At this time of year, athletes who are interested in alternative forms of training (ie cross training) often wonder which exercise device is 'best'. Essentially, they want to know whether cross-country ski machines, rowing devices, stair machines, stationary bicycles or treadmills provide the most beneficial workout when it comes to oxygen consumption, heart rate, caloric expenditure and/or weight loss.

A common answer to this question is that 'the treadmill is the king of all exercise machines' - a contention supported by some classic research carried out at the Medical College of Wisconsin in the US a few years ago. In this investigation, 13 healthy young volunteers (eight men and five women) completed exercise tests on a treadmill, a stair stepper, a rowing ergometer, a cross-country skiing simulator, a regular exercise bike and an Airdyne¨ (an exercise bike equipped with bars which work the arm muscles and upper body). The subjects were fairly lean and moderately fit, with an average VO2max of approximately 50 ml/kg.min(1).

In order to become more familiar with the various machines, all the subjects worked out on each device at least eight different times (each workout lasting about 15 minutes) during a four-week preparatory period. During this time they learned how to use rating of perceived exertion (RPE) to evaluate the intensity of their workouts. The RPE scale used by the Wisconsin researchers ranged from 6 to 20, with 11 representing a 'fairly light' workout, 13 a 'somewhat hard' session and 15 a 'hard' bout of training.

Before the final tests for oxygen consumption and caloric expenditure were completed on each machine, participants completed a five-minute warm-up, followed by two minutes' rest. Immediately afterwards, each of them completed three five-minute stages of exercise at RPEs of 11, 13, then 15, with two minutes of rest between stages. Testing on the six different devices was carried out randomly on separate days.

As mentioned, exercise on the treadmill tended to produce the highest rates of caloric expenditure. For example, during 'hard' exercise at an RPE of 15, treadmill walking or running burned about 850 calories per hour, compared with 700-or-so for the stair stepper, rowing ergometer, and Airdyne¨. The cross-country ski machine checked in at 650, while the stationary bike burned only about 600 calories an hour.

During 'somewhat hard' exercise at an RPE of 13, treadmill exertion again led the field at 700 calories per hour, with stair stepping at 627, rowing at 606, skiing at 595, 'Airdyning' at 509 and regular biking at 498. Treadmilling also racked up greater caloric expenditures during 'fairly light' efforts at an RPE of just 11 - an average of 550 calories per hour, compared with 500-or-so for the stair machine, rower and ski device and 350-380 for the bicycle and Airdyne¨.

These data do seem to support the idea that treadmill exercise is 'best'. After all, the caloric expenditures were estimated directly from the subjects' oxygen-consumption rates, so high expenditure rates implied high rates of oxygen consumption. The logical conclusion is that treadmills promote exercise at the highest-possible percentage of VO2max and thus provide the greatest stimulus for improvements in fitness.

Treadmills might not be the best choice for less fit people
However, a closer look at the study leaves less reason to be sanguine about treadmills. For example, as principal investigator Anne Zeni admitted, the results of the research might not apply to people in the early stages of building fitness. Conceivably, non-fit people with relatively poor overall strength and coordination might actually burn more calories on a stair stepper or rower than a treadmill, since their lack of agility and efficiency while climbing or rowing could lead to unusual rates of calorie burning.
The volunteers in the Wisconsin investigation did not have low overall fitness, however, and that may have actually given treadmilling an important edge over the other exercise devices, given the methodology of the research. As Dr Zeni pointed out, people are usually walking and running by age two and are completely comfortable with both activities in adulthood, even when using a treadmill. Cycling, rowing, skiing and stair climbing are less familiar - and less comfortable - activities.

Thus, in spite of the habituation period, which required each subject to work out several times on each exercise device, most of them probably still felt more relaxed, skilled and confident while walking or running than while engaged in the other activities. Such unequal preparation may have created a situation in which 'hard' (uncomfortable) efforts, for example, could be reached at lower actual intensities and lower heart rates on the non-treadmill machines, leading to lower rates of calorie expenditure. In other words, it was a breeze for the Wisconsin subjects to run at a high level on the treadmill (thus keeping RPE modest even when exercise intensity was high) but a bit of a struggle to work hard on the other machine, creating high RPEs yet modest caloric expenditure.

Cross-training should be goal-oriented
Of course, that scenario could be totally turned around if fairly fit athletes had greater experience with the alternative exercise devices. For example, a fit individual who trained 3-4 times a week for many weeks on a stair stepper or exercise bike could gradually increase calorie-burning rates (because higher and higher intensities would be selected as fitness improved) until they equalled - or even exceeded - the rates associated with treadmill walking or running. Thus it would be illogical for athletes to bias their cross training toward the treadmill and away from non-treadmill exercise machines simply because of what the Wisconsin researchers reported.
It is important to understand that your choice of cross training should depend on the ultimate goals you hope to achieve. If your greatest need is to enhance the brute strength of your legs, for example, it would make more sense to engage in strenuous workouts on a stair climber than to use a treadmill, even if the latter did lead to a greater overall caloric expenditure. Remember that rowing machines are great for building upper-body strength and accentuating spinal-bone fortification, stair machines augment hip and leg-muscle strength and ski devices are terrific for stimulating the cardiovascular system and increasing range of motion around the hips, without overstressing the musculoskeletal system.
Bicycling - despite its abysmal ranking in the Wisconsin research - can actually provide extremely high-intensity workouts, once people have adapted to using stationary bikes; several scientific studies have shown that serious endurance runners have boosted their running capacity after incorporating biking into their overall training. As you think about exercise machines and their potential value for you, hang on to this key principle: the quality of workouts cannot be completely determined by calorie-burning or heart rates; you should choose the machine which is most likely to provide the particular benefits you seek.
In this context, it is important to note that blood lactate levels were highest not during the most intense form of exercise (treadmill running) but during stair stepping and rowing. The latter probably scored high on lactate level because of its intense upper and lower-body involvement; with more muscles working vigorously, there may simply have been a greater outpouring of lactate into the blood. As for stair stepping, from one point of view this simply amounts to walking against increased resistance; to overcome this resistance, powerful fast-twitch muscle fibres, which tend to produce more lactate, are probably recruited. At any rate, athletes who cross train with the specific goal of raising their lactate threshold may want to take a close look at the potential benefits of rowing and stair climbing.
The bottom line? Decide for yourself which exercise device you would like to use, depending on availability, interest, personal comfort and - most importantly - your specific cross training goals. To decrease the risk of boredom, alternate workouts on your chosen machine with sessions on one or more of the other devices. If you work like this, there is absolutely no way anyone can say that your preferred exercise machine is 'worse' than any other device for your fitness.

Owen Anderson

References

1. Journal of the American Medical Association, vol 275 (18), pp 1424-1427, 1996