In general, the Rhesans are physically weak, however, they make up for that with their strength in "psionics" as some would call it. They suffer from an extreme form of muscle atrophy, something that only recently was reversed.
The Rhesan skeletal structure is, for all intents and purposes, very similar to that of the average human, save for a few key differences. First, it features two extra arms, second, it's feet have four toes each, third, it's heels are sightly raised above the ground.
The Rhesans have many of the same organs as Humans, such as a heart, brain, lungs, kidneys, a liver, and the sort. Inside their brain is a cluster of neurons that control their "psionic powers".