Lateral Movement Trainers
The lateral movement trainer (LMT) has caught the attention of scientists for the same reasons it has caught the attention of exercisers across the nation — it’s cheap, it’s portable, it burns mega-calories, it trains the cardiovascular system, it’s no-impact and it’s safe.
Walk into a club these days and instead of the familiar pounding disco sounds, hear a strange chonk, shhhhhhh, chonk, shhhhhhh, chonk… Curious? Peek into the aerobics parquet and watch a group of determined faces seemingly skating right where they stand, side to side, gliding smoothly on a stationary piece of slick material, known as a slide board. The slide board, also referred to by a variety of brand names, is better known in the exercise science world as a lateral movement trainer (LMT). But before you get caught up in the hype that often accompanies new products, and before you make the decision to acquire a set of boards for a new aerobic conditioning class, let’s take an objective look at LMTs.
What is an LMT?
An LMT is simply a slab of slick material, anything from formica to plexiglass to composites such as high-density polymers, or a sandwich of diverse materials, much like a snow ski. It measures about 2 feet wide by 5 to 12 feet long, with a padded block at each end. The best built are rigid and have adjustable bumpers to provide different sliding distances and, therefore, serve a wide clientele with different degrees of cardiovascular fitness. Becoming somewhat more popular are the vinyl slides that can be rolled like a sleeping bag to save space. Nylon booties (part of the package) worn on top of the usual athletic shoes are required footwear, and the only other needed maintenance is a bottle of polish to keep the board slick.
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.
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. What does the NCSA cost?
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.
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.
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.
|Approximate caloric expenditure for a
30-minute workout on the LMT.
|In calories: first number = females
(120 lbs.)/ second number = males (170 lbs.)
|Slides per minute
Sample beginning training and variations
Start slowly and progress slowly
|Repetitions are slides per set —
from side to side once
|1st two days
|2nd two days
|Work two days/rest 1
For more advanced programs, decrease the frequency and duration of rest-time between sets, and increase sets and reps. Other advanced variations and things to do during rest periods and between slides for a circuit training effect include:
* Push-ups, by grasping the stop block and pushing up and down just like on the floor.
* One-leg or two-leg lunges, by grasping the stop block and lunging to the rear, except instead of jumping backward, slide the body backward.
* Adding aerobic moves with the arms at the end of each slide.
* Carrying arm weights while sliding or swinging the arms hard like a speed skater.
According to a class leader, almost anything that can be done in dance aerobics, can be adapted to the LMT, including spinning a 180- or 360-degree turn in mid-slide, and kicking the leg high at the end of the slide, both in front and in back of the body.
Bergfield, J.A. & T.E. Anderson. Achieving mobility, strength, and function of the injured knee. In L.Y. Hunter & F.J. Funk (eds.) Rehabilitation of the Injured Athlete. St. Louis: C.V. Mosby, 1984.
Gray, G., J.A. Peterson & C.X. Bryant. Plane sense. Fitness Management, April, 1992.
Harrelson, G. Use of the slide board following anterior cruciate ligament reconstruction. Sports Medicine Update, Winter, 1991.
Kneedspeed Literature pamphlet.
The Training Camp Inc. Pamphlet; information on slide techniques and specifications.