and Ralph Paffenbarger, all notable researchers, during these trials. A principal collaborator in these trials was Dr. Ronald Krauss at Lawrence Berkeley National Laboratory (LBNL), who was keenly interested in understanding how subclasses of lipoproteins (the particles that transport cholesterol and triglyceride in the blood) were affected by exercise, diet, drugs and other factors. Much of my involvement in these trials was working with Dr. Krauss on lipoprotein subclasses. In 1988 I was invited by Dr. Krauss to work with him at LBNL.

In the succeeding years I continued to work closely with Dr. Krauss in studies of lipoprotein heterogeneity. In both high-density lipoproteins (HDL) and low density lipoproteins (LDL) there is a spectrum of different particles that can be identified from one-another by gradient gel electrophoresis. These particle subclasses are important because they appear to convey different degrees of cardiovascular disease risk. I have created statistical methods for analyzing these particle distributions and have applied them to studies of family members, diet, drugs, and physical activity.

In 1991 I started the National Runners' Health Study. Access to Runner's World magazine subscribers was particularly helpful in creating the cohort. I recruited over 55,000 runners by 1996, but lacked any real financial support for this study. However, by 1995 work by Drs. Blair, Pate, Haskell, Paffenbarger and others brought physical activity to a position of prominence in preventive medicine. However, the guidelines for physical activity by various organizations largely emphasized moderate-intensity activity (such as brisk walking). Physician-supplied medical data collected on the National Runners' Health Study suggested that much of the health benefits from physical activity might require greater intensity and durations than was being advocated by these guidelines. This led to a series of debates between Steven Blair and myself regarding how much physical activity was beneficial, and to funding by the National Heart, Lung, and Blood Institutes for the National Runners' Health Study. This support also facilitated the creation of a National Walkers' Health Study to test whether walking and running were equally beneficial for reducing cancer and heart disease risks. Additional funding by the Department of Defense covered the