Chapter 10: Jumping and Landing

things to consider about muscles influencing vGRF attenuation ?

- when landing take as much time as possible to absorb force ( flex the hips knees and ankles as much as possible) -try to find sweet spot where you can dampen landing phase but gain energy to jump again quickly during sports

What are the goals of jumping?

-Maximize vertical velocity of COM at takeoff -Maximize horizontal distance -Involve somersaults/twists during flight

what is the purpose of the long jump?

Maximize horizontal distance b/w takeoff and landing positions

what are the types of jumps that influence how high we go?

countermovement and squat jump

9 step process to jump has...

greater amount of muscle activity therefore greater vertical velocity at takeoff which corresponds with greater time in the air

what does landing begin with ?

ground contact and ends when COM stops moving downward

how much does countermovement vertical jump increase contraction force?

hip muscles are at 313 Nm vs 183 Nm during squat jump

why is muscle sequence important during vertical jump?

proximal to distal ( hip, knee , gastroc) -by starting at hip we can transfer energy to knee then to ankle which allows for greater overall force production while conserving energy

Why do we land the way we land?

the purpose of this is to reduce the amount of body mass involved in initial collision with ground -allow lower extremity to absorb energy of impact and prepare for subsequent propulsive movement -reduce forces acting on the body by increased distance that COM travels while these forces act on the body (creating greater amount of time to allow muscles to contract to slow body down)

what are the phases of springboard diving?

-Approach- only for forward and reverse(other dives were just standing still) -Hurdle- movements to raise/lower COM before takeoff -Takeoff- final depression and recoil of board -Flight- while they're in the air -Entry- when they hit the water

what is the role of two joint muscles during vertical jump?

-Redistribute mechanical energy generated by concentric action of single-joint muscles to optimize performance -the gastroc allows for the ankle to produce more force because it is a two joint muscle and gets energy from the knee which gets energy from the hip

what are the different types of spring board diving?

-forward dive -backward dive -reverse dive -inward jump

what is a forward dive?

-several steps to approach -facing the water - GRF is posterior to COM causing them to propels forward and do a front flip

what is the actual optimal takeoff angle for long jump?

20° when running 29° when standing

significance of mechanical energy during vertical jump

-Approximately 21% of work done to extend knee comes from hip extensors -Nearly 25% of work done to PF ankle comes from knee -allows bulk of lower extremity muscle mass to be located proximally (Moment of inertia reduced Resistance to hip rotation reduced Angular velocity at hip increased which makes Movement more efficient)

how do two joint muscles act as stiff cables to help with mechanical energy during vertical jump?

-Contraction by hip extensors will not only extend the hip but will pull on the stiff cable (RF) and tend to extend the knee -Appears as work done at the knee -Similarly, vasti muscles extend knee, which transfers energy through gastroc to appear as work done at ankle

what factors influence vGRF attenuation?

-Cushioning material in footwear -Surface properties -muscles

how does cushioning material in footwear influence GRF attenuation?

-Cushioning material in footwear Conflicting evidence whether it attenuates forces or not;May even increase impact forces ( bc individual doesnt try to land softer when they have cushioned shoes bc they can't feel it)

what contributes to long jump distance covered?

-Displacement of COM(Most important factor) -Lean of the body at takeoff and landing ( having forward lean at takeoff and backward at landing) -Forward at takeoff -Backward at landing

how does muscle influence GRF attenuation?

-Eccentric muscle activity may serve as dampening element to absorb energy of impact ( lengthening of muscle absorbs energy) -Additional muscle activation cannot occur during passive phase of landing, so muscle activity must occur before ground contact ( initial 50 ms, no muscles are recruited, a lot of muscles work on feed forward system so muscle contraction occurs before ground contact in anticipation)

when does the passive phase of landing occur?

-First 50-80 ms after feet come in contact with ground -No additional muscle activation can occur in response to sudden impact forces -point in which we don't recruit muscles in response to sudden impact of forces

what happens during landing?

-Generally, forefoot strikes ground first -Rapid dorsiflexion followed by by knee and hip flexion

how does angular momentum effect a spring board diver?

-Impulse during recoil determines magnitude and direction of angular momentum during flight phase ( for instance To perform forward somersault, impulse must produce angular momentum pointing inward) -angular momentum does not change during flight phase ( only force is gravity at this point) -angular momentum of individual segments can change

how does fatigue play a part in muscles and ground reaction force during landing?

-Likely reduces ability to absorb energy of impact -May see altered co-activation strategies to maintain stability

how does surface properties influence GRF attenuation?

-Peak impact forces do not vary substantially with different surfaces -Believed that kinematics of landing override adaptation to surface

what is the purpose of dorsiflexion and hip and knee flexion during landing?

-Reduce amount of body mass involved in initial collision with ground -Allow Lower Extremity to absorb energy of impact and prepare for subsequent propulsive movement -Reduce forces acting on body by increasing distance that COM travels while these forces act on body

how is the time over which the GRF is applied to the foot during landing important?

-Tissues that absorb these forces are viscoelastic ( deformation and reformation aren't the same) -Sensitive to rate of loading -As rate of loading increases, so does stiffness to absorb more force/unit deformation

how does the diving board create a reaction force to the diver?

-as board is depressed it stores elastic energy ( returns the energy to diver on recoil) -effect is to exert torque about COM

what is a squat jump?

-begin in squat position and jump up as high as possible -has no initial downward movement

what contributes most to vertical jump height?

-countermovment jump -hip ( because it produces a great amount of torque and angular velocity compared to other joints)

what is the distance jumped during long jump dependent on?

-dependent on time in air -Determined by vertical velocity at takeoff ( needed to make feet leave ground) -trade off between the two ( 9 step allows for greatest amount of distance covered; point where greatest vertical velocity and greatest horizontal velocity) -force at take off is greater during 9 step in Y direction and X direction

how does the rectus femoris help with mechanical energy transfer during vertical jump?

-during takeoff the hip and knee are extended -rectus femurs acts as antagonist while lengthening at one end an shortening on the other ( lengthen at hip shortening at knee) -Net muscle length does not change substantially and contraction velocity is low therefore low work at hip joint -Allows two-joint muscles to exert high forces during contraction (energy generated by proximal one joint muscles transferred to two joint muscles at the distal joint as work ( f x distance- amount of energy the force gives to the object )

grf during somersault

-has two force peaks -first one 12 x body weight -second one 15 x body weight -midfoot elevates one of the peaks when landing ( could correspond to injury reduction)

what do you want to improve to improve vertical jump height?

-improve the muscles in the lower extremities -maximize the ability to transfer energy from two joint muscles to one joint muscles -focus on exercise that lengthen and shorten repetitively

why can we jump higher with countermovement jump?

-lengthening and shortening muscle contractions about the knee and ankle vs squat jump that goes from isometric to shortening contraction - use of hip and knee -muscle activity -mechanical energy transfer -more initial speed at takeoff for more vertical displacement

during countermovement jump at takeoff what happens to velocity ?

-lower self down first with the goal of disporportionately raising self -our lowering velocity is less than raising velocity ( slow and controlled) -greater acceleration going upward

pre-activation of muscles and landing

-may be related to task demands -Quads may demonstrate more pre-activation when jump follows landing -During landing-only movements; Muscles = dampening elements -During jump following landing Musculotendinous units serve as springs

what is a countermovement jump?

-moving in opposite direction of intended jump ( down and up quickly) -moving down before jumping up -goal maximize vertical velocity at takeoff -goal is maximum vert height

what is a backward dive?

-standing approach -facing the board -GRF is anterior to COM causing them to do a back flip

what is an inward dive?

-standing approach -facing the board -GRF posterior to COM cause them to do front flip -rotation toward dive board - if they miss they will hit front of head on diving board

what is a reverse dive?

-take several steps for approach -facing the water -GRF is anterior to COM causing them to do a back flip

How does the GRF in relation to COM during Long Jump effect the jumper?

-the vGRF does not pass directly thru the COM at takeoff, jumper experiences angular momentum during flight phase -Must rotate arms and legs to control ( if it went straight up through COM they would jump straight up then straight back down)

what is the optimal takeoff angle for long jump?

45° Requires horizontal and vertical velocity of COM to be similar - only if relative height is zero -we can't do this because humans would have to slow down horizontal velocity

what does max height depend on?

Depends on amplitude(how many muscle fibers we recruit) and timing of muscle activity in the legs

when does the active phase of landing occur?

Eccentric muscle activity generated to resist Lower Extremity flexion( as we land on feet our hips knees will go into rapid flexion) Goal: bring body's motion to zero ( meaning we want COM to stop going downward)

how should the approach be for long jump?

Length of approach to jump must be adequate to obtain 10 m/s horizontal velocity at beginning of takeoff -Once obtained, must get as much vertical velocity as possible while minimizing decline in horizontal they Have approx. 100 ms to increase vertical velocity

what is jumping?

Movement that causes the COM to project upward and the feet to leave the ground

What exercises should be used if athlete needs to perform many max intensity jumps?

Ones that stress the RF and gastroc at low velocity -Squats -Heel raises

Why do we not takeoff at optimal angle?

because Horizontal velocity needs to be greater than vertical velocity -but at 45 degrees we would have to decrease our horizontal velocity

what happens if you don't have dorsiflexion during landing?

increase in vGRF and increased force in ankle knee or hip ; injury ; wont be able to land is efficently

what increases vertical ground reaction force during landing?

increased BMI

what exercises could we use to improve vertical jump height?

ones that involve all parts of the Lower extremities -Power clean and snatch -Hang clean -Plyometrics

sub phases of landing?

passive( defined by lack of resistance that muscles cause during landing) and active (defined by muscles activating; contracting eccentric manner)

what is most critical during takeoff during springboard diving?

reaction force -the board provides reaction force to the diver -pressing down on board -lifting up off board ( timing aspect to maximize reaction force to diver)

how do muscle provide elastic energy during landing?

storage of energy during eccentric muscle loading associated with countermovement jump