Active Voice: The Power of Fitness
By Francisco B. Ortega, Ph.D., and Michael Sjöström, M.D., Ph.D.

Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.

Francisco B. Ortega, Ph.D., is a Research Associate Fellow at Karolinska Institutet in Sweden and at the University of Granada in Spain. His research focus includes the study of physical activity and fitness and their associations with physiological and psychological health outcomes. Michael Sjöström, M.D., Ph.D., is the head of the Unit for Preventive Nutrition at Karolinska Institutet in Sweden. His research focus includes the improvement of current methodology to objectively assess physical activity and fitness at the population level, as well as to investigate applications of physical activity as a public health tool. This commentary presents Ortega’s and Sjöström’s views associated with the research article they and their colleagues published in the Oct. 2011 Medicine & Science in Sports & Exercise® (MSSE).

Physical fitness is a set of attributes related to a person’s capacity to perform physical activity. Among the different physical fitness components that have been studied in relation to health, the component most intensively studied is cardiorespiratory fitness. Since the classical studies conducted by professors Jerry Morris and Ralph Paffenbarger, there have been an enormous number of investigations, particularly those led by Steve Blair, using data from the Aerobic Center Longitudinal Study. This research has consistently shown that cardiorespiratory fitness is one of the most powerful predictors of all-cause and cardiovascular disease morbidity and mortality. The meta-analysis published by Kodama et al. in JAMA on cardiorespiratory fitness in relation to morbidity and mortality, and many other recent studies published in top medical journals, highlight the clinical relevance of cardiorespiratory fitness assessment. In this context, our group has coordinated the EU-funded ALPHA project (Assessing Levels of Physical Activity and fitness at population level). After two to three years of systematically reviewing the available evidence, developing tools and consulting with international experts, the ALPHA project led us to develop an evidence-based ALPHA fitness test battery, which is freely available (including videos) on the ALPHA website.

We want to use this opportunity to encourage physical fitness assessment in epidemiological studies, sport and health centers, and schools as a powerful indicator of health status. Since we are aware that fitness testing might not be feasible in certain situations, our group explored the potential of a self-reported fitness measure, namely IFIS, the International Fitness Scale. We observed that IFIS is a useful, valid and reliable self-reported tool to subjectively assess health-related physical fitness in youth. IFIS is currently available in nine different languages (English, Spanish, French, German and Austrian German, Greek, Flemish, Hungarian, Italian, and Swedish) and can be freely accessed at

In our recent study published in MSSE, the longitudinal relationship between cardiorespiratory fitness and health outcomes has been further supported. Based on data from Estonian and Swedish children who were originally part of the European Youth Heart Study, we observed that improvements in fitness from childhood to adolescence (five-year follow-up) were associated with a reduction in the risk of developing overweight/obesity. Because individual changes in fitness are strongly correlated with changes in daily energy expenditure and physical activity, change in fitness from one time point to another is a good marker of change in physical activity.

Based on our findings and currently available literature, we believe that promoting fitness through physical activity from early stages of life is a promising strategy to fight against overweight and obesity, as well as to improve physical and mental health of individuals.