physicians condemn squat,
citing how destructive they are to knees, despite scientific
studies and millions of personal experiences to contrary. One
sports medicine doctor explained to me why squats were considered
to be bad for knees. He was actually telling me this between
his sets of squats! Since sports medicine doctors only see people
with injuries, one can guess why they may have developed this
belief. The individuals they treat certainly do not constitute
a random sample, let alone a representative population, which,
as any scientist knows, is essential to even attempt to formulate
The NSCA position statement notes
"Some reports of high injury rate may be based on biased
samples. Others have attributed injuries to weight training,
including squat, which could have been caused by other factors.
Injuries attributed to squat may result not from the exercise
itself, but from improper technique, pre-existing structural
abnormalities, other physical activities, fatigue or excessive
An early study suggested, deep knee bends with weights (squats)
were hazardous to ligamentous structures of knee. Later studies
conclude squats improve knee stability if lifting technique does
not place rotary
stresses on the knee (Fleck and Falkel, 1986). The NSCA state:
"Squats, when performed correctly and with appropriate
supervision, are not only safe, but may be a significant deterrent
to knee injuries."
to propaganda, prominent weight training authorities demonstrate
squat with knees flexing forward at same distance as hips flex
backwards. Fredrick Hatfield, Ph.D., the first man to squat over
800 lbs, recommends knees to extend over feet with back more
upright for quadriceps development. "Strength
Training for Young Athletes" by Steven
J. Fleck, PhD and William
J. Kraemer, PhD, illustrate parallel squats with knees extending
beyond feet (knees moving forward with same magnitude as hips
Torque force is necessary for muscles and joint structures
to adapt to respected overload. If knee does not travel forward
during the barbell squat, quadriceps muscles (ie: knee extensors)
are not significantly exercised. On the other hand, injury may
result if knee or lower back experience greater torque forces
than to what they are accustomed.
Fry et. al. (2003) examined hip and knee torque forces of
variations of parallel barbels squats and concluded appropriate
joint loading during this exercise may require knees to move
slightly past the toes.
Torque through hip active not only activate the Gluteus
Maximus and Adductor
Magnus, but also three heads of the Hamstrings
which cross both the hip and knee. Torque through knee activate
knee, the dislocating forces of the quadriceps are countered
by stabilizing forces of hamstrings. See diagram of countering
forces next to Hamstring
Weakness. Also see Knee
During execution of a barbell squat, knees and hips travel
in opposite directions away from the foot, or away from center
of gravity. Torque forces increase both through knee and hip
joints as exerciser desends. The greatest torque forces are experienced
when initiating the rise out of bottom position.
Try this simplified qualitative method in determining relative
torque forces in the knee and hip joints. First, take a photograph
of barbell squat in a full descent with a perspective perpendicular
to joints plane. Draw a line of force through resistance on its
center of gravity, straight up and down,
parallel to force of gravity. Gravity acting on both body mass
and added mass (barbell) contribute to resistance. Incidentally,
compression forces act upon joints during squat stance. On barbell
squat, center of gravity is over instep (between forefoot and
heel). If it is not, individual will fall over, toward center
Now, draw three separate horizontal lines, perpendicular to
line of force from each joint articulation (ankle, knee, and
hip) to line force. If image is not exactly viewed from the side,
"horizontal" lines can be drawn in perspective to picture
as shown. Once diagram is complete, a relative comparison can
be made on the torque forces of the hip, knee, and ankle.
Typically the torque forces in the barbell squat are slightly
greater for the stronger hip joints as compared to the knee joint,
although both the knee and hips travel in opposite direction
away from the line of force. Generally speaking, during a powerlift
type squat (bar lower behind the shoulders and a wider stance),
knee does not travel forward as far as bodybuilding
type squat. The hips typically travel back further with torso
bent forward on powerlift type squat. This emphasizes stronger
hip extensors and adductors and consequently reduces knee extensor
involvement. Knee torque is further reduced by a wide stance.
Also see Qualitative
Torque Analysis (comparison image to above)
The practice of adopting foot rotation to selectively strengthen
individual muscles of quadriceps is not supported by literature
(Boyden 2000; Signorile 1995). Knee
rotation during squat can increase risk of injury (Fleck
and Falkel, 1986). Signorile, et. al. states:
"Extreme outward toe point greatly reduces stability,
it does not allow the proper drift of hips as lifter descends...
Extreme inward toe points are equally dangerous, coupling same
problems of stability, base size and lower body drift with added
danger of bringing knees together...this movement would place
high stress on all connective tissues."
Full (Deep) Squat
(1996) illustrates safe position of a deep squat with the knees
extending beyond toes. Kreighbaum explains how deep
squat can be performed with little chance of injury to knee.
The variables of concern:
- speed of descent
- size of calves and thighs
- strength of controlling muscles
The primary danger to knee occurs when tissues of calf and
thigh press together, altering center of rotation back to contact
area creating a dislocation effect. The danger of knee injury
in this situation may be prevented if either of the following
factors are present:
- center of gravity of body system is kept forward of altered
center of rotation
- muscles of thigh are strong enough to prevent body from resting
or bouncing on calves.
Kreighbaum concludes deep squat is of little danger to knees
unless these variables and factors are disregarded. Certainly,
only limited type of athletes and performers may have the need
to perform a full squat. Olympic weightlifters commonly bounce
out of full front squat with near maximum resistances during
& Jerk and Snatch.
Incidentally, wide stance during Olympic-style
squat further reduces knee torque forces. Reportedly, those
proficient in Polzunec movement in style of Ukrainian national
folk dance appear to experience few orthopedic problems (up until
middle ages where their incident of orthopedic problems seems
to be no greater than general population) despite their ability
to perform a seemingly contraindicative movement for decades;
body upright, bounding from one leg to the other in deepest squat
position. Also see Over
During lower portions of deep squat, lower back may flex if
is inadequate. The risk of low back injury is increased if muscles
of lower back are not strong enough to support the flexed spine
or joint structures have not progressively adapted to such stress.
Flexibility exercises can be performed if hip flexibility is
insufficient for deep, or full, squats. See Full
Squat Flexibility and Deep
The squat can decrease knee injury (NSCA) and increase
leg power (Adams, 1992) when implemented into a sound strength
and condition program. Early in off season, squat training will
develop foundation for more sports specific training, such as
plyometric work. See Conditioning
The strength and conditioning coaches may choose from a variety
of squat movements. The type(s) of squat(s) prescribed should
prepare athlete for specific biomechanical stresses demanded
by sport as well as other conditioning exercises. Coaches commonly
squat (wide stance, bar low on back, little knee torque)
at exclusion exercises with greater knee torque, namely Olympic
style front squat and bodybuilding
style squat. Coaches cite the importance of hip extension
strength and power. The Glutes are after all, the most powerful
muscles of the body.
Exercises that are most beneficial for sports performance
are generally those that are similar to the type of forces and
counter forces experienced on the playing field. See Training
Specificity and Resistance
Training for the Reduction of Sports Injury. The coach must
consider the unique biomechanic requirements of the sport, as
well as the requirements of each athlete's position. The hip/knee/ankle
torque ratio should be similar to actual biomechanics experienced
on playing field. Motor skills such as blocking, jumping,
leaping, etc. generally involve greater knee and ankle torque
than what is required of the traditional 'powerlifting' squat.
The 'bodybuilding' squat and power
training such as Olympic-style weightlifting and plyometrics,
require a higher ratio of knee/ankle versus hip torque than the
Conversely, some coaches cite knee injuries as a reason to
avoid any other squat than the 'powerlifting style' squat when
in fact the risk of knee injury may be attributed to other factors.
See squat safety above
and Exercise Safety: Causes
of Injury and Sports
If the body has not adapted to a greater
torque force, injury can result. It is not necessary to avoid
torque force if muscles and joint structures can adapt. See adaptation criteria.
Of hip and knee joint, knee is more vulnerable to injury than
hip due to structural and functional differences. Certainly,
if an individual has had a history of knee pain associated with
these types of movements, squat can be modified to to place more
torque on hip and consequently less on the knee joint. Based
on the above analysis, this can be accomplished two ways. Simply,
by not squatting down all the way (e.g. 90°) both knees and
hip do not experience as great of torque forces. Although, this
decrease may be offset by tendency to add more weight to exercise.
Alternatively, by bending at hip more than the knee, the knee
will travel forward less, as in powerlifting type squat. Recall,
quadriceps will not be exercised as intensely since there is
less torque on knee joint. In addition, since balance must be
maintained over the feet, bending over not only transfers more
torque to hips, the torque forces through spine (lower back)
increase, another vulnerable joint for some. Certainly a compromise
must be made to evenly distribute torque force between knee and
hip/lower back, particularly when both knees and lower back are
If the ankle is not flexible enough
to allow knee to travel forward sufficiently, the back will need
to be bent forward more to maintain center of gravity within
foot base. Consequently, lower back will be subjected to greater
torque forces. Squatting with feet wide apart can alleviate part
of the problem, allowing back to be positioned more upright.
This solution does not, however, distribute equal stresses on
quadriceps and glutes as would be possible with adequate ankle flexibility.
Until flexibility can be restored, a temporary solution is
to elevate the ankles on board or platform. This will allow knees
to travel forward same distance as hip travels backwards. Elevating
heels may present a risk to individuals with adequate ankle flexibility
who have not adapted to greater torque forces through knee. In
which case, knees can potentially travel forward more than what
they are accustomed to. Even when elevating heels with insufficient
ankle flexibility, resistance should begin light and progress
only 5-10% every workout until a true workout weight is achieved,
so joint adaption can occur.
Obviously, individuals who are at higher risk for specific
types of knee pain may choose to perform powerlifting
squat while avoiding certain exercises specifically designed
to emphasize quadriceps' involvement by increased knee torque
hack squat, leg
extension). Likewise, individuals who are prone to particular
types of lower back problems may favor the weighted
squat or leg
press while avoiding certain exercises specifically designed
to lower back involvement by increased lower back torque (e.g.
- Boyden G, Kingman J, Dyson R, (2000). A comparison of quadriceps
electromyographic activity with the position of the foot during
the parallel squat. J Strength Cond Res. 14(4): 379-382.
- Fleck, S.J. and Falkel, J.E. Value of Resistance Training
for the Reduction of Sports Injuries. Sports Medicine,
3, 61-68, 1986.
- Fry AC, Smith JC, Schilling BK. Effect of knee position on
hip and knee torques during the barbell squat. J Strength Cond
Res. 2003 Nov;17(4):629-33.
- Hatfield, F.C. (1989). Power: A Scientific Approach, Contemporary
Books, pg. 158.
- Kraemer, W.J., Fleck, S.J. (1993). Strength Training for
Young Athletes, Human Kinetics.
- Kreighbaum, E., Katharine, B.M. (1996). Biomechanics; A Qualitative
Approach for Studying Human Movement, Allyn & Bacon, 4, Pgs
- National Strength and Conditioning Association. The Squat
Exercise in Athletic Conditioning, NSCA Position Statements.
- Signorile JF, Kwiatkowksi K, Caruso JF, Robertson B, (1995).
Effect of foot position on the electromyographical activity of
the superficial quadriceps muscles during the parallel squat
and knee extension. J Strength Cond Res. 9:182-187.
Most line drawings from Trainer