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
R
R
R
R
O
O
O
O
O
X1
X2
X3
X4
X5
O
O
O
O
O