Rapid Spike in Hip Adduction Strength in Early Adolescent Footballers: A Study of 125 Elite Male Players From Youth to Senior.

PURPOSE: To investigate the differences in hip adductor and abductor muscle strength in elite male footballers from youth to senior level. METHODS: We tested 125 players from the under-13-years (U'13) to senior squads of a Danish male professional football club in this cross-sectional design study. Hip adductor and abductor force (in newtons), torque (in newton meters), normalized torque (in newton meters per body mass), and adduction-to-abduction ratio were measured using handheld dynamometry. RESULTS: Between U'13 and senior level, adductor force increased by 104%, torque by 127%, and normalized torque by 21%. Abductor force increased by 78%, torque by 126%, and normalized torque by 17%. For incremental differences between age groups, significant increases were observed between the ages of U'13 to U'14 (18%-39%) and U'14 to U'15 (19%-33%) for all strength measures (P ≤ .021). No incremental difference was observed for adductor-to-abductor ratio. CONCLUSIONS: The large increases in hip adductor and abductor strength occurring between the ages of U'13 and U'15 offer insight into the strength capabilities and stress demands in these players, which may relate to injury vulnerability, and facilitate clinicians in selecting best-suited exercise interventions.

Hip adduction strength and provoked groin pain: A comparison of long-lever squeeze testing using the ForceFrame and the Copenhagen 5-Second-Squeeze test.

OBJECTIVES: To compare long-lever squeeze testing using the ForceFrame and the Copenhagen 5-Second-Squeeze test (5SST) for assessment of hip adduction strength and provoked groin pain in elite male soccer players. DESIGN: Cross-sectional study. SETTING: Pre-season testing at facilities of a Danish professional 1st tier soccer club and academy. PARTICIPANTS: Elite male soccer players (n = 83, mean age; 16 ± 2.7 years) from U13, U14, U15, U17, U19 and senior teams cleared for full training and match participation. MAIN OUTCOME MEASURES: Maximum isometric hip adduction strength (Nm/kg) and provoked groin pain (NRS 0-10). RESULTS: Hip adduction strength was 16% lower in the ForceFrame. A Bland-Altman plot showed a systematic bias (-0.47 Nm/kg, 95% CI [-0.57; -0.38]) and lack of agreement (95% limits of agreement: -1.31; 0.39 Nm/kg). In the ForceFrame, provoked groin pain was less intense (median NRS 0 [IQR: 0-1] vs. 5SST: 1 [IQR: 0-3], p < 0.001) and reported by fewer players (NRS >0) (27% [n = 22] vs. 5SST: 61.4% [n = 51], p < 0.001). CONCLUSIONS: The ForceFrame and the 5SST lack agreement and are not interchangeable methods. This may have implications when selecting a method for screening and detecting early groin problems in male soccer players.

Hamstring and Quadriceps Muscle Strength in Youth to Senior Elite Soccer: A Cross-Sectional Study Including 125 Players.

PURPOSE: Increasing age, high quadriceps strength, and low hamstring muscle strength are associated with hamstring strain injury in soccer. The authors investigated the age-related variation in maximal hamstring and quadriceps strength in male elite soccer players from under-13 (U-13) to the senior level. METHODS: A total of 125 elite soccer players were included from a Danish professional soccer club and associated youth academy (first tier; U-13, n = 19; U-14, n = 16; U-15, n = 19; U-17, n = 24; U-19, n = 17; and senior, n = 30). Maximal voluntary isometric force was assessed for the hamstrings at 15° knee joint angle and for the quadriceps at 60° knee joint angle (0° = full extension) using an external-fixated handheld dynamometer. Hamstring-to-quadriceps strength (H:Q) ratio and hamstring and quadriceps maximal voluntary isometric force levels were compared across age groups (U-13 to senior). RESULTS: Senior players showed 18% to 26% lower H:Q ratio compared with all younger age groups (P ≤ .026). Specific H:Q ratios (mean [95% confidence interval]) were as follows: senior, 0.45 (0.42-0.48); U-19, 0.61 (0.55-0.66); U-17, 0.56 (0.51-0.60); U-15, 0.59 (0.54-0.64); U-14, 0.54 (0.50-0.59); and U-13, 0.57 (0.51-0.62). Hamstring strength increased from U-13 to U-19 with a significant drop from U-19 to the senior level (P = .048), whereas quadriceps strength increased gradually from U-13 to senior level. CONCLUSION: Elite senior soccer players demonstrate lower H:Q ratio compared with youth players, which is driven by lower hamstring strength at the senior level compared with the U-19 level combined with a higher quadriceps strength. This discrepancy in hamstring and quadriceps strength capacity may place senior-level players at increased risk of hamstring muscle strain injuries.