Muscle blood flow (Q) and metabolic response to exercise can very within species and may depend upon whether measurements were made in vivo or in situ. It has been suggested that to some extent these variations in muscle Q and metabolism may be the result of a reduction in muscle performance after the surgery of in situ preparations. In contrast, the development of the novel human in vivo preparation often described as dynamic knee-extensor exercise by Andersen and Saltin in 1985 is only minimally invasive. This preparation has revealed human muscle Q which far exceed those previously measured and allows the metabolic response of a single dynamically exercising muscle group to be studied. The use of this human exercise model was not the focus of this symposium, but each contributing author has worked extensively with this and other preparations to investigate muscle blood flow and metabolism in exercise. Thus, the purpose of this symposium was to bring together these new insights into muscle Q and metabolism in exercising muscle studied in vivo and in situ.