1 334spo All Lectures

8/2/2019 1 334spo All Lectures

1/134

334SPO Mechanics of theMusculoskeletal System

Animal tissues

Structure

Function

Biomechanical properties

Including failure

Lectures from RJ & AP: 20 hours for 334SPOand 239SPO, 12 hours for 333SPO/335SPO

Tutorials/Labs/workshops RJ et al: 10hours (often in vivoassessments)

Reading list

Marking criteria & CW proformas

Timetable & corrections

Notice board

CUOnline

Online quizzes (1 tutorial)


2/134

What Happened 2007/8232SPO?Mean scores

= excellent, 1 = very bad

Module well organised: 3.75

Module met aims and Objectives: 4.00

Teaching methods effective: 3.75

Assessment methods effective: 4.00

Satisfied with this module: 4.50

Effective lecturer RJ: 5.00

Specific comments

Liked the small group tutorials Liked the book of lecture notes at the start

Wanted last lab earlier in the year (it is now)

Wanted more information on handouts (there isnow)

Lectures to be done on PowerPoint (they arenow)

94% of students attended >60% of taughtclasses

64% of students passed 232SPO pre resit


3/134

Attendance

Significant relationship betweenattendance and module mark

R2 = 0.205 P = 0.002

0

1020

30

40

50

60

7080

0 20 40 60 80 100 120

Lecture attendance (%)

Modulemark(%)


4/134

Resourcesmodule handbook:

Books

Videos

CUOnline site

Quiz

Practice short answer quizzes for each book

chapter Module handbook

Timetable

Tutorial topics list

Handouts

Journal articles to download

References stated on many handouts

Some on CUOnline 334SPO site

Some in library or via library portal

Some via document supply service or ask Rob


5/134

Module marks 2010/11

34SPO (BSc Sport and Ex Sci students)

50% for 1500 word CW essay (term 2)

50% for 2 hour Exam

33SPO/335SPO (BSc Sports Therapy students


50% for Critical appraisal of physiologicalscenario. Maximum 1500 words (Mike Pricewill set this)

39SPO (BSc Rehab Eng; BSc Assist Tech)


50% for 30 minute phase test (term 1)

Turnitin: submit essay to Turnitin via

CUOnline site.

Can submit draft to check, pre real

essay submission


6/134

Labs/Workshops

Whole body analysis

Kinematics: 2D low speed videoanalysis

Usage of electromyography andelectrogoniometer

Tissue mechanics

Instrom bone mechanics and workloop muscle mechanics


7/134

Structure andProperties of

MaterialsWhat is the material composed of?

How do we test the biomechanicalproperties of the material?

What are the biomechanical properties?

What should the material be used for?


8/134

Muscle Structure

Muscle

TendonTendon

erve supply

Blood supply

Muscle

fibres

Thick filaments

Thin filaments

Muscle Sarcomere


9/134

Muscle filament structureThin filament

Helical arrangement

(i) Double strand of actin monomers

(grey and white circles)

(ii) Troponin complexes (black circles)

and Tropomyosin (black lines)

which regulate actinomyosin interactions

Thick filament

Myosin: heads, neck and body

Bare zone


10/134

Myosin moleculestructure

Heads

Neck

Hinge

Body

Myosin heavy chains

Head (S1 region) has ATP and actin binding sites

Neck (S2 region) pivots on hinge

Body embedded in thick filament

Myosin light chains stabilise head and neck region

Myosin light chains


11/134

Optical Trap Technique

Isolated actin and myosin filaments

Actin filament attached to plastic beads

Laser beams hold the beadsLasers can move actin filament

Lower actin filament towards freemyosin molecules

Interaction causes beads to move

Very low forces pico Newtons pN

Laser beam Laser beam


12/134

How is force produced?

ATP bound to Myosin head (S1 region)

ATP broken down

Myosin head binds to actin

Myosin head rotatesRotation stretches neck (S2 region)

This causes force to be produced

ADP & Pi & energy released

ATPADP + Pi + energy

Heads (S1)

Neck (S2)

Hinge

Body


13/134

ATPrigor

S1 head

S2 neck

Actinbinding

sites

Body

Myosin molecule

ATP

ADP

Pi

Hydrolysis

ATP

Dissociation

NB. 2 sites for

heads!

ATP Binding and hydrolysis


14/134

Force ProductionDuring isometric activity = constant length and active

so = constant metric = length

While isometric there is no movement of the thick anhin filaments with respect to each other

PiADP

Pi + energy

B

ADP

B

ADP

B

ADP

S2 stretches

Force

neck

B=body

Head

Actin binding site

More stretch of neck (S2 region) = more force


15/134

Force-velocity Relationship

Thick

ilament

Thinfilament

A) Filament sliding

ADP

B

S2 stretch

aster velocity of shortening = less myosin heads bind

and neck stretches less

increased shortening velocity = decreased force

B) S2 head rotation

During concentric actions (muscle shortening and active)

Velocity

Forc


16/134

Full Cross-bridge Cycle(Diagramme)

ATP

ATP

ATP

ADP

Pi PiADP

Pi + energy

ADP

ADP

ADPrigor

Force

produce


17/134

Full Cross-bridge cycle

Myosin is bound to actin (rigor state)

ATP binds to myosin

Myosin dissociates from actin

ATP is hydrolyzed and myosin head

rotates

Myosin binds to actin

Phosphate and energy release

Rotation of head causes force

production


18/134

The Muscle Switch:activation

Depolarization of nerve

Depolarization of muscle membrane

ACh Neuromuscular junction

Calcium release from SR

Depolarization of T-tubules

Sarcoplasmic

reticulum

T tubul

Surface membrane

Nerve

ACh

receptor


19/134

The Muscle Switch:

Levelofrespo

nse

Nerve

Tim

Muscle

AP AP Ca2+ Force

Calcium in cytoplasm binds to troponin C

Change in shape of troponin T

Troponin I no longer physically blocking actin

binding site

Strong binding of myosin head with actin binding sit

Force production


20/134

Calcium Binding

ActinActin

Tn-T

TM (Tropomyosin)

Tn-I

Tn-C

Binding site

Tn-T

Actin

TMTn-I

Tn-C

Strong AM

binding

Weak AM

inding

Tn-I inhibits Myosin ATPase

Calcium concentrationincreases

Cross-section through thin filament

Troponin complex = TnC, TnT, TnI

Relaxed

Active


21/134

Muscle Relaxation

Cessation of neural stimulus Decreased Calcium release

Decreased calciumconcentration decreaseschance of calcium binding toTnC

Decreased muscle force

Calcium binding in cytoplasm byparvalbumin

Further decreased Calciumconcentration

Decrease in calcium binding byTn-C

Calcium pumped fromcytoplasm to sarcoplasmicreticulum (requires ATP)


22/134

Whose muscle is it anyway?

Muscle mechanics similar betweenvertebrate species

Frog muscle main one used as easy touse!

Why little human data?

Ethics problems of invasive experiments

Experimental rigor of non-invasive

These lectures

Will use any muscle data as typical of

vertebrate muscle

Will try to highlight any relevant humandata where available


23/134

Muscle MechanicsMuscle fibres vs. whole

muscle vs. sarcomerein vivo =in life; in vitro= in glass; in situ= inlace

Whole muscle simulates in vivo

Easier to dissect

Larger preparations have:

Increased risk of anoxia (diffusion distance)

Increase in passive structures

Increased problems of diversity of fibreorientation

Muscle>muscle fibre bundle>muscle fibre>

sarcomere

O2

Parallel fibredPennate fibred


24/134

Sarcomere levelCould use a muscle biopsy

Chemical treat muscle (skinned) to

remove membranes

Clamp single fibre so only monitoring a

single sarcomere

Use chemical solutions to:

Activate (high calcium concentration)

Relax (low calcium concentration)

Measure force-length properties

Length

Force


25/134

Fibre/muscle level

Muscle removed from animal and test:

Whole muscle

Fibre bundle

Single fibre

Electrical stimulation (via nerve/direct)

Activates muscle

Force production

Different types of studies

Isometric = constant length Isotonic = constant force

Isovelocity = constant speed

Work loop (simulate in vivo)

Force-velocity


26/134

Muscle rig

Oxygenated

Ringer

Krebs inalt solution) Ringer out

Muscle

MotoForce transducer

Platinum electrodes

Salt solution composition to mimic blood plasma

and includes an energetic substrate e.g. glucose

Temperature regulation of salt solution

35 to 37C for mammalian work

historically 0 to 20C for ease!


27/134

Isometric Tests of Muscle

Force

Stimulation (V

Twitch: used to optimise muscle lengthand stimulation amplitude

Tetanus: used to optimise stimulation frequency

Force

Stimulation

Time

Response

Stim. frequency =

# of stimuli per secondfused

unfused

Multiple stimuli cause multiple releases of calciumLeading to summation of twitches and greater force


28/134

Isometric Times

Twitch

Tetanus

Time

Stimulus

Force(%maximum)

THPT

THPTet

HPT = time to half peak twitch

PHR = time from peak twitch to half relaxation

HPTet = time to half peak tetanus

etPHR = time from peak tetanus to half relaxation

Rates of activation and relaxation


29/134

Force-length Curve

Force

1

3

2

4

1SarcomerLength

2 3

4

Passive

(collagen)

Total

Active

Sarcomere

Actin binding

sites covered

Only bare zonuncovered on

thick filament

Nooverlap


30/134

Titin filamentsTitin

Z line M line

Titin (also sometimes referred to asonnectin)Runs from Z line to M lineTwo sections of titin with differenttiffnesses

These correlate to the mechanicalmodels of muscle passive stiffness

So titin has two functionsProvides passive stiffness (protective)Stability of sarcomere structure


31/134

Force-velocity(Isovelocity version

Force

Stimulation

Length

Velocity

ForceFmax

aster Vmax

lower Vmax

Tim

Vmax = maximum

shortening velocity

Fmax = maximumtetanic force

Can compare muscles:


32/134

Eccentric vs ConcentricWhat is the difference?

Eccentric = lengthening and active Concentric = shortening and active

When might eccentric force be important?

large external force braking/controlling movement

Velocity

Force

ConcentricEccentric

0

Isometric

peed and direction of movement affects forceia stretch of myosin neck and # of cross-bridges


33/134

Power output-force/velocityCurves

Velocity

Power

OutputPeak P.O. at V/Vmax of

c. 0.3-0.4

Force

Power

Output

Peak P.O. at F/Fmax of

c. 0.3-0.4

ower output (P.O.) = force velocity

V = velocity

Vmax = maximum

velocity

F = force

Fmax = maximum

force

Velocity

Force


34/134

Efficiency

Work output energetic costenergy cost in ATP

work done = Force distance

Power output = work done time taken

Efficiency

Maximum efficiency around 0.3 to 0.4 V/Vmax


35/134

Tendon Tendon

Parallel fibred muscle

Increased length

TendonTendon

Pennate muscle e.g. Bipennate, multipennate

ncreased physiological cross-sectional area,

measured perpendicular to fibre longitudinal axis)ncreased force

Lower fibre length,

E.g. gastrocnemius, soleus, quadriceps

E.g. Extensor digitorum longus

Muscle Pennation

Angle of

pennation

Longitudinal axis


36/134

Design of MuscleImagine we have a muscle of constant volume

We can alter the muscle length but this will alsochange muscle cross-sectional area

What effects would such changes have on musclemechanics?

Muscles with higher cross-sectional area = highforce production, good for stabilizing limbs

A fictional muscle

one sarcomere long

but many sarcomeres wide

Muscle length

Musclecross-sec

tionalarea


37/134

Design of Muscle 2Each sarcomere generates force and pulls thesarcomere next to it

Along the length of a muscle some of the forceswill effectively cancel each other out

Essentially we just need to count the number ofsarcomeres across the cross-sectional area (the

sarcomeres at the end) to determine the forceproducing capacity of the muscle

Longer muscle: 4 sarcomeres wide

Wider muscle: 12 sarcomeres wide

So wider muscle would produce

3 times more force

FF

width

Length


38/134

Design of Muscle 3

Longer muscle: 3 sarcomeres long

Wider muscle: 1 sarcomere long

If we assume each sarcomere can

shorten at the same speed

The longer muscle would produce

3 times more shortening speed

FF

width

Length

Longer muscles = higher absolute speed,acceleration and deceleration

peed = distance moved time taken for movement

Acceleration = change in speed time taken forchange


39/134

Wider muscle but same length

For review see Lieber, R. & Friden, J. (2000) Muscle & Nerve23 1647-1666 (not in library: ask Rob)

Length

Force Larger PCSA:

Smaller PCSA

Velocity

Force

Larger PCSA:

Smaller PCSA

sometric force-length curves

Same length = same range of motion

sovelocity force-velocity curves

ame length = same maximum shortening velocity

Higher force at all

lengths

Higher force at all

velocities

0


40/134

Longer muscle but same PCSA

Force

Length

Force

Shorterfibres

Longer fibres

Velocity

horter

bres

sometric force-length curves

ame cross-sectional area = same maximum force

Longer fibres

Longer muscle has

larger ROM

sovelocity force-velocity curves

ame length = same maximum shortening velocity

Longer muscle has

higher Vmax, so lower V/Vmaxat each V, so higher force



41/134

Human MusclePennation Effects

Fibre Length

PCSA

Pennation angle 0-30

Fibre length ROM (range of motion)

Fibre physiological csa F maximum

Increased pennation tends to causeecreased fibre length

soleus

EDL SemitendinosusFDL

Less pennate

more pennate



42/134

Muscle PennationAssume muscle of fixed volume

If used lower pennation angle (moreparallel fibred)

longer fibred and longer muscle

Faster shortening velocityGreater range of motion

But pennate muscle fibres do not need

to shorten as fast as the muscle!pennate muscle = higher PCSA = highe

force

So produce more force at same velocity

Pennation changes during activation!

Increased pennation angle as shorten



43/134

Muscle rolesPower (FV)

e.g. for jumping

long muscle for high speed

high csa for high force

Acceleration to rapidly increase speed

long fibres and muscle

Brakesstabilisation

high force

high pcsa, high pennation

Endurance/efficiency

reduce energetic cost?

slower fibre type

minimise muscle size


44/134

Effects of Muscular Fatigue

Decreased force production at any speed

Slower activation and relaxation rates

Decreased maximum shortening

velocity

Test muscle properties

Fatigue muscle

Test muscle properties

Fatigue tests (performance over time)

Fatigue resistance(endurance)

orce

Time

Fresh

Fatigued

Isometric Isovelocity

Force

Velocity

Fresh

Fatigued


45/134

Why use work loops?Isometrics measure at constant length

Isovelocity at constant velocityIsotonic at constant force

In vivoall these conditions are likely to vary

I.e. dynamic

Work loop technique (also called oscillatorywork technique) to simulate/approximate invivo

Isotonic/isovelocity overestimate power output

Isometric underestimate rate of forceactivation and relaxation

All these ignore passive properties of muscledue to collagen etc

James, R.S., Young, I.S., Cox, V.M., Goldspink, D.F.,and Altringham, J.D. (1996) Pflugers Archive432 767-774.


46/134

Work loops

Time

ength

Activity

Force

Plot force against length

o create work loop

The area of the loop net work done

.g. James, R.S., Altringham, J.D., and Goldspink, D.F.995 J Ex Biol. 198 491-502

1 length change

cycle

his example uses a sinusoidal length change waveform

strain

e.g. 0.10 (5%)

stress

strain


47/134

Why use stress and strain?

Measurements normalised (realtive) to muscle size

tress (N.m-2) = force (N) cross-sectional area (m2)

train = length change initial length

= L L0

.g. 0.1m 1m = 0.10 (i.e. 10% length change)train has no units

Force

L0L


48/134

Passive Stress-strain curves

Stress (force csa)

Strain

(length change initial length

Modulus of elasticity/stiffness/Youngs modulus

= stress strain = the slope of the line =

tiff = lots of force required to cause a small strain

.g. bone more stiff than muscle

x

y

y x


49/134

Elasticity 1

Perfectly elastic material (doesnt exist)

tress-strain relationship is linear and identica

n extension and compression of material

Energy required to stretch the material =

nergy released during shortening

No net energy cost to undergo length change

cycle

Stress

Strain

We are now considering passive properties

Elasticity = wish to return to original shape

.g. length


50/134

Stress

Strain

Perfectly viscous material

Deforms when force is appliedWhen force stops the material does

ot return to its original shape.

e. no elastic recoil

Blue tac is fairly viscous!

Elasticity 2


51/134

Strain

Visco-elastic material

Stress

Biological materials (e.g. muscles and tendons

equire energy input during stretch which is

ot fully returned during recoil

Area within work loop = net energy required to

undertake length change cycle

Work (energy) = force distance

Elasticity 3


52/134

Muscle stress-strain curves 1

Strain

Stress

Stress

Stress

Strain

Strain

During stretch:

Work (energy) input

During shortening

Work (energy) output

Net work done on the material

during the length change cycle

(energy cost)

Passive


53/134

Muscle Stress-Strain curves 2

Strain

Stress

Stress

Strain

Work input to stretch

work done on the muscle

by antagonist or other external force

Work output

Stress

Strain

Net work

Active when shortening

concentric exercise)

During

shortening

work is done

by the muscle

Net work done by muscle during length change cycl


54/134

Ultimate Properties ofTissue

The maximal performance of a tissuebefore it breaks (total failure occurs) Strength Extensibility Toughness

Vary between tissues

Vary between parts of body

Depends on cost of failure!


55/134

StrengthThe maximal stress (force csa) a material can

withstand before it breaks

Failure strength

stress at failure

Yield strength

(damage begins)

i.e.. micro damage

Strain

Stress

Ultimate strength

(maximal stress)

Plastic

Deformation (damage)

Elastic

Deformation

o no damageHookes law)

e.g. bone stress-strain curve:


56/134

Extensibility

The maximal strain a material can be subjectedto before it breaks

Breaking point

Stress

Strain

Strength

Extensibility

Maximal strain

Maximalstress

Tendon extensibility > bone

Bone strength > tendon


57/134

The energy required to break a material

= the area under the stress-strain curve

Energy (work) = Force distance

Stress

Strain

Less tough

More tough

(but less strong

and more extensible

Toughness

Large area


58/134

Typical Mechanical Properties ofMammalian TissueMuscle Tendon Cortical

Bone

Mild Steel

Maximalextensibilitystrain)

0.25 0.09 0.02 0.1

Ultimateensile

strengthMPa)

0.4 90 150 400

UltimateToughnessKJ kg-1)

? 5.6 25 Higherthan bone

Modulus ofelasticityGPa)

Low orhigh cf.tendon

1.5 20 200

Pa = 1N m-2

000 Pa = 1 KPa 1000 KPa = 1MPa

000 MPa = 1GPa

Compact bone = cortical bone

Tensile = during stretch (under tension)Modulus of elasticity = slope of stress-strain curv

stiffnessStiffness higher in active than passive muscle

low


59/134

Shear vs. Tension

ForceForce

Material in tension

Fracture

Force

Force

Material in shear

Fracture

Forces applied are directly opposite to each other

orces applied are parallel but not directly opposite to

ach other


60/134

Compression vs. Bending

ForceForce

Material in compression

Fracture

Material in bending

Fracture

Forces applied are directly opposite to each other

Compression

Force ForceTension


61/134

Safety Factors

If we could design a person:

How would you decide how strongto make the long bones in your leg?

Consider:

function of structure

direction and magnitude of loadingcost of production of structure

cost of repair


62/134

How safe is the structure?

afety factor = Failure stress functional stress

e.g. failure stress (strength) = 4 MPa

functional (everyday) stress = 2 MPa

Safety factor = 4 MPa 2 MPa = 2

Cost of failure Vs. cost of structure

e.g. broken leg bone c.f. broken finger

Increased material = increased cost

synthesis and maintenance

(replacement & repair) costs

material and locomotory costs(including overcoming inertia)

internal space cost

weight = locomotory cost (muscleactivation; higher in lower limbs)

Safety Factors


63/134

Complications inSafety Factors

Variation in expected loaddepend on direction of impact

e.g. in long bones usually loaded in

compression and tension, weaker in

shear

Deterioration in material

previous damage

ageing

Unpredictable strength of material

Increased strength if loads less

predictable and tissue more

mportant for survival

weight

Ground reaction

force


64/134

Safety Factors in Bone1.4 - 4 for bone (i.e. failure stress

functional stress) e.g. Weightlifter: backbone safety factor 1.0-1.7

Bone remodeling in shape, elasticity,

density and mass

density = mass volume

Load dependent tissue growth and atrophy

Atrophy: astronauts in microgravity (lower

loading so decreased osteoblast activity )

Growth (hypertrophy): exercise (weightlifters,

tennis players)

Load generates strain

Strain causes micro damage

damage induces remodeling (overcompensation)

OR strain detected by nerves in periosteum (bon

sheath)?

all, S.J. (2007)Basic Biomechanics. Boston: McGraw-Hill


65/134

Leg Bone Stresses

Stress on long bone at impact depends on angle unpredictable

curved bones bend focussing peak force

predictable)

Higher strength at focus (minimise bone weight

nd minimise locomotory cost)

High strength and safety factor along bone length

for compression and tension

Lower strength for side impact (shear)

Use force platform to measure forcesinverse dynamics to calculate bone stresses

Ground reaction force

weight


66/134

Bending

Fracture

Compression

Force ForceTension

predictable focus of forces

strengthen here

Force

Force

Shear forces:


67/134

Measurement ofin vivo action

Muscle activity: Electromyography

surface (external) EMG electrode cuffs

problems of cross-talk (interference from

other muscles): so better on larger muscles conductance of skin changes between

people, with exercise: affects signal

internal EMG electrode wires

ethical issues signal is definitely from the muscle of

interest

Muscle

TendonTendon


68/134

EMG signals

Raw EMG indicates motor unit actionpotentials

indicates duration of action potential

doesnt indicate muscle force or timing

of force production

force rise and relaxation delayed with

respect to EMG onset and finish

Integrated EMG (IEMG)calculation of amplitude of action

potential

affected by subcutaneous tissue, firing

rate, # active muscle fibres

Measurement ofin vivo action 2

Raw EMG

IEMG

Time

Amplitude


69/134

Measurement ofin vivo action 3

Muscle lengthDirect measurement: Sonomicrometry

crystals implanted into muscle

measure time taken between crystals

calculate distance

Calculation from joint angles 1: use external markers on joints

use motion analysis to track movement of

markers to calculate changes in joint angle assumptions of tendon vs. muscle strain

E.g. James, R.S., Altringham, J.D., andGoldspink, D.F. (1995) J Exp Biol. 198 491-502: onCUOnline

Mouse ankle angle for EDL and soleus musclelengths

2: use X-ray video or cine to track bone movement

could use markers on tendon ends

Direct measurement via ultrasound

emitter receiver


70/134

Strain from joint angles

Mouse muscle strains calculated from anklejoint angles (measured from high speed video)

See James et al. (1995) J. Exp. Biol. 198 491-

502. [Figure 7]: On 232SPO CUOnline siteBut when are the muscles active?

NB. EMG from rat Nicolopoulos-Stournaras &Iles (1984) J. Zool. Lond. 203 427-440.

Muscle functioning as? power producer =

active and shortening; stabiliser if active andnear constant length

0 150 300 450 600

2.4

2.6

2.8

3.0

LIMB CYCLE PHASE (0)

0 150 300 450 600

2.2

2.4

2.6( )

SoleusEDL

train = change in length initial length

Velocity = length change time

EMG

EMG

strain


71/134

In vivo (in life) V/Vmax

V/Vmax

V = in vivoshortening velocity

Vmax = maximum shortening velocity

Mouse soleus trot 0.20 0.31

Mouse soleus gallop 0.34 0.48

Mouse EDL trot 0.24 0.39

Mouse EDL gallop 0.37 0.52

Remember peak power produced atV/Vmax c. 0.3 0.4

So peak muscle power at trot?

See James et al. (1995) J. Exp. Biol.198 491-502. [Table 2].

Force

Velocity


72/134

In vivo (in life) SLSarcomere length-force curve based on ratfilament lengths and isometric (constantlength)

Calculated range of sarcomere lengths used invivo

Calculated sarcomere length at L0 (length for

maximal in vitroforce)In vivolength ranges close to maximal force

Descending limb usage

See James et al(1995) J. Exp. Biol. 198 491-502.[Figure 6].

100

80

60

40

20

0

1.0 1.5 2.0 2.5 3.0 3.5 4.0

soleus in vivosoleus L0

EDLin vivo

EDL L0

Sarcomere Length m

Force(%

maximum)

passivactive


73/134

Real work loopsActive = anticlockwise

Passive = clockwise

Loop represents net work performed (Work =F d)

Passive usually low (collagen) and representsthe work required to cycle the muscle throughone stride

stress falls during shortening due to Force-velocity relationship and shorteningdeactivation

stress

strain

active

passive

Concentric activity

Time

ength


74/134

Real work loops 2Mouse EDL at 8Hz cycle frequency

James et al. (1995) J. Exp. Biol. 198 491-02 [Figure 5]

ncreased muscle starting length =ncreased passive work

ncreased strain = increased passive work

ncreased velocity = increased passivework

Passive due to: collagen & otheronnective proteins

L0

+ 10% L

+ 20% L0

Sarcomere length

Passive

(collagen)

Active

orceL

0

+ 10% L0

0% strain at each length


75/134

Mouse soleus work

cyclefrequency

Network/cycle(Jkg-1 )

Cycle frequency (Hz)

0 2 4 6 8 10

0

2

4

6

8

10

12

14

Work decreases with cycle

(velocity increases causingforce to decrease & work todecrease)

0 2 4 6 8

0

5

10

15

20

25

30

35)

POWEROUTPU

T(W

kg-1

CYCLE FREQUENCY (Hz)

Power = work cycle frequency

= work done time taken

Work measured in Joules (J); power in Watts (W)

Frequency = # per second

Same strain

different stres

NB mice tend to tro

trot c. 5 to 6 Hz


76/134

Strain complicationsSonomicrometry on Bufo americanus

semimembranosus (SM) muscle (hipextensor)

Differential strain along muscle length invivoand in vitro

muscle architecture caused thisAhn et al(2003) J. Physiol. 549 877-888. in library

Sonomicrometry

implants

Distal tendon

(towards toes

Proximal tendon

Pennation changes during activitytrain = change in length initial length


77/134

Strain from sonomicrometryBufo americanusSM

Ahn et al(2003) J. Physiol. 549 877-888. inlibrary

strain differs between regions

velocity differs

different regions of muscle acting ondifferent part of force-length and force-velocity curves

Central segment

Distal segment

Time

Strain

Central segment = increased strain and increasedvelocity


78/134

How active is a muscle?

EMG vs. in vitro

cannot determine % activity from invivo to relate to stimulation to apply in

vitro

best approximations during maximal

activity e.g. sprinting and jumping

assume all of muscle active

Compartmentalisation of muscle

activityCycling of fibres?

increase fatigue resistance

active activeinactive

Complications in muscleactivity


79/134

Fibre typesType ISO

Red (s)Slow

Type IIAFOG

Red (f)FR

Type IIBFG

WhiteFFContractiontime

long short short

Mitochondriaand SDH

high high Low

ATPase atpH 10.0

low high high

Glycogencontent

low high High

Fatigueresistance

high high Low

contraction times = activation, relaxation

OG = fast oxidative glycolytic

R = fast & more fatigue resistant; FF = fast and more

atigueableDH = succinate dehydrogenase (a marker enzyme for

xidative metabolism)

ATPase = myosin ATPase staining (commonly used

to determine fibre type)

Glycogen stores especially important to fuel glycolysis

ifferent fibre types for different jobsMixed muscle fibre types in muscles


80/134

Isoforms of MuscleProteins

Overall phenotype of muscle fibre depends onwhich muscle protein isoforms are expressed

Slow and fast isoforms exist of:

Thick filament proteins

Myosin heavy chain (many)

Myosin light chains

Most thin filament proteins

Tropomyosin

Troponin-C

Tn-T (many)

Tn-I

No known isoforms of actin in skeletal muscle


81/134

Detecting MuscleProtein Isoforms

Determine composition by gelelectrophoresis

e.g. Sodium Dodecyl Sulphatepolyacrylamide gel electrophoresis(SDS-PAGE)

isoforms move in gels according tosize, mass or electrical charge

In humans: co-expression of MHC

isoforms within a fibre: I + I

I + IIA

IIA + IIA

IIA + IIB

IIB + IIB

IIX

Many possible combinations of isoform

combinations

contractile

speed


82/134

Detecting MuscleProtein Isoforms 2

contractile

speed

An example gel


83/134

Myosin HeavyChain Isoforms

Vmax

% MHCIIB

Larsson and Moss (1993)J Physiol 472 595-614.in library

Myosin heavy chain type IIB (fast glycolytic)

In human soleus and quadriceps muscle fibres


84/134

Myosin Lightchain (MLC) Isoforms

Vmax

Ratio of myosin light chain 3 to myosin light chain 2

n rat muscle fibres with same MHC content

Ratio of alkali MLCs : no effect on force

General finding that fibre type has little effect on force

faster muscles produce a little bit higher stress

Bottineli and Reggiani (1995)Eur J Physiol 429 592-94. Not in library

Vmax = maximum muscle shortening velocity


85/134

Histochemical fibre typing 1

Freeze muscle in liquid nitrogen

Cut thin sections (um)

Chemicals used to stain muscleaccording to enzyme activities

SDHase (succinate dehydrogenase)staining (Krebs/TCA cycle) so indicatehow oxidative the muscle is

Myosin ATPase staining indicates

contractile rateAssess ratios of I : IIA : IIB

Semi-quantitative (indicative)

Biochemical activity measurementsare better

e.g. SDHase quantification of enzymeactivity

IIIA

IIB


86/134

Histochemical fibre typing 1

SDHase Myosin ATPase

ibre type I IIA IIB

DHase activity high high low

ATPase activity low high high

dark = fastestarker blue = more oxidative


87/134

Isometric Properties ofFast and Slow Muscle

Force

Stimulation

Twitch

Tetanus

Force

Stimulation

FastSlow

aster muscle = faster activation rate (as fasteralcium release from SR) and faster relaxation rate (as

aster calcium binding [parvalbumin] and reuptake to

R [sarcoplasmic reticulum] via calcium pumps)

Time

Fast

Slow


88/134

Fast vs. slow muscle PO

Cycle Frequency (Hz)

P

oweroutput(W

/kg)

slow

fast

Poweroutput

(%offirstloop)

Duration of activity (s

slow

fast

faster muscles produce more force at anyshortening velocity, therefore more power

Theoretical relationships between fast and

slow muscle for power output and fatigueresistance

Trade-offs.. between sprint and endurancetype activities

SprintEndurance

Power = force velocityelative power in Watts per kilogramme of muscle


89/134

Fast vs. slow muscle PO 2

CYCLE FREQUENCY (Hz)

0 4 8 12 16 20 24

POWEROUTP

UT(W

/kg)

0

50

100

150

Mouse muscle power output-cycle frequency

curvesExtensor digitorum longus extends the toesand is a faster muscle (higher Vmax) producing3 times as much power (power to flick toesforward during swing phase)

soleus is an ankle extensor (stabilisation roleduring stance)

ight: Data from

ames et al. (1995)Exp. Biol. 198 491-502

Mouse EDL & soleus

soleus

slower

EDL faster

stride

maximalgallop

stride trotting

(normal speed)stride

slowest

walk


90/134

Muscular Fatigue

Time

Force

Faster fibres fatigue here IIB

Slower fibres

fatiguing here

IIA

Cycle Number

Force(mN

)

0

20

40

60

80

100

120

140

0 30252015105

A

Above: Theoretical pattern of fatigue

NB effect of fibre type

Below: Pattern of fatigue measured inXenopus

aevis gastrocnemius. all fibres maximally activatedll the time

n 232SPO CUOnline:

Wilson, James & Van Damme (2002)J. Exp. Biol. 205 1145-1152.

IIB fibres fatiguing

slowest fibres

IIA fibres fatiguing


91/134

Fatigue effects on work loopsMouse EDL muscle (a faster muscle)Wilson and James (2004) Proc. Roy. Soc. Lond. B.

(Suppl.) 271 S222-S225. On 232SPO CUOnline

Stress (force per musclecross-sectionalarea) decreases with fatigue

-0.05 0.05

50

100

150

Stress(kNm-2 )

Strain ( L0)

A

1

15

35

0.00 0.05 0.10 0.15 0.20

0

50

100

150

Stress(kNm-2)

Time (s)

1

15

35

B

force

decreased

force-velocity

relationship

changed:

decreased Vma

Relaxation rate

as decreased so

lower to relax

o loop 35 indicates a problem in maintaining force

uring shortening


92/134

Sprint vs. endurance

ntuitive trade-off between sprint and endurance

Endurance performance

Sprintperformance

But in whole animal locomotion normally:

(problems of athlete quality)

Better athlete hypothesis genetics (setting rangeof possible performances) + training andenvironment (determining place in range)

sprint


93/134

Human decathletes Decathletes of similar international

ranking Negative correlation between 100m sprint

(more anaerobic) and 1,500m run (moreaerobic)

Positive correlations between more

anaerobic events: 100m sprint and: longjump, 400m run, 110m hurdles

Negative correlation between shot puttand 1,500m run

Van Damme, Wilson, Vanhooydonck & Aerts (2002)

Nature415 755-756. in library

Why?: fast vs. slow muscles?

positive

relationship

negative

relationship

00m

print

1500m race long jump

100msprint


94/134

Muscle trade-offs betweenSprint and Endurance capacity

End

urance

i.e. how well can force be maintained

during prolonged exercise?R2 = -0.67

0

0.1

0.2

0.3

0.4

0.5

0.6

30 35 40 45 50

Initial power output (W/kg)

Fatigueindexofpower

output(20

thrun/1strun)

sprint

endurance

Bufo viridisgastrocnemius (ankle extensor)muscle

Wilson, James, Kohlsdorf & Cox (2004) J.Comp. Physiol. 174 453-459. on CUOnline


95/134

MoreB

ufo

viri

distrad

e-o

ffs

Max. Power Output (W kg-1

)

30 35 40 45 50

FatigueResistance

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Max. Stress (kN m-2

)

150 200 250 300

FatigueResistance

0.0

0.1

0.2

0.3

0.4

0.5

0.6

B

A

Max. Stress (kN m-2

)

150 200 250 300

Max.PowerOutput(Wkg-1 )

0

10

20

30

40

50

60

C

e

ndurance

endurance

sprint

sprint

sprint

sprint


96/134

Mouse Trade-off Correlations

Mouse EDL work loops & isometrics(constant length)

Work loop sprint and endurance

+ve: Maximal isometric tetanic force &Maximal work loop force

+ve: Maximal work loop force and

power-ve: Maximum work loop power andwork fatigue resistance

-ve: Maximum work loop force and work

loop fatigue resistance

Wilson, R.S. and James, R.S. (2004) Proc. Roy. Soc.Lond. B. (Suppl.) 271 S222-S225. On 232SPOCUOnline


97/134

Sprint and Endurance trainingMale rats trained on a treadmill for 10 weeks

Tested passive stress-strain relationship

Sprint or endurance training increased passivemuscle strength (maximal stress) andtoughness (maximal energy) and stiffness

(change in stress change in strain) but notextensibility (maximal strain)

endurance: lots of lower speed and force

training compared with sprint training

sprint

endurance

control

Strain (length change initial length)

Stress(

force

csa)

Muiz et al (2001)Acta Physiol Scand173 207-212


98/134

What causes muscle fatigue? Why do mammalian muscles fatigue during

high intensity activity?

lactic acid build up unlikely to be the cause at low temperatures lactic acid causes fatigue

at physiological temperatures: minimal effect

impaired calcium release probable

during fatigue less calcium released from SR

so incomplete muscle activation

Mouse EDL work loops at 35C James et al(2004) J. Appl. Physiol. 96 545-552. On

232SPO CUOnline and in library

Power output in fatigued muscle increasedwith10mM caffeine treatment whencompared with controls

Calcium is stored in SR when the muscle isat rest

during fatigue calcium phosphate precipitatesin SR?

Caffeine enhancing opening of calciumchannels in sarcoplasmic reticulum

Remember that Calcium binds to TnC during

activation (muscle switch) so increased force


99/134

10mM Caffeine effects

What causes increase in power output?

-20

30

80

130

180

-5 5 15 25 35 45 55

Time after fatigue run (min)

Maxim

umw

orkloop

stre

ss(kN

m-2)

0

20

40

60

80

100

120

140

-5 5 15 25 35 45 55

Time after fatigue run (min)

Pow

eroutputrelativet

opre-

fatigue(%)

10mM caffeine

Controlwashout

re fatigue

fatigued

Other methylxanthines have similar effects


100/134

Effect of 70uM caffeine on PO So could caffeine improve an athletes

performance? 70M caffeine in blood plasma in

humans (very high caffeine is fatal)

No effect on fatigued muscle but affectsnormal muscle

Mouse EDL work loops

Time from start of caffeine incubation (min)

-20 0 20 40 60 80 100Poweroutput(%oftheoretic

alcontrol)

92

94

96

98

100

102

104

106Washout

James, R.S., Kohlsdorf, T., Cox, V.M. and Navas, C.A. (2005)

Eur. J. Appl. Physiol. 95 74-82.


101/134

What determines

muscle phenotype?Embryonic phenotype

determined by genotype

Birth

Plastic Phenotype

Innervation (EMG)

Volume of work

Peak forces

Hormones(e.g. testosterone

Growth

e muscle phenotype alters to reflect changing

emands made upon the muscleenvironmental effects)

gene expression


102/134

Cross-innervation studies960s cross-innervation experiments on mammals

DL = flexor digitorum longus

FDL soleus

soleus nerveFDL nerve

g. Buller et al. (1960) J Physiol 150 417-430. In library

Twitch force

Stimulation

FDLsoleus

FDL soleus

soleus nerveFDL nerve

Twitch force

Stimulation

FDLsoleus

erves cut and rejoined to itself (sham operated) orother muscle

Experimental

ham operated (rejoined to themselves)


103/134

Development and GrowthIn humans

During foetal development fibrenumber increases (hyperplasia) i.e.development of new fibres to increasemuscle size

Once born muscle developmentconsists of repair to damaged cellsand growth by fibre hypertrophy (i.e.

increase in fibre size)

Fibre hypertrophy: increased numberof myofibrils in muscle fibre =

increased fibre size (increased cross-sectional area)

Although new fibres cannot be formedfibre composition can change


104/134

Growth & DevelopmentAs animal gets older mechanics may

changeMuscles and bones grow in length andwidth

Muscle stretch

Body weight increase so greater forcesinvolved

Minimal escape/prey captureperformance?

Scaling relationshipssmaller animals have faster muscle

protein isoforms so faster stridefrequency

larger animals higher stride length

sprint speed dependent on stridefrequency and stride length

Response to environment

Respond to changes


105/134

Muscle Adaptationto new length

If muscle under stretche.g. growth of limb bones

Length

Force

L1 L2

ResponseAddition of new sarcomeres to length

Maximal active force at longer (L2)resting length

If muscle to slack at rest, atrophy and

hortening (L3)e.g. in plaster cast

L3


106/134

Scaling: Fish Body size effects

Total body length (cm)

5 10 20 30Maximumvelocity(bodylengthss-1)

1

5

10

20

Sculpin swimming

James & Johnston (1998) J. Exp. Biol. 201 913-923. On232SPO CUOnline

As body size increases relative maximumswimming velocity decreases (absolutespeed fairly constant)

so smaller fish using higher stride frequency:how?


107/134


5 10 20 30

V0(musclelengthss-1)

1

2

5

10


5 10 20 30Timetopeak

twitchforce(ms)

10

20

50

100


5 10 20 30Peaktwitchto50%

relaxation(ms)

10

20

50

100


5 10 20 30

Laststimulusto50%

tet

anusrelaxation(ms)

10

20

50

100

Fish mechanicsSculpin fast muscle: Isometrics & Isovelocity

ames et al. (1998) J. Exp. Biol. 201 901-912.

calcium

binding or

pumping?


108/134

Explain fish mechanics?


5 10 20 30

M

yosinATPaseactivity

(u

molreleasedmg-

1min-1)

0.2

0.5

1

2

Sculpin study continued.

Changes in TnI isoformfaster isoform in smaller fish

No changes in thick filament proteins MLC, MHCNo changes in other thin filament proteins:

TnC, TnT, actin or Tm

Affects rate of ATP breakdown


109/134

Mammalian scaling ofmuscle properties

Vmax (maximum shortening velocity)measurements in rat, cat and horsesoleus single muscle fibresRome, Sosnicki & Goble (1990). J. Physiol. 431, 173-185. inlibrary

Large decrease in Vmax of type I musclefibres with increased body size

Smaller decrease in Vmax

of type IIBmuscle fibres with increased body size

Smaller animals tend to have

Faster muscle fibresHigher stride frequencies (strides s-1)

Lower stride length (shorter legs)

Larger animals: slower more efficientmuscles (e.g. decreased calcium pump cost)


110/134

Further Evidence onscaling

Xenopus laevisadductor magnus (slower) andsartorius (faster) muscles from frogs ofdifferent sizes

Work loop experiments to look at cycle

frequency that yielded maximal powerAltringham, Morris, James & Smith (1996) Experimental BiologyOnline1 (6): this is available online for free. You can search for the

journal name via Google

Body Mass (g)

Cyclefrequency(Hz)

slower muscle, larger decreasein cycle frequency for maximal power

sartorius

adductor magnus


111/134

Why should temperatureaffect locomotion?

Temperature affects enzyme activity rates e.g. myosin ATPase

therefore can affect rates of mechanics

e.g. activation rate

Range of muscle temperatures lower in warm

blooded (endothermic) animals but basic

effects the same as in cold blooded(ectothermic) animals

Temperature

Enzymeactivity

o increase temperature causes increase rates.ventually denaturation occurs

rate at which enzyme works


112/134

Human temperature effects

Heating/cooling legs in water thigh muscle 39.3, 36.6, 31.9, 29.0C

Cycle ergometer Sargeant (1987) Eur J Appl Physiol. 56 693-698.

Increased temperature caused

Increased peak force

Increased power

Increased rate of fatigue

Linane, Brooks, Cox and Ball (2004) Eur J ApplPhysiol. 93 159-166.

Full immersion of human in 43C caused 1%increase in muscle power output during subsequentcycling

Why?


113/134

Pedalling rate (rev./min)

Maximumpeak

force(N)

Sargeant (1987)

39.3

36.631.929.0

Thigh muscle temperatures

Maximumpeak

power(W)

Pedalling rate (rev./min)

29.0

39.3

31.9

Hotter muscles have higher maximal shortening V,

igher rates of activation and relaxation. so produce

more force at any velocity than colder muscles

i.e velocity


114/134

Human temperature effects 2

Heating/cooling hands in water

18, 25 or 39C for 30 minutes or inair at room temperature

approximate muscle temperatures of23.5, 28, 32.5 and 37C

Handgrip test: isometric force thenforce-velocity relationship

Binkhorst et al (1977) J ApplPhysiol. 42 471-475. in library

Increased temperature caused

Increased maximal shorteningvelocity

Increased power

No change in maximal isometric


115/134

Temperature Effects on Locomotion

A)

5 10 15 20

Jump

distance(BL)

10

15

20

25

30

35

40

5 10 15 20Jumptake-offvelocity(BLs-1

)

25

30

35

40

45 B)

5 10 15 20

Meanjumppow

eroutput(Wkg

)

100

200

300

400

500

600C)

5 10 15 20Meanswimmingvelocity(BLs-1)

6

8

10

12 D)

Temperature (degrees C)

ana temporaria: Navas, James, Wakeling, Kemp and Johnston (1999)

Comp. Physiol. 169 588-596. see Rob for this

power output per kg muscle mass


116/134

More T. effects on locomotion

Temperature (o

C)

0 5 10 15 20 25 30 35MaximumSwimmingSpeed(ms-1)

0.0

0.4

0.8

1.2

1.6

Xenopus laevis

Wilson, James and Johnston (2000)J Comp. Physiol B 170 117-124.n 232SPO CUOnline


117/134

0 5 10 15 20 25 30 35

TwitchForce(%ofmax.)

60

70

80

90

100

Temperature (oC)

0 5 10 15 20 25 30 35

Tetani

cForce(%ofmax.)

60

70

80

90

100

Effects on Isometric Force

Wilson, James and Johnston (2000)J Comp. Physiol B 170 117-124.

Xenopus laevis gastrocnemius fibre bundles


118/134

Effects on Isometric Times

0 5 10 15 20 25 30 35

TimetoPeaktwitch(s)

20

40

60

80

100

120

140

Temperature (oC)

0 5 10 15 20 25 30 35

TPT

1/2Relax.(s)

0

100

200

300

400

Xenopus laevis gastrocnemius fibre bundles

Wilson, James and Johnston (2000)J Comp. Physiol B 170 117-124.

TPT PTHR


119/134

Overall temperature effectsOn work loops

Increased temperature:More rapid force activation

Increased maximal force output

Increased maximal shortening velocity

so can work at higher cycle frequency

Better maintenance of force duringshortening

More rapid force relaxation

so larger area of work loop = morework

so more power output

higher temperature

lower temperature


120/134

Comparison of species

0

50

100

150

0

1020

3040

05

1015

POW

EROUTPUT(W

kg-1)

TEMPE

RATU

RE(

0C)

CYCLEFREQUENCY(Hz)

12

11

10

9

8 654

3

2

1

7

Increased optimal cyclefrequency for power outputwith temperature

Increased optimal cyclefrequency increases poweroutput

cold vs. warm blooded.


121/134

Eccentric muscle activityMuscle active & being stretched

Extra stretch of myosin neck region(S2) causes:

more rapid force rise

enhanced force production

E.g. quadriceps and gastrocnemiuswhen walking down stairs

stabilise/brake the limb

Eccentric activity before concentric

activity enhances force duringconcentric as well!

Velocity

Force

Concentric

(muscle shortening)Eccentric

muscle lengthening)

0

0 velocity =

isometric


122/134

Eccentric Muscle Stress-Straincurves

Strain

Stress

Stress

Stress

Strain

Strain

Work output

Net work

Active (eccentric exercise)

Work input

energy required

to stretch

low energy outpu

during shortening

as c. passive

net energy costto cycle this muscl

braking action


123/134

Is long jumpingperformance dependent on

tissue mechanics?

Review long jumping performance in differentanimals

Review tissue mechanics in different animals

Conclusions

See James et al. (2007) Journal of Experimental Biologyreview paper on CUOnline


124/134

What does jumping depend upon?

dis distance jumped (e.g. m)

vis take-off velocity (e.g. m s-1)

is take-off anglegis the acceleration due to gravity(approximately 9.8 m s-2)

jump distance largely dependent ontake off velocity

How increase velocity?

Increase acceleration rate

Increase distance over which accelerate

g

vd

2sin2

Centre of mass


125/134

What else does jumpingdepend on?

Wis total average power required forthe jump

L is the distance from the centre ofmass to the tip of the toes

Mb is body mass of the animal

So increase power

Maybe: increase muscle mass, energystorage, increase muscle speed and/orforce?

Increase L by increased relative leglength?

Minimise body mass?

gM

LWd

b

2sin32

Power = force speed


126/134

How can muscle poweroutput be increased?

Increased proportion of fast muscle

fibres in jumping muscles (legextensors)

In jumping frogs:

Jumping muscles 89% fastest fibres

Non-jumping muscles 29%As % of fastest fibres increases from 0

to 100% there was a 57% increase inpower output and 22% increase in stressand increased shortening velocity

NB. Trade off in muscle function

Increased temperature (mainly ectotherms)

Endotherms regulate, ectothermsbehavioural thermoregulation

Increased rates of activation andrelaxation

Increased power output

Energy storage and returnee James et al. (2007) Journal of Experimental Biology

view paper on CUOnline


127/134

Energy storageIn many animals including man

CountermovementActive lengthening of extensor muscle

prior to shorteningForce enhancement

OR rapid early shortening of musclewithout movement of body e.g. frogsFrog muscle produce only c.30% of

power for the jump!

OR catch mechanism (insects)

Elastic potential energy storageMainly in tendons of extensor muscles

Amplifies power

Virtually temperature independent


128/134

Body Size affects muscleperformance

As body size increases Muscle fibre type tends to become slower

(slight decrease in force)

Rate of muscle activation and relaxation tendsto decrease

Maximum relative muscle shortening velocitydecreases (in muscle lengths s-1)

But larger animals have longer muscles

Power output (W kg-1

) and stress unaffected NB PO = F V

So larger animals can afford to have slowermuscle fibre type and still achieve similar powe

output But why are slower fibres useful?

So why dont smaller animals jump as far aslarger animals?

Drag

Shorter limbs so shorter time to accelerate overso need greater peak power, so need fastermuscles


129/134

Body Size affects long jumpperformance

Long jump performance increases withincreased body size

But muscle performance?

Body length (m)

Longjumpdistance(m)

Line indicates 100 W.kg-1 BM

Compare with 100 W kg-1 muscle mass


130/134

Hindlimb length

Hindlimb length increases with increasingbody size

Jumping vs. non-jumping mammals

L

oghindlimblength(cm)

Log cubed root of body mass (g)

merson, S.B. (1985) In Functional Vertebrate MorphologyCambridge: Harvard University Press.

Jumping specialists (mammals)


131/134

MorphologyLeg length

Frog and lizard species with relativelylonger legs tend to jump further

Muscle mass

Jumping c.f. non jumping frog &mammal species increased leg extensomuscle mass

In frogs higher relative muscle mass =

longer jump distance (leg extensormuscle mass as % of body mass)

Muscle architecture Tend to be longer & less pennate in larger

animal speciesSo increased maximum shortening velocity

Muscle insertion more proximal


132/134

Predicting jump performance

Jump performance often assessed as

jump distance or jump take-off velocityOne predicts the other

Domestic cat jump take of velocity:

62%, lean body mass residuals ofhindlimb length and fat massSo fat cats with short legs dont jump as far Harris, M.A. and Steudel, K. (2002) JEB205 3877-3889.

Frog (Hyla multilineata) jump distance:43%, body length residuals of hindlimbmuscle mass and pyruvate kinaseactivity

So frogs with more extensor muscle massand more glycolytic muscle jump further James, R.S., Wilson, R.S., Carvalho, J.E., Kohlsdorf, T.,

Gomes, F.R., Navas, C.A. (2005) PBZ78 857-867.

Jumping performance linked to fitnessin some species


133/134

Accelerated development

Adults (post-metamorphr2=0.01 P>0.05

Juveniles (metamorph)Mb

0.53 r2=0.67 P


134/134

Modelling jumpperformance

In a human like animal: countermovement andcatapult jumps yield similar jump distances >squat jump

Squat jump = no or limited energy storage

In bush baby and insect like animals catapultjump>countermovement jump

Increased muscle shortening velocity

increased jump distance in all animals (moreimportant in human)

Documents

1 334spo All Lectures