A common belief among strength coaches and personal trainers, especially those who work with football players, is that you can become more explosive by lifting heavier and heavier weights. However, as has been scientifically proven, when you lift very heavy weights, the movement is slow, and as a result, you develop slowness especially of the neuromuscular system.
To counteract this negative result, coaches and trainers say you must think explosiveness or try to lift the heavy weight as quickly as possible. The thinking and trying will then bring about greater explosive power. This, however, has not been scientifically substantiated through research nor has it been demonstrated in practice.
The only time you can get positive results from lifting very heavy weights (85-100% of max) to develop greater explosiveness is if you use such training sparingly and you supplement or complement the heavy weight training with explosive training. About 70% of strength work should be in the 70-85% range which actually allows you to develop greater strength than when you lift only in the 90-100% zone.
The increased strength from the lower zone work then enables you to develop more speed and explosive power. Note that you can become stronger over a certain period of time with such training in comparison to using 85-100 % weights!
Explosive training often uses weights, but the speed of execution must be fast to qualify as an explosive exercise. Usually, these exercises take the form of jumps or throws, i.e., jumping with weights or catching and throwing (repelling) heavy objects, whether it be weights, medicine balls, etc.
For more information on this topic, read Build A Better Athlete by Dr. Michael Yessis.