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Flashcards in Internal Forces 2 Deck (20):

What % of ACL injuries are from non-contact?



How does the ACL work?

What is its main function?

What is it made up of?

Connects the femur and tibia - made of Type I collagen

Stability when rotating

Anteromedial (flex tighter), Posterolateral (ext tighter)


What is the role of ACL in sport?

What are the 3 forces when pivoting?

Keeps the forward shift
When pivoting 3 forces are apparent:
Internal Rotation, Dynamic Valgus and Anterior Translation


How can non-contact injuries be prevented?

By altering the biomechanics of the athletes movement:
Reduce frontal plane loading and increase sagittal plane knee joint angles


What is the Q-angle knee valgus?

What happens if the Q angle increases?

Line drawn from the ASIS to patella then patella to tibial tubercle

Risk of patella sublaxation (dislocation)


What are the normal Q angles for males and for females?

14 degrees male, 17 degrees female


What did Taylor find in 2016 on double leg landings?

Double leg landings may not represent single leg biomechanics due to different neural demands


What did Clarke find in 2015 about ACL patients?

Higher max knee flexion and hip flexion
Also had higher knee abduction


Why is drop jumping often chose over other jumps when testing for ground reaction forces etc?

What are the variables that are measured?

Higher perceived intensity
Must minimise contact time and maximise jump height

Impact load rate (10-90%), average and peak impact force/propulsive force


How does neural control play a part in internal forces?

Gammas keep Intrafusal fibres the right length - either lengthening or shortening them
Therefore regardless of extrafusal length, they can still give the CNS information


What did McDonagh and Duncan find in 2002 on adding a false floor onto a drop jump?

Did this to alter time to ground contact - 85ms and 50ms
Double the amplitude on EMG for gastrocnemius, biceps and rectus femoris


What is the relationship between internal forces and joint contributions?

Similar muscles/external forces used at drop heights of 1.0m and 0.6m
Reduced contribution of the hip and increase of the ankle during the energy absorption phase


What did Hollman find in 2013 with a relationship to strength?

Transverse hip motion correlated with frontal knee motion
Reduced isometric hip extensor and peak gluteals correlated with increase knee valgus


What percentages of variance did single leg triple jumps and timed hops account for (Baldon 12)

65% and 55%


What 3 ways is surface instability training used?

Rehab (restores neural factors)
Core Training (increases muscle activation)
Unstable (reduces max strength and power)


What are some of the limitations and considerations for dynamic instability training?

Limitations --> little consideration for adaptations

Considerations --> must reflect real-world training programmes


What were the differences between internal forces using the BOSU and MT?

BOSU (ankle) MT (hip)
Hip - left peak moments higher than MT
Ankle - right peak moments higher than BOSU


What were the different energy contributions when dropping onto the BOSU/MT?

DJ at 0.6m high
Hip extension - BOSU lower than MT
Ankle extension - BOSU higher than MT


What were the findings related to dropping onto the BOSU, Trampoline and a mixture?

BOSU - emphasis on the ankles, increased contact time

Trampoline - vertical posture replaced energy lost by the surface, loss of stretch reflex on landing

Mix - demanding to learn 2 different skills


What are the practical implications of instability training?

1) When the instability is removed does the neuromuscular system recalibrate despite lower specificity

2) If adapted - would be no altered mechanical/NM effects

3) Must include familiarisation - trained athletes may not be instability trained