The effect of lower limb training programs on muscular support of the knee and prevention of ACL injury

C h a n g e s in loading on t h e k n e e and k n e e f l e x i o n following l o w e r limb training p r o g r a m m e s i m p l e m e n t e d to a s s e s s the e f f e c t on risk of k n e e injury & p r e v e n t i o n , J. Cochrane~*, D. Lloyd~,Thor. Besier~,& Tim.Ackland~ 'UniversityOf WesternAustralia ~AustralianinstituteOf Sport Anterior cruciate ligament (ACL) injuries in sport are common (OIson, 1997) and most occur during noncontact cutting manoeuvres. ACL failure occurs when the ligament load exceeds its strength. Lowering the external load applied to the knee and increasing knee flexion angle may reduce ligament loading, but different types of training may alter the way people load and stabilise the knee. It has been proposed that strength training may compromise while balance training may improve stabilisation. Thus do current training methods alter external knee load and increase knee flexion angle in cutting manoeuvres? Sixty football players were assigned to different training programmes- free-weights; machine-weights; balance-training; machine-weights and balance-training (machine/balance); or a control group. There were 12 weeks of training, 3 times per week, for 30 minutes. Subjects were tested at weeks 0 and 13, which involved performing running, sidestepping, and crossover cutting. Knee kinematics and kinetics were measured using Vicon motion analysis system. Important results in relation to knee injury risk were found. Varus/valgus (VV) knee moments experienced in the peak push-off phase were 35% lower (p<0.05) after balance-training. These moments were also significantly less than all other groups post training. There was an increase in the W moment from pre to post training in the free-weights group. Prior to training all groups had similar peak knee extension angles, while following training the balance and machine/balance groups had significantly (p<0.05) greater knee flexion than the other groups. The balance-training group had decreased VV knee loading and increased knee flexion, which indicates that this training may decrease the risk of ACL injury. However, the current training methods of strength training, especially free-weights training, appear less favorable for reducing injury risk.

T h e e f f e c t of l o w e r limb training p r o g r a m s on m u s c u l a r support of t h e k n e e and p r e v e n t i o n of A C L injury J. Cochrane ~2., D. Lloyd~,T. Besier',T. AckJand:,& B. Elliot 1 'UniversityOf WesternAustralia 2AustralianinstituteOf Sport Anterior cruciate ligament (ACL) injuries in sport are common (Olson, 1997) and most occur during noncontact cutting manoeuvres. ACL failure occurs when the ligament load exceeds its strength. Hamstrings and quadriceps co-contraction can reduce ligament loading but different types of training can alter the levels of cocontraction. Strength training may decrease co-contraction, while balance-training may have the opposite effect and improve muscle stabilisation of the knee. Thus do some of the current training methods increase alter co-contraction in sporting manoeuvres and alter the risk of ACL injury? Sixty football players were assigned to different training programmes- free-weights; machine-weights; balance-training; machine-weights and balance-training (machine/balance); or a control group. There were 12 weeks of training, 3 times per week, for 30 minute& Subjects were tested at weeks 0 and 13, which involved performing pre-planned and unanticipated running, sidestepping, and crossover cutting. Muscle activation, kinematics and kinetics were measured using fully instrumented Vicon motion analysis system. Co-contraction was significantly decreased (p<0.05) following training in the sidestepping to 30° manoeuvres in the peak push-off phase for the freeweights group. In the 60° sidestepping tasks the free-weights & machine/balance groups significantly decreased while the balance group significantly increased co-contraction. Balance-training increased cocontraction in sporting manoeuvres and may therefore decrease the loading of the ACL. The current training methods of strength training, especially free-weights training, appear less favorable for joint stability and reducing injury risk. It is recommended that balance-training be implemented with strength training to reduce the risk of ACL injury. 89