & Buck 2009).
- Self-Esteem: Physical activity has also been shown to increase self-esteem (McAuley & Blissmer 2000).
Volume is the total amount of physical activity accumulated over a period of time, usually a week. Research has shown that volume is more important for health benefits than exercise duration or intensity (U.S. Dep. 2008).
- 0-150 minutes a week: Any amount of physical activity is beneficial. In fact, the incremental gains from the first 150 minutes of aerobic exercise a week are the largest (see chart) (U.S. Dep. 2008).
- 150-300 minutes a week: Adults are recommended to get at least 150 minutes per week (30 minutes a day, 5 days a week) of moderate intensity aerobic exercise or at least 75 minutes of vigorous intensity aerobic exercise, or an equivalent combination of the two (O’Donovan & Blazevich 2010). Substantial health benefits accrue to individuals meeting this target (all of those listed in the first section except colon cancer, breast cancer, and substantial weight loss).
- 300+ minutes a week: Adults who get at least 300 minutes of aerobic exercise a week gain the health benefits of those who exercise 150 minutes a week, but to a greater degree (see chart). Individuals who exercise 300 minutes a week also gain protection from colon and breast cancer as well as an increased likelihood of weight loss (U.S. Dept 2008).
- Strength training: Strength training offers the independent benefits of muscular strength, endurance, and mass. It assists in the maintenance of basal metabolic rate and lean body mass (to aid weight loss). Strength training also promotes independence and helps prevent falls in the elderly (Pollock & Franklin 2000). Strength training for at least 30 minutes on 2-3 non-consecutive days a week is recommended. Research supports doing 8-12 repetitions of 8-10 different exercises targeting all major muscle groups. (O’Donovan & Blazevich 2010).
Duration is the length of continuous time an individual spends exercising during an average session. Duration has little effect on the health benefits of exercise.
- Bouts of less than 10 minutes: There has been little research studying bouts of less than 10 minutes, although some studies have shown that these short bouts of exercise are just as effective as bouts of 10 minutes or longer (Strath & Holleman 2008).
- 10 minute bouts: Exercising in 10 minute bouts has been shown to be as effective as exercising in longer continuous bouts (Murphy & Blair 2010).
- Spread out to at least 3 days a week: Individuals who exercised in longer bouts on 1-2 days a week had a lower mortality risk relative to inactive individuals. However, the overall mortality risk was lowest for individuals who spread their exercise out over at least 3 days a week (Lee & Sesso 2004).
The intensity of an activity is measured by its Metabolic Equivalent (MET). The MET of an activity is measured by the rate of energy expended during that activity relative to the rate of energy expended while at rest. Low intensity activities (standing, walking slowly, and doing most household chores) have an MET between 1.1 and 2.9. Moderate intensity activities (walking fast, doubles tennis, and biking slowly) have an MET between 3.0 and 5.9. Vigorous activities (jogging, swimming, singles tennis and biking fast) have an MET of 6.0 or higher. As a rule of thumb, people engaged in moderately intense physical activities can talk, but not sing. People engaged in vigorous physical activities cannot say more than a few words without taking a breath (U.S. Dep. 2008).
- Low: Prolonged time spend sitting has been associated with increased mortality risks, independent of exercise levels (Patel & Bernstein 2010). Taking short low-intensity activity breaks from sitting has been show to counteract many of these negative outcomes (Healy & Dunstan 2008). Additionally, low intensity exercise has been found to produce the most positive effects on mood (Reed & Buck 2009).
- Moderate: All of the health benefits listed in the first section can be attained through moderate intensity exercise. As a general rule, an individual needs 2 minutes of moderate intensity exercise to gain the same health benefits of 1 minute of vigorous intensity exercise (O’Donovan & Blazevich 2010).
- Vigorous: Vigorous activity has been shown to improve aerobic fitness better than moderate intensity activity as measured by VO2max (Swain 2007). Vigorous activity also appears to reduce the risk of cardiovascular disease (Swain & Franklin 2006), body fat (Tremblay & Despres 1990) and all-cause mortality (Wen & Wai 2011) to a greater degree than moderate activity, after controlling for total energy expended.
- Children aged 5-16: Children have been found to need more exercise than the average adult. Children are recommended to get at least 60 minutes of moderate-to-vigorous aerobic exercise a day (U.S. Dep. 2008).
- Individuals 65 and older & disabled: Individuals aged 65 and older as well as those who are disabled are recommended to meet the guidelines for adults aged 18-65 if possible. If not possible, these individuals are recommended to get as much exercise as their health will allow (U.S. Dep. 2008).
- Can you exercise too much? It is possible to exercise too much. Overtraining can cause various types of injury. In extreme cases, too much exercise can cause sudden cardiac arrest, especially in those with coronary artery disease and those who are habitually inactive (Haskell 2007). Continuous moderate to high intensity exercise of over 1.5 hours has been shown to temporarily depress the immune system for 3-24 hours (Gleeson 2007). Overtraining has also been shown to cause fatigue, performance decline and mood disturbance (Meeusen & Duclos 2006). There is a point where these risks overtake the incremental benefits of added exercise. While it appears to be above 420 minutes a week, where exactly that point is has not yet been determined.
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