Instead of reinventing the wheel, equipment manufacturers typically take an existing technology and make it more interactive through various computer, video and ergonomic enhancements. The standard workout article typically presents a muscle-building routine and an aerobic workout, then explains how to combine both into a complete training regimen. Equal but separate, to turn an ignominious phrase on its head. But what if muscle building and aerobics could be pursued simultaneously in one session? Competitive bodybuilders could use it precontest to get cut without losing muscle mass, or cycle it into their off-season training to increase their strength. Hardcore ironheads who train till they drop could get there fast following such a double-barreled approach, while fitness competitors could get a full-body workout and burn a ton of calories at the same time.

The original lyrics are deconstructed and reassembled at will by a rapper riding shotgun on the groove. Fitness is a good thing to have in your life. The instructor--a striking woman dressed in an oversized black T-shirt and baggy black sweatpants, with a shock of braids tied up overhead--glides effortlessly to the right in an intricate sequence of hip-hop dance steps. The 30-odd students behind her mimic each move to a T. “Turn it, turn it!” she yells, and everyone reverses field. “Grapevine! Do it!” Only by screaming into a handheld mike can she momentarily raise her voice above the music. “Grapevine, grapevine! One more, one more! Five, six, seven . . . Whe-e-e-e-e-e-e-w! All right!” After 10 minutes of this, the instructor stops the tape. By now her students are sweating rivers and sucking wind, but they appear to be having the time of their life.

For all types of exercise, your warm-up activities should: Take each of the joints through full range of motion. Increase body temperature. Get you psychologically tuned to what your body will be doing. Physiological reasons for warming up. Warm-ups help the body and its muscles to perform more effectively by: Slowly increasing muscle temperature. Serving as a dry run, which alerts the individual to potential musculoskeletal and other problems that may occur at higher intensity. Reducing the risk of exercise-related heart problems by increasing coronary blood flow. Improving the elasticity of soft tissues. Preventing early lactic-acid buildup and fatigue. Stimulating motor units of the muscles in preparation for a heavier workload.