your muscles - the only "window" into your body

Note that each of those effects from stair climbing (burning calories, positively stressing the cardiovascular system, potential strength increases, and positive changes in the immune and endocrine systems) are caused by making the muscles work. Extra calories are burned only because the leg muscles are working harder from the activity. The heart starts beating faster to supply nutrients to the working muscles, as well to remove waste products from them. If an increase in strength is stimulated, it would be because the muscles have been loaded, fatigued, and stressed sufficiently. All the physical benefits are fundamentally caused by making the muscles work.

Demanding muscular loading is the fundamental cause for triggering a cascade of positive changes throughout your body. Even for the cardiovascular system, the stimulus is making the muscles work, and the cardiovascular system kicks into higher gear simply as a support system for the working muscles. (In other words, the heart and lungs can’t jump out of your body and hop on the stair climber to exercise themselves. The only way to “get at” your cardiovascular system through exercise is by making the muscles work.)

A big advantage of effective strength training when compared with other exercise methods (like stair climbing) is that strength training gives you the opportunity to make your muscles work much harder than stair climbing or other exercise choices. If you’ve ever trained your leg muscles to “momentary failure” on the leg press machine in slow-motion form, you know firsthand how strength training works your muscles hard! Since strength training can make your muscles work harder than other activities (like stair climbing), you can stimulate as good or better benefits in all of the body’s systems (including the muscles, cardiovascular system, lungs, endocrine system, immune system, and general metabolism) than you can with other activities.