Summer temperatures or intense workouts in hot environments increase your chance for heat stroke.

"There's nothing worse than when you are having an intense workout and Ruben comes on," he said, "but it seems to always happen to me."

Ask your health care provider before trying these intense workouts, especially if you have joint problems.

Over the next year, she cut her calories to 1,800 a day, started cycling, and built up to intense, short workouts.

But once you are there, the machine offers an intense workout in a relatively short amount of time.

A small piece of fruit, "just enough to give you energy for a more intense workout."

He put the 85 football players who showed up for spring practice through an intense workout.

Its promoters say it gives a more intense workout in half the time.

Yet a toddler in a pool partially filled with water may get the most intense workout of any.

After all, who wants an energy crash 45 minutes into a 10-mile hike or intense workout?