Lifting heavy weights does not make you slower, in fact, it makes you faster!
A common myth and concern we hear from our athletes is that if they lift too heavy they will start getting slower.
Done properly strength training should serve to make an athlete faster and more explosively.
The myth most likely comes from athletes who lift in a bodybuilding style (high reps, slow tempo, isolated muscles and movements) who then gain excessive amounts of extra slow twitch muscle mass.
Athletes should instead focus on lifting for neural adaptation. Heavy weights, high intent to move and lower volumes of work.
http://www.coreadvantage.com.au/blog/2016/intent-to-move
For all things speed training head over to our playlist on YouTube: https://www.youtube.com/watch?v=vldfypMgcyY&list=PLLGwYUBXVGQWj1XlIIw__u-Q-jq2m_FLj