THE SQUAT: ANALYSIS

Overview

Benefits of the Squat Myths about the Squat What the Squat

Actually Does Safety

Technique Common Errors Learning the Squat Variations

Benefits of the Squat

Core strength Lower body hypertrophy Sport / Real-life specific strength gains Bone Mass? Mobility

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

Narrow Stance

87-118% shoulder width More knee translation More knee shear Uses plantar flexors to help restrain

knee translation

Wide Stance

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

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

Jo

int

An

gle

NS

MS

WS

Effect of Stance on Muscle Recruitment (Escamilla, et al., 2001)

Peak EMG activity for different squat stances

020406080

RF VL VM

Lat.

Ham

Med. H

am

Gastro

c

Muscles

% M

VIC NS

WS

Stance and muscle recruitment (IEMG)

0

1

2

3

4

5

6

7

8

9

10

Ad. Long.Descent

Ad. Long.Ascent

Muscles/motions

Mic

ro

vo

lts

NS

WS

GM GM

What about other muscles? (McCaw & Melrose, 1999)

GM Desc.

Stance and the Knee (Escamilla, et al. 2001)

0

1000

2000

3000

4000

5000

Flex TF

Compr.

FlexPCL tens.

FlexPF Comp.

NS

WS

Ext. Ext. Ext.

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.

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

Results of Klein’s Study

Squats and Knee Instability

0.00%20.00%40.00%60.00%80.00%

Medial Lateral ACL PCL

Ligaments

% w

ith

Ins

tab

ility

S Left

S Right

NS Left

NS Right

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.”

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.”

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.”

Since then...

No one has been able to duplicate Klein’s results

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

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

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.

Squat and ACL

How the squat reduces ACL tension:Hamstring activityGastroc activityIt’s weight bearing (joint compression)(Neitzel, J.A. & G.J. Davies, 2000)

PCL and the Squat (Escamilla, et al, 2001)

PCL Tension and the Squat

0500

100015002000

Knee Angle

Fo

rce

Force

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.

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).

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?

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.

Peak Muscle Activity during the Squat (Escamilla, et al., 2001)

KA at Peak MVIC during Squat

0

20

40

60

80

100

RF VLVM LH MH

Gastro

c

Muscle

Kn

ee

An

gle

KA Peak

What About Bar Placement? “High-bar” squats

Bar around C7 vertebraeTheory: more upright,

more quadriceps development

Used primarily by Bodybuilders and Olympic-lifters

“Low-bar” squatsBar around spine of

scapulaTheory: more lean, more

focus on hips and lower back, more weight can be lifted

Used primarily by Powerlifters

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

High-Bar vs. Low-Bar

Moments of Force

0

50

100

150

200

250

300

350

Hip Knee

Joint

Mo

me

nt

(Nm

)

High

Low

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