If genetics are good, plyo’s all day long.
Incidentally, My 40 times lowered considerably when I dropped weights all together. Slow, heavy movements, increasing mass etc did nothing for my 40. In fact pilates, stretching everyday, reducing muscle mass & conditioning the “pilates powerhouse” did more for me than 2 years of weights ever did.
I’m still trying to work out how heavy weights translates to higher explosive limb movements. 1000lb squatters can’t cross the road without turning red. The rubbish that is spoken about Westside lifters, olympic weightlifters all being fast, etc. Thats BS. I’ve seen skinny guys running faster 40’s than guys lifting in the gym for years. Look at Kim Collins, Carl Lewis etc. I once read Carl Lewis’s times increased when he started lifting. How true?.
My question would be how long after the weights were deleted before the 40 times came down? It could be they did help but did so some time after they were removed.