MY WIFE AND I are both at that "certain age" where, from everything we've heard and read, strength training is of paramount importance for general fitness. Before we invest in something like the Bowflex, we were wondering if any aerobic exercise routines such as the popular Tae Bo routines would provide necessary strength training. Do you have any information and/or opinions? - J.F.

Tae Bo and the similar "cardio kickboxing" workouts can give a good workout: A recent study by the American Council on Exercise found one session can burn 350 to 450 calories an hour (not the 500 to 800 sometimes claimed), roughly equivalent to an hour of brisk walking or light jogging. ACE said kickboxing can increase strength and flexibility and improve coordination and reflexes, but to avoid muscle and joint injury newcomers should learn safe techniques and progress gradually.

If you're looking specifically for strengthening, however, it seems most authorities believe we get better results and safer workouts by doing some exercises specifically for strength training and others for cardiovascular benefits - no single workout covers all. (Sorry.) Some aerobics exercises also tend to tone better than build muscle; to raise the metabolism (to help burn weight) we need to build more muscle, not just tone what we have. I see something like Tae Bo as another variable to throw into the mix, to substitute for one of the workouts once or twice a week, but not for either of them all the time.

I think one reason Tae Bo is popular - besides the fun of punching and kicking, and the charisma of Billy Blanks - is it's an interval workout (alternating hard and easy) which can make a noticeable difference for folks who have been, say, going on the same bike machine or treadmill at the same speed for the same amount of time for months or years.

I'm interested in buying a used ERG machine. My younger brother has been training with one for crew racing, and has gotten great results. Any idea where I can find one on the cheap? - C.K.

I presume you mean the Concept II rowing ergometer, commonly called "The Erg" in rowing circles. It's very hard to find used, though, since it's well-made and a good aid for consistent and good exercise. Your best shot for a used one (which probably still wouldn't be cheap) might be watching the newspaper classified ads, and even then it's a long shot. (I'm still kicking myself for not buying a used one I saw advertised about 15 years ago.) You could keep an eye on the bulletin board at the Pocock Rowing Center (3320 Fuhrman Ave. E., Seattle; 206-328-0778) or, if you're patient, you might be able to pick up a used one there next February, right after the annual indoor rowing event. If you wind up getting one new ($765 plus $36 shipping to Seattle), it's often less expensive direct from the company: www.concept2.com or 800-245 5676.

Fred Meyer sells "soy nuts" in the bulk section. Do you know if these have the same nutrition value as the soybeans in Pacific Northwest's Taste article on edamame? - M.D.

They're not even close. According to the U.S. Department of Agriculture Nutrient Database (www.nal.usda.gov/fnic/cgi-bin/nut(underscore)search.pl), one cup of edamame (boiled, drained, no salt) has 254 calories, 22 grams of protein, 20 grams carbohydrate, 12 grams fat and 8 grams fiber. Roasted, no-salt soy nuts, however, have 810 calories, 61 grams protein, 58 carbohydrate and 44 fat. Most other nutrient levels are likewise higher in the roasted beans, whose lower water content means more per cup. A couple of exceptions: calcium (261 mg. in the boiled, 237 in the roasted) and vitamin C (4 mg. both ways).

After reading in your column about chromium picolinate being harmful I checked my multi-vitamin and noticed that it contains 65 mcg of chromium (alone). Should I be concerned about chromium by itself interacting with other compounds? - L.B.

Not according to John Vincent, one of the University of Alabama researchers who found that chromium picolinate causes DNA breakage, which in some cases can lead to genetic mutations and cancer. "Simple chromium compounds don't do this," Vincent said. "They have to have ligands - something that binds to chromium - that make the properties just right and picolinate is one of those ligands."

Molly Martin is assistant editor of Pacific Northwest magazine. ------------------------------- NOTEBOOK

Weightlifting for kids?

Children can do strength-training exercise, according to a report in the journal Pediatrics, but they need a different kind of workout than adults. An eight-week study of children ages 5 to 11 in a YMCA after-school program in Boston found a group that lifted moderate weight 13 to 15 repetitions gained three times the upper-body strength and one-third more leg strength than those who lifted heavy weights for five to six reps (which is more effective in adults) or those who did no exercise at all (usually not effective at any age).

More fitness education?

Trish Root, coordinator for the physical education department at North Seattle Community College, is trying to ascertain interest in starting a two-year A.S. degree program there in Exercise Science/Fitness Education. She plans to distribute a questionnaire to health clubs at the beginning of fall quarter, but in the interim the survey is available at http://nsccux.sccd.ctc.edu/(TILDE)pe

Training with arthritis

The demand for fitness instructors who can help folks with arthritis easily outweighs the supply, but help is out there: Diane Sowinski, co-founder of the Fitness and Exercise Referral Service and a specialist on exercising with arthritis, plans two sessions for personal trainers, "Training Clients With Arthritis," Sept. 11 in Bellingham and Nov. 17 in Olympia. They're $65 each. For information call the Arthritis Foundation, 206-547-2707.