Cordyceps sinensis (Cs) and Rhodiola rosea (Rr) are herbs used in traditional Chinese medicine to treat a multitude of ailments as well as to enhance performance. The purpose of this research was to examine the effects of a formula containing Cs and Rr (Cs-Rr) on circulatory dynamics, specifically muscle tissue oxygen saturation (Sto(2)), in male subjects during maximal exercise. This study followed a double blind, randomized, placebo-treatment, pre-post test design. Capsules were administered to 8 subjects who were randomly assigned to 1 of 2 groups. The treatment group received Cs-Rr, and the control group received a placebo. All subjects performed 2 exercise stress tests to volitional fatigue on a cycle load ergometer. There were no significant (p </= 0.05) differences in Sto(2) slope, Sto(2) threshold (Sto(2T)), Vo(2)max, ventilatory threshold (V(T)), or time to exhaustion (T(E)) between or within the treatment or control group. In conclusion, Cs-Rr did not significantly enhance Sto(2).