Strength is a measure of of your raw physical power. It affects how much you carry, and the damage of all melee attacks. Now you instantly gain 1 point!”— In-game description
For each rank taken in the Strength Training perk tree, the Sole Survivor will gain access to a 1 extra point in Strength. Strength Training can be taken a total of 10 times, making this a 10-ranked perk.
As each S.P.E.C.I.A.L. skill can only be set to 1, at minimum, taking Strength Training 10 times is a waste, as no S.P.E.C.I.A.L. stat can be raised above 10.