Cosmopolitan's Cross-Impact Aerobics (1991)

Impossibly thin, gorgeous, and busty — she's a Cosmo girl, after all — Lynda Kelly is the host of Cosmopolitan's Cross-Impact Aerobics, a pleasant, relatively easy-to-follow mixed-aerobics tape for beginning-level exercisers. The 20 minutes of ''dancey'' aerobics are broken into several sequences, and the viewer can follow the instructor for high- impact moves or follow the class for the safer, easier, low-impact version. But Kelly assumes the viewer knows dance terms like the ''grapevine'' and moves through the steps without any explanation — tough, if you're a novice.

The video has some serious omissions: namely, a sketch of aerobics' main benefit (cardiovascular fitness); an explanation of what the target heart rate is and how long you have to sustain it to meet the minimum requirements for cardiovascular fitness (answer: 60 to 90 percent of your maximum heart rate, sustained continuously for at least 20 minutes); and a demonstration of how to take your pulse to see if you're in your target heart rate zone. With such important omissions, the tape misses the mark. Back to you, Jane. C-