Department of Biomechanics, Performance Analysis and Strength & Conditioning, Olympic Training and Testing Centre Westphalia, Dortmund, Germany.
Institute of Movement and Neuroscience, German Sport University, Cologne, Germany.
Sports Biomech. 2024 Jul;23(7):831-845. doi: 10.1080/14763141.2021.1893376. Epub 2021 Mar 16.
The Nordic Hamstring Exercise (NHE) effectively strengthens the knee flexors. Typically conducted without assistance, extended knee angles are not reached with sustained muscle activation in the presence of insufficient eccentric strength and/or fatigue. This might impair the desired neuromuscular adaptations and assessment accuracy. This study investigated kinetic and kinematic differences between assisted and unassisted NHEs (3 × 3 repetitions) performed by sixteen male sprinters (22 years, 181 cm, 76 kg). Kinetic (peak moment, impulse) and kinematic parameters (e.g., time under tension, range of motion to excessive downward acceleration (ROM) were investigated. All analysed parameters significantly differed between assisted and unassisted NHEs (p ≤ 0.003; 0.635≤ ηp² ≤ 0.929) favouring assisted execution, except for peak moments and maximal hip flexion. Repetition 1 of assisted NHEs revealed 21% higher impulses rising to 82% during repetition 9. Equivalent interactions of mode and repetition became apparent for time under tension, ROM, mean and fractional angular velocity. Unassisted NHEs elicited substantially greater inter-repetition fatigue (rep1 vs. rep9): +79% fractional angular velocity (d = 1.01), -41% impulse (d = 1.53), -31% ROM (d = 0.99) and -29% time under tension (d = 1.45). Assisted NHEs ensured higher execution quality and lower between-participant variability by facilitating a controlled full-ROM movement. Three sets of 3 NHEs sufficed to induce substantial fatigue within and across sets.
北欧腘绳肌训练（NHE）有效地增强了膝关节屈肌。通常在没有辅助的情况下进行，在缺乏足够的离心力量和/或疲劳时，无法达到延长的膝关节角度，并保持持续的肌肉激活。这可能会损害所需的神经肌肉适应和评估准确性。本研究调查了 16 名男性短跑运动员（22 岁，181 厘米，76 公斤）进行的辅助和非辅助 NHE（3×3 次重复）之间的动力学和运动学差异。研究了动力学（峰值力矩、冲量）和运动学参数（例如，张力下时间、运动范围到过度向下加速（ROM）。所有分析的参数在辅助和非辅助 NHE 之间差异显著（p≤0.003；0.635≤ηp²≤0.929），有利于辅助执行，除了峰值力矩和最大髋关节屈曲。辅助 NHE 的重复 1 显示冲量增加了 21%，在重复 9 时增加到 82%。在张力下时间、ROM、平均和分数角速度方面，模式和重复的等效相互作用也很明显。非辅助 NHE 引起的重复间疲劳要大得多（rep1 与 rep9）：分数角速度增加 79%（d=1.01），冲量减少 41%（d=1.53），ROM 减少 31%（d=0.99），张力下时间减少 29%（d=1.45）。辅助 NHE 通过促进受控的全 ROM 运动，确保了更高的执行质量和更低的参与者间变异性。三组 3 次 NHE 足以在组内和组间引起显著的疲劳。
