REGULAR ARTICLE Cross-sectional trends in cardiovascular fitness in Swedish 16-year-olds between 1987 and 2007 Örjan B Ekblom (orjan.ekblom@gih.se) 1,2 , Elin AM Ekblom Bak 1,3 , Björn T Ekblom 1,3 1.A ˚ strand Laboratory of Work Physiology, Swedish School of Sport Sciences, Stockholm, Sweden 2.Department of Clinical sciences, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden 3.Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden Keywords Adolescents, Aerobic fitness, Sweden, Trend Correspondence O ¨ rjan B Ekblom, A ˚ strand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, PO Box 5626, 114 86 Stockholm, Sweden. Tel: +46 8 16 14 63 | Fax: +46 8 660 75 11 | Email: orjan.ekblom@gih.se Received 23 September 2010; revised 13 December 2010; accepted 20 December 2010. DOI:10.1111/j.1651-2227.2010.02135.x ABSTRACT Aim: We sought to investigate the temporal trends in estimated maximal aerobic capacity in adolescents (mean age 16.1). Methods: Analyses were based on data from three population-based samples, col- lected in 1987 (n = 221), 2001 (n = 537) and 2007 (n = 265). Subjects underwent sub-maximal ergometer testing. Absolute and relative aerobic capacities were estimated using the A ˚ strand-Ryhming nomogram. Results: Compared to 1987, values for estimated relative and absolute maximal aerobic capacities were lower in 2001 and 2007, and values in 2007 were lower com- pared to 2001, in both boys and girls, except for absolute capacity between 1987 and 2001 in girls. The differences over time did not differ between genders. Absolute values changed from 3.0 and 2.5 L / min in 1987 to 2.5 and 2.2 L / min in 2007, for boys and girls, respectively. Relative values changed from 46.5 and 45.9 mL / min / kg in 1987 to 35.0 and 36.6 mL / min / kg, in 2007, for boys and girls, respectively. Conclusion: Based on earlier reports on the relationship between aerobic capacity and metabolic risk, the results from the present study provide argument that future public health will be affected negatively. Low physical fitness in children seems to play an important role in the risk of the metabolic syndrome independently of overweight status (1–3), although level of adiposity seems to interfere to some extent (4,5). Furthermore, A ˚ berg et al. (6) recently reported a positive association between aerobic fitness during late adolescence and aspects of cognitive functioning as well as educational achievements later in life. Data indicates further that increases in aerobic fitness between ages 15 and 18 pre- dicted cognitive performance age as 18. Temporal trends in aerobic fitness are therefore important to study to be able to foretell potential changes in the public health and to iden- tify groups at risk, because numerous studies have shown relationships between low aerobic fitness and several poten- tial risk factors. Based on both sub-maximal tests and different forms of performance tests, population-based studies on secular trends in aerobic fitness (VO 2max ) or performance in chil- dren and young adolescents have been reported interna- tionally from the 1930s up to 2003 (7–17). Generally, levels have been declining in most studies, as indicated by data on direct measured VO 2max from both Scandinavia (12) and other parts of the world (10,11) as well as from estimation of aerobic fitness in field-based maximal testing (7–9). Freedson and Goodman (10) found no change in measured VO 2max in 38 different non-randomly selected samples from 1938 to 1993. This is confirmed by Eisenmann and Malina in boys (11). Also, Fredriksen et al (12) found a steady decline in VO 2max in both genders during about the same period of time in Scandinavian samples. These trends are partly supported by evaluation of aerobic fitness based on field-running maximal tests. Tomkinson and Olds (7) reported an increase in aerobic performance until 1960s, but thereafter values showed a decline until 2002. Similar results from field testing have been reported by others (8,9). More recently, Houtari et al. (14) report declining perfor- mance in Finnish youths between 1976 and 2001, based on a 2000-m running test. Albon et al. (15) used a shorter run- ning test in New Zealand 10- to 14-year-olds, between 1991 and 2003, also reporting a decline in fitness with time. A recent study on Danish adolescents (18) shows a decreased work capacity but unchanged calculated aerobic capacity. In Swedish adolescents, Westersta ˚ hl et al. (19) found declining results in 1995, compared to 1974, in a run–walk test, indicating decreased aerobic fitness. In a previous study based on a sample of 16-year-olds, (20) boys aged 16, we report lower level of VO 2max , estimated from sub-maximal cycle ergometry in 2001 compared to 1987. However, no Acta Pædiatrica ISSN 0803–5253 ª2011 The Author(s)/Acta Pædiatrica ª2011 Foundation Acta Pædiatrica 2011 100, pp. 565–569 565