The lateral trainer was first described in clinical research by Bergfield and Anderson as an ideal exercise modality to "achieving mobility, strength and functions of the injured knee." Originally developed to rehabilitate torn anterior cruciate ligaments of the knee in 1984, the LMT simulates ice skating and has gained popularity not only as a rehabilitative device, but as a conditioning exercise. How do LMTs work? Learning a basic workout on the LMT may require some instruction on the part of the leader, and the realization that some people will initially be less coordinated than others. Nylon booties are fitted over a pair of supportive shoes; any athletic shoe will do, but court shoes and cross-trainers provide more lateral support. Instructions to step on the LMT should be accompanied by a caution about its slick surface. Clients should then carefully push off the block with the side of the foot hard enough to reach the other side; the power needed for the push-off will be learned in a few repetitions. Leaders should instruct participants to keep their hands in front of the body for balance and the body slightly leaning forward. For very beginners, or as an extra safety precaution, it is usually best to learn with an understanding partner whom a slider can lean on (literally). Pairing up the class also decreases initial apprehension.

Which muscles do LMTs exercise?

As a skate simulator, the hip and the knee extensors and flexors do most of the work; however, with a little creativity, the LMT easily works the entire body. The LMT uses body weight and the inertia it generates as resistance. Although it requires concentric (muscle shortens) extension of the hip and knee for the push-off phase, it also uses the posture muscles in a static (isometric or non-moving) contraction during the sliding phase. And in order to overcome the inertia, it uses the hamstrings in an eccentric (muscle lengthens) contraction throughout the slide. As in skating, the push-off motion requires use of the whole hip extensor muscle group (gluteals), and the whole knee extensor muscle group (quadriceps, mainly). The calf is also working. Ankle extensors (plantar flexors) such as the gastrocnemius and soleus, contract on the push-off phase. During the slide, muscles remain tightened to overcome the inertia generated; working hard are the hamstrings, which remain in a static contraction throughout the slide and help slow the body in the braking phase when hitting the stop. Because of the lateral motion, the inside and outside of the thighs, hip abductors and adductors also enter all phases in the slide motion. Finally, because of the bent forward position required to maintain balance, posture muscles are also getting a workout; mainly these are back extensors, a series of muscles that keep the spine upright, and abdominals, rectus abdominis, and internal and external obliques that wrap around the sides and keep the body from swaying sideways when hitting the stop block.

Although the LMT employs the entire body for balance, the device is mainly a lower-body workout in terms of muscle strengthening and development, and an intense aerobic and anaerobic workout of the cardiovascular system. The bottom line for class leaders -- start and end the class by stretching the entire body, primarily the legs, and include specific stretching exercises for the hamstrings and adductors, reported by research subjects to be the most sore after prolonged workouts.

Cardiovascular benefits

The calorie burning power of the LMT became a subject of tall claims by more than one manufacturer, which triggered several research studies at the Exercise Physiology Laboratory at the University of Nevada at Las Vegas. Principal investigator Steve Krause found that, when left to exercise without controls, that is, at a pace that was comfortable to them, subjects burned 10 to 13 Calories per minute on average. That is the equivalent of running 7.5 to 8.5 miles per hour, or eight- to seven-minute miles. In another study it was shown that this caloric expenditure value increased with: LMT board length, the longer the board the more calories burned; cadence (or slides per minute), the more slides-per-minute the more calories burned; posture, the more pronounced the forward lean, the more calories used. Adding arm movements like those of a speed skater, with hand weights if necessary, can meet the training needs of the most physically fit clients.

Table 1 summarizes the approximate caloric expenditures for three board lengths and cadences. Just for reference, in the studies above, the average fit individual slid at about 35 slides per minute on a long board (their height plus 18 inches), 43 slides per minute on a medium board (their height plus 9 inches), and 51 on a short board (equal to their height). When the board was kept at 7 feet for everyone, the average slide rate was 40 (slide from left to right was counted as one slide). The caloric costs were derived from oxygen consumption, which was comparable to 85 to 100 percent of the tested individuals' maximum oxygen capacity (V02). This is considered fairly high intensity, and although reducing the cadence or shortening the length of the board lessens the workload, individuals who are not fit should go easy at first and take frequent breaks. Heart rates elicited by the board easily reached the 190s for most individuals; some reached their predicted maximum heart rate while sliding, and the average heart rate when subjects chose their own pace was 173. Since training heart rates depend on intensity, in order to stay aerobic, leaders may have to choose shorter boards, slow the slide rate, and take frequent breaks when teaching beginning classes.

One problem with high-intensity, high-caloric-expenditure workouts is that not everyone possesses good enough cardiovascular fitness to do them. But it is also true that most everyone can train their cardiovascular system to work up to a non-stop 20-minute workout on the LMT, given time and perseverance. Krause reported that several healthy college-age volunteers had to be dropped from the studies because they could not complete an eight-minute workout on the LMT. Taking into consideration that for cardiovascular improvement, a person has to sustain a reasonable intensity (60 to 80 percent of maximum capacity) for at least 20 minutes, the LMT may be somewhat limited for beginners, unless they are already in good cardiovascular condition from another exercise mode.

Safety precautions

In terms of safety from injuries, the LMT receives high marks in published literature. The product was first conceived to rehabilitate knee ligaments that had been injured by a lateral blow and, therefore, provides good strengthening of the knee joint with little injurious stress. Unlike stepping, aerobic dance and running, to name a few, the LMT is completely a non-impact exercise. In fact, some models have a slanted side stop, so that the sole rides on top of the surface of the stop instead of hitting it with the lateral part of the foot. This provides a better push-off and less discomfort to the side of the foot, similar to a skate on the ground or ice. The LMT is also boasted as a true closed-chain exercise, a nomenclature given to exercises that utilize more than conventional one-plane movements, and that use the body and its natural movements as resistance (see Fitness Management, April 1992).

Three safety considerations were derived from personal experience, subjects' comments and Krause's research. First, individuals with lower-back problems are advised to maintain a straighter position on the LMT. Because of the slight forward lean required to maintain balance while sliding, some people with prior low-back problems may find it difficult, if not impossible, to use the LMT. Even people with no prior back problems may experience a slight lower-back discomfort after the first few slides while working out and in the following days.

Lateral training can also lead to delayed onset muscle soreness. Specifically, the adductors, hamstrings and hip extensors (gluteals) are prone to delayed muscle soreness after a slide session, both because sliding uses the rarely worked adductor muscle group, and because the eccentric muscle contractions of the hamstrings required to overcome the inertia tend to produce more soreness than concentric contractions. On the bright side, toning the inside of the thighs and the area between the hamstrings and the gluteals, which is usually difficult with many other conventional exercises, happens automatically on the LMT.

Finally, a third caution: Encourage those who do not want to build bulky muscles while using this exercise modality to find a speed skater who doesn't have massive quadriceps and hip muscles. If a client is the type who tends to build muscle easily, the slide will strengthen, empower and build all leg and hip muscle groups rapidly, as will any repeated skating workout.

Practical recommendations

Comprehensive beginning and advanced workouts are available from manufacturers, as are illustrative videos. The cited literature also contains a sensible progression for increasing strength, power and cardiovascular conditioning. The important point to remember is that shorter boards, fewer slides per minute and frequent breaks between slides can give a beginner a fair chance at enjoying a LMT program. Leaders should attempt to review some of the literature and try out a LMT, if one can be obtained, prior to investing planning time and money in a LMT class.

Table 1