as charlie says "exercise anywhere strengthens muscle everywhere via the “crossover effect”.
The nervous system controls movement, thus training one movement may not train other muscles directly but will still have a neural effect that is transfered elsewhere.
Check this thread out for more info:
http://www.charliefrancis.com/community/showthread.php?t=4139&highlight=crossover+effect
“Weights for speed bundle” is a product here in the store section, click on the link up top for more info on that