Test-retest reliability of the isometric soleus strength test in elite male academy footballers.

Abstract

BACKGROUND
Currently there is no reliability data is available for the isometric soleus strength test (ISST), commonly used as a monitoring tool in elite football settings. ISST for other muscle groups, most notably the hamstrings, is utilised to identify injury risk and readiness to train/play.

PURPOSE
To profile athletes efficiently, performance practitioners require optimal measures that are reliable. The aim of this study was to investigate the test-retest reliability of the ISST of the soleus and validate a standardised protocol for its use within an elite male football population.

STUDY DESIGN
The present study represents a test-retest reliability single cohort study.

METHODS
Thirty elite male footballers (age = 22.8±5.0 years, height = 180.0±0.08 cm, weight = 70.57±4.0 kg) performed the ISST, through 3 maximum 3-second hold efforts with 1-minute rest between repetitions and 48 hours between tests, in each test. The test was performed mid-competitive season. All data bilaterally was checked for normality through a Shapiro-Wilk Test before a Pearson’s Correlation and Bland-Altman’s analysis was performed.

RESULTS
Test-retest reliability demonstrated high reliability for ISST bilaterally (Right: ICC 0.89; Left: ICC 0.79, p<0.05). Standard errors of measurement (SEM) (%) was 8.75% and minimal detectable change (MDC) was 35.55 (N) for Peak Force (PF) measures of the ISST. Levels of agreement were found bilaterally for ISST (Right: p=0.09, CI: -153.21-10.95; Left: p=0.52, CI: -139.81-72.33).

CONCLUSION
This study demonstrated high reliability for the ISST. The ISST is a valid and reliable method for assessing PF characteristics of the soleus in elite male academy footballers. This test may be beneficial for performance practitioners for profiling soleus function of athletes. Findings indicate that the ISST displays high test-retest reliability in elite male academy football populations and should be considered in performance profiling of the athlete.