Near infrared spectroscopy (NIRS) provides a non-invasive means of continuously monitoring tissue oxygenation, which may be useful for diagnosis of acute compartment syndrome (ACS). Placement of these sensor pads on the surface of the skin must be such that light penetrates the intended compartment without inadvertently obtaining measurements of an adjacent compartment. The objective of this study is to examine whether the NIRS measurements of each compartment truly represent the tissue perfusion of the intended compartment, as indicated by the predictable decrease in muscle oxygenation of a given compartment in response to muscle fatigue. The investigators hypothesize that the tissue oxygenation values of the stimulated compartment will significantly decrease following muscle stimulation, indicating that the intended muscle compartment was successfully isolated. Additionally, the investigators hypothesize that NIRS values of unstimulated muscle compartments will not change from baseline.

Inclusion Criteria:

• 18-75 years old
• no current extremity injuries
• willing to provide written informed consent

Exclusion Criteria:

• history of any anatomy-altering surgery to the extremity in question
• history of peripheral vascular disease
• history of pulmonary disease

The study sample will consist of healthy volunteers recruited from the principle investigator's private practice.