You get it from Riley on Iron Island.
find it the solecean ruins
you can get it in pokemon platinum!
strength
By using the move strength.
his or her level and exp.
Maylene is located at Veilstone in Pokemon Platinum. Maylene is a gym leader and is unaware of the amount of strength she possesses.
In the Unown Cave, east of Soleacon Town.
use strength
lost tower 5th floor
You can use any Pokemon that is able to learn Strength to push rocks.
its a hm and its called strength
beat bryon in the steel gym, canalve city
go to iron island and riley gives u strength when u talk to him