Nautilus allows you to enhance your flexibility + endurance  while at the same time improving your muscular strength and cardiovascular fitness. Nautilus represents efficiency in action 

When you exercise properly on a Nautilus machine, your body is stimulated to become stronger. And it will become stronger if you don't overdo the stimulation and do provide it with adequate rest and recovery time

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However, in addition to building muscular strength, Nautilus training will also improve the capacity of you heart and lungs. According to physiologists, the simplest means by which one can determine whether or not a cardiovascular training effect has taken place is for the trainee to measure his or her heart rate elevation for a sustained period of time, generally the heart should be kept beating at 70 to 85 percent of its maximum rate (the predicted maximum being 220 minus the individual's age). The key to obtaining cardiovascular benefits on Nautilus is to train with sufficient intensity to raise your heart rate into the target zone and sustain it there for 10 to 20 minutes.

Traditionally, most protocols would have you perform some intense strength training, followed by several minutes of rest, and then repeat the process. Such lifting is typically carried on for one to two hours, which diminishes the potential aerobic effect of the exercise session. Proper Nautilus training modifies both the intensity/duration of the exercise session and the length of the rest periods between exercises. Instead of lifting extremely heavy weights for very brief fifteen-to-twenty-second periods with long rests in between, less resistance is used and the lifting and lowering portions of each repetition are performed slowly and smoothly for approximately one minute. Then, within fifteen seconds, the trainee quickly moves to the next exercise on the circuit and performs another 60-second's worth of rhythmic muscle contraction. This continues throughout a maximum of twelve Nautilus exercises and will effectively raise the trainee's heart rate to the upper limits of his or her target heart-rate zone. During the approximately 10-15 seconds that the trainee takes to move from one exercise to the next, his or her heart rate will decrease to the target zone's lower limits. But with the start of another exercise, the heart rate will again increase. According to Dr. Darden:

A reasonably fit young adult's heart rate might be elevated to 170 beats per minute for the majority of twelve exercises and drop to no lower than 140 beats per minute during the brief intervals between exercises. His average heart rate for the entire fifteen-minute workout would be 155 beats per minute. Such a workout will definitely improve cardiovascular fitness. Progressive conditioning occurs as the trainee increases the resistance and decreases the time between exercises

One recent comparative study of three different groups measured the increase in oxygen capacity that occurred over a ten-week training period. The results showed that Nautilus circuit trainees enjoyed the same aerobic conditioning benefits that runners did, and both the Nautilus group and the running group were superior in that respect to the free-weight trainees. Furthermore, the running group trained 50 percent longer than the Nautilus group: 30 minutes three times per week as opposed to 20 minutes three times per week. Published in a 1985 issue of Research Quarterly for Exercise and Sport, this study of 36 male college students also showed that the Nautilus group decreased their skin-fold fat measurements more than the other groups.

ENHANCING FLEXIBILITY WITH NAUTILUS

For flexibility to improve, your limbs must be stretched into positions that extend beyond their normal range of movement. It takes heavy resistance to produce such a degree of stretching. This stretching is provided during the lowering portion of rotary movements performed on most Nautilus machines.

For example, the Nautilus Pullover machine can progressively stretch your upper back muscles and shoulder girdle. The Duo Hip and Back machine stretches your buttock muscles, and the double chest machine stretches your chest. The muscles of your inner thighs are stretched on the hip adduction machine.