Test-Retest Reliability of the 20-Metre Shuttle Run Test in a Cohort of Police Trainees

The 20-metre Multistage Fitness Test (20-m MSFT) is commonly used to measure aerobic capacity in police trainees as an entry gateway or exit requirement. However, its test-retest reliability, or consistency of scores for individual candidates across successive days, has not been determined. The aim of this study was to evaluate the test-retest reliability of the 20-m MSFT in police trainees. Retrospective data for 13 police trainees who completed the 20-m MSFT on two occasions 48 hours apart (Trial 1 and Trial 2) were provided. Paired sample t-tests were used to detect differences between individual performances with intraclass correlation coefficients (ICC) investigating the test-retest reliability. A Bland Altman plot was created to inspect the limits of agreement between the two measures. Alpha levels were set at 0.05 whereby a p value of >0.05 indicated no significant difference in mean scores between the two trials. No significant differences (p=0.821) between the mean total numbers of shuttles completed in Trials 1 (mean = 70.4±19.7 shuttles; Level 8-9) and 2 (mean = 69.8 ±21.3 shuttles; Level 8-9) were found. Six trainees achieved higher total shuttle scores for Trial 1 (+8.0 ±3.2 shuttles) while seven trainees achieved higher total shuttle scores for Trial 2 (+5.9± 5.1 shuttles). Test-retest reliability across trials was ‘excellent’ (ICC(3,1)=0.922 [95%CI 0.766-0.976], mean difference between scores = 0.55±8.37 shuttles). While the 20-m MSFT has excellent test-retest reliability the small amount of variability in results suggests that retesting of candidates who fail to meet any discriminatory standard by a small margin should be considered.