Hi, Lizgo! I too am an instructor although I do not teach any studio modes like hi/lo, step, kickbox or boot camp. However, I too have read the literature that discourages using handweights while engaging in even moderately paced aerobic activity and I agree with it. Most researchers have found that the very minimal increase in caloric expenditure is far outweighed by the risks to the shoulder joint, the neck and back, and the knee joint when trying to move the arms quickly (as is usually the case in any aerobic activity) with a concentrated load at the end of the arm lever.
A big part of it has to do with momentum: the increased momentum that the weight load creates is often greater than the shoulder's ability to control, stop and return the movement; thus connective tissues can be damaged.
Also, weight loads at the end of a long lever (arms OR legs) significantly alter one's center of gravity in a very unnatural and unsuitable way, paving the way for low back instability.
Further, I believe studies have also shown that when weights are added to aerobic work, range of motion is unconsciously taken down, as is the pace of the movement, as the body compensates for the increased weight; obviously, this is counterproductive to the goal of increased aerobic workload.
All of that to say: hand weights are really not a good idea for fast-paced aerobic work that incorporates a big range of motion for the upper body. You'll note that Cathe has designed several circuit-style workouts; however, it is noteworthy that she separates the circuit segments away from the faster-paced cardio work. There are many kickbox devotees who like to use weighted boxer-style hand gloves while doing kickboxing with upper body drills; I say again this is risky. I know pro boxers' gloves do have a weight load (between 2-5 lbs.) but they have been training for years, and their training drills are nothing like those of the studio exerciser.
Just my $.02 - hope it helps.
Annette Q. Aquajock
