I'm obsessed with maximizing efficiency. I noticed that most of the exercises with most muscles, the torque required isn't constant. For example when doing a bicep curl, the load is low at the bottom and the top.
A problem with variable load exercise, is that you are kind of wasting your time at the start and the when the torque is low. High weight causes higher mechanical tension and increases hypertrophy. But if half of the time you are doing low weight, it's like doing muscle cardio. You have to rest between sets otherwise the metabolic stress in your localized muscle group gets so high that you cannot continue with your exercise. So in a way, doing a variable load exercise increases metabolic stress, wastes time, and doesn't get a lot of progress done.
So would it make more sense to lift weights at the highest tension and keep that angle for as long as you can?
Or would it make sense to create a variable tension machine that changes the weights based on the angle and position of its user?
Another problem with variable tension exercises is that when the user starts fatiguing, their form suffers, and they start to cheat, or the user can do the exercise, but stall at peak torque and fail abruptly. Since the torque was low on the eccentric movement, and the torque was low at the start of the concentric movement, the user feels like they have more strength and energy than they actually do, and then again when they try to do another rep, they hit the peak of the torque curve and fail. However if there was a variable load machine, the user would gradually fatigue, and would have a better understanding of their current condition.