TRAINING AFFECTS KNEE KINEMATICS AND KINETICS IN CUTTING MANEUVERS IN SPORT CASEY GRAHAM TIFFANY MEIER MICHELE BENANTI

Purpose Investigate the effects of strength training and balance training on the knee joint loading and lower limb kinematics during sporting maneuvers. Sporting maneuvers? – Running – Cutting (fast lateral stepping)

Variables Independent Variable – The four separate groups of the study: – 1) Machine Weights only > pin-loaded isotonic machines for leg curl and leg press exercises – 2) Free Weights only > leg curl and squat exercises with free weights – 3) Balance training only > single/double-legged static balancing, single/double-legged squats using wobble boards, tilt boards, mini trampolines, and Swiss balls – 4) Machine Weights + Balance training > combination of machine weight exercises and balance exercises – 5) Control group > instructed to carry out normal team training

Variables Dependent Variables: – Results from the running and cross-cutting knee angle measurements (anticipated and unanticipated) – Applied knee moments (placement) collected by motion data sensors – Measurements of knee flexion angle and knee moments in different phases of WA and PPO.

Hypothesis This study has four collective hypotheses: – 1) Balance training reduces the applied loading on the knee during sporting maneuvers – 2) Strength training using machine-based resistance increases loading on the knee joint during sporting maneuvers – 3) Strength training using free weights increases loading of the knee joint to the same level as machine-based resistance training – 4) Combined balance and machine-based resistance training results in no significant change in knee joint loading during sporting maneuvers because their potential effects would counter-act each other.

Methods Sampling 50 healthy males from an Australian football team No history of lower limb pain or injury Limited previous exposure to endurance, strength, or balance training Randomly assigned to the 5 independent variable groups

Methods Treatment All training groups exercised for 30 minutes, 3xweek, for 12 weeks Machine-based and Free weights group followed a progressive overload plan, starting at 80% of 1-rep. max. – 3 sets of 8 repititions, 3xweek

Methods Treatment Combination of machine weights and balance training: – 15 minutes of balance training exercises – 15 minutes of machine weight -Control Group was instructed to carry on normal team training program

Methods: Testing Knee Angles Kinematic and kinetic (varus vs. valgus) variables were taken from each subject as they performed sidestepping maneuvers at 30 and 60 degree knee angles and straight line running All maneuvers performed pre-planned and unanticipated Subjects performed 3 trials of each maneuver, preplanned and unanticipated (not specified what marks an unanticipated event) Order of trials were randomized to prevent subject anticipation To reduce effects of learning, subjects given a 3-min. rest between trials.

Methods: Testing Motion Analysis Used six-camera Vicon 370 motion analysis system with a force plate Motion date obtained using UWA marker set attached to knee and hip joint centers to collect valid load data via the Vicon camera Subjects jumped on force plate, while camera monitored 3-demensional knee placements and load exerted on to knee

Methods: Testing Knee Angle Measurements This test is built off of the motion analysis test Researchers analyzed the knee during different phases of placement: Weight Acceptance (WA) and peak push-off (PPO) The knee joint moments were assessed by dividing data by the subject’s height x weight. This would establish an idea if the athlete was exerting more or less load on his knee in comparison to his body composition

Results Balance Training - Results of the study indicated that balance training tended to induce positive changes in knee joint loading, which reducing risk of ACL injury > reductions in peak valgus movements and internal rotation Machine Weights – Results appeared to increase the load on the knee, which increases strain on ACL Free Weights - Results for indicated an increase in internal knee rotation during PPO. However, the researchers observed that if the flexion of the knee had been at around 45 degrees, the load on the ACL would’ve been less, and less damage would’ve been done.

Results Machine + Balance – Where balance training appeared to reduce risk for ACL injury, and weight machines tended to increase it, the combination group had neutral results Control – This group demonstrated an increase in peak valgus movement during WA movement, but that was about it. The increase in the valgus movement may be attributed to variations of typical in-season training.

EXTERNAL VALIDITY Even though study only involved males, the end of the article generalized to all athletes: – “The take home message for ATHLETES and coaches is that balance training may reduce the risk of ACL injury.” – Women are more anatomically prone to ACL tears, it may have been beneficial to have the study include women as well. However, we do not think that this would’ve changed the study’s results, it may have strengthened overall findings The results of the study indicate that balance training helps in reducing ACL injury risk

EXTERNAL VALIDITY Given that the results indicate that balance training reduces ACL injury risk, the conclusion that athletes should practice balance training is understandable GOOD EXTERNAL VALIDITY!

CONSTRUCT VALIDITY Construct Validity of Independent Variable (Training Groups): – This construct was defined by either balance training, weight-machine training, free-weight training, a combination of machine-weight and balance training, and a control group that just did in-season training. – Good construct validity for IV because there are multiple groups to be assessed, so they looked at several ways to measure construct.

CONSTRUCT VALIDITY Contstuct Validity of Dependent Variable (Test Results): – This construct is defined by the myriad of tests the researchers performed to assess the effectiveness of the various training regimes in reducing ACL injury. – Researchers had multiple tests to determine effectiveness of multiple training programs. All of the tests were good indicators of the constructs. Therefore, this constitutes good construct validity for the DV

INTERNAL VALIDITY Pre and Post tests performed There were multiple groups and random assignment, so this makes single and multiple group threats null. THIS LEAVES ONLY SOCIAL THREATS! – Imitation/diffusion of treatment: Members of the control group could start practicing balance techniques on their own, and this could skew the results. However, the results do not show that this happened. – Overall, good internal Validity!

INTERNAL VALIDITY R O X 1 O R O X 2 O R O X 3 O R O X 4 O R O X 5 O