Just to be clear: I think the exercise system is stupid and that they make extreme claims. An effective exercise program would include more varied training, including longer, lower-intensity efforts. That said, if the machine is as much of an ass-kicker as it’s reputed to be, most people wouldn’t be capable of actually using the thing for 4 full minutes. If you could, you’d probably be in darn good shape. You could do much worse things for your health than aim for that time goal on the machine.
Cardiac adaptations and links to performance are complicated. This study shows that while there are recognizable heart adaptations in older athletes over controls, there wasn’t always a clear relationship between adaptations due to sprinting vs. endurance training and overall performance. This meta-study shows that strength athletes do have favorable heart adaptations, counter to the perception that only endurance athletes have good heart health, and that athletes with combined strength and endurance training have the most favorable adaptations.
Lactate threshold training, which is now seen to be a better measure of overall performance than VO2-max, is influenced much more by intensity than by length of effort. If you improve your lactate threshold, you can work closer to your maximal effort (i.e. VO2-max) for longer periods of time, and thus perform better. You can’t work at the edge of your maximum capabilities for very long at all, even if you’re an elite athlete, so these kinds of training sessions are going to be short intervals mixed in with recovery periods of either lower or no activity.
In addition, you don’t actually need to keep your heart rate in your training zone for longer than 30 minutes. If you’re doing steady-state training, you are supposed to keep your heart rate up for a minimum of 10 minutes, but benefits drop off rapidly for efforts that last longer than 30 minutes. In other words, thirty minutes is around where you hit the point of diminishing returns; longer isn’t necessarily better, it’s just longer. Upping the intensity rather than increasing the duration, or doing more frequent training sessions (increased volume) is better than just doing what you’re doing for a longer time each session. Short-duration, high-performance athletes are actually advised to limit their endurance training to prevent losses of strength and power.
You could be pretty darn fit with sub-maximal training lasting only 10–20 minutes, mixed in with intense interval training a couple of times a week, or from doing strength training with minimum HIIT sessions, about 3 a week. Even better would be mixed training that challenges you with strength training, high intensity cardio, and lower intensity cardio at various times. The workouts on the site I posted earlier are mostly “weightlifting,” but considering that you’re usually doing bursts of higher intensity and lower intensity activity and keeping heart rates up to between 70 and 90% of max rates, it’s often cardio training in disguise.