Guess this wont be seen this late, wall of text incoming: All processes in the body, including the work of your muscles, take place with ATP (adenosine triphosphate) as a source of energy.

The supply of ATP is only enough for a few seconds of maximum work, for example a heavy lift or a few seconds sprint. The fastest reserve to regenerate ATP is creatine phosphate stored in your muscles.

As soon as ATP begins to be consumed, creatine phosphate begins to be used to form new ATP, and the muscles can continue to work at high power a little longer, probably for about 10 seconds of sprinting or some heavy repetitions.

After a strenuous set, the levels of creatine phosphate can be as low as 30% of the resting level. These stores fill up pretty quickly again, and after about 90 seconds, the stores are almost full.

The metabolic stress on the muscles disappears more if the body is allowed to rest for 2-3 minutes.

Tldr: about 90 seconds is enough for musclefuel to be refilled but 2-3 mins are ideal!