During certain bowel surgeries for cancer (colorectal surgery), individuals frequently have to be placed in a head-down position to enable surgeons have optimal access to the cancer site. This position usually also involves bending the hips and knees while supporting the legs in stirrups. However, lying in this position for long periods of time can lower the flow of blood to the legs, which can potentially cause injury. This rare but severe consequence is called Well-Leg Compartment Syndrome (WLCS). If WLCS is not diagnosed quickly, it can lead to other difficult complications and a significant delay in recovery. Unfortunately, because the individual is under anaesthesia, diagnosis is delayed in many cases. There is very little information in the medical literature about how this damage to the legs progresses over the course of the surgery. To better understand how WLCS, how well blood vessels work during surgery will be assessed. The flow of blood and oxygen in the calf muscle will be assessed in 25 individuals placed in a head-down position during colorectal surgery. Likewise, blood samples will be obtained in order to measure the biological markers that may contribute to the development of WLCS.