I have practically no physical strength.
Koichi doesn't have stamina to do 80 push-ups.
The fever weakened his body, but he was still strong enough to drink water by himself.
You have your body power. This is just another way to say physical strength. Watch out, if you use too much of your physical strength you may run out of physical stamina and endurance completely! They're tied together, so make sure to pace yourself.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.