Editorial

It was in the autumn of 1997 when Han Kemper and myself were playing with the thought to pull together a symposium for the 1998 ACSM annual meeting. Having just completed another measurement round of the Amsterdam Growth and Health Longitudinal Study we were interested to learn to what extent our findings would be consistent with those of other, more or less comparable longitudinal studies that had also started collecting data from early age onwards. As former physical educators and current public health professionals we felt that all presentations should pivot around the relationship between lifestyle in youth and cardiovascular disease risk factors later in life. From a primary prevention standpoint it is extremely important to have good insight in these relationships, since it is often debated that the early prevention of cardiovascular disease should take place already from early age onwards. The fact however is that to date little is known about these relationships. This is not surprising, as is pointed out in the introduction to this supplement by our colleague Dr. Jos Twisk, given the fact that such information can only come from either experimental trials with lifetime follow-up or from longitudinal studies that start at early age. Experimental studies of this nature will most likely never take place, but there are a few longitudinal studies around that we thought would serve our purpose. Because of the limitation in time set by the ACSM program committee we decided to restrict ourselves to two North-American studies (i. e. the Muscatine Study and the Bogalusa Heart Study) and two European Studies (i. e. the Leuven Longitudinal Study on Lifestyle, Fitness and Health and our own Amsterdam Growth and Health Longitudinal Study). At the Orlando ACSM annual meeting oral presentations from these studies were given by Drs. Kathleen Janz, Theresa Nicklas, Johan Lefevre and Jos Twisk, respectively. As the outcome of this ACSM symposium we decided to produce a series of papers that should be published as a supplement issue to a peer-reviewed journal. We decided also to focus specifically on the significance of physical activity and physical fitness in youth for adult cardiovascular disease risk, rather than the initial broader lifestyle scope. Reason for this focus was twofold: firstly we felt that because of this focus we would get a more comprehensive set of papers, allowing better in between study comparisons and therefore better interpretation of the findings, and secondly we felt that emphasising in these papers the relationship between physical activity and physical fitness in youth and cardiovascular risk later in life could be of use in the Public Health debate regarding the significance of lifelong physical activity. This focus led to the conclusion that we should include other comparable and valuable longitudinal studies as well. Consequently, data from the Northern Ireland Young Hearts Project and from the Danish Youth and Sports Study are included in this supplement. The focus also created a “problem” since the Bogalusa Heart Study has no youth physical activity, nor physical fitness data available, making it impossible to directly address the primary focus of this supplement. The Bogalusa Heart Study is, however, able to provide valuable information on the relationship between, cardiovascular disease risk factors early in life and cardiovascular disease risk factors later in life and therefore included in his supplement.

The production of this supplement was a bit like a longitudinal study in itself. In order to produce a worthwhile end product both the editors and the authors needed perseverance, stamina and patience. But like the outcome of longitudinal studies as opposed to other study designs, the outcome of this series of papers in one supplement issue to a scholarly journal is likely to be better than the outcome of any of these papers as a stand alone publication, thereby making the long production time of this supplement worthwhile. Instrumental in the production have been the peer reviewers, who have done a tremendous job in critically reviewing the papers published in this supplement. I would like to thank Drs. Lars Bo Andersen, Colin Boreham and Chris Riddoch for kindly fulfilling this job. Finally, the production of this supplement issue to the International Journal of Sports Medicine would not have been possible without substantial financial support from both the Dutch Ministry of Health, Welfare and Sport and our own Institute for Research in Extramural Medicine, VU University medical centre. Both deserve our gratitude.

Doing longitudinal research is fun most of the time. Subjects are being “chased”, data are being collected and being analysed, with researchers getting stuck sometimes, but getting us meaningful results in the long run. The point is in longitudinal research, like in cooking, to convert the ingredients into something edible. In my opinion our cooks have served us well: I trust you'll like their pudding.