Changes in nuclear magnetic resonance (T2) relaxation of limb tissue with bed rest

Bed rest is used to simulate the effects of weightlessness on human physiology. A spinecho procedure was used to image the lower leg of 15 normal male volunteers before and after 5 weeks of horizontal bedrest. In addition to noninvasively measuring muscle size changes, accurate T2 images were produced to investigate possible relaxation time changes immediately (2–4 h) and 1–2 days after bed rest. Subcutaneous fat showed no change in T2, bone marrow showed a decrease, and muscle showed no change immediately after bed rest but increased 1–2 days following reambulation. © 1987 Academic Press, Inc.