Nardon Mauro, Ferri Umberto, Caffi Giovanni, Bartesaghi Manuela, Perin Cecilia, Zaza Antonio, Alessandro Cristiano
School of Medicine and Surgery/Sport and Exercise Medicine, University of Milano-Bicocca, Milan, Italy.
School of Medicine and Surgery/Physical and Rehabilitative Medicine, University of Milano-Bicocca, Milan, Italy.
Front Sports Act Living. 2024 May 20;6:1418598. doi: 10.3389/fspor.2024.1418598. eCollection 2024.
Neuromuscular fatigue causes a transient reduction of muscle force, and alters the mechanisms of motor control. Whether these alterations increase the risk of anterior cruciate ligament (ACL) injury is still debated. Here we compare the biomechanics of single-leg drop jumps before and after the execution of a fatiguing exercise, evaluating whether this exercise causes biomechanical alterations typically associated with an increased risk of ACL lesion. The intensity of the fatiguing protocol was tailored to the aerobic capacity of each participant, minimizing potential differential effects due to inter-individual variability in fitness.
Twenty-four healthy male volunteers performed single leg drop jumps, before and after a single-set fatiguing session on a cycle ergometer until exhaustion (cadence: 65-70 revolutions per minute). For each participant, the intensity of the fatiguing exercise was set to 110% of the power achieved at their anaerobic threshold, previously identified by means of a cardiopulmonary exercise test. Joint angles and moments, as well as ground reaction forces (GRF) before and after the fatiguing exercise were compared for both the dominant and the non-dominant leg.
Following the fatiguing exercise, the hip joint was more extended (landing: Δ=-2.17°, = 0.005; propulsion: Δ=-1.83°, = 0.032) and more abducted (landing: Δ=-0.72°, = 0.01; propulsion: Δ=-1.12°, = 0.009). Similarly, the knee joint was more extended at landing (non-dominant leg: Δ=-2.67°, < 0.001; dominant: Δ=-1.4°, = 0.023), and more abducted at propulsion (both legs: Δ=-0.99°, < 0.001) and stabilization (both legs: Δ=-1.71°, < 0.001) hence increasing knee valgus. Fatigue also caused a significant reduction of vertical GRF upon landing (Δ=-0.21 N/kg, = 0.003), but not during propulsion. Fatigue did not affect joint moments significantly.
The increased hip and knee extension, as well as the increased knee abduction we observed after the execution of the fatiguing exercise have been previously identified as risk factors for ACL injury. These results therefore suggest an increased risk of ACL injury after the execution of the participant-tailored fatiguing protocol proposed here. However, the reduced vertical GRF upon landing and the preservation of joint moments are intriguing, as they may suggest the adoption of protective strategies in the fatigued condition to be evaluated in future studied.
神经肌肉疲劳会导致肌肉力量暂时下降，并改变运动控制机制。这些改变是否会增加前交叉韧带（ACL）损伤的风险仍存在争议。在此，我们比较了疲劳运动前后单腿跳的生物力学，评估该运动是否会引起通常与ACL损伤风险增加相关的生物力学改变。疲劳方案的强度根据每个参与者的有氧能力进行调整，以尽量减少由于个体体能差异导致的潜在不同影响。
24名健康男性志愿者在进行一组直到力竭的自行车测力计疲劳训练（节奏：每分钟65 - 70转）前后进行单腿跳。对于每个参与者，疲劳运动的强度设定为其无氧阈值时所达到功率的110%，无氧阈值先前已通过心肺运动试验确定。比较了优势腿和非优势腿在疲劳运动前后的关节角度和力矩以及地面反作用力（GRF）。
疲劳运动后，髋关节伸展增加（着地时：Δ=-2.17°，P = 0.005；蹬地时：Δ=-1.83°，P = 0.032）且外展增加（着地时：Δ=-0.72°，P = 0.01；蹬地时：Δ=-1.12°，P = 0.009）。同样，膝关节在着地时伸展增加（非优势腿：Δ=-2.67°，P < 0.001；优势腿：Δ=-1.4°，P = 0.023），在蹬地（双腿：Δ=-0.99°，P < 0.001）和稳定阶段（双腿：Δ=-1.71°，P < 0.001）时外展增加，从而增加了膝外翻。疲劳还导致着地时垂直GRF显著降低（Δ=-0.21 N/kg，P = 0.003），但在蹬地时未出现这种情况。疲劳对关节力矩没有显著影响。
我们观察到疲劳运动后髋关节和膝关节伸展增加以及膝关节外展增加，这些先前已被确定为ACL损伤的风险因素。因此，这些结果表明，在此处提出的根据参与者量身定制的疲劳方案执行后，ACL损伤风险增加。然而，着地时垂直GRF降低以及关节力矩保持不变很有意思，因为这可能表明在疲劳状态下采用了保护策略，有待在未来研究中评估。
