and How this Might Affect Sprinting Ability and Kicking Performance

Per Aagaard

Institute of sports science and clinical biomechanics, University of Southern Denmark

paagaard@health.sdu.dk

8th MuscleTech Network Workshop · Barcelona October 3rd-4th 2016

Neuromuscular Plasticity in Quadriceps Function in Response

to Training

Brainmotor cortexcerebellum

Spinal cord

efferent motorneurons

sensory afferent neurons

Muscle

Drawing modified from Sale 1992

The Neuromuscular System Neuromuscular function - motor cortex, cerebellum - spinal cord circuitry - efferent motorneuron output - sensory afferent feedback

Brainmotor cortexcerebellum

Spinal cord

efferent motorneurons

sensory afferent neurons

Muscle

Drawing modified from Sale 1992

The Neuromuscular System

Exercise & Training

Adaptive changes in neuromuscular

function

ECC strength, explosive strength

Neuromuscular function - motor cortex, cerebellum - spinal cord circuitry - efferent motorneuron output - sensory afferent feedback

Improvements in functional capacity: sports performance (i.e. acc capacity),

injury risk

Exercise

SportsPerformance

Brainmotor cortexcerebellum

Spinal cord

Muscle

Neuromuscular adaptations related to...

- maximal ECCentric muscle strength

- explosive muscle strength (RFD)

Functional consequences for Sprinting Ability and Kicking Performance

OUTLINE

can be evaluated by use of...

Muscle electromyography (EMG) recording intramuscular & surface

Evoked spinal motoneuron responses: H-reflex, V-wave recording

Transcranial magnetic / electrical stimulation of cortical neurons and subcortical axons, motor evoked responses (MEP)

Interpolated muscle twitch recording superimposed during MVC

Changes in neuromuscularChanges in neuromuscular functionfunction induced byinduced by training training

10 0 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

HM

H M

10 ms

2 mV

Changes in neuromuscularfunction evoked by training, disuse, injury, aging, etc

Neuromuscular Plasticity in Quadriceps Function

Effects of resistance training on maximal eccentric muscle strength)

10 0 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

Types of muscle contraction

Eccentric muscle contractionmuscle generating contractile force while lengthening

Concentric muscle contractionmuscle generating contractile force while shortening

Isometric muscle contractionmuscle generating contractile force while maintaining constant length

Types ofTypes ofmuscle contractionmuscle contraction

Eccentric muscle contractionmuscle generating contractile forcewhile lengthening

Concentric muscle contractionmuscle generating contractile forcewhile shortening

Isometric muscle contractionmuscle generating contractile forcewhile maintaining constant length

Eccentric

Concentric

Isometric

High eccentric strength in agonist muscles

… provides enhanced capacity to decelerate (brake) movements in very short time

- fast SSC actions (i.e. rapid jump takeoff)

- fast changes in movement direction (i.e. rapid side-cutting)

Why is ECCentric muscle strength important?

High eccentric strength in antagonist muscles

...provides enhanced capacity for antagonist muscles to decelerate and stop movements at the end-ROM

increased protection of joint ligaments (i.e. ACL) and joint capsule structures Aagaard et al., Am J Sports Med 1998

Why is ECCentric muscle strength important?

Hamstring muscles are exposedto extreme lengthening changes and

high eccentric forces during sprint running

medial H: ST/SM musclelateral H: BFcl muscle

Simonsen et al. 1985

Musclelengths

EMGon-off

periods

High level of ECCentric hamstring strength

reduced incidence / full absence [very strong individuals]

of muscle strain injury in elite football players Croisier et al, Am J Sports Med 36, 2008 (n=462 professional football players)

Why is ECCentric muscle strength important? High eccentric knee flexor strength

From Aagaard & Thorstensson. Neuromuscular aspects of exercise: Adaptive responses evoked by strength training, Textbook of Sports Medicine (Eds. Kjær et al) 2003

Velocity

Contractile Force / Strength

percent of Vmax

-40 -20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Arbitrary U

nitsM

uscl

e Fo

rce

(isom

etric

= 1

00%

)

isom

etric

CONcentricECCentric

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

Muscle Force (isom

etric = 100%)

The Force-Velocity relationship in skeletal musclerecorded during maximal ECC and CON contraction

Isolated animal muscle preparations

From Aagaard & Thorstensson. Neuromuscular aspects of exercise: Adaptive responses evoked by strength training, Textbook of Sports Medicine (Eds. Kjær et al) 2003

Velocity

Contractile Force / Strength

percent of Vmax

-40 -20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Arbitrary U

nitsM

uscl

e Fo

rce

(isom

etric

= 1

00%

)

isom

etric

CONcentricECCentric

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

Muscle Force (isom

etric = 100%)

ECC >> CON (+50-100%)

The Force-Velocity relationship in skeletal musclerecorded during maximal ECC and CON contraction

Isolated animal muscle preparations

Contraction Speed

Contractile Force / Strength

percent of Vmax

-40 -20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Arbitrary U

nits

concentriceccentric

From Aagaard & Thorstensson. Neuromuscular aspects of exercise: Adaptive responses evoked by strength training, Textbook of Sports Medicine (Eds. Kjær et al) 2003

Mus

cle

Forc

e (is

omet

ric =

100

%)

isom

etric

CONcentricECCentric

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

Muscle Force (isom

etric = 100%)

Intact human quadriceps muscle:maximal voluntary activation(Westing et al 1990)

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

The Force-Velocity relationship in skeletal musclerecorded during maximal ECC and CON contraction

Contraction Speed

Contractile Force / Strength

percent of Vmax

-40 -20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Arbitrary U

nits

concentriceccentric

From Aagaard & Thorstensson. Neuromuscular aspects of exercise: Adaptive responses evoked by strength training, Textbook of Sports Medicine (Eds. Kjær et al) 2003

Mus

cle

Forc

e (is

omet

ric =

100

%)

isom

etric

CONcentricECCentric

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

Muscle Force (isom

etric = 100%)

Intact human quadriceps muscle:electrical muscle stimulationsuperimposed onto maximalvoluntary contraction(Westing et al 1990)

Katz B, J. Physiol. 96, 1939

Contraction Speed

Contractile Force / Strength

percent of Vmax

-20 0 20 40 60 80 1000

20

40

60

80

100

120

140

160

180

0

20

40

60

80

100

120

140

160

180

Edman KAP, J. Physiol. 404, 1988

Arbitrary U

nits

concentriceccentric

The Force-Velocity relationship in skeletal musclerecorded during maximal ECC and CON contraction

Neural aspects of maximal ECC muscle contraction - assessing neural inhibition in the neuromuscular system

Brainmotor cortexcerebellum

Spinal cord

Muscle

TEST SETUPIsokinetic dynamometry

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

Aagaard et al, J Appl Physiol 2000

90o

10o

90o

10o

Neuromuscular activity m. quadriceps [untrained individual]

Calculating mean filtered EMG amplitude (iEMG)

Calculating mean filtered EMG amplitude (iEMG)

slow CONC contractionpre training

slow ECC contraction pre training

Aagaard et al, J Appl Physiol 2000

Untrained individualsReduced neuromuscular activity ( quadriceps EMG amplitude)

during maximal ECC contraction

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

**

***

* *

**

*

percent

EMG RF

EMG VM

EMG VL

Knee angular velocity

60

70

80

90

100

Per

cent

60

70

80

90

100

Per

cent

60

70

80

90

100

Per

cent

concentriceccentric

100

120

140

160

180

200

240

Per

cent

( o s-1 )

30-30-240

force momentquadriceps

percent

percent

percent

Average quadriceps EMG and strength

Aagaard et al, J Appl Physiol 2000

Untrained individualsReduced neuromuscular activity ( quadriceps EMG amplitude)

during maximal ECC contraction

***

**

*

mean EMG Quadriceps

Knee angular velocity

60

70

80

90

100

Percent

concentriceccentric

100

120

140

160

180

200

240

Percent

( o s-1 )

30-30-240

Quadricepsforce moment(percent)

(percent)

* *

*

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000 fast ECC slow slow CONC fast

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

Neuromuscular activity appears to be reduced during maximal voluntary ECCentric muscle contraction, indicating that motoneuron activation is inhibited (untrained subjects) Aagaard 2000, Andersen 2005, McHugh 2002, Komi 2000, Kellis & Baltzopoulos 1998, Higbie 1996, Amiridis 1996, Seger & Thorstensson 1994, Bobbert & Harlaard 1992, Westing 1991, Tesch 1990, Eloranta & Komi 1980, Duclay & Martin 2005, Duclay et al 2008, Gruber 2009, Abbruzzese 1994, Sekiguchi 2001 & 2003, Duclay et al 2011

surface EMG amplitude (iEMG, aEMG)

evoked motorneurone response (H-reflex)

MEP, CMEP responses (TMS, CMS) [unchanged or elevated MEP/CMEP ratio]

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

Inhibited neuromuscular activity during maximal ECCentric muscle contraction

HM

HM

10 ms

2 mV

Neuromuscular activity during ECCentric muscle contractions

Effects of conventional resistance training?

Mom

ent of Force (N

m)

knee angular velocity ( o s-1)

-120 24012030-30-2400

100

200

300

400

velocity of training

50o

peak ***

*

**

**

**

eccentric concentric

HR group (n=7)

*

Quadriceps muscle strength, Elite football playersBefore and after 12 weeks strength training

Aagaard et al, Acta Physiol Scand 1996

Heavy-resistance strength training (8 RM loads)

Effects of strength training on maximal eccentric and concentric muscle strength

Conventionel heavy-resistance strength training

ECC strength, CONC strength Aagaard 2000, Andersen 2005, Seger 1998, Aagaard 1996, Hortobagyi 1996, Timmins 2016, Higbie 1996, Colliander & Tesch 1990, Narici 1989, Komi & Buskirk 1972

No changes in maximal ECCentric muscle strength following low-resistance strength training Aagaard 1996, Duncan 1989, Takarada 2000, Holm Aagaard et al 2008

Effects of heavy-resistance strength training

on maximal ECC muscle strength

Aagaard et al, J Appl Physiol 2000

***

**

*

mean EMG Quadriceps

Knee angular velocity

60

70

80

90

100

Percent

concentriceccentric

100

120

140

160

180

200

240

Percent

( o s-1 )

30-30-240

Quadricepsforce moment(percent)

(percent)

* *

*

***

**

*

mean EMG Quadriceps

Knee angular velocity

60

70

80

90

100

Per

cent

concentriceccentric

100

120

140

160

180

200

240

Per

cent

( o s-1 )

30-30-240

Quadricepsforce moment(percent)

(percent)

* *

*

Post

Pre

Heavy-resistance strength training (14 wks) Reduced suppression in quadriceps EMG amplitude during ECC contraction ECCentric muscle strength

PRE TRAINING POST TRAINING

Average quadriceps EMG and strengthAverage quadriceps EMG and strength

Andersen LL, Andersen JL, Magnusson SP, Aagaard P 2005

Neuromuscular activity during maximal eccentric muscle contraction

- effects of resistance training

Gain in maximal ECC muscle strength strongly related to the improvement in neuromuscular activity (r=0.89, p < 0.001)

Andersen, Aagaard et al. 2005

slow ecc norm EMG

0 20 40 60 80 100 120 140

slo

w e

cc m

omen

t of f

orce

0

20

40

60

80

100

120

R2 = 0.77, p<0.001

% ECC norm EMG at 30o/s

%

EC

C T

orqu

e at

30o /

r = 0.89, p<0.001

Effects of heavy-resistance strength training:

- reduced inhibition in motorneuron activation during ECC contraction neuromuscular drive

ECC muscle force production

Neuromuscular activity during maximal ECCentric muscle contraction

Effects of conventional resistance training

Functional consequences: - faster SSC muscle actions - Power in SSC movements - faster decelerations (sidecutting etc)

- ECC antagonist muscle strength (joint protection, reduced risk of injury)

Neuromuscular activity during maximal ECCentric muscle contraction

Effects of conventional resistance training

Effects of heavy-resistance strength training:

- reduced inhibition in motorneuron activation during ECC contraction neuromuscular drive

ECC muscle force production

subj LN

RF EMG

VM EMG

VL EMG

Force MomentNm

uVolts

uVolts

Time ( miliseconds )

0

100

200

300

-1500

1500

-1200

1200

-400 0 400 800 1200 1600 2000 2400 2800

-1000

1000uVolts

Fig.1Aart14F1a.jnb

Time (milliseconds)

Aagaard et al. 2002

Force Moment

VL EMG

VM EMG

RF EMG

Neuromuscular Plasticity in Quadriceps Function

Effects of resistance training on explosive muscle strength / Rapid Force Capacity (RFD))

Neuromuscular Plasticity in Quadriceps Function

Effects of resistance training on explosive muscle strength / Rapid Force Capacity (RFD))

subj LN

RF EMG

VM EMG

VL EMG

Force MomentNm

uVolts

uVolts

Time ( miliseconds )

0

100

200

300

-1500

1500

-1200

1200

-400 0 400 800 1200 1600 2000 2400 2800

-1000

1000uVolts

Fig.1Aart14F1a.jnb

Time (milliseconds)

Aagaard et al. 2002

Force Moment

VL EMG

VM EMG

RF EMG

Why is RFD important ?

Ground contact times…

110 - 160 msec in long jump 180 - 220 msec in high jump 80 - 120 msec in sprint running Luhtanen & Komi 1979, Dapena & Chung 1988, Zatsiorsky 1995, Kuitunen et al. 2002

Time to reach peak force production in human skeletal muscle…

300 - 500 msec Sukop & Nelson 1974, Thorstensson et al. 1976, Aagaard et al. 2002

TIME IS LIMITED...

1000

2000

3000

4000

5000

0

0.20 0.4 0.6 0.8

Time (seconds)

Forc

e (N

)

RFD = Force / Time

For

ce

Time

max Force

Rate of Force Development (RFD)

Aagaard et al, J Appl Physiol 2002

1000

2000

3000

4000

5000

0

0.20 0.4 0.6 0.8

Time (seconds)

Forc

e (N

)

RFD =RFD = Force / Time

Fo

rce

Time

max Force

m. quadriceps femoris

Maximal Explosive Muscle Strength‘Rapid Force Capacity’

Contractile RFDAssessed by isokinetic dynamometry

RFD = Force / Time

= slope of Force-time curve

RFD = Force / Timepeak tangential slope

RFD = Force / Timemean tangential slope 0-30 ms

RFD = Force / Timemean tangential slope 0-50 ms

RFD = Force / Timemean tangential slope 0-100 ms

RFD = Force / Timemean tangential slope 0-200 ms

Maximal isometric quadriceps contraction, static knee extension

Aagaard et al, J Appl Physiol 2002

-1000 -500 0 500 1000 1500 2000 2500 3000

-800

-400

0

400

800

0

400

800

lowpass filtered

raw EMG signal

Time (miliseconds)

uVol

t

rectified EMG signal

uVol

t

highpass filtered

subj LN

RF EMG

VM EMG

VL EMG

Force MomentNm

uVolts

uVolts

Time ( miliseconds )

0

100

200

300

-1500

1500

-1200

1200

-400 0 400 800 1200 1600 2000 2400 2800

-1000

1000uVolts

Fig.1Aart14F1a.jnb

Time (milliseconds)

Aagaard et al. 2002

Force Moment

VL EMG

VM EMG

RF EMG

subj LN

RF EMG

VM EMG

VL EMG

Force MomentNm

uVolts

uVolts

Time ( miliseconds )

0

100

200

300

-1500

1500

-1200

1200

-400 0 400 800 1200 1600 2000 2400 2800

-1000

1000uVolts

Fig.1Aart14F1a.jnb

Time (milliseconds)

Aagaard et al. 2002

Force Moment

VL EMG

VM EMG

RF EMG

Isometric Quadricepsknee extensor moment signal

Rectified EMG signal (grey)lowpass filtered EMG signal

raw EMG signal highpass filtered

VL muscle

RFD = Moment/time

Recording of neuromuscular activity and RFD

Del Balso & Cafarelli, J Appl Physiol 2007 [soleus muscle]

Influence of neuromuscular activity on RFDRapid force capacity (RFD) is strongly influenced by the

magnitude of neuromuscular activity at onset of contraction

RFD

iEMG

r = 0.91 p<0.001

Effects of resistance training

Training-induced changes in RFD

and neuromuscular activity

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (msec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl . Physiol. 2000

Neuromuscular Plasticity in Quadriceps functionContractile Rate of Force Development (RFD)

Pre and post 14 wks of heavy-resistance strength training

RFD Contractile Rate of Force Development Assessed during maximal isometric quadriceps contraction

Forc

e M

omen

t( N

m )

(miliseconds)Time

-100 0 100 200 300 400

0

50

100

150

200

250

300

Pre training

Post training

art14F2.jnb

Fig.2

MVC post339 Nm

MVC pre291 Nm

Forc

e M

omen

t( N

m )

(miliseconds)Time

-100 0 100 200 300 400

0

50

100

150

200

250

300

Pre training

Post training

art14F2.jnb

Fig.2

Aagaard et al, J Appl Physiol 2002

Pre to post training differences: * p < 0.05, ** p < 0.01error bars: SEM

Nm

/ se

c#

* **

peak msec20010050300

500

1000

1500

2000

2500

3000

3500

#

#

* **

*

**

RFDRFD Contractile Rate of Force Development Contractile Rate of Force Development

Aagaard et al.J. Appl. Physiol. 2002

Pre and post 14 wks of heavy-resistance strength training

Pre to post training differences: * p < 0.05, ** p < 0.01

RFD Contractile Rate of Force Development Assessed during maximal isometric quadriceps contraction

Pre and post 14 wks of heavy-resistance strength training

Aagaard et al, J Appl Physiol 2002

Neuromuscular activity and rapid force capacity (RFD)Moment-time curve and filtered EMG signals at -200 to +600 ms

Nm

uVolts

uVolts

Time ( milliseconds )

0

100

200

0

800

0

800

-200 0 200 400 600

0

600uVolts

Force Moment

VL EMG

VM EMG

RF EMG

time of onset of force

-75 ms

onset of EMG integration

Aagaard et al, J Appl Physiol 2002

Pre to post training differences: * p < 0.05, ** p < 0.01

( uV

olt )

100 miliseconds50 ms30 ms

**

**

**

**

*

integrated for

RF

VLVM

0

50

100

150

200

250

300

350

400

450

Fig.6art14F6.jnb

mea

n E

MG

am

plitu

de, M

AV

*

uVol

t

VLVM

RF

Pre trainingPost training

VL vastus lateralis

Neuromuscular activity and rapid force capacity (RFD) quadriceps mean integrated EMG divided by integration time (MAV)

Aagaard et al, J Appl Physiol 2002

Pre to post training differences: * p < 0.05, ** p < 0.01

RF

( uV

olt )

100 miliseconds50 ms30 ms

**

**

**

**

*

integrated for

RF

VLVM

0

50

100

150

200

250

300

350

400

450

Fig.6art14F6.jnb

mea

n E

MG

am

plitu

de, M

AV

*

uVol

t

*

*

RF rectus femoris

Neuromuscular activity and rapid force capacity (RFD) quadriceps mean integrated EMG divided by integration time (MAV)Pre training

Post training

Aagaard et al, J Appl Physiol 2002

Pre to post training differences: * p < 0.05, ** p < 0.01

RF

( uV

olt )

100 miliseconds50 ms30 ms

**

**

**

**

*

integrated for

RF

VLVM

0

50

100

150

200

250

300

350

400

450

Fig.6art14F6.jnb

mea

n E

MG

am

plitu

de, M

AV

*

uVol

tVM vastus medialis

*

Neuromuscular activity and rapid force capacity (RFD) quadriceps mean integrated EMG divided by integration time (MAV)Pre training

Post training

Aagaard et al, J Appl Physiol 2002

Pre to post training differences: * p < 0.05, ** p < 0.01

( uV

olt /

s )

75 miliseconds50 ms30 ms

*

derived over

RF

VLVM

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

**

**

**

Fig.7art14F7.jnb

Rat

e of

EM

G ri

se, R

ER

*

*

**

VLVM

RF

Neuromuscular activity and rapid force capacity (RFD) Rate of EMG rise (EMG/t)

Pre trainingPost training

100 mV

200 ms

Aagaard et al, J Appl Physiol 2002

Heavy-resistance strength training

Increased neuromuscular drive ...in initial 200 msec of contraction

Increased maximal Rate of Force Development (RFD)

100 Nm

-2500

2500

3000

-3000

-4000

4000

pos it ion

Moment

E MG VL

E MG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

1000

2000

3000

4000

5000

0

0.20 0.4 0.6 0.8

RFDRFD = = Force / Time

For

ce

Time

max Force

Training induced changes in rapid muscle force (RFD)

Heavy-resistance strength training

Increased neuromuscular drive ...in initial 200 msec of contraction

Increased maximal Rate of Force Development (RFD)

100 Nm

-2500

2500

3000

-3000

-4000

4000

pos it ion

Moment

E MG VL

E MG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

Increased RFD along with increases in iEMG

Häkkinen & Komi 1986, Häkkinen 1985, 1998, Van Cutsem 1998, Barry 2005 Aagaard 2002, Suetta 2005, Del Balso & Cafarelli 2007, Vila-Chã 2010, Tillin Folland 2014

Elevated rate of EMG rise Aagaard 2002, Barry 2005, Del Balso & Cafarelli 2007, Blazevich 2008

Training induced changes in rapid muscle force (RFD)

Heavy-resistance strength training

Increased neuromuscular drive ...in initial 200 msec of contraction

Increased maximal Rate of Force Development (RFD)

100 Nm

-2500

2500

3000

-3000

-4000

4000

pos it ion

Moment

E MG VL

E MG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

Functional consequences: - enhanced acceleration - faster movement speeds - elevated muscle force and muscle power during fast movements- more rapid movement execution

Training induced changes in rapid muscle force (RFD)

Heavy-resistance strength training

Increased neuromuscular drive ...in initial 200 msec of contraction

Increased maximal Rate of Force Development (RFD)

100 Nm

-2500

2500

3000

-3000

-4000

4000

pos it ion

Moment

E MG VL

E MG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

Training induced changes in rapid muscle force (RFD)

???

Specific adaptation mechanisms

Heavy-resistance strength training

Increased neuromuscular drive ...in initial 200 msec of contraction

Increased maximal Rate of Force Development (RFD)

100 Nm

-2500

2500

3000

-3000

-4000

4000

pos it ion

Moment

E MG VL

E MG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et al., J. Appl. Physiol. 2000

Training induced changes in rapid muscle force (RFD)

maximal firing frequency of individual motorneurons (motor units) Van Cutsem 1998, Kamen & Knight 2004, Christie & Kamen 2010

number of ‘discharge doublets’ in the motorneuron (motor unit) firing pattern Van Cutsem 1998

Potential adaptation mechanisms

Increased motorneuron discharge rates following strength training!

post trainingpre training

0

50

100

150

200

0

50

100

150

200

Based on data fromVan Cutsem, J. Physiol. 1998

Post > Pre, P < 0.001

Mot

or U

nit

firin

g ra

te (H

z)

I. II. III.

Interspike intervals

I. II. III.

**

* *

Aagaard, Exerc. Sports Sci. Reviews 2003 - data adapted from Van Cutsem et al, J Physiol 1998

10 ms

2.4 ms

4.2 ms

4.8 ms

Changes in RFD and Motorneuron discharge rates following 12 wks ballistic resistance training [TA muscle, 40-50% 1RM]

Increased motorneuron discharge rates following strength training!

post trainingpre training

0

50

100

150

200

0

50

100

150

200

Based on data fromVan Cutsem, J. Physiol. 1998

Post > Pre, P < 0.001

Mot

or U

nit

firin

g ra

te (H

z)

I. II. III.

Interspike intervals

I. II. III.

**

* *

Aagaard, Exerc. Sports Sci. Reviews 2003 - data adapted from Van Cutsem et al, J Physiol 1998

10 ms

2.4 ms

4.2 ms

4.8 ms

Changes in RFD and Motorneuron discharge rates following 12 wks ballistic resistance training [TA muscle, 40-50% 1RM]

Maximal motorneuron firing frequency increased by 60-80% following 12 wk ballistic-type resistance training

increased contractile RFD

and How this Might Affect Sprinting Ability

and Kicking Performance

Neuromuscular Plasticity in Quadriceps Function in Response to Training

Bret et al, J Sports Med Phys Fitness 2002n=19 male elite track & field sprinters, French regional to national level

Relationship between SPRINT capacity and maximal lower limb muscle strength in track & field sprinters

Average 100-m speed vs Maximal muscle strength

26 28 30 32 34 36 38Leg extensor strength

concentric half-squats (N/kg Bw)

Run

ning

spe

ed

mea

n 10

0-m

ave

rage

(m/s

)

9.4

9.0

8.6

8.2

7.8

r = 0.74, p<0.001

1-RM Squat strength

Relationship between SPRINT capacity and maximal lower limb muscle strength in football players

Short sprint (acceleration) vs Maximal muscle strength

Acceleration capacity 10-m sprint

r = 0.94, p<0.001

Wisløff et al, Br J Sports Med 2004n=17 male elite football players, international level

Wisløff et al, Br J Sports Med 2004n=17 male elite football players, international level

1-RM Squat strength

r = 0.71, p<0.01

Maximum speed capacity 30-m sprint

Relationship between SPRINT capacity and maximal lower limb muscle strength in football players

Long sprint (max speed) vs Maximal muscle strength

Relationship between vertical JUMP capacity and maximal lower limb muscle strength in football players

Vertical jump height (CMJ)

1-RM Squat strength

Wisløff et al, Br J Sports Med 2004n=17 male elite football players, international level

r = 0.78, p<0.05

Tillin, Folland et al, J Sports Sci 2013 [static squat]

Short 5-m sprint times (<1 s) (n=10)

Long 5-m sprint times (≥1 s) (n=8)

Rapid force capacity - Rate of Force Development (RFD) Effects of RFD on acceleration capacity

Elite rugby players (n=18)

Isometric leg extensor RFD measured at 0-50-250 ms

Tillin, Folland et al, J Sports Sci 2013 [static squat]

Elite rugby players (n=18)

Isometric leg extensor RFD measured at 0-50-250 ms

indirect measure of Relative RFD at 100 ms

5-m sprint time

Rapid force capacity - Rate of Force Development (RFD) Effects of RFD on acceleration capacity

Helgerud, Rodas et al, Int J Sports Med 2011n=21 male elite football players, UEFA Champions’ League

Half-squat resistance training with 4-RM loads in 4 reps × 4 sets performed concurrently with regular soccer training, Twice a week for 8 weeks (16 sessions)

+52% +47% +5% +3% +2%

Influence of resistance training on sprint capacity in football...

Strength training: 4 sets of 6-RM of high-pull, jump squat, bench press, back half squat, and chin-up exercises. High intensity interval training: 16 intervals each of 15-s sprints at 120% of individual maximal aerobic speed. For 8 wks, twice per wk (16 sessions in total)

Influence of resistance training on sprint capacity in football...

Strength training: 4 sets of 6-RM of high-pull, jump squat, bench press, back half squat, and chin-up exercises. High intensity interval training: 16 intervals each of 15-s sprints at 120% of individual maximal aerobic speed. For 8 wks, twice per wk (16 sessions in total)

vertical CMJ height 10-m sprint time 30-m sprint time

Relative changes with training

4%

5.5% 3%

Influence of resistance training on sprint capacity in football...

Effects of resistance training on kicking performance in elite football players

Maximal ball release speed pre-post 12 wks of resistance training

Aagaard et al, Acta Physiol Scand1996n=22 male elite football players

HR: Heavy resistance 4 sets, 8 reps (8 RM)LR: Low resistance 4 sets, 24 reps (24 RM)LK: Loaded kicking movments 4 sets, 16 reps (16 RM)CO: Control group; No strength training

70.075.080.085.090.095.0

100.0105.0110.0115.0120.0

HR LR LK CO

Velo

city

(km

per

hr)

Kicking performance

Before training

After Training

70.075.080.085.090.095.0

100.0105.0110.0115.0120.0

HR LR LK CO

Velo

city

(km

per

hr)

Kicking performance

Before training

After Training

70.075.080.085.090.095.0

100.0105.0110.0115.0120.0

HR LR LK CO

Velo

city

(km

per

hr)

Kicking performance

Before training

After Training

Aagaard et al, Acta Physiol Scand1996n=22 male elite football players

HR: Heavy resistance 4 sets, 8 reps (8 RM)LR: Low resistance 4 sets, 24 reps (24 RM)LK: Loaded kicking movments 4 sets, 16 reps (16 RM)CO: Control group; No strength training

70.075.080.085.090.095.0

100.0105.0110.0115.0120.0

HR LR LK CO

Velo

city

(km

per

hr)

Kicking performance

Before training

After Training

70.075.080.085.090.095.0

100.0105.0110.0115.0120.0

HR LR LK CO

Velo

city

(km

per

hr)

Kicking performance

Before training

After Training

70.075.080.085.090.095.0

100.0105.0110.0115.0120.0

HR LR LK CO

Velo

city

(km

per

hr)

Kicking performance

Before training

After Training No effect of 12 wks of resistance training (slow-heavy, fast-power, or functional exercise) on maximal ball kicking speed ...

Effects of resistance training on kicking performance in elite football players

Maximal ball release speed pre-post 12 wks of resistance training

SUMMARY

Neuromuscular Plasticity in Quadriceps Function in Response to Training

Neuromuscular Plasticity in Quadriceps Function

Adaptive changes in rapid force capacity (RFD) & ECC muscle strength induced by resistance training

SUMMARY

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et a l., J. Appl. Physiol. 2000

motorneuron inhibition during ECC contraction ECC strength Aagaard 2000, Andersen 2005, Duclay 2008

►

Neuromuscular Plasticity in Quadriceps Function

Adaptive changes in rapid force capacity (RFD) & ECC muscle strength induced by resistance training

SUMMARY

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et a l., J. Appl. Physiol. 2000

motorneuron inhibition during ECC contraction ECC strength Aagaard 2000, Andersen 2005, Duclay 2008

Neuromuscular activity at force onset (0-200 ms) RFD Aagaard 2002, Barry 2005, Del Balso & Cafarelli 2007, Schmidtbleicher & Buehrle 1987

►

►

Nm

uVolts

uVolts

Time ( milliseconds )

0

100

200

0

800

0

800

-200 0 200 400 600

0

600uVolts

Force Moment

VL EMG

VM EMG

RF EMG

Neuromuscular Plasticity in Quadriceps Function

Adaptive changes in rapid force capacity (RFD) & ECC muscle strength induced by resistance training

SUMMARY

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et a l., J. Appl. Physiol. 2000

►

►

►Nm

uVolts

uVolts

Time ( milliseconds )

0

100

200

0

800

0

800

-200 0 200 400 600

0

600uVolts

Nm

uVolts

uVolts

Time ( milliseconds )

0

100

200

0

800

0

800

-200 0 200 400 600

0

600uVolts

Nm

uVolts

uVolts

Time ( milliseconds )

0

100

200

0

800

0

800

-200 0 200 400 600

0

600uVolts

Force Moment

VL EMG

VM EMG

RF EMG

Force Moment

VL EMG

VM EMG

RF EMG

motorneuron inhibition during ECC contraction ECC strength Aagaard 2000, Andersen 2005, Duclay 2008

Neuromuscular activity at force onset (0-200 ms) RFD Aagaard 2002, Barry 2005, Del Balso & Cafarelli 2007, Schmidtbleicher & Buehrle 1987

Rate of EMG rise (RER) Rate of Force development (RFD) Aagaard 2002, Barry 2005, Del Balso & Cafarelli 2007, Blazevich 2008

Neuromuscular Plasticity in Quadriceps Function

Adaptive changes in rapid force capacity (RFD) & ECC muscle strength induced by resistance training

SUMMARY

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et a l., J. Appl. Physiol. 2000

motorneuron inhibition during ECC contraction ECC strength Aagaard 2000, Andersen 2005, Duclay 2008

Neuromuscular activity at force onset (0-200 ms) RFD Aagaard 2002, Barry 2005, Del Balso & Cafarelli 2007, Schmidtbleicher & Buehrle 1987

Rate of EMG rise (RER) Rate of Force development (RFD) Aagaard 2002, Barry 2005, Del Balso & Cafarelli 2007, Blazevich 2008

Maximal motorneuron firing frequency RFD Van Cutsem 1998, Patten et al 2001, Kamen & Knight 2004, Christie & Kamen 2010

motorneuron firing: incidence of discharge ‘doublets’ RFD Van Cutsem 1998

►

►

►

►

►

... And How this Might Affect Sprinting Ability and Kicking Performance

SUMMARY

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et a l., J. Appl. Physiol. 2000

Neuromuscular Plasticity in Quadriceps Function

Adaptive changes in rapid force capacity (RFD) & ECC muscle strength induced by resistance training

... And How this Might Affect Sprinting Ability and Kicking Performance

Sprinting ability, including long sprint and short sprint (acceleration capacity) can be increased in high-level football players by means of heavy-resistance strength training

►

SUMMARY

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et a l., J. Appl. Physiol. 2000

Neuromuscular Plasticity in Quadriceps Function

Adaptive changes in rapid force capacity (RFD) & ECC muscle strength induced by resistance training

... And How this Might Affect Sprinting Ability and Kicking Performance

Sprinting ability, including long sprint and short sprint (acceleration capacity) can be increased in high-level football players by means of heavy-resistance strength training

Kicking performance measured as maximal ball flight speed does not seem to be positively affected by resistance training, at least not when performed for short periods of time (8-12 wks)

Kicking actions may be performed faster, due to RFD ((?))

►

►

►

SUMMARY

100 Nm

-2500

2500

3000

-3000

-4000

4000

position

Moment

EMG VL

EMG VM

EMG RF

Time (m sec)0 1000 2000 3000 4000 5000

uVolt

uVolt

uVolt

Time (msec)0 1000 2000 3000 4000 5000

slow concentric contractionpre training

slow eccentric contraction pre training

Neural drive m. quadriceps

Aagaard et a l., J. Appl. Physiol. 2000

Neuromuscular Plasticity in Quadriceps Function

Adaptive changes in rapid force capacity (RFD) & ECC muscle strength induced by resistance training

Bangsbo & Andersen, Power Training in Football 2013

Physiological changes associated with strength/power training in football players

Bangsbo & Andersen, Power Training in Football 2013

Physiological changes associated with strength/power training in football players

?

Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark;▼

Institute of Sports Medicine Copenhagen, University of Copenhagen

Michael KjærPeter MagnussonCharlotte SuettaMette ZebisUlrik FrandsenPeter KrustrupLars HvidJakob Nielsen

Jesper L. AndersenPoul Dyhre-PovlsenErik B. SimonsenTony BlazevichLars L AndersenMarkus JakobsenEmil SundstrupAnders Jørgensen

Acknowledgements

"... The analysis comprised 510 subjects and 85 effect sizes (ESs), nested with 26 experimental and 11 control groups and 15 studies ..."

"... Results: There is a transfer between increases in lower body strength and sprint performance as indicated by a very large significant correlation (r = -0.77; p = 0.0001) between squat strength ES and sprint ES ..."

Slow-type jumper(Landing type drop jump)

Fast-type jumper(Bouncing type drop jump)

Tcontact = 361 ms 272 ms

Dyhre-Poulsen et al, J Physiol 437, 1991

Motorneuron excitability and ECC performanceElite (National Team) volleyball players - Drop Jump test

Brainmotor cortexcerebellum

Spinal cord

efferentmotor neurons

sensoryafferentneurons

Muscle

Drawing modified from Sale 1992

Enhanceddescending

motor drive fromhigher CNS centres

Increasedspinal motoneuron

excitability

Resistance training Resistance training improved neuromuscular function improved neuromuscular function

Aagaard P. Exercise and Sports Science Reviews 31, 2003

maximal muscle strength rapid force capacity maximal muscle power eccentric muscle strength

Nerve impulses

Nerve impulses

explosive strength (RFD)

Neural and muscular adaptations with resistance training

Morphological * 6-12 RM loads adaptation Maximal muscle strength“muscle volume training” mechanisms Explosive muscle strength (Rate of Force Development) Neural 1-8 RM loads adaptation Eccentric muscle strength “explosive type training” mechanisms **

* muscle cross-sectional area (CSA) Narici 1989, Aagaard 2001

CSA, type II muscle fibres (type II MHC isoforms) Andersen & Aagaard 2000, Aagaard 2001

changes in muscle architecture (fibre pennation) Aagaard 2001, Seynnes 2007, Blazevich 2007

** neural drive to muscle fibres ( iEMG) Narici 1989, Schmidtbleicher 1987, Aagaard 2000, 2002

motoneuron excitability, supraspinal motor drive Aagaard 2002, Del Balso & Cafarelli 2007

EMG depression in ECC contraction Aagaard 2000, Andersen 2005

Aagaard, Exercise Sports Science Reviews 2003

Strength training in the elderlyStrength training in the elderly: enhanced explosive muscle: enhanced explosive musclestrength (RFD) may result in strength (RFD) may result in improved functional performanceimproved functional performance

Improvements in functional capacity: performance in activities of daily living (horizontal gait speed, stair walking, chair rising)

Neuromuscular function - motor cortex, cerebellum - spinal cord circuitry - sensory afferent feedback - efferent motorneuron output

Training

Adaptive changes in neuromuscular

function

ECC strength, explosive strength

Effects of resistance training

Is RFD also improved during dynamic SSC muscle actions ???

Neuromuscular Plasticity in Quadriceps functionContractile Rate of Force Development (RFD)

Force Plate Methodology Analysis of leg extension force (GRF) and power during maximal jumping

Body centerof mass (BCM)

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Vertical ground reaction force GRF (Fz)

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

Force plateForce plate

amplifier

Data acquisition:Sampling: 1000 samples/sAcquisition interval: 5 s

12 bitSampling card

Vertical ground reactionforces of body center ofmass

-1000

0

1000

2000

0 1000 2000 3000 4000

0

1250

2500

-9.81

0.00

9.81

-1.0

0.0

1.0

2.0

-0.28

-0.14

0.00

0.14

eccentric phase concentric phase

Time (msec)

Vertical Force Fz

Center of MassPower

Center of MassVelocity

Center of MassPosition

Center of MassAccelerat ion

New

ton

Wat

tsm

eter

/sec

met

erm

eter

/sec

2

1a 1b 2

Caserotti, Aagaard et al. Eur J Appl Physiol 2001, Scand J Med Sci Sports Exerc 2008

0 1000 2000 3000 4000

0

2500

5000

-2500

0

2500

5000

-1.0

0.0

1.0

2.0

-0.28

-0.14

0.00

0.14

Time (msec)

Vertical Force Fz

Power

Velocity

New

ton

Wat

tsm

eter

/ se

c

eccentricpeak power Pecc

concentricpeak power Pcon

Rate of Force DevelopmentRFD = ΔFz /Δt

eccentricpeak velocity Vecc

concentricpeak velocity Vcon

-1000

0

1000

2000

0 1000 2000 3000 4000

0

1250

2500

-9.81

0.00

9.81

-1.0

0.0

1.0

2.0

-0.28

-0.14

0.00

0.14

eccentric phase concentric phase

Time (msec)

Vertical Force Fz

Center of MassPower

Center of MassVelocity

Center of MassPosition

Center of MassAcceleration

New

ton

Wat

tsm

eter

/sec

met

erm

eter

/sec

2

1a 1b 2

Jakobsen, Aagaard et al, Human Movement Sci 2012

dynamic RFD measured from acc-dec transition point (peak Vdownward) to +50 ms

CMJ Power testingChanges in dynamic RFD and CMJ performance

with resistance training

Pre and Post 12 wks heavy-resistance strength training (ST)

Jakobsen, Aagaard et al, Human Movement Sci 2012

Vertical ground reaction force Fz pre and post training

Rate of Force

DevelopmentRFD = ΔFz /Δt

prepost

CMJ Power testingChanges in dynamic RFD and CMJ performance

with resistance training

Pre and Post 12 wks heavy-resistance strength training (ST)

Vertical ground reaction force Fz pre and post training

Rate of Force

DevelopmentRFD = ΔFz /Δt

prepost

CMJ Power testingChanges in dynamic RFD and CMJ performance

with resistance training

Pre and Post 12 wks heavy-resistance strength training (ST)

Kinetic parametersRFD +78%Ppeak +10%LL Stiffness +38%

Jump executionJump Height +17%Tecc-phase -17%Tcon-phase -11%

Jakobsen, Aagaard et al, Human Movement Sci 2012

Vertical ground reaction force Fz pre and post training

Rate of Force

DevelopmentRFD = ΔFz /Δt

prepost

CMJ Power testingChanges in dynamic RFD and CMJ performance

with resistance training

Pre and Post 12 wks heavy-resistance strength training (ST)

Kinetic parametersRFD +78%Ppeak +10%LL Stiffness +38%

Jump executionJump Height +17%Tecc-phase -17%Tcon-phase -11%

Jakobsen, Aagaard et al, Human Movement Sci 2012

STRONG NEUROMUSCULAR COMPONENT: Strong positive correlations were observed between pre-to-post gains in Hamstring rate-of-EMG rise (RER) and increases in CMJ RFD (r = .83, p < 0.01) and lower limb stiffness (r = .80, p < 0.01).

Jakobsen, Aagaard et al,

Human Movement

Sci 2012

Lateral Quadriceps (VL)

Medial Quadriceps (VM)

Center Quadriceps (RF)

Lateral Hamstrings (BF)

Medial Hamstrings (ST)

Lateral Gastroc (GL)

Medial Gastroc (GL)

Vertical ground reaction force (Fz)

CMJ and EMG testing Pre and Post 12 wks resistance training