The Jedi Path, Pg 72 - Part III: Padawan - Form V Lightsaber Combat: Shien/Djem So
"Form V is the most physically demanding of all combat styles. While Form IV requires speed and agility, Form V requires strength. Jedi without the natural ability to overpower their opponents should study another form. Conversely, Jedi of towering stature and imposing musculature may choose to focus on Form V, particularly because it requires less agility than other forms."