Explosive movement in the older men: analysis and comparative study of vertical jump.

BACKGROUND: Loss of power has been demonstrated to have severe functional consequences to perform physical daily living tasks in old age. PURPOSE: This study aimed to assess how moment and velocity were affected for each joint of the lower limbs during squat jumping for older men in comparison with young adults. METHODS: Twenty-one healthy older men (74.5 ± 4.6 years) and 22 young men (21.8 ± 2.8 years) performed maximal squat jumps. Inverse dynamics procedure was used to compute the net joint power, moment and velocity produced at the hip, knee and ankle joints. RESULTS AND DISCUSSION: Vertical jump height of the elderly was 64 % lower than the young adults. The maximal power of the body mass center (P maxbmc ) was 57 % lower in the older population. For the instant at P maxbmc , the vertical ground reaction force and the vertical velocity of the body mass center were 26 % and 35 % less in the older adults than in the young adults, respectively (p < 0.05; ES = -1.64 for vertical ground reaction force; p < 0.05; ES = -1.10). A lower value of the hip (-60 %), knee (-72 %) and ankle (-68 %) joint powers was observed in older adults. This was explained by both lower values of joint moments (-64, -57 and -61 % for the hip, knee and ankle, respectively) and angular velocities (-59, -49 and -52 % for the hip, knee and ankle, respectively). CONCLUSION: 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.

Asymmetry of Inter-joint Coordination during Single Leg Jump after Anterior Cruciate Ligament Reconstruction.

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.

Measurement of pelvic motion is a prerequisite for accurate estimation of hip joint work in maximum height squat jumping.

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-HAT was greater than θUL-pelvis in all conditions. WUL-HAT overestimated WULpelvis by 33%, 39%, and 49% in conditions pelvisF, pelvisN, and pelvisB, respectively. It was concluded that θUL-pelvis should be measured when the mechanical output of hip extensor muscles is estimated.

Age-related differences of inter-joint coordination in elderly during squat jumping.

BACKGROUND: Explosive 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. METHODS: Twenty-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. RESULTS: The 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. CONCLUSION: In 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.

Contralateral limb deficit seven months after ACL-reconstruction: an analysis of single-leg hop tests.

BACKGROUND: Following ACL-reconstruction, the non-injured leg (NIL) is used as a reference to assess injured leg (IL) recovery. However, deficits have been reported in the NIL questioning its use as a reference. The aim of this study is to assess whether NIL deficits are present while jumping after ACL-reconstruction. METHODS: Thirteen males who had undergone ACL-reconstruction and 16 healthy subjects took part in the experiment. Jumping performance was assessed during a single and a triple hop for distance. Jumping performance, kinematic and kinetic data were recorded during single leg squat jumps. Values for both the NIL and the IL were compared to those of a control group (CG). RESULTS: Jumping performance for single and triple hop for distance and single leg squat jump was lower in the NIL than in the CG (p=0.004, p=0.002, and p=0.016, respectively). During the squat jump, the knee joint was more extended and the ankle plantar-flexion was greater at take-off while the peak total moment was 15% lower in the NIL than in the CG (p=0.002, p=0.002, and p=0.009, respectively). We found consistent evolutions in the NIL and the IL compared to the CG for jumping performance, initial joint angles, and peak total moment during the squat jump, but the opposite was found for the ankle and knee joint angles at squat jump take-off. CONCLUSIONS: Jumping strategies are impaired in the NIL after ACL-R during jump tasks with some deficits matching those observed in the IL and some specific to the NIL. LEVEL OF EVIDENCE: III, Case control study.

Motion alterations after anterior cruciate ligament reconstruction: comparison of the injured and uninjured lower limbs during a single-legged jump.

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 = 23.3 ± 3.8 years, mass = 81.2 ± 17.0 kg) who underwent ACL-R took part in this study 7.3 ± 1.1 months (range = 6-9 months) after surgery. INTERVENTION(S): Kinematic and kinetic analyses of a single-legged 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 (F1,9 = 23.3, P = .001), whereas the push-off phase duration was similar for both lower limbs (P = .96). Knee-joint extension (F1,9 = 11.4, P = .009), and ankle plantar flexion (F1,9 = 22.6, P = .001) were less at takeoff for the IL than the UL. The hip angle at takeoff was not different between lower limbs (P = .09). We found that total moment was 14% less (F1,9 = 11.1, P = .01) and total power was 35% less (F1,9 = 24.2, P = .001) for the IL than the UL. Maximal hip (P = .09) and knee (P = .21) power was not different between legs. The IL had 34% less maximal ankle power (F1,9 = 11.3, P = .009) and 31% less angular velocity of ankle plantar flexion (F1,9 = 17.8, P = .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.