Within- and Between- Session Reliability of the Spider Drill Test to Assess Change of Direction Speed in Youth Tennis Athletes

Agility or Change of Direction Speed (CODS) is a critical physical attribute in a sport such as tennis, which is categorised by frequent and multiple changes of direction. Recently, a CODS test called the 'spider drill' has been used to assess tennis athletes' ability to change direction. To the authors' knowledge, no study has solely assessed its reliability and compared this with other commonly-used CODS tests; thus, this was the aim of the study. Ten nationally ranked youth tennis athletes (age: 15.1 ± 2.6; mass: 66.4 + 17.2 kg; height: 163.0 + 16.2 cm) completed three trials of the spider drill, modified t-test and pro-agility test on two separate testing occasions. All CODS tests had low typical percentage error, both within-sessions (CV = 1.8 - 4.1%), and between session (CV = 1.2 - 3.7%). The SEM was also consistent within tests both within- and between- testing sessions. Within-session test-retest consistency illustrates strong reliability for the spider drill (ICC = 0.93, 0.95), modified t-test (ICC = 0.79, 0.83), however for pro-agility session 2 fell outside of the accepted threshold (ICC = 0.88, 0.69). These trends were similar when assessing between-session consistency, with both the spider drill and modified t-test providing high levels of reliability (ICC = 0.95 and 0.97 respectively). However, the pro-agility fell outside of the accepted threshold (ICC = 0.66), with 95% confidence intervals wide-ranging in nature (95% CI: 0.11 - 0.9). These results suggest that the spider drill and modified t-test are both reliable tests when measuring CODS within youth tennis athletes. Strength and conditioning practitioners could consider changes in excess of ± 1.1% as meaningful (based off the SDD) when assessing CODS through the spider drill or modified t-test within youth tennis athletes.