Stretching Prior to Lifting Reduces Force Production

Yes, this is true. Most studies that I read state that stretching a muscle prior to a maximal lift will reduce the force production 2-5%. Keep in mind that these studies also have a subject perform a stretch for a specified amount of time and then immediately go perform a maximal lift. 

Here's how I train my athletes without reducing force production.

1. I don't PNF or AIS stretch them on testing or maximal effort days.

2. We alternate dynamic warm up days with PNF days.

3. When we PNF stretch, I don't immediately have them perform a maximal lift. Generally, after we stretch, we go through a movement prep period and then progress towards they're daily percentage.