They're the current technological solution, but they're essentially proxies to condense a naturally occurring process into a more efficient process; weight mach

They're the current technological solution, but they're essentially proxies to condense a naturally occurring process into a more efficient process; weight machines and treadmills provide an efficient method to work out whatever systems your exercise regime is designed to affect. But what you're after is the resulting byproduct of that exercise, not that exercise itself. Similar to how biking uses the same inputs as walking, but makes it more efficient. So if your goal is to get somewhere as efficiently as possible rather than walking in and of itself being the goal, you're going to bike instead. Then comes along the car and you're no longer constrained to the natural capabilities of your body in order to travel, and it's a whole new ballgame. Exercise has a lot of health benefits because it causes things in the body. From stretching things to tearing muscle fiber to causing your body to generate and release different hormones and steroids (and many, many other effects). The technological solution the OP wants is something which simulates the effects of exercise on the body but without the exercise itself. Such as nanomachines that can be designed to stress test different components of the body and keep them active or that cause the same types of micro-tears in muscular tissue that weight lifting does. As we learn more about the body, and we make smaller and smaller machines that are capable of operating from within the body, we can leverage those machines and that knowledge to directly maintain an ideal state of fitness regardless of externalities such as an individuals predilection or capacity for the level of working out needed to maintain that ideal state.