People work out in an open-air gym next to the beach in Barcelona, Spain. AP

When it comes to weight-resistance exercise, you can choose free weights such as dumbbells or barbells. Or weight machines, which are often driven by cables or levers. You can use resistance bands or tubes to build strength. Or try pushups and pullups — old standbys that create muscle overload by using your own body weight.

These four basic options for strength training present fitness possibilities for young or old or beginners. And they offer flexibility for use in the gym, your home or in a hotel room during travel.

You'll probably wind up using a combination of the four, and they all have their pros and cons. They are appropriate for all ages and can be augmented with aerobic exercises like walking or runn

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