Behan Fearghal P, Maden-Wilkinson Thomas M, Pain Matt T G, Folland Jonathan P
Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, Loughborough University, Leicestershire, United Kingdom.
School of Sport, Exercise, and Health Sciences, Loughborough University, Leicestershire, United Kingdom.
PLoS One. 2018 Jan 23;13(1):e0190903. doi: 10.1371/journal.pone.0190903. eCollection 2018.
Females experience higher risk of anterior cruciate ligament (ACL) injuries; males experience higher risk of hamstring strain injuries. Differences in injury may be partially due to sex differences in knee flexor (KF) to knee extensor (KE) muscle size ratio and the proportional size of constituent muscles.
To compare the absolute and proportional size, and mass distribution, of individual KE and KF muscles, as well as overall size and balance (size ratio) of these muscle groups between the sexes.
T1-weighted axial plane MR images (1.5T) of healthy untrained young males and females (32 vs 34) were acquired to determine thigh muscle anatomical cross-sectional area (ACSA). Maximal ACSA (ACSAmax) of constituent muscles, summated for KF and KE muscle groups, and the KF:KE ratio were calculated.
Females had 25.3% smaller KE ACSAmax (70.9±12.1 vs 93.6±10.3 cm2; P<0.001) and 29.6% smaller KF ACSAmax than males (38.8±7.3cm2 vs 55.1±7.3cm2; P<0.001). Consequently, females had lower KF:KE ACSA ratio (P = 0.031). There were sex differences in the proportional size of 2/4 KE and 5/6 KF. In females, vastus lateralis (VL), biceps femoris long-head (BFlh) and semimembranosus (SM) were a greater proportion and sartorius (SA), gracilis (GR) and biceps femoris short-head (BFsh) a smaller proportion of their respective muscle groups compared to males (All P<0.05).
Sex differences in KF:KE ACSAmax ratio may contribute to increased risk of ACL injury in females. Sex discrepancies in absolute and proportional size of SA, GR, VL and BFlh may contribute further anatomical explanations for sex differences in injury incidence.
女性前交叉韧带（ACL）损伤风险较高；男性腘绳肌拉伤风险较高。损伤差异可能部分归因于膝屈肌（KF）与膝伸肌（KE）肌肉大小比例以及组成肌肉的相对大小的性别差异。
比较男女个体KE和KF肌肉的绝对大小、相对大小以及质量分布，以及这些肌肉群的整体大小和平衡（大小比例）。
获取健康未受过训练的年轻男性和女性（32名男性和34名女性）的T1加权轴向平面磁共振图像（1.5T），以确定大腿肌肉的解剖横截面积（ACSA）。计算组成肌肉的最大ACSA（ACSA max），汇总为KF和KE肌肉群，并计算KF:KE比例。
女性的KE ACSA max比男性小25.3%（70.9±12.1 vs 93.6±10.3 cm²；P<0.001），KF ACSA max比男性小29.6%（38.8±7.3cm² vs 55.1±7.3cm²；P<0.001）。因此，女性的KF:KE ACSA比例较低（P = 0.031）。在2/4的KE和5/6的KF的相对大小上存在性别差异。与男性相比，女性的股外侧肌（VL）、股二头肌长头（BFlh）和半膜肌（SM）在各自肌肉群中的比例更大，而缝匠肌（SA）、股薄肌（GR）和股二头肌短头（BFsh）的比例更小（所有P<0.05）。
KF:KE ACSA max比例的性别差异可能导致女性ACL损伤风险增加。SA、GR、VL和BFlh的绝对大小和相对大小的性别差异可能为损伤发生率的性别差异提供进一步的解剖学解释。
