Step Aerobics Fulfills Its Promise: High on Fitness, Low on Impact

by Michele Scharff Ohm, Ph.D. and Henry N Williford, Ed.D., FACSM

When step aerobics became popular in health clubs in the early 1990s, it was anecdotally referred to as a "high fitness-low impact" mode of exercise. Scientists were skeptical at first, particularly in light of the known injuries caused by other aerobic dance programs (1). It turns out that the industry claim of high fitness-low impact is valid. And low impact aerobics effectively trains the cardiovascular system.

This article describes the physiological and mechanical effects associated with several step techniques. It also describes step techniques that can be used to promote fitness goals without promoting or increasing impact.

A 1993 study (2) evaluating the energy cost of "basic" stepping without any arm movements showed that step height is the most important factor in energy cost (Figure 1). The intensity of basic stepping on a 6-inch platform is comparable to low intensity-low impact aerobic dance (3). On the highest platform (12 inches) the intensity is substantially greater and similar to high impact aerobic dance at a medium intensity. Therefore, when the cardiovascular fitness levels of the participants are varied, adjusting the platform height is a highly viable method for individualizing exercise intensity.

The energy cost of more choreographed stepping, which includes a greater variety of maneuvers and dynamic arm movements, is higher than the basic step exercise technique (4,5). On 6- and 8-inch steps the intensity during choreographed step aerobics is similar to medium intensity high-impact aerobic dance. On 10- to 12-inch steps, the intensity is similar in intensity to high-impact aerobic dance (3). One study found that adding continuous arm movements to a traditional step protocol increased the heart rate and energy cost by approximately 10%, which is similar to a 2-inch increase in platform height (6).

Figure 1 - Step height and body weight account for
the greatest variation (82%) in the energy cost of
"basic bench stepping" exercise. Collectively, the
remaining variables account for 3.5%.

Some instructors add hand or torso weights to further increase the effect of upper body involvement. It takes 2-pound, hand-held weights to increase the energy expenditure by 1.0 kilo-calories per minute (Kcal/min) which is the same as a 2-inch increase in step height (4). However, 2-pound handheld weights can be limiting. Step aerobics instructors have reported experiencing acute pain and fatigue in their shoulders after 10 minutes of step aerobics with 2-pound, handheld weights (3).

Choreographed Step Workouts.

Figure 2 - Pyramid of Step Maneuvers.
The design of the Pyramid is based on exercise intensity

Choreographed step workouts also include foot-strike sequences, on and off the step, and increased movement about the platform. The Pyramid of Step Maneuvers (Figure 2) shows that some of these movements are substantially more intense than others. Maneuvers toward the top of the pyramid require an energy cost of 10 or more metabolic equivalents (METS). An energy cost as high as 13 METS can be attained when performed on a 12-inch step (4). A 4-inch platform, by comparison, provides an intensity of about 5 METS. Simultaneously combining lower body and upper body choreography may produce an exceedingly high intensity on 10- and 12-inch platforms (4). If the instructor elects to teach highly choreographed sequences, he or she should guide participants to use moderate step heights.

if the instructor elects to teach highly choreographed sequences, he or she should guide participants to use moderate step heights.

The step aerobics techniques reviewed to this point can yield an exercise intensity similar to higher impact activities—but without the same impact forces. Stepping on higher platforms (8 and 10 inches) with the addition of dynamic arm movements and the choreographed style on moderate step heights support the "high fitness-low impact" claim attributed to step aerobics.

Danger

Three additional variables have been introduced to the practice of step aerobics. They are speed, impact style, and step position. These techniques, however, can be extremely intense and/or can generate very high impact forces (see Figure 3).

Stepping speed, in particular, has received much attention. The normal range of speed associated with the majority of step aerobics workouts varies between 30 and 32 cycles per minute (i.e., 120 to 128 metronome beats per minute). At these speeds, platforms ranging from 4 to 10 inches place the majority of participants within the accepted (50-85% of VO2max) training zone (2,4,5). At faster speeds (i.e., 32 to 34 cycles per minute), the exercise intensity approximates 95% of VO2max (8), which greatly exceeds the recommended aerobic exercise range (9). A recent study reported that four of 10 subjects had to cease exercising during step aerobics at the faster speeds because of exertional fatigue (8). The study subjects had a mean VO2max of 34.5 milliliter per kilogram per minute and possessed step exercise experience. This shows that the standard speed range (30 to 32 cycles per minute) provides an energy cost that is sufficient to stimulate cardiovascular fitness in moderately fit adults. Imposing speeds greater than this may impart an exercise demand that is too intense for many participants.

Figure 3 also shows the effects of impact style and step position to modify intensity. The "propulsion" impact style of step aerobics includes airborne hops and leaps. Propulsion impact is controversial because, bio-mechanically, it is more high impact (10). Unlike propulsion impact or accelerated speeds, the "straddle" step position is the only method among the three shown in Figure 3 that increases intensity without increasing impact. Thus, the contention that step aerobics is a low-impact activity is accurate depending on the techniques that are employed.

Figure 3 - Differences in the relative intensity of step aerobics based on selected speech position, and routine style. Significant differences were found between each of the paired conditions (e.g., BSS >; BSI; p < 0.05).

Instructional Techniques Which Significantly Increase the Energy Cost of Step Aerobics

Higher Platform
Arm Movements
Hand-Held Weights
External Weight Loading
Choreographed Routines
Accelerated Cadence
Propulsion
Straddle Position

More About Impact.

Table 1 presents information about the impact associated with different step exercise methods (force is expressed in multiples of body weight). Fundamental step movements (i.e., "basic" and "knee raise") at 30 cycles per minute on band 8-inch platforms elicit a modest impact force that is comparable to walking and low impact aerobic dance (11). These step maneuvers fulfill the "low impact" description. The "basic" step performed at the same platform height with propulsion (i.e., basic "leap" step), however, results in a relatively marked increase in impact. The other propulsive maneuvers ("straddle jump" and plyometric "lunging") yield even higher impact forces. Table 1 shows that movements incorporating airborne jumps and plyometric like techniques produce impact forces that are comparable to higher impact activities such as jogging and high impact aerobic dance. Finally, stepping at accelerated speeds not only produces an intensity that is too high for most individuals, the impact forces can also be higher than those experienced during jogging and high impact aerobic dance (11). The value of exceeding 32 cycles per minute is questionable and not supported by research.

Table 1 - Impact Forces Times Body Weight

Movement	Height	Force
“Basic” Step	6”	1.41
“Basic” Step	8”	1.56
“Knee Raise”	8”	1.56
Basic “Leap” Step	6”	1.82
“Straddle Jump”	6”	2.29
Plyornetric “Lunging”	8”	2.91
“Accelerated Speed” Routine	8”	2.85
Walking	N/A	1.24
Jogging	N/A	2.26
Low Impact Aerobic Dance	N/A	1.52
High Impact Aerobic Dance	N/A	2.65

Propulsive techniques and faster speeds substantially increase the impact of step aerobics. These techniques also yield impact forces that are similar to jogging and high impact aerobic dance.

Figure 4 - Novices and instructors tended to elicit similar,
overall peak forces during the dismount stage of each stepping cycle.
However, the data plotted at approximately 0.25 seconds
shows that the instructors reactively dissipate or absorb the impact

Instructors should be aware of the risk of speed and propulsion. If used, the propulsive style should be done in intervals so that the greater impact and higher cardio-respiratory demand are alternated with the more moderate demands of the fundamental step movement.

Start Newcomers Out Easily.

People who are new to step aerobics do not have the mechanical skills of experienced steppers. They absorb step exercise impact forces differently. Figure 4 shows vertical ground reaction force curves for novices and instructors. The peak force is experienced at approximately 0.27 seconds in both groups. However, immediately prior to this point instructors generate a change in the shape of the landing curve. Not so in novices. Experienced instructors acquire an ability to make force-absorbing adjustments in their landing technique prior to the point of peak impact, a skill not yet attained by novice bench steppers (10).

Instructors should be aware of the value of formal instruction of step exercise techniques, especially those related to the mechanics of the feet and knees. Aerobic dance participants, after receiving technique instruction and being given time to practice, demonstrate modifications and reductions in the magnitude of impact when they perform high-low impact routines (11). The instructor should include technique instruction and brief practice sessions before classes. Thereafter, a training progression that proceeds from lower platforms, slower speeds, and lower impact step maneuvers should be prescribed.

How Many Times A Week

After being appropriately initiated into step aerobics, how often should one participate and what types of fitness gains can be expected? Cross-sectional studies of high impact aerobic dance indicate that the risk of injury markedly increases when the exercise frequency exceeds four episodes a week (1). Therefore, if an instructor employs accelerated speeds or propulsive impact styles, he or she may be placing participants at a risk for injury, particularly if they engage in the activity more than four times per week?.

At a frequency of three sessions per week, choreographed step aerobics (with limited propulsion intervals) was shown to improve cardiovascular fitness by 16%, equal to running (12). However, the step exercise style used in this study was not strictly low-impact; propulsion maneuvers were incorporated. A second step study, using less propulsive choreography, reported a lower, but significant, 11% improvement in cardiovascular fitness (13).

Aqua Stepping

A training study using "aqua stepping" gives additional insight about fitness and impact (14) . In this study, female subjects trained for seven weeks on 8-inch platforms in water that was waist to chest deep. The pre-training fitness level of the subjects was above average, but the aqua step program still improved aerobic power by 8%. Aqua stepping may turn out to be the truest "high on fitness, low on impact" step format. Instructors could encourage participation in aqua step, especially for overweight or orthographically limited individuals.

Step Aerobics to Reduce Fat

No significant changes in body fat were detected in one of the step studies or in the aqua step investigation (3); however, a third study reported a statistically significant change in body composition partially because of an increase in fat free mass (13). The effectiveness of step aerobics in reducing body fat is still open to question.

Table 2 - Time (minutes) to burn 300 kcats for various body weights and heights

Weight		Platform Height
Pounds	Kg	6”	8”	10”
120	54.43	40	38	36
130	58.97	36	34	32
140	63.50	34	32	30
150	68.04	32	30	28
160	72.57	30	28	26
170	77.11	28	26	24
180	81.65	26	24	22

The time necessary to expend 300 kcal ranges substantially depending on body weight and step height.

For health purposes, a 50% reduction in any time value will yield the minutes of step aerobics

needed to meet the 150 kcal criterion.

The time necessary to expend 300 kcal ranges substantially depending on body weight and step height. For health purposes, a 50% reduction in any time value will yield the minutes of step aerobics needed to meet the 150 kcal criterion. The inconsistent research findings may be related to the amount of energy expended during classes with a 30-minute aerobic section (12). For example, on the 6-, 8-, and 10-inch platforms employed in the first study, the subjects expended an estimated 225-285 kcal/workout which is less than that recommended for effectively changing body composition. The ACSM criteria for weight loss specifies an energy expenditure of 300-500 kcal/exercise session, a minimum of 3 days per week (9). Table 2 shows the time required to expend at least 300 kcal during step aerobics for various body weights. In addition, the relatively recent 150 kcal per day health criterion suggested by the Surgeon General's Report can be readily calculated from this table. Depending on the individual's body weight and selected platform height, Table 2 shows that 30 minutes of step aerobics may not elicit an expenditure of 300-500 kcal. In terms of exercise prescription, if weight loss is an important fitness goal, the instructor should make appropriate adjustments in exercise duration, frequency, and/or platform height to increase energy expenditure.

Cross-sectional data concerning the body fat percentage of step aerobics instructors appears to support the validity of adjusting duration and frequency (15). Body fat in step exercise leaders was about 19% which is lower than the typical (23-25%) range in 30-year-old females. In this study the instructors had over 2 years of step aerobics teaching experience and taught four to five 45-minute classes a week. The higher frequency of teaching and longer class duration accumulated during a 2-year period resulted in a greater overall expenditure of calories when compared with those in the 7-week aqua step and the 10-week step versus running study.

The step aerobics instructors also exhibited several upper and lower body strength characteristics that were similar to those in women who actively weight train (15). Many instructors incorporate muscular strength and endurance activities using resistive devices such as weights and surgical tubing after their step exercise segment. Therefore, other physical fitness changes may result from step classes that incorporate additional exercise activities.

High on fitness, low on impact? Step aerobics exercise certainly provides a stimulus sufficient to improve aerobic fitness when performed 3 days per week. The intensity can be changed by altering platform height, style of choreography, and speed. However, faster speeds and propulsive maneuvers increase the impact force to levels that surpass jogging and may be too intense, or potentially injurious, for many participants. The activity may also prove effective in reducing body fat if appropriate modifications are employed. These modifications include a longer exercise duration, a higher platform, and/or a greater exercise frequency --- none of which increase the impact.

Authors

Michele Scharff Olson, Ph.D. is an associate professor at Auburn (University at Montgomery and research administrator for the Auburn Montgomery Human Performance Laboratory. She's been an ACM member since 1991. Dr. Montgomery is also an ACE Academy Faculty Member and a continuing education provider for AMA. Much her research is about women and aerobic dance exercise.

Henry Williford D., FACSM is a professor at Auburn University at Montgomery and the director ((the Human Performance Laboratory there. He’s been a Fellow of the American College of Sports Medicine since 1988. In 199Z Dr: Williford was awarded the title of Auburn-Montgomery Distinguished Research Professor.

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