Although there are many ways to increase the intensity of an aerobic workout, The FIRM has chosen the "high impact with weights" method for their new cardio series, much to my surprise and dismay. The cover recommends Cardio Burn for intermediates and advanced, but it's best used by strong, experienced exercisers who know their limits, know good exercise technique, and know when and how to modify moves for their level of fitness. A weighted ball and dumbbells are used during the 6 minute warm-up/stretch -- a surprising and debatable innovation. The 21 minutes of aerobic interval training includes high-impact, very fast-paced (160 bpm) floor aerobics, slower paced aero-toning with weights(120 bpm) and advanced-paced (132 bpm) step aerobics. The aerobics segment opens with a 4.5-minute step routine that includes karate kicks on and off the step and a combo of jump-squats over the step and power lunges (this has a tricky rhythm to it and isn't cued well). The 11.5 minutes of high-impact floor aerobics includes running in place, jumping jacks, skipping, calf pumps (wide stance jumps), plyo jump squats, and plyo jump spins while holding dumbbells. The aerobics closes with a tall-box climb, then you pick up your barbell for lunges, hover squats and dips, and dumbbells for plies. Push-ups (2 sets), biceps curls (1), and French presses (2) and kickbacks (1) for triceps are alternated with the lower body toning. Shoulders and arms are also worked with light weights during the aerobics. Abs are worked for 3.5 minutes with varied combos of three moves: basic upper and reverse crunches and an unusual oblique crunch to the side.

While it's great to challenge your body with new exercises, this workout, like the others in this challenging FIRM Cardio series, has minimal instruction, few technique reminders, and no modifications shown or mentioned for the high-impact aerobic moves. Plyo jumps (with and without weights) should be approached with caution, they can be very hard on the knees...as can some of the lunge variations that are introduced. You need plenty of recovery time after a workout this intense...once or twice a week is plenty. You'll see Tamela and her routines again...they're used in many of the new FIRM Parts workouts.

This "Classic" FIRM workout uses both continuous stepping with dumbbells (for some upper body toning) and a tough floor toning routine to effectively focus on the lower body. The step aerobics begins with four easy-to-follow routines on what the FIRM calls a "low" 10-inch box (a normal height step works fine). Two of these routines use dumbbells to (over)work the shoulders and biceps with many fast-paced upper body sets. In the last step routine you simply hold heavy weights during alternating sets of "tall box" step-ups and squats. This 11-minute routine is tough enough the first time through. If you do the "aerobic rewind," your legs should feel the burn after the full 22 minutes of weighted stepping.

After a set of triceps extensions, you move to the floor for 9 minutes of abs. For the 18 minutes of lower body toning you wear ankle weights and hold a dumbbell on your thigh. Kneeling hamstring lifts, push-ups, inner and outer thigh lifts and pelvic lifts are alternated to give each muscle group just enough overload, then a rest. Without repeating the step aerobics, the workout is 47 minutes, with the rewind it's close to an hour. LaReine leads this FIRM Classic with good cuing and demonstrates good form but gives minimal instruction so this intense lower body workout is best suited for experienced strength trainers.

Whenever I'm pressed for time but want intensity, I choose this energetic FIRM Classic which combines step and floor aerobics with heavy and light dumbbell toning. I enjoy alternating between Susan's methodical weight training intervals and Kai's lively floor and step aerobics. After 22 minutes of nonstop stepping, squatting, lunging, dipping and kicking, my legs are usually exhausted and after eighteen sets of shoulder exercises my upper body is too. Beginners, don't try this at home!

The 23 minutes of interval training includes two fast-paced, higher-impact floor aerobics routines and three dumbbell toning routines on the step. (The dumbbell moves are too fast in the first step routine. Do these reps at half tempo: lift as you step up-up, lower as you step down-down.) The first two toning intervals focus primarily on the legs with sets of squats, lunges, dips and plies with heavy dumbbells. The last standing toning segment concentrates on the shoulders, back and triceps. The workout ends on the floor with pushups, six minutes of intense ab crunches and a much-needed floor stretch. Advanced exercisers will enjoy this compact, fast-paced, invigorating workout. Intermediates: stick to light weights, pace yourself and you'll still feel the burn!

Designed for crosstraining with The Tortoise upper body barbell workout, The Hare uses light dumbbells for minimal upper body toning, heavy dumbbells for tall box step-ups, ankle weights and dumbbells for floor leg toning and a very short step (they use 2 inches!) for step aerobics. Six ballroom dance tunes (a fun change from the usually basic and repetitious FIRM step footwork) alternate with four standing toning intervals. Two are floor aerobics with dumbbell toning for the shoulders, biceps and triceps. The other toning intervals work the quads and glutes with step-ups onto a high box with heavy dumbbells. Next, leg and abs routines alternate on the floor. One leg seems to work forever, doing 3 sets each for hamstrings, inner thigh and outer thigh. Next comes a tough routine of ab crunches, then pelvic lifts and it's back to leg exercises for the other leg. Done? No way--there's a second ab routine. That's intensity!

Tracie is a meticulous and thorough instructor. Her instructions and cuing are clear and she demonstrates great form. This workout has plenty of variety and alternates high and low intensity. It flows along at a brisk pace and calls for endurance. As the introduction warns, don't expect to do the entire workout your first time through. (Beginners: give this workout a try. There are only five upper body exercises with weights. Many of these ballroom routines don't add arm movements until halfway through the tune, giving you plenty of time to learn the footwork. You can get a challenging leg toning workout by starting with a 6- or 8-inch step-up box and no weights for the lying leg routines.)

This workout is a compilation of 29 minutes of aerobic routines, with and without dumbbells, from the FIRM Classic Workouts (Volumes 2 through 6). Each routine is introduced by a guest trainer who prepares you for the props needed, either step or dumbbells. After a long and gentle six-minute warm-up and stretch, the aerobic workout alternates between five step routines and four mixed-impact floor routines. Two of the step routines use light dumbbells during slow, smooth step-ups. Three other step routines use no dumbbells and minimal arm movements. The floor aerobic routines from Volume 2 are the toughest, with squats, leg lifts and lunges paired with upper body work for the shoulders, biceps and triceps.

This is not a beginner workout. Good form is shown throughout, but instructions, postural alignment, lower impact options and weight training tips are not to be found. You should know weight training basics before you try this one. Many of these combination exercises should be done at a slower pace and some fast arm movements need to be modified.

Compiled from the toughest aerobic tunes of the FIRM's six Classic workouts, this workout is higher in impact and intensity as well as longer than Not So Tough Aerobics. Here the aerobics alternates between low-impact floor and step routines that use light dumbbells for shoulder, biceps, and triceps exercises and high-impact floor routines with no weights and minimal arm work. Because the floor aerobic routines include jumps, rocking horses and plyo squats, it's difficult to turn this into a low-impact workout without making major changes.

Many of the upper body exercises with dumbbells need to be done at half the speed shown. Slowing these reps down would give more effective strength gains with less chance of injury. This is not a workout for inexperienced, uncoordinated or unconditioned exercisers. The assumption is not only that you know how to perform every exercise with correct form, but that you can get through all 38 minutes of this fast-paced workout without needing modifications for safety and better results.

The use of light dumbbells, a variety of step heights and a fast-paced tempo make this the most aerobic FIRM tape in recent years. Three instructors alternate leading the short, varied routines, randomly moving from the floor to a tall step to a lower step. The warm-up is a skimpy three minutes with the stretches starting after only a minute and a half. Three floor aerobic intervals are fast-paced and higher-impact, with fast and slow jumps, bunny hops, jogging, rocking horses and skating hops. Five more aerobic routines use the step but no weights. Three are on the low step, using very basic footwork and two are tall box "climbs." Dumbbells are used for two low-step routines and one floor aerobics. All this adds up to a 28-minute high-energy aerobic workout.

After the cooldown and stretch, the toning begins with full body "planks," followed by push-ups and lower back exercises. Upper crunches with a dumbbell on the chest start the ab work, then a unique upper/lower ab combination exercise is introduced: the challenging "rock and lift, extend and twist." It has an unusual rhythm and much intensity--the abs feel the burn quickly. The aerobic variety and the constant change of pace and props make this tape dynamic and entertaining. Because there are no modifications mentioned or shown for the fast-paced high-impact aerobic moves and only minimal instructions for the unusual and advanced toning exercises, this workout is best for an experienced exerciser.