Does the Dynamics Strength Index Associate with the Swimming Performance in Age-Group Swimmers?

The Dynamic Strength Index (DSI) is highly valuable for assessing an athlete's training level in terms of neuromuscular strength and power. The normative data for DSI ratios and relationships to other performance (i.e., counter movement, sprint and swimming performance) have been examined. Since it is not known whether percentage DSI is well related with swimming performance particularly in age-group swimmers, we investigated the associations between DSI and the performance in 50-m sprint swimming across four different swimming techniques. Thus, 120 (67 boys and 53 girls) age-group swimmers (age: 12.0 ± 1.0 versus 11.9 ± 0.9 years old, height: 154.6 ± 12.3 versus 153.4 ± 11.2 cm, body mass: 46.7 ± 12.2 versus 45.7 ± 9.1 kg, maturity offset: -4.8 ± 1.2 versus -1.9 ± 1.1yrs) were recruited for this study. Inverse relationships between DSI and the performance of front crawl (r = -0.55, p = 0.02) and butterfly (r = -0.53, p = 0.04) were observed in girls and trend of inverse connection exhibited between DSI and 50-m time across all four techniques in girls. The DSI is useful in evaluating age-group sprinting performance and provide normative data for ballistic and isometric peak force measures.