Part of a larger presentation on the squat exercise.

2. Overview
 Benefits of the Squat
 Myths about the Squat
 What the Squat
Actually Does
 Safety
 Technique
 Common Errors
 Learning the Squat
 Variations

3. Benefits of the Squat
 Core strength
 Lower body hypertrophy
 Sport / Real-life specific strength gains
 Bone Mass?
 Mobility

4. Myths
 Stance width effects muscle recruitment
 Stance width/angle of the feet effect the
knees
 Angle of the feet effects muscle
recruitment
 Squats are bad for the knees
 Bar placement effects muscle
recruitment

5. Narrow Stance
 87-118% shoulder width
 More knee translation
 More knee shear
 Uses plantar flexors to help restrain
knee translation

6. Wide Stance
 158-196% shoulder width
 Vertical shins (I.e. little knee translation)
 Horizontal thighs

7. Effect of Stance on Joint Angle (Escamilla,
et al., 2001)
Joint Angles at Maximum Knee
Flexion
0
20
40
60
80
100
120
140
160
180
200
Hip Trunk Thigh Shank Knee
Joint
JointAngle
NS
MS
WS

8. Effect of Stance on Muscle Recruitment
(Escamilla, et al., 2001)
Peak EMG activity for different squat
stances
0
20
40
60
80
R
F
VL
VM
Lat.Ham
M
ed.Ham
G
astroc
Muscles
%MVIC
NS
WS

9. Stance and muscle recruitment (IEMG)
0
1
2
3
4
5
6
7
8
9
10
Ad. Long.
Descent
Ad. Long.
Ascent
Muscles/motions
Microvolts
NS
WS
GM GM
What about other muscles? (McCaw & Melrose,
1999)
GM
Desc.

10. Stance and the Knee (Escamilla,
et al. 2001)
0
1000
2000
3000
4000
5000
Flex
TF
Compr.
Flex
PCL tens.
Flex
PF Comp.
NS
WS
Ext. Ext
.
Ext.

11. Foot Angle?
 0 vs. 30 degrees, no effect on tension or
compression
 No difference in hamstring, quadricep,
or gastroc activity
 Escamilla, R.F. (2001). Knee
biomechanics of the dynamic squat
exercise. MSSE, 33(1), 127-141.

12. Squats Bad for the Knees
 Where this comes from:
 Karl Klein’s 1961 study
 128 deep squatters; “Pan-American games
weightlifters from 1959, weightlifters from
Texas, weightlifters from Austin universities”
 386 beginning weight lifting students,
basketball players, and gymnastic students,
never done deep squats

13. Results of Klein’s Study
Squats and Knee Instability
0.00%
20.00%
40.00%
60.00%
80.00%
Medial Lateral ACL PCL
Ligaments
%withInstability
S Left
S Right
NS Left
NS Right

14. Klein’s Conclusions
 “…the deep squat, is basically
responsible for the production of the
ligament instability found.”
 “…the deep squat exercise,…should be
discouraged from the standpoint of its
debilitative effect on the ligamental
structures of the knee.”

15. Klein’s Conclusions, Cont.
 “In weight training, no more than a 1/2
squat be used… In the squatting
position the thighs should not reach the
right angle or slightly less than parallel
with the floor. The feet should be flat on
the floor.”

16. How Well was the Study Done?
 How instability was measured.
 Klein’s comments to potential detractors:
 “…one has to accept the fact that an
experienced tester is capable of
demonstrating the evidence of stability and
instability of ligaments with relative ease.”

17. Since then...
 No one has been able to duplicate
Klein’s results

18. What the Squat Actually Does
 Tibiofemoral compression
 ACL/PCL tension
 Patellofemoral compression
 Muscle recruitment

19. Tibiofemoral Compression
 Too much could damage the menisci
and articular cartilage.
 Serves to resist translation of tibia
relative to femur (I.e. protects cruciate
ligaments).
 WS squats demonstrate greater levels
of TF compression.
 TF compression increases as the knees
flex, decreases as they extend

20. ACL Tension
 Escamilla has not observed ACL tension
during the squat (Escamilla, et al., 2001)
regardless of stance.
 This is thought to be due to hamstring
activity.
 This is in contrast to leg extensions,
where the ACL is loaded as the knee is
near full extension.

21. Squat and ACL
 How the squat reduces ACL tension:
 Hamstring activity
 Gastroc activity
 It’s weight bearing (joint compression)
 (Neitzel, J.A. & G.J. Davies, 2000)

22. PCL and the Squat (Escamilla, et
al, 2001)
PCL Tension and the Squat
0
500
1000
1500
2000
Flexion
Extension
Knee Angle
Force
Force

23. Squat and the Cruciate
Ligaments
 Escamilla recommends avoiding squats
greater than 50-60 degrees of knee
flexion with PCL injuries.
 The lack of anterior shear indicates that
the squat may be appropriate for ACL
patients.

24. Patellofemoral Compression
 Increases as the knees flex and
decreases as the knees extend.
 Escamilla suggests avoiding knee
flexion of greater than 50 degrees when
suffering PF pathologies (stress is
greatest from 50-80 degrees).

25. Muscle Recruitment
 Quadriceps:
 Activity increases as
knee flexes, decreases
as knees extend.
 Peaks at 80-90 degrees
of knee flexion, does not
increase after 90
degrees of flexion.
 Vastus lateralis and
medialis produce 40-
50% more activity than
the rectus femoris.
 Hamstrings:
 More active during
ascent (especially lateral
hamstrings).
 Working isometrically
throughout?

26. Muscle Recruitment, cont.
 Gastrocnemius:
 Activity increases as the knees flex and
decreases as the knees extend.
 Acts to restrict knee translation.
 May also fire isometrically.

27. Peak Muscle Activity during the Squat
(Escamilla, et al., 2001)
KA at Peak MVIC during Squat
0
20
40
60
80
100
R
F
VL
VM
LH
M
HG
astroc
Muscle
KneeAngle
KA Peak

28. What About Bar Placement?
 “High-bar” squats
 Bar around C7 vertebrae
 Theory: more upright,
more quadriceps
development
 Used primarily by
Bodybuilders and
Olympic-lifters
 “Low-bar” squats
 Bar around spine of
scapula
 Theory: more lean, more
focus on hips and lower
back, more weight can
be lifted
 Used primarily by
Powerlifters

29. Wretenberg, P., et al. (1996)
 Swedish strength athletes; 8 Olers, 6
Plers, all national caliber
 65% of 1-RM studied
Olympic Lifters Power Lifters
Mean Age (years) 19 32
Mean Bodyweight (kg) 82 87
Mean 1-RM (kg) 154.38 255

30. High-Bar vs. Low-Bar
Moments of Force
0
50
100
150
200
250
300
350
Hip Knee
Joint
Moment(Nm)
High
Low

31. Results...
 High-bar more upright, joint moments
more evenly distributed between hip and
knee
 Low-bar move hip involvement than
high-bar
 Actually, powerlifters showed higher
normalized EMG activity for RF, VL, and
BF than weightlifters