Background:Previous studies suggested that the age of peak performance in freestyle swimming was 17 years for women and 19 years for men. Data on the age of peak swimming performance in other swim strokes such as backstroke are lacking. The present study investigated the changes in (i) swimming speed and (ii) age of peak swimming speed across years for elite female and male backstroke swimmers competing at both national and international level. Methods:The changes in age and swimming speed in 50m, 100m and 200m were analyzed for elite backstroke and freestyle swimmers at national level (i.e. Switzerland) and international level (i.e.finalists of World Championships) on 50m long coursefrom 1994 to 2011. Results: For all distances and disciplines, women reached the age of peak swimming speed at a younger age ( 18-23 years) than men ( 21-26 years). The age of peak swimming speed in backstroke and freestyle swimmers at national level was 1-2 years younger than in swimmers at international level. The age of peak swimming speed increased significantly (p<0.01) between 1994 and 2011 in 50m backstroke for women from 16 to 22 years and in 50m freestyle for men from 22 to 23 years in swimmers at national level. No changes in the age of peak swimming speed were observed in swimmers at international level for both swim styles across time for both sexes (p>0.05). Swimming speed increased across years in all distances and disciplines except for 50m backstroke in women at international level (p>0.05). Conclusion: Women reached in all disciplines the age of peak swimming speed at a younger age than men. Swimmers at national level were younger than swimmers at international level. Swimming speed increased in all distances and disciplines across years in swimmers competing at both national and international level. AbstractIntroduction Previous studies suggested that the age of peak performance in freestyle swimming was ~17 years for women and ~19 years for men. Data on the age of peak swimming performance in other swim strokes such as backstroke are lacking. The present study investigated the changes in swimming speed and age of peak swimming speed across years for elite female and male backstroke swimmers competing at both national and international levels. Materials and methodsThe changes in age and swimming speed in 50 m, 100 m and 200 m were analysed for elite backstroke and freestyle swimmers at national level (i.e. Switzerland) and international level (i.e. finalists of World Championships) on the 50-m long course from 1994 to 2011. Results For all distances and disciplines, women reached the age of peak swimming speed at a younger age (~18-23 years) than men (~21-26 years). The age of peak swimming speed in backstroke and freestyle swimmers at national level was ~1-2 years younger than in swimmers at international level. The age of peak swimming speed increased significantly (P < 0.01) between 1994 and 2011 in 50-m backstroke for women from

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