Validity, reliability, and normative data on calf muscle function in rugby union players from the Calf Raise application

Abstract

We examined the validity and reliability of biomechanical outcomes extracted using the Calf Raise application of three calf muscle tests. We then established normative calf muscle function values for male rugby union players accounting for rugby-related factors (position, level) alone and together with clinical factors (age, leg dominance, BMI, previous injury). In total, 120 athletes performed three single-leg calf muscle tests. Twenty athletes participated in application validation; 18 in test–retest reliability; and all in establishing normative equations. Validity of application outcomes against 3D motion and force plate data was good-to-excellent (CV ≤ 6.6%, ICC ≥0.84). Test–retest reliability was good across outcomes following familiarisation (CV < 10%, ICC ≥0.83). Forwards produced superior power than backs during the bodyweight (59 W, p = 0.007) and weighted (73 W, p < 0.001) power tests. Playing level influenced power outcomes (p < 0.009). Super Rugby players were more powerful than Club (both power tests), Provincial (both power tests), and International (bodyweight power). Backs completed more repetitions (3 repetitions, p = 0.001) and positive displacement (30 cm, p = 0.001) than forwards during endurance testing. When accounting for clinical factors; BMI, age, and previous injury explained some of the differences observed between positions and levels. This study provides initial benchmark values of calf muscle function in rugby union.