You may have noticed that the graph in Example 6 shows that the number of calories burned by males is greater than the number of calories burned by females for each sport. This is true because, according to the Mayo Clinic, men usually have less body fat and more muscle than women of the same age and weight. The human body burns more calories to maintain muscle, whether during activity or at rest.

Did you know that you can go cross country skiing with your dog? To learn more about cross country skiing, visit xcski.org. These are just a few of the things you can do at xcski.org:

• View a listing of cross country skiing resorts.
• Check the snow conditions for various regions of the country.
• View a list of cross country skiing equipment and services.

Sample answer:

One reason that the Swedish athletes may have had a higher oxygen uptake than American athletes is because of differences in training and conditioning.