Reliability and criterion-related validity of the 20-yard shuttle test in competitive junior tennis players

Abstract

Anna Eriksson,1 Fredrik R Johansson,2 Maria Bäck3–5 1Rehab City Östermalm, Primary Health Care, 2Department of Environmental Medicine, Musculoskeletal and Sports Injury Epidemiology Center, Karolinska Institutet, Stockholm, 3Department of Occupational Therapy and Physiotherapy, Sahlgrenska University Hospital, 4Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, 5Department of Medical and Health Sciences, Division of Physiotherapy, Linköping University, Linköping, Sweden Purpose: This study adds to the previous work in the field of sport-specific fitness testing by evaluating a tennis-specific agility test called “the 20-yard shuttle test”. The aim of the study was to evaluate the test–retest reliability, the inter-rater reliability, and the criterion-related validity of the 20-yard shuttle test on competitive junior tennis players. Participants and methods: Totally, 34 Swedish tennis players (13 girls), mean age 14±1.6 years, participated in the study. To examine test–retest reliability, the subjects performed the 20-yard shuttle test three times on the same day and then the same procedure was repeated after 3 days. To test the inter-rater reliability, the time was measured with a stopwatch simultaneously by two different raters. The time recorded manually was compared to the gold standard of digital timing to evaluate the criterion-related validity. Results: Excellent test–retest reliability was found both within the same day (intraclass correlation coefficient [ICC] 0.95) and between days (ICC 0.91). Furthermore, the results showed excellent inter-rater reliability (ICC 0.99) and criterion-related validity on both test occasions (ICC 0.99). Conclusion: We have provided introductory support for the 20-yard shuttle test as a reliable and valid test for use in competitive junior tennis players. The ease of administration makes this test a practical alternative to evaluate physical fitness in order to optimally train the athletes. Keywords: agility, physical fitness, physiotherapy, performance