Biomechanics Final SG - Butler

What is sports biomechanics? What does it focus on?

Sports Biomechanics

• The application of mechanical principles to study human motion during sports

Focuses on:

• decreasing injuries

• Increasing performance

Biomechanics principles

• What are the 5 biomechanics principles?

• What is passive and active shock absorption? What if active absorption is decreased?

Biomechanics principles

• Transfer of energy

• Movement strategy

• Joint excursion

• Dynamic stability

• Shock absorption

Passive shock absorption (where we want to limit)

• Bone, cartilage, meniscus, ligament

Active shock absorption (where we want to increase absorption)

• Eccentric muscle contraction, dynamic stabilization

If decrease active absorption → increase passive compensation = increase risk of injury

Biomechanics principles - more on dynamic stability

• How is it achieved? What is it?

• Poor neuro muscular control of the LE will cause what three risks?

• For risk 1, what is it? What motion at the ankle and the foot? Absorption of the GRF relying on _____ ______ rather than ______ ______.

• For risk 2, what is it? Shock absorption of the GRF relying on _____ ______ rather than ______ ______. Increases loads for what joint? Failure to utilize? Due to the failure to hip hinge, this shows?

• For risk 3, what is is? Poor control of what over what, causing increased loads on what joint?

• Cutting tasks are reported as the cause of ____% of non-contact ACL tears in collegiate basketball & soccer players. What are the biomechanical risk factors for this this? (4)

Dynamic stability

• Achieved through neuromuscular control of LE biomechanics. Athlete’s ability to stabilize the joints in all planes (sagittal / frontal / transverse)

• Poor NMC of LE is a significant contributor to knee injury risk:

Risk 1 – Dynamic Knee Valgus

• Frontal / transverse plane collapse of the LE

• Ankle eversion

• Foot pronation

• Decrease absorption of GRF → relying on static stabilizers rather than dynamic

Risk 2 – Increased Knee Extension (stiff, decreased flexion)

• Stiff, extended knee landing

• Decrease shock absorption of GRF relying on static stabilizers rather than dynamic

• Increased knee joint loads

• Failure to utilize posterior chain

  • Fail to hip hinge in landing → decreased hip control → Increased hip IR / Add → Increase valgum

Risk 3 – Lateral Trunk Deviation (leaning over stance limb)

• Asymmetric loading – too much load on one LE compared to the other

• Poor control of the COM over BOS → increased knee joint loads

Cutting tasks are reported as the cause of 57% of non-contact ACL tears in collegiate basketball & soccer players

Biomechanical risk factors that have been identified

• knee abduction / dynamic LE valgus

• lateral trunk displacement over injured leg

• decreased hip–knee flex angle

• decreased PF angle

Biomechanics of Cutting / Change of Direction

• Trunk

  • How should it move, and what would a negative finding look like and cause?

• Pelvis

  • How should it move, and what would a negative finding look like and cause?

  • Facilitate force transfers in which direction?

  • Knee

  • How should it move, and what would a negative finding look like and cause?

  • Should be flexed about how many degrees? This is for _______ control.

• Foot

  • How should it move, and what would a negative finding look like and cause?

  • Foot should land where relative to the body?

Trunk position

• Should rotate & lean in the direction of cut

• (-) ↑ lateral trunk flexion over the plant foot → knee joint loads

Pelvis

• Should follow trunk and rotate in direction of cut

• (-) Rotation toward plant foot = femur IR

• Facilitates force transfer towards direction you want

Knee

• Should remain in line with hip & ankle

• (-) ↑ dynamic knee valgus angle → ↑ knee load

• Should be flexed ~30° for eccentric control

• (-) decreased Knee flex = increased GRF

Foot

• Should land flat or toe-to-heel (to decrease brake force)

• (-) Heel-first → ↑ horizontal braking forces → ↑ GRF

• Should land close to the body

• (-) Wide cut width → ↑ knee loading

Classifying Movement Pattern Dysfunction

• Ligament dominance

  • What is it, what is its cause?

• Quadriceps dominance

  • What is it, what is its cause?

• Leg dominance or residual injury deficits

  • What is it, what is the cause?

• Trunk dominance “core” dysfunction

  • What is it? What is the cause?

Ligament Dominance

• LE valgus at landing, Dynamic valgus

• Foot placement not shoulder-width apart, Poor frontal plane knee control

Quadriceps Dominance

• Excessive landing contact noise

• Stabilizing the knee by primarily activating the quads, creates a stiff knee position

Leg Dominance or Residual Injury Deficits

• Thighs are not equal side-by-side during flight. Asymmetrical loading

• Foot placement is not parallel (front-to-back), Foot contact timing not equal

Trunk Dominance / Core Dysfunction

• Thighs do not reach parallel (peak of jump)

• Pause between jumps, Does not land in same footprint, Poor control of COM over BOS, ↓ proprioception

Clinical assessment tools

what is it? What tasks can be used? How to interpret scale? Stats?

Qualitative

• Qualitative assessment of single leg loading

  • what is it? What tasks can be used? How to interpret scale? Stats?

• Expanded cutting alignment scoring tool (ECAST)

  • what is it? What tasks can be used? How to interpret scale? Stats?

• Movement screening for volleyball

  • what is it? What tasks can be used? How to interpret scale?

Quantitative

• Knee ankle separation ratio (KASR)

  • what is it? What tasks can be used? How to interpret scale?

• Acceptable valgus during a hop task

  • during IC? Max flexion?

-Qualitative-

Assessment of Single-Leg Loading – QASLS

• What is it?

  • A scoring of inappropriate movement strategies for single-leg tasks

• What tasks can be used?

  • Applied to dynamic SL tasks (SL squat, etc.)

• How to interpret score

  • Increase score = decreased quality of movement

  • 0 = not present

  • 1 = present

  • Cut off score >2 suggested

• Stats

  • check intra- / inter-reliability

  • check validity compared to 3D motion capture

Expanded Cutting Alignment Scoring Tool – ECAST

• What is it?

  • Qualitative analysis of trunk & LE alignment during a 45 degree cutting task (frontal plane)

• What tasks can be used?

  • 45 step cutting tasks

• How to interpret score

  • increased score = increased risk

  • 0 = not present ; 1 = present

• Stats

  • check validity against 3D motion capture

Movement Screening for Volleyball

• What is it?

  • Risk factor assessment for volleyball players

• What tasks can be used?

  • SL squat

  • DL vertical jump

  • SL drop land

• How to interpret score?

  • An observational screening to find common faults (trunk lean, dynamic valgus, etc.) in sagittal & frontal planes

-Quantitative-

Knee ankle separation ratio (KASR)

• What is it?

  • Measures distance between knees/ankles

• What tasks can be used?

  • Drop vertical jump or hop tasks; any DL activity

• How to interpret score

  • In drop vertical test:

    • 1.0 = knee perfectly aligned with ankles; <1.0 Knee valgus; > 1.0 = Knee varus

    • <0.8 = ACL injury risk (excessive knee valgus). EX if KASR is 0.7 = BAD!

Acceptable valgus during a hop task

• IC < 5 degrees ; Max flexion < 8 degrees.

UE sports biomechanics

• What are the pitching phases/biomechanics? (6)

1. Wind up

2. Stride

3. Arm cocking

4. Acceleration

5. Deceleration

6. Follow through

Pitching phases/biomechanics

• Entire motion takes how long?

• Angular velocities?

• Ball release distraction forces are _____ times body weight

  • Increase ball velocity causes?

• Use of entire kinetic chain is important to?

• Entire motion is about 2 seconds

• Angular velocities

  • >7000 / seconds @ shoulder

  • > 3000 / seconds @ elbow

• Ball release distraction forces = 1.5 body weight

  • Increase ball velocity = increase forces at elbow and shoulder

• Use of entire kinetic chain is important to transfer energy from lower body to upper body

Wind up

• For forces and torque, are they high or low?

• Starts?

• Ends?

• What supplies the forward momentum?

• Low forces, Low torque

• Starts: when pitcher begins to lift lead leg

• Ends: when lead leg reaches max height

• Push off force of trail leg supplies the forward momentum

Stride

• Starts?

• Ends?

• Stride length? What if its too short or too open?

• Knee flexion degrees needs to be? This it to?

• Pelvis should?

• Shoulders needs to? degrees for abd, horizontal abd, ER? What if horizontal abduction is excessive at foot contact?

• Elbow flexion degrees?

• Starts: End of wind up

• Ends: @ foot contact with foot at closed angle (pointing to 3rd base)

  • pitcher pushes off the mound to move towards home plate

• Stride length: distance from hind leg ankle to lead ankle divided by height . 85% of height is ideal.

  • Too short: not enough time to achieve optimal shoulder ER. Caused because of decreased SL balance, decreased hip strength.

  • Too open: Pelvis rotates too soon, leading to increased shoulder and elbow stress

• Knee flexion about 45 degrees to absorb GRF

• Pelvis should begin to rotate forward to name plate

• Shoulders remain parallel to home plate

  • 90 degrees abd, 20 degrees horizontal abd, 45 degrees ER

  • Excessive horizontal abduction at foot contact increases anterior forces at shoulder

• Elbow flexion to 90 degrees.

Kinematic chain

• Foot contact is important because it?

• What is the KEY to maximizing the kinetic chain?

• Requires what two things?

• Foot contact is the source of energy that transmits up the body to maximize power output

• Proper timing between rotation of the pelvis and upper trunk is key to maximizing the kinetic chain

• Requires adequate spinal mobility and dissociation

Arm cocking

• From what to what?

• Trunk position? What should it not be and why? treatment?

• Shoulder position max ER is? What if its too much and too little? Treatment?

• Elbow position? What if its too little trunk angle and too little elbow flexion + early horizontal adduction?

• Where is tensile strains observed along what locations? Highest at? Compressive forces observed along what location?

• Scapular positioning: why is it important?

• Upper trunk and pelvis reach max velocity when?

• Dissociation of _____ and ______ control

• From foot contact to max shoulder ER

• Trunk position should have a slight forward lean at foot contact

  • Backward lean = increase shoulder and elbow joint loading because of decreased momentum arm. Treatment would be core strengthening and trunk proprioception training.

• Shoulder positioning max ER is about 170 degrees

  • Too much ER: Increase internal impingement and elbow torque. Treatment would be shoulder proprioception training and strengthening

  • Too little ER: Usually due to decrease abduction. Treatment would be increasing ER ROM at 90 degrees abduction, and ensure adequate abduction ROM and strength.

• Elbow position → should be at 90 degrees angle to trunk and flexed 90 degrees.

  • Lower angle to trunk post increases horizontal abduction at the shoulder which increases stress on anterior shoulder

  • Too little elbow flexion combined with early horizontal add with cause “leading with the elbow”

• Tensile train observed along anterior shoulder and medial side of elbow is the highest at the late cocking phase. Compressive forces observed along posterior shoulder and lateral side of elbow.

• Scapular positioning is important to maintain a stable base for humerus. Max ER → into max IR at > 7000 degrees / second.

• Upper trunk and pelvis reach max velocities at late cocking

• Dissociation of upper and lower trunk control.

Acceleration

• Starts when?

• Ends when?

• IR velocity is? Shoulder IR with rapid _____ _____.

• At ball release, the shoulder should maintain?

• Trunk position should have? This maintains what? Trunk forward flexion is how much? What if its too little?

• Lead knee should be what during this phase and Why? Decreased in this motion is due to?

• Starts: Max ER

• Ends: Ball release

• IR velocity is > 7000 degrees / seconds (shoulder IR with rapid elbow extension)

• At ball release, the shoulder should maintain 90 degrees abduction and elbow flexion at 25 degrees.

• Trunk position → should have slight tilt toward glove hand (10 - 20 degrees) which maintains the shoulder abducted.

  • Too little trunk lateral flexion = side arm throwing mechanism compromised increasing medial elbow stress.

• Lead knee should be extended during this phase to decelerate forward hip motion.

  • Decrease knee extension = poor quad strength or unstable BOS.

Deceleration

• When does this take place?

• Tensile strain is noted where? This is to do what?

• Compressive forces observed along what area?

• Highest _____ control of ERs

• Highest _____ tension

• Immediately following ball release

• Tensile strain noted on the posterior shoulder to decelerate the shoulder and control horizontal adduction

• Compressive forces observed along the anterior aspect of the shoulder

• Highest eccentric control of ERs

• Highest posterior tension

Follow through

• When does this happen?

• Increased range of?

• Requires what motion? What if this motion is too little?

• Body moves in a forward direction until the arm stops moving

• Increases range of closed kinetic chain hip IR

• Requires increased hip IR ROM

  • Too little IR = CAM + Pincer impingement

Summary of injury risk for

• Max ER (Late cocking)

  • Greatest force on _____ shoulder

• Ball release (follow through)

  • Greatest force on _____ shoulder

  • Requires what two things to decelerate the body and arm?

• Arm slot (the good 90 abduction)

  • Elbow is not maintained at ______ to trunk, causing?

• Kinetic chain

  • Failure to utilize at all phases of the pitch increase the stress to what structures?

  • Requires good ________ of trunk and pelvis

• Max ER (Late cocking)

  • Greatest force on anterior shoulder

• Ball release (follow through)

  • Greatest force on posterior shoulder

  • Requires good balance and core strength to decelerate the body and arm?

• Arm slot (the good 90 abduction)

  • Elbow is not maintained at 90 degrees to trunk, causing medial elbow stress

• Kinetic chain

  • Failure to utilize at all phases of the pitch increase the stress to the shoulder and elbow

  • Requires good dissociation of trunk and pelvis

Abnormal gait: Neurological gaits

• Parkinson gait

  • What is the posture like and how does that affect the COG?

  • People with this gait have a shuffling like motion, this means no what? (4)

  • rigidity or spasticity? Bradykinesia or akinesia?

  • People with this gat may demonstrate freezing, this means?

  • What is festination?

  • This gait it typically found in what conditions? (3)

• Hemiplegic gait

  • What is it?

  • What two motions happen to the affected hip?

  • Ankle in _______ with weak ______ and ______.

  • Knee and hip move into what motion to compensate during floor clearance?

  • Typically found in what condition?

• Ataxic gait

  • What is typically seen in this gait? (3)

  • What conditions is this typically found in?

• scissoring gait

  • What happens to the BOS in this gait?

  • LE _______ due to _______ spasticity

  • Spastic dorsi or plantarflexion? This causes to the toes to?

  • Legs end up crossing what?

  • What condition is this typically found in?

• Waddling gait

  • This gait occurs due to? This causes what to occur at the hip and what to occur at the trunk?

  • What condition is this typically found in?

• Parkinson gait

  • Flexed posture of neck, trunk, hips and knees → moves COG anterior

  • Shuffling → NO heel strike, toe off, arm swing, or pelvic rotation.

  • Rigidity and bradykinesia

  • Freezing = difficulty initiating steps

  • Festination → urge to take short quick steps

  • Found with PD, Wilson disease and cerebral atherosclerosis

• Hemiplegic gait

  • Unliteral weakness

  • IR and Add of affected hip

  • Ankle in drop foot with weak plantarflexion and inversion (equinovarus)

  • Knee and hip move into flexion to compensate during floor clearance

  • Found with strokes

• Ataxic gait

  • Decreased coordination, staggering movement, widen BOS

  • found in cerebellar disease

• scissoring gait

  • Narrow BOS

  • LE adduction due to Add spasticity

  • Spastic plantarflexion (equinovarus). Causes toes drag on the floor

  • Leg cross midline

  • Found with spastic CP

• Waddling gait

  • Glute med weakness (bilaterally)

  • Pelvic drop on both sides (contralateral drop during stance) and trunk lean (ipsilateral in stance)

  • Found with muscular dystrophy

Abnormal gait: MSK gaits

• Trendelenburg gait

  • What are the causes of this gait? (2 primary 1 compensatory)

  • This creates what at the pelvis and what at the trunk?

• Lurching gait

  • What are the causes of this gait? (1 primary and 1 compensatory)

  • This causes what to occur? What does it mean if this occurs during stance VS during swing?

• Circumduction gait

  • What are the causes of this gait? (3 compensatory)

  • What 4 things occur during this gait?

• Steppage gait

  • What are the causes of this gait? (4 compensatory)

  • This causes what to occur during swing?

• Antalgic gait

  • What is the cause of this gait? (4 primary)

  • This causes what to occur? Reasons? (4)

• Leg length discrepancy gait

  • This gait occurs due to? This can be seen in what conditions?

  • Compensatory gait that occurs cause the pelvis to do what? Causes the hip and knee to do what?

• Trendelenburg gait

  • Possible causes:

    • Primary: weak hip abductors on reference limb, adductor contracture on reference limb

    • Compensatory: Leg length discrepancy → short contralateral limb

  • Creates:

    • contralateral pelvic drop on swing limb during stance on reference limb

    • ipsilateral trunk lean on reference limb during stance

• Lurching gait

  • Possible causes:

    • primary: stance (weak hip extension)

    • Compensatory: swing (weak hip flexion)

  • Creates: Backward lean of trunk

    • During stance: LOG moves posterior, decreased hip extension torque

    • During swing: compensation for inadequate hip flexion

• Circumduction gait

  • Possible causes:

    • Compensatory: advance the limb and clear the foot when hip flexion, knee flexion, and dorsiflexion are inadequate.

  • Creates:

    • Hip hike, hip flexion, forward rotation of pelvis, abduction of hip → in stance phase

• Steppage gait

  • Possible causes: Compensatory

    • Inadequate knee flexion in initial swing for toe clearance

    • Inadequate dorsiflexion in mid swing for toe clearance (Foot drop, L5 radiculopathy, peroneal palsy)

    • Excessive contralateral knee flexion (shorten stance limb)

    • Long swing limb

  • Creates:

    • Excessive hip flexion and knee flexion during swing

• Antalgic gait

  • Possible causes:

    • Primary: pain in reference limb due to pain at the trunk, hip, knee, ankle

  • Creates:

    • Decreased stance time on reference limb, decrease step length on opposite limb

  • Reasons:

    • Knee pain → decrease weight bearing

    • Forefoot pain → avoided toe off

    • Heel pain → increase toe weight bearing instead

    • Hip pain → decrease weight bearing

• Leg length discrepancy gait

  • Occurs due to asymmetrical length of pelvis, tibia, and femur. Conditions that cause this are scoliosis and contracture

  • Compensatory gait

    • Pelvis: Drop on short side in stance with increase plantarflexion

    • Hip and knee: Longer limb presenting with increased hip flexion and knee flexion to help decrease length

Trunk deviations

• What is it? Causes? (2 primary, 1 secondary, 1 compensatory, 1 contracture)

Forward trunk lean in stance

• Causes:

  • Primary: skeletal deformity, decrease hip extension strength (pelvis falls forward, trunk follows)

  • Secondary: excessive anterior pelvic tilt

  • Compensatory: quad weakness (provides passive knee extension force by placing COM anterior to knee)

  • Hip flexion contracture: without compensatory lordosis → trunk follows pelvis into flexion

Pelvis deviations

• Posterior pelvic tilt (Causes at stance (1 primary 1 secondary) and at swing (1 secondary))

• Anterior pelvic tilt (causes at stance (2 primary 1 secondary))

PPT

• At stance: Primary HS tightness; secondary hip flexion weakness

• At swing: Secondary hip flexion weakness

APT

• At stance:

  • Primary hip flexion contracture and hip extension or abdominal weakness

  • Secondary due to forward trunk lean

Hip deviations

• Hip hike: what is it and what are the causes (1 for initial swing 1 for mid swing)?

• Thigh medial rotation: what is it and what are the causes (2 primary 1 compensatory)

Hip hike

• Excessive elevation of pelvis in swing on reference limb

• Possible causes:

  • Compensatory toe clearance when there is not enough knee flexion in initial swing or not enough hip flexion and dorsiflexion in mid swing.

Thigh medial rotation

• Position of femur with femoral condyles facing medially

• Possible causes

  • Primary: Skeletal deformity (femoral anteversion), decreased motor control

  • Compensatory: to increase knee stability due to weak quads in stance

Ankle/foot deviations

During stance phase

• Early heel off

  • When does this happen

  • Possible causes (2 primary and 1 compensatory)

• No heel off

  • When does this happen

  • Possible causes (2 primary 1 secondary)

• Excessive pronation

  • What is it?

  • Possible causes (2 primary, 2 secondary, 1 compensatory)

• Excessive inversion (pes cavus)

  • What is it?

  • Possible causes (2 primary, 1 secondary)

• Foot slap

  • What is it and when does it occur

  • Possible causes (1 primary)

• Flat foot contact

  • What is it and when does it occur

  • Possible causes (1 secondary and 1 compensatory)

• Forefoot contact

  • What is it and when does it occur

  • Possible causes (1 primary and 2 secondary)

• Abbreviation heel contact

  • What is it and when does it occur

  • Possible causes (2 primary, 1 secondary, 1 compensatory)

During swing phase

• Contralateral vaulting

  • What is it and when does it occur

  • Possible causes (3 compensatory)

During stance phase

• Early heel off

  • At midstance

  • Possible cause

    • Primary: PF contracture, overactive PF

    • Compensatory: to accommodate short reference limb

• No heel off

  • At terminal stance

  • Possible causes

    • Primary: weak PF (surgical lengthening of Achilles tendon), Forefoot pain

    • Secondary: inadequate toe extension

• Excessive pronation

  • More calcaneal/forefoot eversion

  • Possible causes

    • Primary: skeletal deformity (hindfoot valgus), weak posterior tibialis

    • Secondary: compensated forefoot varus, genu valgum

    • Compensatory: decrease ankle dorsiflexion

• Excessive inversion (pes cavus)

  • More calcaneal/forefoot inversion)

  • Possible causes

    • Primary: skeletal deformity (hindfoot varus), equinovarus contracture

    • Secondary: due to genu varum

• Foot slap

  • Rapid plantarflexion at heel strike

  • Possible causes

    • Primary: weak DF (common peroneal nerve palsy, L4 - L5 nerve injury)

• Flat foot contact

  • IC made with both hindfoot and forefoot

  • Possible causes

    • Secondary: knee flexion contracture

    • Compensatory: weak quads

• Forefoot contact

  • Initial ground contact made with forefoot

  • Possible causes

    • Primary: not enough DF or Knee extension

    • Compensatory: to accommodate shorter limb, heel pain

• Abbreviation heel contact

  • Shortened interval of heel at initial contact

  • Possible cause

    • Primary: weak DF, PF contracture

    • Secondary: knee flexion contracture

    • Compensatory: weak quads

During swing phase

• Contralateral vaulting

  • Excessive PF of opposite stance limb in swing on reference limb

  • Possible causes

    • Compensatory: to lengthen stance limb and achieve swing toe clearance because of → longer swing limb, not enough knee flexion in Initial swing, not enough DF in mid swing

Knee deviations

• Rapid knee extension (extensor thrust)

  • When does this occur

  • Possible causes (2 primary 1 secondary)

• Not enough knee flexion (stiff leg gait)

  • What is this and when does it occur

  • Possible causes (3 primary)

• Rapid knee extension (extensor thrust)

  • After IC

  • Possible causes

    • Primary: weak quads, decreased motor control

    • Secondary: due to PF contracture

• Not enough knee flexion (stiff leg gait)

  • Knee remains in extension during LR

  • Possible causes

    • Primary: Weak quads, decrease motor control, knee pain

Observational gait analysis

• What is it?

• Goal?

• Qualitative assessment can occur through?

• Camera placement?

• Walking condition?

• Footwear?

• Clothing?

• Reference limb?

Observation of a patients gait

Goal: Identify specific deviations from “normal” gait pattern

Qualitative assessment: through videos, apps, photos, real time assessment.

• Camera placement: Level consistent, lateral anterior and posterior views

• Walking condition: treadmill vs level ground, speed

• Footwear: barefoot (unshod) and sneakers (shod)

• Clothing: ensure visibility of all joints

• Reference limb: limb of primary concern

JAKC’s observational gait analysis

• What is it? How does it categorize deviations?

• For each of the following joints how does the JAKC differ?

  • Ankle

  • Calcaneus and toes

  • Knee and thigh

  • Pelvis

  • Trunk

(FOR THIS BUTLER SAID DONT STRESS ABOUT THE OBSERVATIONAL GAIT ANAYLSIS TOOL, JUST KNOW ITS USED TO ACCESS GAIT)

Jan Adams and Kay Cemy (JAKC)

• Categorizes deviations into 3 gait tasks

  • Weight acceptance

  • Single limb support

  • Swing limb advancement

Ankle

Calcaneus and toes

Knee and thigh

Pelvis

Trunk