Research Review By Demetry Assimakopoulos©

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Date Posted:

June 2012

Study Title:

Effect of Functional Stabilization Training on Lower Limb Biomechanics in Women

Authors:

Baldon RM, Lobato DFM, Carvalho LP et al.

Author's Affiliations:

Department of Physical Therapy, Sao Carlos Federal University, Brazil; School of Physical Education and Sport, Ribeirao Preto, University of Sao Paulo, Brazil.

Publication Information:

Medicine and Science in Sport and Exercise 2012; 44(1): 135-145.

Background Information:

It has been shown that female athletes who participate in sports involving pivoting and jumping motions are 2-6 times more likely to suffer from non-contact ACL injury and patellofemoral pain syndrome (PFPS) when compared to male athletes. The recent increase in incidence of these injuries is likely due to the growing number of females participating in high level sports over the last 30 years. Because of this, several laboratories around the world have sought to find a kinematic reason for this trend. Over time, studies have shown that women exhibit greater knee abduction during single-leg squats and while landing from a jump task, and that women have greater hip adduction and tibial internal rotation during ambulation. It is this poor dynamic control of the knee in the transverse plane which is thought to predispose women to ACL injury and PFPS.

These biomechanical faults are linked to poor hip abductor and lateral rotator activation during functional tasks. Now, researchers and clinicians are attempting to create and utilize lumbopelvic rehabilitative exercises to correct or reduce these poor lower limb mechanics in effort to reduce the overload on the patellofemoral joint and ACL. Going forward with this trend, the authors of this study attempted to verify the effects of core and lower limb functional training to positively influence dynamic control of the lower limb.

Pertinent Results:

Kinematic Measurements:
No differences were observed between the two groups, pre-intervention. The post-intervention Training Group (TG) showed reduced knee abduction excursion compared to the pre-intervention TG group and the control group (CG) after intervention. Also, post-intervention pelvic depression and femoral adduction excursions were significantly reduced compared to the pre-intervention TG, but not compared to the pre- and post-intervention CG. Additionally, femoral lateral rotation excursion was significantly greater in the post-intervention TG compared to both the pre-intervention TG and CG at both data points.

Functional Measurements:
The post-intervention single-leg triple hop test (SLTH) for the TG was significantly higher than the SLTH of the pre-intervention TG. It was, however, not significantly greater than the SLTH of the pre- and post-intervention CG. The triple hop time was decreased post-intervention in the TG compared to pre-intervention. It was not significantly different from the CG, both pre- and post-intervention. The TG was said to improve in the performance of both functional tests by approximately 12%. No significant difference was observed between the TG and CG at baseline in either functional test, or between the CG at baseline and after 8 wk.

Isokinetic Measurements:
Post-intervention eccentric knee extensor torque was significantly greater in the post-intervention TG group. Additionally, eccentric hip abductor, hip medial rotator, hip lateral rotator and knee flexor torques were significantly greater in the post-intervention TG group compared to the pre-intervention TG group, but were not greater than the CG group at any data point.

The researchers note that the improvements in eccentric hip abductor, hip lateral rotator and hip medial rotator peak torques in the TG group were 11%, 21% and 14%, respectively. They also state that improvements in knee flexor and extensor torque in the TG were 8% and 16%, respectively. No significant differences were observed for any of the isokinetic tests between the TG and CG at baseline, or between the CG at baseline and after 8 wk, with the exception of the reduction in the eccentric knee flexor torque.

Clinical Application & Conclusions:

Only those in the TG group, who performed the functional knee stabilization protocol, exhibited positive changes in lower limb kinematics, functional performance and eccentric strength of the knee and the hip musculature. Specifically, these subjects showed decreased knee abduction, femoral adduction and pelvic depression, and increased femoral lateral rotation after only 8 weeks of functional exercise intervention. These kinematic changes have been associated with a reduction the risk of injury to the ACL and patellofemoral joint.

Additionally, the TG showed positive changes in the SLTH and the three hop tests – an indication that functional exercises targeting the core, hip abductors and lateral rotators have the power to enhance lower limb propulsion force in the saggital plane, thus leading to better performance.

Study Methods:

Twenty-eight healthy recreational female athletes were recruited from a university population. A non-randomized controlled pilot study was performed on two groups:
  1. A training group (TG) who carried out the functional lumbopelvic stabilization protocol; and
  2. a control group who were not provided with an exercise program.
Each participant was asked to continue to perform their recreational athletic activities as usual.

Testing:
Before and after the 8-week intervention, each participant underwent a series of kinematic, functional and isokinetic assessments. The kinematic assessment included a digitally recorded single-leg squat test. To effectively assess the single-leg squat, each participant was outfitted with 9 reflective markers and were asked to squat to 75° of knee flexion. The kinematic variables measured during the performance of this test were the excursion of the level of the contralateral pelvis (looking for Trendelenburg’s sign), femoral adduction/abduction and femoral medial/lateral rotation.

Each participant was assessed functionally using the single-leg triple hop test (SLTH). The subjects performed this on their dominant leg, with their hands behind their back, so as to eliminate generation of momentum from the upper limbs. They were then asked to execute three consecutive maximum jumps while balancing on their dominant leg as quickly as possible. The longer the distance travelled and the shortest time achieved to complete the jump were each used in the statistical analysis.

Eccentric hip and knee torques were measured using an isokinetic dynamometer, both in the side-lying and seated positions. The researchers chose to measure these muscles eccentrically, because these muscles must work eccentrically to control femoral adduction and medial rotation during functional activities.

Training protocol:
The participants of the TG group underwent 3 days per week of training for 8 weeks. The average duration of each training session was approximately 80 minutes. Overall, there were 3 phases of training: 1) Non-weight bearing, 2) Weight-bearing exercise, and 3) Functional training. Exercises were progressed when the subject could perform an exercise while maintaining a neutral spinal position and without the presence of delayed onset muscle soreness for 48 hrs after the previous training session. Progression was achieved by increasing the resistance (0.5 – 2 kg for free weights, and 1 resistance band level).

Training Phase 1 (weeks 1-2):

Main objectives:
  • To enhance motor control and endurance of the transverses abdominus (TvA), multifidus (1), hip abductor and hip lateral rotator muscles
  • Exercises were carried out in multiple postures – quadruped, prone sitting and standing, and while on labile platforms (i.e. stability ball).
  • 2 sets of 15 reps; 10 sec isometric muscle contraction for quadruped and prone postures, and 10 reps with 10 second isometric muscle contraction for sitting and standing postures.
  • Isotonic hip exercises were executed using a volume of 2 sets of 20 repetitions, with 5 second isometric muscle contraction after the concentric phase of the motion.
  • Isotonic knee exercises were executed using a volume of 2 sets of 20 repetitions.
Exercises:
  • Side-lying hip abduction/lateral rotation/extension
  • Prone hip extension/lateral rotation with knee
  • Quadruped hip lateral rotation/abduction/extension
  • Clam exercise
  • Single-leg stance on an unstable platform
  • Seated Swiss ball exercises
Training Phase 2 (weeks 3-5):

Main Objectives:
  • Increase the strength of the hip abductor and lateral rotators, and the knee flexor and extensor muscles
  • Exercises were performed using a volume of 3 sets of 12 reps with 2 minutes of rest between sets
Exercises:
  • Knee Side bridge
  • Knee Front bridge
  • Upper extremity extension with elastic resistance performed on a single-leg
  • Resisted single-legged external hip rotation in a semi-squat position
  • Hip hiking
  • Single leg stance on an unstable platform with ball throwing
Training Phase 3 (weeks 6-8)

Main Objectives:
  • To learn the optimal lower limb alignment during functional activities
  • All training volumes from Training Phase 2 were maintained for Training Phase 3.
Exercises:
  • Full side bridge
  • Full front bridge
  • Balancing on a swiss ball – knees
  • Single-leg squat on step with dynamic valgus knee force
  • Stair decent while resisting a dynamic knee valgus force

Study Strengths / Weaknesses:

Strengths:
  • Inclusion of core exercises into the training program
  • Use of a control group
  • Use of difference training phases, which have different objectives. This is much more realistic and sport specific
  • Inclusion of a population that reflects the population that the study should be generalized to
Weaknesses:
  • Lack of randomization

Additional References:

  1. Richardson C, Hodges P & Hides J. Therapeutic exercise for lumbopelvic stabilization. A motor control approach for the treatment and prevention of low back pain. 2nd ed. Edinburgh: Churchhill Livingston; 2005: 185-219.