Re: A Biomechanical Comparison of Back and Front Squats

[Guest guest]

Hi

Here are relevant extracts from the paper:

" " ...The subjects were required to attend two sessions lasting

about 1 hour each during a period of approximately 1 week.

The first session was a pretesting session. The subjects were

asked to warm up on a stationary bike for 3–5 minutes at

the beginning of the first session. Their one-repetition maximum

(1RM) was determined by having the participants lift

approximately four to five short sets of both front squats

and back squats (order chosen randomly) at increasing loads

until reaching their maximum load. They were allowed to

rest for 5 minutes between sets, or until they felt

sufficientlyrested, and then they were asked to repeat the above

steps for determining 1RM, this time performing the other squat

variation.

The same relative weight (70% 1RM) was used for each squat technique; therefore,

knee kinetics and muscle activity were compared directly between the front and

back squat (14Interestingly, the two squat variations were similar in some ways

and quite different in others. For example, net shear anterior/posterior) forces

at the knee did not vary with bar position, whereas net compressive forces and

extensor

moments increased for the back squat. More specifically, our subjects lifted

61.8 kg during the back squat and 48.5 kg for the front squat. The lower

anterior/posterior (shear) forces measured by Stuart et al. can be attributed to

the use of a lower mass during testing (22.7 kg compared with 61.8 kg used

here).

In our study, the back squat resulted in higher net

compressive (proximal/distal) forces on the knee than the

front squat. Escamilla et al. (15) studied the effects of

technique variations on knee biomechanics during the back

squat and leg press and have reported higher compressive

force values than the current values (approximately 32.1 vs.

10.8 N_m_kg21) Although more mass was lifted during the traditional

back squat, bar position did not influence muscle activity. Because

the muscles tested were equally active during the front squat

while lifting less mass, it is presumable that the same workout

can be achieved with less compressive forces on the knee.

It seems the extra load lifted during the back squat (the

average 1RM for the back squat was 88.3 kg ½ranging from

52.3 to 125 kg_, compared with 69.2 kg ½ranging from 45.5

to 102.3 kg_ for the front squat) is what accounts for the

increased compressive forces and extensor moments observed

during these lifts. This information suggests that front squats

could be advantageous for people with knee problems such as

ligament and meniscus tears, and for general long-term joint

health. Front squats could also be useful for individuals with

shoulder problems that limit their range of motion, making it

hard to grip the bar during the regular back squat. " "

======================

Carruthers

Wakefield, UK

>

> Hi

>

> This is interesting, however I would like to see the actual squats

> performed, for me I tend to experience more knee discomfort

following

> training blocks of front squating and not following block of back

squats.

> My knee issues may be described in another post, but I find this

> characterisation interetsting. Also normaly the weight that I

handle in

> back squats is much higher than in front squats, doe this influence

> compressive loading, and torque mentioned in the study?

>

> Regards

> Nick Tatalias

> Johannesburg

> South Africa

>

> 2008/12/14 carruthersjam

>

> >

> > A Biomechanical Comparison of Back and Front Squats in Healthy

> > Trained Individuals.Gullett JC, Tillman MD, Gutierrez GM, Chow JW.

> >

> > J Strength Cond Res. 2008 Nov 8. [Epub ahead of print] Links

> >

> > The strength and stability of the knee plays an integral role in

> > athletics and activities of daily living. A better understanding

of

> > knee joint biomechanics while performing variations of the squat

> > would be useful in rehabilitation and exercise prescription. We

> > quantified and compared tibiofemoral joint kinetics as well as

muscle

> > activity while executing front and back squats. Because of the

> > inherent change in the position of the center of mass of the bar

> > between the front and back squat lifts, we hypothesized that the

back

> > squat would result in increased loads on the knee joint and that

the

> > front squat would result in increased knee extensor and decreased

> > back extensor muscle activity. A crossover study design was used.

To

> > assess the net force and torque placed on the knee and muscle

> > activation levels, a combination of video and force data, as well

as

> > surface electromyographic data, were collected from 15 healthy

> > trained individuals.

> >

> > The back squat resulted in significantly higher compressive forces

> > and knee extensor moments than the front squat. Shear forces at

the

> > knee were small in magnitude, posteriorly directed, and did not

vary

> > between the squat variations. Although bar position did not

influence

> > muscle activity, muscle activation during the ascending phase was

> > significantly greater than during the descending phase.

> >

> > The front squat was as effective as the back squat in terms of

> > overall muscle recruitment, with significantly less compressive

> > forces and extensor moments. The results suggest that front squats

> > may be advantageous compared with back squats for individuals with

> > knee problems such as meniscus tears, and for long-term joint

health.

> >

> > ============================

[Guest guest]

> My logic tells me that if you lift

> more load you recruit more muscle fibres, does the EMG recived the

> extra

> number of fibres being recruited, lets say the amplitude of each

> recruitment

> is the same (the maximum recruitment for each motor unit as the load

> is

> heavy enough to require the maximum out of a motor unit), but the

> number of

> these units being recruited may change yet the amplitude still reads

> the

> same and thus a conclusion that activation is the same, when it is

> not.

Thanks Nick

Good thought!!

J

Jerry Telle

Lakewood CO USA