Assessing Isometric Hip Adductor and Abductor Strength in Elite Youth Soccer Players: Does Hip-Flexion Angle Matter?

Isometric hip strength is a risk factor for hip and groin injuries in soccer and is assessed at various short lever positions (i.e. a hip-flexion angle of 45-90 degrees). Here, the effects of hip flexion angle on peak adduction and abduction force, adduction-to-abduction ratio (ADD:ABD), and relationship between test-positions was assessed. Twenty-four male soccer players (Age 17.4 ± 0.8 years) completed 3 testing sessions across 2-weeks, during which peak adduction and abduction force and ADD:ABD were assessed at either 45-, 60-, and 90-degrees of hip-flexion on a fixed frame dynamometer. Players completed three 5-s maximal voluntary contractions in each, and the tests were completed in counterbalanced order. Robust repeated measures ANOVA’s were used to compare peak force and ADD:ABD between positions, with significance set at P<0.05. Pearson’s correlations were used to quantify associations between peak force on each test. Significant differences were observed in adduction between 45- and 60-degrees (right -25.9 ±23.1N (±95% confidence limit); left -33.4±19.1N); 45- and 90 degrees (right 46.8±23.2N; left 32.6±19.9N) and 60- and 90-degrees (right 72.7±22.9N; left 66.1±19.9N). Significant differences were also observed in abduction between 45- and 90-degrees (right 32.2±20.8N; left 25.7±21.1N) and 60 and 90-degrees (right 42.4±20.9N; left 41.6±21.3N). Very large correlations between tests were observed in adduction and abduction, respectively (r = 0.77 to 0.87). However, prediction errors were also large (~40N). ADD:ABD was highest at 60-degrees (1.10). In conclusion, peak adduction and abduction force varies between short lever testing positions. While strong associations between testing positions exist, large prediction intervals are evident, and these tests should not be used interchangeably.