Most of them, really. A sword relies on pressure to do its work, so strong-arming isn't necessary (a 10 N on a square millimeter of area is still 10,000 Nm of pressure, more than enough to wound). Of course, some muscle is necessary, but not the sort of power seen in anime shows or implied in theater (stage blades are twice to three times as heavy as real ones due to their thick edges). Anything that you bring to the table should be enough, you will grow the rest quickly enough.
Both kenjitsu and fencing rely heavily on not hitting your opponent's blade or using leverage against them rather than strength (a push contest never ends in your favor- Murphy's second law of swordplay). If I push your tip out of the way with the guard of my sword, it doesn't matter if I'm a little girl and you are Arnold Schwartzenegger, I will win. The same goes for cutting, technnique trumps strength.
I would suggest fencing, personally, but my opinion is a bit biased.
Fencing Club at UH