The architectural determinants of skeletal muscle function ......tendon strains of the lower...
Transcript of The architectural determinants of skeletal muscle function ......tendon strains of the lower...
![Page 1: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/1.jpg)
Tim Butterfield PhD ATC FACSM
Departments of Rehabilitation Sciences and Physiology
Center for Muscle Biology
College of Health Sciences
Division of Athletic Training
University of Kentucky
Marjorie A. King Research to Reality Presentation
January 10, 2016
The architectural determinants of skeletal muscle
function, and how they can be used to optimize
our rehabilitation protocols
![Page 2: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/2.jpg)
Return to Play?
Adapted from CL Brockett et al. Medicine and Science in Sports
& Exercise (2004)
![Page 3: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/3.jpg)
Clinical Translational
“bench to bedside”
1. See a problem clinically
2. Delve into the literature
3. Design a model
4. Translate to human
![Page 4: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/4.jpg)
Muscle Strain Injury
• Account for 70% of cases in sports med Garrett, 1990
• During a 16 year period collegiate athletes suffered 21,784 muscle-
tendon strains of the lower extremity (LE) Agel et. al., 2007
• Re-injury rates: AFL 34% Brockett et al., 2004
• After 1 year of return to sports, re-injury rate was 70% Sherry and Best,
2004
![Page 5: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/5.jpg)
Cyclists vs Runners
R= -0.83
RF
Mom
ent
RF Length
R= 0.66
RF
Mom
ent
RF Length
Adapted from Herzog et al., MSSE 1991
![Page 6: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/6.jpg)
Chicken or Egg?
Athletes select sports that fit their muscle function
OR
Muscle can adapt to performance demands of
the sport
![Page 7: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/7.jpg)
When you hear ‘muscle’
think sarcomere
Purves et al., Life: The Science of Biology, 4th Edition
![Page 8: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/8.jpg)
Sarcomere structure
Alternating light/dark bands
Dark:
A band – myosin containing force producing cross bridges
Light
I band - actin only
Z-disk – anchor for actin
sarcomere
![Page 9: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/9.jpg)
Sarcomere structure
Arranged in parallel
Arranged in series
sarcomere
Sarcomere number is predictive of function
![Page 10: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/10.jpg)
Physiologic Cross-Sectional Area
(PCSA) – Isometric force generation
Architectural Parameters
![Page 11: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/11.jpg)
Advantages?
• Parallel Sarcomere Number
– Influences PCSA
• Increased isometric force
PCSA ≈ Fi
![Page 12: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/12.jpg)
Physiologic Cross-Sectional Area
(PCSA) – force generation
FL/ML ratio – fibre velocity
– fibre extensibility
Architectural Parameters
![Page 13: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/13.jpg)
Advantages?
• Serial Sarcomere Number
– Dynamic
• Contractile velocity (concentric)
LF ≈ V
![Page 14: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/14.jpg)
1.0
0.5
0 0 0.2 0.4 0.6 0.8 1.0
Force / Power [normalized]
Force
Power
Velocity
[normalized]
![Page 15: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/15.jpg)
1.0
0.5
0 0 0.2 0.4 0.6 0.8 1.0
Force / Power [normalized]
Force
Power
Velocity
[normalized]
![Page 16: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/16.jpg)
1.0
0.5
0 0.2 0.4 0.6 0.8 1.0
Force
Velocity
2.0
Concentric Eccentric
![Page 17: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/17.jpg)
Advantages?
• Serial Sarcomere Number
– Dynamic
• Contractile velocity
– Static
• Flatter appearance of Force-Length
Relationship (FLR)
• Increased extensibility (eccentric)
![Page 18: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/18.jpg)
The FLR
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Force [Normalized]
Sarcomere Length [µm]
1.27 3.65 2.00 2.25
Ascending Descending
Plateau
![Page 19: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/19.jpg)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Force [Normalized]
Muscle Length [Normalized]
0.6 1.0 1.4
Ascending
Descending
Plateau
![Page 20: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/20.jpg)
Muscle:
Sarcomere number: 5000
Optimal length for sarcomere force production: 2.0µm (2x10-6m)
At what length does the muscle produce optimal force?
Example:
10 mm
![Page 21: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/21.jpg)
Muscle:
Sarcomere number: 5000
Optimal length for sarcomere force production: 2.0µm (2x10-6m)
At what length does the muscle produce optimal force?
What if you add 1000 sarcomeres in series?
Example:
12mm
![Page 22: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/22.jpg)
•Fibre arrangement within muscle is a major determinant of
1. functional properties
2. contractile properties
Muscle fibre architecture parallel unipennate
bipennate fusiform
Fibre arrangement is the greatest determinant of muscle function!
![Page 23: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/23.jpg)
Muscle Architecture
tendon
aponeurosis
![Page 24: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/24.jpg)
Muscle Architecture - Examples
Leiber, Skeletal Muscle Structure, Function & Plasticity, 2002.
![Page 25: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/25.jpg)
Muscle Architecture - FL/ML
Based on architecture,
what is the major
(primary) function of
each muscle?
velocity or force?
![Page 26: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/26.jpg)
Muscle Architecture
In general,
Hamstrings & dorsiflexors: •high FL/ML ratio
•low PCSA
Functionally designed for:
•high excursions
•high velocities
Quads & plantarflexors: •low FL/ML ratio
•high PCSA
Functionally designed for:
•force production
![Page 27: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/27.jpg)
Tabary et al. 1976
High correlation between joint angle
and sarcomere number
Passive stretch = increased serial
sarcomere number
McComas, 1996
Can we influence these
properties?
![Page 28: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/28.jpg)
Williams et al., 1986
4 days immobilization and
stimulation
11% increase in length (~2000
sarcomeres in series)
![Page 29: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/29.jpg)
What happens during
immobilization?
Alteration of muscle architecture = atrophy
1. Loss of sarcomeres in series
2. Loss of sarcomeres in parallel
![Page 30: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/30.jpg)
Force [Normalized]
Muscle Length [Normalized]
0.6 1.0 1.4
Ascending
Descending
Plateau
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Exercise Effect on Sarcomere Number
![Page 31: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/31.jpg)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
50 60 70 80 90 100 110 120 130 140 150 160
Tibiotarsal Joint Angle [degrees]
Jo
int
Mo
me
nt
[Nm
]
R2 = 0.99
R2 = 0.98
0.5
0.6
0.7
0.8
0.9
1
1.1
75 85 95 105 115 125
FLR Post Chronic Exercise (short)
2.3±1.7o
![Page 32: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/32.jpg)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
50 60 70 80 90 100 110 120 130 140 150 160
Tibiotarsal Joint Angle [degrees]
Jo
int
To
rqu
e [
Nm
]
R2 = 0.99
R2 = 0.99
0.5
0.6
0.7
0.8
0.9
1
1.1
70 80 90 100 110 120 130 140
FLR post chronic exercise (long)
9.6±1.9o
![Page 33: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/33.jpg)
0
20
40
60
80
100
120
140
50 60 70 80 90 100 110 120 130 140 150 160
Tibiotarsal Joint Angle [degrees]
% In
cre
ase in
Jo
int
To
rqu
e
* * * ** * ** *
*
*
*
Increase in Isometric Torque
Butterfield and Herzog Pflugers Archiv, 2006
![Page 34: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/34.jpg)
Summary of Results
• Muscle sarcomere number adapts to
eccentric exercise rapidly
• We can influence the magnitude of the
adaptation by altering working range
![Page 35: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/35.jpg)
18
19
20
21
22
Fib
er
Le
ng
th [
mm
]
0
1
2
4 4.5 5 5.5 6 6.5 7 7.5 8 8.5Time [seconds]
EM
G S
ign
al
[no
rmalized
]
Butterfield et al., J Appl Physiol, 2005
![Page 36: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/36.jpg)
18.5
19.5
20.5
21.5
Fib
er
Len
ng
th [
mm
]
0
1
2
20 20.5 21 21.5 22 22.5 23 23.5
Time [seconds]
EM
G S
ign
al
[no
rma
lize
d]
Butterfield et al., J Appl Physiol, 2005
![Page 37: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/37.jpg)
Vastus Intermedius
Butterfield et al., J Appl Physiol, 2005
![Page 38: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/38.jpg)
Vastus Lateralis
Butterfield et al., J Appl Physiol, 2005
![Page 39: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/39.jpg)
Summary of Results
• Muscle responds to exercise by altering
sarcomere number
– Exercise specific
– Optimizes function for demands
– Greater starting length during eccentric results
in greater sarcomere number addition
![Page 40: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/40.jpg)
So what?
Adapted from CL Brockett et al. Medicine and Science in Sports
& Exercise (2004)
![Page 41: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/41.jpg)
LeStayo et al., Clin Orthop Rel Res 2009
Clinical Translation - Strength
![Page 42: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/42.jpg)
Clinical Translation - Strength
![Page 43: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/43.jpg)
L Lepley et al., 2015 Knee
Clinical Translation - CAR
![Page 44: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/44.jpg)
L Lepley et al., 2015 Knee
Clinical Translation - CAR
![Page 45: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/45.jpg)
• Length dependence and exercise specific
adaptations
– Be aware of muscle architecture and function
• Quads vs hamstrings
• Be aware of demands of sport
Clinical Translation
![Page 46: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/46.jpg)
Eccentric exercise
1. Follow guidelines for any strength and
conditioning program with respect to
progression
![Page 47: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/47.jpg)
Eccentric exercise
1. Follow guidelines for any strength and
conditioning program with respect to
progression
2. Keep in mind, that peak eccentric force
can be up to 2x peak isometric force! I. Must take injury into consideration
II. Standing unloaded eccentrics
![Page 48: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/48.jpg)
Eccentric exercise
3. Progressively increase the length at which
eccentric exercises are applied
e.g. Hamstrings:
a. Can start with “hamstring lowers”
![Page 49: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/49.jpg)
From CL Brockett et al. Medicine and Science in Sports &
Exercise 33(5), 783-790 (2001)
![Page 50: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/50.jpg)
Eccentric exercise
3. Progressively increase the length at which
eccentric exercises are applied
e.g. Hamstrings:
a. Can start with “hamstring lowers”
b. prone knee extensions
a. Short length to long
c. Progress to sitting knee extensions
a. Short length to long
![Page 51: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/51.jpg)
Eccentric exercise
4. Progress from slow speeds to high speeds
a) Keep the F-V property in mind.
Very slow velocity = less tension
Moderate to high velocities have little influence on
tension!
![Page 52: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/52.jpg)
Take Home Message
• We can influence muscle architecture, and thus alter
function
• Be aware of inherent function of the muscle
• Force vs excursion
• Eccentric vs concentric
• Hamstrings should always be exercised eccentrically
• Apply exercise prescription to optimize these parameters
• Pay specific attention two joint muscles to during rehab
![Page 53: The architectural determinants of skeletal muscle function ......tendon strains of the lower extremity (LE) Agel et. al., 2007 • Re-injury rates: AFL 34% Brockett et al., 2004 •](https://reader031.fdocuments.net/reader031/viewer/2022011906/5f3aa5c6bbb8086aab773ebc/html5/thumbnails/53.jpg)
Thank you!