Exercise is one of nature's magic bullets. It protects against heart disease, diabetes, some forms of cancer, and dementia.

It relieves stress and reduces the odds of depression, hot flashes, and even colds, and improves sleep, bone health, sex, and wound healing. Kudos if you already knew all that, but are you missing some other salient facts? Take our quiz to find out how many exercise facts you know.

Exercise Facts Quiz:

About how far, on average, does an adult have to walk or run to burn the calories in one chocolate M&M candy?

a) The width of a tennis court

b) The length of a tennis court

c) The width of a football field

d) The length of a football field

Without the right type of physical activity, a healthy person starts to lose muscle in which decade of life?

a) 20s

b) 30s

c) 40s

d) 50s

e) 60s

Without weight or resistance training, how much muscle is typically lost per decade?

a) 1-2%

b) 2-4%

c) 3-5%

d) 4-6%

When they get older, women are twice as likely as men to lose muscle to a point of becoming frail.

a) True

b) False

Unless they want to develop big, bulky muscles, women should lift only light weights.

a) True

b) False

Which of these is most effective for preserving and building bones?

a) Swimming

b) Dancing

c) Both are equally effective

To get all the aerobic benefits of exercise, all you need to do is walk at a moderate pace for 30 minutes daily on most days of the week.

a) True

b) False

1. d) The length of a football field, not including end zones. As a rule of thumb, most people burn about 100 calories per mile of walking, jogging, or running.
2. b) Healthy muscles grow until around age 30, and then gradually start to shrink unless they are challenged by weight or resistance training.
3. c) Without weight or resistance training, both men and women typically lose 3-5 percent of muscle per decade after age 30. Loss of muscle leads to a higher proportion of fat, even if there is no weight gain, slowing down metabolism and increasing risks for weight gain, osteoporosis, diabetes, and frailty, which predisposes older people to debilitating falls.
4. a) A British study of more than 600 otherwise healthy men and women, between the ages of 64 and 74, found that 8.5 percent of women were frail, compared to only 4.1 percent of men.
5. b) Although this is a common belief, a female body doesn't naturally have sufficient levels of muscle-building hormones to develop bulky muscles. Weights should always be sufficient to challenge muscles; otherwise, weight-lifting exercises won't produce optimum benefits.
6. b) To maintain or improve healthy bones, it's necessary to work against some type of resistance, from gravity or weight, which swimming does not provide. Good options include walking; jogging; dancing; tennis; jumping rope; aerobic exercise on a treadmill, elliptical machine, or stair stepper; or weight lifting or other resistance exercise.
7. b) For anyone who is sedentary, regular walking at a moderate pace is a good start, but as fitness increases, it's necessary to make the activity more challenging by increasing speed and/or intensity-by jogging or walking up hills, for example, or increasing the resistance on an elliptical trainer. This way, your fitness level will continue to increase.