Context: Asymmetries subsist after anterior cruciate ligament reconstruction (ACL-R), and it is unclear how lower limb motion is altered in the context of a dynamic movement.Objective: To highlight the alterations observed in the injured limb (IL) during the performance of a dynamic movement after ACL-R.Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: A total of 11 men (age ¼ 23.3 6 3.8 years, mass ¼ 81.2 6 17.0 kg) who underwent ACL-R took part in this study 7.3 6 1.1 months (range ¼ 6-9 months) after surgery.Intervention(s): Kinematic and kinetic analyses of a singlelegged squat jump were performed. The uninjured leg (UL) was used as the control variable.Main Outcome Measure(s): Kinematic and kinetic variables.Results: Jump height was 24% less for the IL than the UL (F 1,9 ¼ 23.3, P ¼ .001), whereas the push-off phase duration was similar for both lower limbs (P ¼ .96). Knee-joint extension (F 1,9 ¼ 11.4, P ¼ .009), and ankle plantar flexion (F 1,9 ¼ 22.6, P ¼ .001) were less at takeoff for the IL than the UL. The hip angle at takeoff was not different between lower limbs (P ¼ .09). We found that total moment was 14% less (F 1,9 ¼ 11.1, P ¼ .01) and total power was 35% less (F 1,9 ¼ 24.2, P ¼ .001) for the IL than the UL. Maximal hip (P ¼ .09) and knee (P ¼ .21) power was not different between legs. The IL had 34% less maximal ankle power (F 1,9 ¼ 11.3, P ¼ .009) and 31% less angular velocity of ankle plantar flexion (F 1,9 ¼ 17.8, P ¼ .004) than the UL.Conclusions: At 7.3 months after ACL-R, motion alterations were present in the IL, leading to a decrease in dynamic movement performance. Enhancing the tools for assessing articular and muscular variables during a multijoint movement would help to individualize rehabilitation protocols after ACL-R.Key Words: knee, dynamic movement, hop test, rehabilitation Key PointsKinematic and kinetic alterations were demonstrated in the injured leg at 7.3 months after anterior cruciate ligament reconstruction. These alterations led to decreased jump height during a single-legged squat jump in the injured leg. Enhancing tools for assessing articular and muscular variables during a multijoint movement would help to individualize rehabilitation protocols after anterior cruciate ligament reconstruction.

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Little is known about the contralateral asymmetry in inter-joint coordination after anterior cruciate ligament reconstruction (ACL-R) during multi-segmental movements. This study aimed to evaluate inter-joint coordination asymmetry between the injured (IL) and non-injured leg (NIL) in patients after ACL-R during single-leg jumping. 12 male patients having undergone ACL-R (7.3 months post-surgery) and 12 healthy males performed maximal vertical single-leg jumps with the right and left leg. The kinematics of each jump were recorded. The inter-joint coordination between the ankle, knee and hip joints was assessed by computing the continuous relative phase (CRP) and its variability. The effect of the group and leg was tested with a mixed linear model. The CRP and its variability were similar between the dominant and non-dominant leg of the healthy group. By contrast the CRP of the coupling ankle/knee and ankle/hip was smaller (p<0.01) for IL in comparison to NIL in the ACL-R group (-30% and -22% respectively). The CRP variability of the couplings ankle/knee and knee/hip was greater (p<0.05) for IL compared to NIL (+23% and +40% respectively). In conclusion, the jumping strategy assessed through the analysis of inter-joint coordination was still affected in ACL-R patients, which may be a cause of re-injury.

In experiments investigating vertical squat jumping, the HAT segment is typically defined as a line drawn from the hip to some point proximally on the upper body (eg, the neck, the acromion), and the hip joint as the angle between this line and the upper legs (θUL-HAT). In reality, the hip joint is the angle between the pelvis and the upper legs (θUL-pelvis). This study aimed to estimate to what extent hip joint definition affects hip joint work in maximal squat jumping. Moreover, the initial pelvic tilt was manipulated to maximize the difference in hip joint work as a function of hip joint definition. Twenty-two male athletes performed maximum effort squat jumps in three different initial pelvic tilt conditions: backward (pelvisB), neutral (pelvisN), and forward (pelvisF). Hip joint work was calculated by integrating the hip net joint torque with respect to θUL-HAT(WUL-HAT) or with respect to θUL-pelvis(WUL-pelvis). θUL-HATwas greater than θUL-pelvisin all conditions. WUL-HAToverestimated WUL-pelvisby 33%, 39%, and 49% in conditions pelvisF, pelvisN, and pelvisB, respectively. It was concluded that θUL-pelvisshould be measured when the mechanical output of hip extensor muscles is estimated.

This study showed a lower joint power when performing vertical jump. This smaller power resulted from both a lower moment and angular velocity produced at each joint.

After anterior cruciate ligament reconstruction (ACL-R), many studies have reported a deficit of performance on the injured leg during multi-joint tasks. However, the total mechanical joint work (WTotal ), parameter best related to the vertical displacement of the body mass center during vertical jumping, has not yet been studied. The aim of this research was to compare asymmetries between ACL-R subjects and healthy matched subjects, through the analysis of the kinematics and kinetics during a single-leg squat jump. Asymmetries are defined by the Limb Symmetry Index (LSI). A greater LSI was observed for WTotal in the ACL-R group than in the healthy group. There was no difference in LSI for knee joint work between the two groups, while the LSI for hip and ankle joint work was significantly larger in the ACL-R group. This was explained by greater LSI for the hip and ankle joint range of motion in the ACL-R group than in the healthy group. After ACL-R, patients exhibited greater asymmetries than healthy subjects during single-leg squat jump. Physiotherapists should focus on quality execution of multi-joint movement, especially on hip and ankle joints range of motion in order to reduce asymmetries and to improve vertical jumping performance.

BackgroundExplosive movement requires that the individual exerts force and power with appropriate magnitude and timing. These coordination aspects have received less attention despite being a basic prerequisite for daily mobility and physical autonomy, especially in older people. Therefore, the purpose of this study is to characterize the effect of age on inter-joint coordination during explosive movement.MethodsTwenty-one elderly and twenty young participants performed three maximal vertical jumps, while kinematics were recorded throughout each squat jump. Inter-joint coordination and coordination variability were calculated for selected sagittal hip-knee, knee-ankle, and hip-ankle joint couplings using the continuous relative phase method.ResultsThe young participants produced significantly greater jump height performance (0.36 ± 0.07 m vs. 0.12 ± 0.04 m, p < 0.001). The mean absolute continuous relative phase for ankle-knee and knee-hip joint couplings were significantly greater for the elderly in comparison to the young group (p < 0.01 for the both). No significant differences between senior and young participants in the mean absolute continuous relative phase for ankle-hip joint couplings (p = 0.25) was observed. However, there was significantly more variability in inter-joint coordination in the elderly marked by greater continuous relative phase variabilities in ankle-knee, ankle-hip and knee-hip joint couplings (p < 0.001) than those observed in young adults.ConclusionIn this study, seniors demonstrated proximodistal inter-joint coordination but with different delays in the pattern of inter-joint coordination during squat jumps compared to young adults. In addition, a higher continuous relative phase variability in the elderly may be needed to improve stability or compensate for strength deficits in jump achievement.

The aim of this explorative study was to determine the most effective physical training program to reduce neuromuscular risk factors of Anterior Cruciate Ligament (ACL) tear and to improve jumping performance. Twentyfour female basketball players were divided into three groups: Specific Physical Training Group (SPTG), combined specific Physical and Mental Training Group (PMTG) and Control Group (CG). The training program was conducted over a period of eight weeks including two sessions per week during basketball practice. Dynamic valgus, Peak Vertical Impact Force (PVIF), Rate of Force Development (RFD), and jumping performance were measured at pre-and posttests. When all the participants were pooled, statistics showed a decrease (-36%) in dynamic valgus. No significant results were observed for PVIF and RFD. Jumping performance improved by 12% in SPTG and remained constant in PMTG and CG. Adding specific physical training to basketball practice should be the most effective program to prevent ACL tear while improving jumping performance in young female basketball players.