1. Lifting weights does not cause you to gain weight. Eating in a caloric surplus for a prolonged period of time does. Athletes often severely underestimate how difficult it would be to gain the type of mass that would inhibit their performance (think bodybuilder size).
2. Professional athletes are not small, yet somehow they’re still the most elite athletes on the planet. Using baseball as an example: the average MLB player weights about 2.75x their height in inches.
3. Lifting weights, and producing more force, will make you FASTER...not slower. Speed is equal to Stride Length X Stride Frequency, both of which can be trained in the weight room.
4. You’re an athlete, not a powerlifter. You should be training all of the qualities that transfer to your sport. Force is just 1 of those qualities. It should not be the ONLY area of focus in your program. Sprinting, jumping, performing movements in multiple planes is important.