Relationships Between Modifiable Risk Factors of Hamstring Strain Injury

Abstract

Abstract Ripley, NJ, Comfort, P, and McMahon, JJ. Relationships between modifiable risk factors of hamstring strain injury. J Strength Cond Res XX(X): 000–000, 2023—The aims of this study were to determine whether any relationship exists between eccentric hamstring strength and isokinetic strength imbalances and bicep femoris long head (BFLH) architecture. Eighteen physically active men (age 24.7 ± 4.3 years, height 181.9 ± 7.2 cm, mass 84.9 ± 12.9 kg) had resting BFLH muscle architecture assessed using ultrasound, with images taken at the midmuscle belly. Measures of isokinetic strength of the knee extensors and flexors involved subjects performing 3 maximal effort repetitions of concentric knee extension and eccentric knee flexion at 60°·s−1. Good-excellent relative reliability (intraclass correlation coefficient ≥0.86) and low variability (coefficient of variation <10%) were observed for all variables. Relative BFLH fascicle length (FL) demonstrated significant moderate-to-nearly-perfect associations with isokinetic measures identified as hamstring strain injury risk factors (p < 0.05, r = 0.38–0.92), whereas absolute BFLH FL was not significantly or meaningfully associated with isokinetic measures (p = 0.07–0.961, r = 0.01–0.30). Relative BFLH FL should be considered when assessing resting BFLH muscle architecture because it is potentially a more appropriate measure of injury risk because of its greater association with strength measures. However, absolute BFLH FL may have a greater usefulness during growth, maturation, and individual proportions.