Biomechanics in Sports, Technical University of Munich, Munich, Bavaria, Germany.
Human Movement Science, Technical University of Munich, Munich, Bavaria, Germany.
PLoS One. 2024 Oct 28;19(10):e0312843. doi: 10.1371/journal.pone.0312843. eCollection 2024.
Hamstring injuries are associated with decreased hamstring strength. Matinlauri et al.'s 90:20 Isometric Posterior Chain Test (90:20 IPCT) efficiently assesses hamstring strength, but has not been validated so far. Furthermore, their rather unprecise original instruction allows high variability in test execution. We added a new instruction and variables and examined, whether this measure leads to increased reliability and validity. We assessed hamstring strength of 23 sport students via the 90:20 IPCT under the original instruction, to exert vertical force, and our new instruction, to exert vertical and horizontal force. Instead of only using bare vertical force as variable under the original (Fz_V) and our new instruction (Fz_VH), we also calculated the resultant force (Fres_VH) and the applied torque onto the force place (M_F_ortho_VH). To test for validity, we correlated the outcome variables with peak torque of gold standard dynamometry. Furthermore, we measured muscle activities of the mm. rectus femoris, biceps femoris, semitendinosus, and gluteus maximus under our new instruction and compared them to those under the original variable (Fz_V) via one sample t-tests. To evaluate reliability, tests were repeated on two separate days, for which we calculated intra class correlation coefficients (ICCs) and coefficients of variation (CVs). Our new instruction and variables (Fz_VH, Fres_VH, M_F_ortho_VH) showed better validity (mean r = 0.77, r = 0.81, and r = 0.85) and equally good or better reliability (ICCs: 0.87, 0.89, and 0.94; CVs: 4.7%, 4.1%, and 4.7%) than the original instruction and variable (Fz_V) (mean r = 0.70; ICC: 0.91; CV: 5.6%). There were no differences in muscle activities between the variables and instructions of the 90:20 IPCT. We recommend our new instruction and the applied torque onto the force plate as it makes the 90:20 IPCT a more reliable and valid tool to assess hamstring strength.
腘绳肌损伤与腘绳肌力量下降有关。Matinlauri 等人的 90:20 等长后侧链测试（90:20 IPCT）能够有效地评估腘绳肌力量，但迄今为止尚未得到验证。此外，他们的原始指令相当不精确，导致测试执行的变异性很高。我们添加了一个新的指令和变量，并研究了这是否会导致更高的可靠性和有效性。我们使用 90:20 IPCT 对 23 名运动学生进行了腘绳肌力量测试，原始指令是施加垂直力，新指令是施加垂直和水平力。我们没有仅使用原始指令（Fz_V）和新指令（Fz_VH）下的垂直净力作为变量，还计算了合力（Fres_VH）和力的施加扭矩（M_F_ortho_VH）。为了测试有效性，我们将结果变量与黄金标准测力的峰值扭矩相关联。此外，我们还在新指令下测量了股直肌、股二头肌、半腱肌和臀大肌的肌肉活动，并通过单样本 t 检验将其与原始变量（Fz_V）下的肌肉活动进行比较。为了评估可靠性，我们在两天内重复进行了测试，为此我们计算了组内相关系数（ICC）和变异系数（CV）。我们的新指令和变量（Fz_VH、Fres_VH、M_F_ortho_VH）显示出更好的有效性（平均 r = 0.77、r = 0.81 和 r = 0.85）和同等或更好的可靠性（ICC：0.87、0.89 和 0.94；CV：4.7%、4.1% 和 4.7%）比原始指令和变量（Fz_V）（平均 r = 0.70；ICC：0.91；CV：5.6%）。90:20 IPCT 的变量和指令之间的肌肉活动没有差异。我们建议使用我们的新指令和施加在力板上的扭矩，因为它使 90:20 IPCT 成为评估腘绳肌力量更可靠和有效的工具。
