Abstract
Fatigue has been proposed to increase the risk of knee injury. This study tracked countermovement jump, knee isometric strength, and kinetics and kinematics in 8 female soccer players (experimental group) during an anticipated sidestep maneuver before and after two matches played over a 43-h period. Time points were: Before and after match 1 (T0 and T1), 12 h after the first match (T2), and immediately after the second match (T3). A control group participated only in practice sessions. Isometric knee extension strength decreased by 14.8% at T2 (p = 0.003), but knee flexion was not affected until T3, declining by 12.6% (p = 0.018). During the sidestep maneuver, knee joint degrees of flexion at initial contact was increased by 17.1% at T3, but maximum knee and hip angle at initial contact were unchanged. Peak resultant ground reaction force (GRF) increased by 12.6% (p = 0.047) at T3 (3.03 xBW) from 2.69 xBW at T0, while posterior GRF was significantly higher than T0 at all three subsequent time points (T1 = 0.82 ± 0.23 xBW, T2 = 0.87 ± 0.22 xBW, T3 = 0.89 ± 0.22 xBW). Anterior tibial shear force increased significantly (p = 0.020) at T3 (1.24 ± 0.12 xBW) compared to T1 (1.15 ± 0.13 xBW), an 8.8% increase. Lateral tibial shear force was significantly higher at both T1 (0.95 ± 0.20 xBW) and T3 (1.15 ± 0.38 xBW) compared to T0 (0.67 ± 0.25 xBW). These findings suggest that participation in a soccer match has significant effects on both physical performance parameters and kinetics/kinematics during a sidestep cut, but these can be more pronounced after a second match with short rest.
Highlights
Injuries to the anterior cruciate ligament (ACL) continue to be all too common in sports, and cause both short-term and long-term cost and medical problems [1,2]
The results of the study show that while a single soccer match can change some biomechanical factors related to knee injury risk, the risk is significantly enhanced by participation in a second match with less than 48 h of rest for those athletes playing the greatest number of minutes
Following the second match, peak resultant ground reaction force (GRF) (Figure 5A) and anterior tibial shear force (Figure 6A) were increased, in addition to further increases in posterior GRF and lateral tibial shear force, all with large effect sizes, except for posterior GRF. Values for both posterior and resultant GRF were very similar to values from previous research on female soccer players performing a sidestep cut, which ranged from 2.6–2.8 xBW for vertical GRF and 0.7–0.8 xBW for posterior GRF [29]
Summary
Injuries to the anterior cruciate ligament (ACL) continue to be all too common in sports, and cause both short-term and long-term cost and medical problems [1,2]. Women are significantly more likely than men to suffer ACL injury [3,4], and most of those are non-contact in nature [5,6]. There is higher risk of injury during change of direction maneuvers, and increased anterior tibial forces are thought to be associated with higher strain on the ACL [5]. Several recent reviews point out that the kinematic and kinetic risk factors for non-contact ACL injury are not consistently present after a single bout of fatiguing exercise [10,11,12]
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