Running injuries are common, usually causing athletes to cease or significantly reduce participation in a particular sport. The recent development of aquatic treadmills (ATM), an alternative to land treadmill (LTM) running, provides another option. The use of an ATM provides an individual the opportunity to run in an environment that creates much lower impact or ground contact forces compared to what is experienced on land. Forces 2-3 times that of a person’s body weight may be experienced on land while in water these forces are about 1 times body weight. This cumulative reduction in force lowers the risk of overuse injury and decreases the possibility of lost time to exercise. Another consideration with ATM is whether the energy expenditure during running in an ATM is comparable to running on a land treadmill. Therefore, this study sought to examine the energy expenditure (oxygen consumption, VO2) relationship between varying jet resistances and running speed on an ATM versus running on a level LTM. Healthy subjects ran on a LTM at three self-selected running speeds whileVO2 was measured. In ATM subjects ran as speeds identical to LTM but water jet resistances corresponding to 0, 20, 40, 60, 80 and 100% jet capacity were used to provide additional resistance during running. In terms of energy expenditure LTM was greater than ATM when 0 or20% jets were used. By 40% jets energy expenditure was similar between LT Mand from 60-100% jets ATM was greater than LTM. Knowing what jet resistance is used in ATM allows for the estimation of running speed on LTM to create similar amounts of energy expenditure. These results allows someone with orthopedic restrictions to exercise in ATM and gain similar benefits of energy expenditure as LTM.