Cranking to power a laptop

I was watching a guy talking about that they want to create a laptop that gives you a 1:10 ratio of cranking vs. operation time. A human cranking with a good generator that doesn't lose a lot in the process of converting the energy could give a 100 watts output for a few minutes after which he will start getting tired and the output will decrease. So what this guy is talking about is only achievable if you can get your laptop to function under 10 watts. Which is a feasible number, and actually it is currently at 8 watts with a target of 2 watts. Now the other option is mentioned was to hang a heavy rock on a pulley that would rotate your generator and you would just pull the rock up when it's approaching the ground to sustain the electricity generation. Here he has done a lot of imagination. Let's say you have a 5 kg rock, you hang it 2 meters high. The energy you stored in that rock is mgh which is 5*10*2. This is 100 joules. If you even have the 2 watts laptop, 100 joules will sustain you for 50 seconds. So it seems you need a 100kg rock, along with a pulley and a rope that could support that, and even then, it would give you roughly a quarter hour of operation time.

I believe that our devices had gone far beyond our capability to generate their power by pedaling. We either need extremely power efficient devices that operate in the range of 0.1-0.5 watts, or we need to generate the power in another way.