1. Avoiding The Tragic “Accident”:
Biomechanics You Need To
Know
The absolute first priority for anyone training with weights
should be to avoid a catastrophic injury.
That should be obvious, but consider the following:
·
In
1972, Muscular Development magazine reported on a Pennsylvania man, found dead
in his home, on his bench press, with the bar across his throat. He apparently missed his lift, the bar landed
on his chest, and rolled to his throat, strangling him.
·
In
2002, Flex magazine reported on a competitive bodybuilder, performing a barbell
squat with 675 pounds for a photo shoot.
As he bent his knees, he lost control of the descent, landing on his
knees, then falling backwards with the weight.
His quadriceps and patellar ligaments were torn, resulting in multiple
surgeries, months of rehab, and putting his ability to walk at risk.
·
In
2003, Club Industry magazine reported on a lawsuit brought by a man using a
Smith machine for squats. He wasn’t able
to control the descent of the bar, the machine did not have bottom stops, and
so his spine was crushed between the bar and the floor, leaving him
quadriplegic.
·
In
2007, a college football player, after performing the step-up exercise with 185
pounds on a bar across his shoulders, twisted an ankle returning the bar to the
rack, and fell with the barbell. He
suffered injuries to his spine and, again, his ability to walk was put at risk.
·
In
2009, a college football player, bench pressing 275 pounds with a spotter,
missed the lift, dropped the bar on his throat, and had to have 3 emergency
surgeries on his vocal cords, adam’s apple and neck.
These instances, which involved a range of trainees from guys
working out at home and in commercial gyms to high level athletes, are always
reported as tragic, freak accidents.
And it is tragic that these people suffered life-altering injuries doing
something that was supposed to be life-enhancing, and that clearly they weren’t
intending on getting injured, so in that sense, these are accidents.
But what is
especially tragic is that even though these are standard exercises, the
injuries they could cause are predictable and preventable. An analysis of even the most fundamental
biomechanics suggests that the “freak” occurrence is when you push these
exercises hard and don’t get
hurt. Squats and bench press are
especially dangerous, because your spine, and your throat, face, and jaw are
between the barbell and gravity. Here
are the biomechanics you need to know to avoid a catastrophic injury:
·
Free weights “get
heavier” as you bend.
·
You can lower
more weight than you can lift.
·
The bones and
muscles of the spine aren’t suited for top-heavy loads.
·
Balancing on one
leg or a split stance relies on small muscles of the hip and deep muscles of
the spine.
·
Putting the
weight back relies on much smaller muscles than the ones that lifted it.
Free
weights “get heavier” as you bend.
Anyone who
has done a squat or bench press with a barbell knows this to be true. Put the bar on your shoulders to start the
squat, and while you’re standing with your knees and back straight, the weight
is manageable. Same with the bench press, as you take the bar off the rack and
your elbows are straight. As soon as you
break the lock at the knees and elbows, the weight starts to get heavier,
becoming heaviest the closer you get to the bottom.
But it’s not
“heavier”; it’s the same barbell.
Something changed from lockout to sticking point, but it isn’t the
weight. It’s the moment arm, or the
lever through which the weight acts.
The clearest way to demonstrate
Moment Arm is with a Seesaw. Walk up one
side of a seesaw (for demonstration purposes only, don’t try this at home) and
stand directly over the axle. No matter
what you weigh, conceivably, you could balance both sides of the plank off the
ground, because your weight is directly over the axis. But if you take one step to either side, or
even shift your weight, the plank tips.
By moving your weight away from the axis, you introduce a moment arm,
making your same weight “heavier”.
With the
barbell squat and bench press, when the weight is directly over your joints,
it’s the same as standing over the axle.
“Lockout” is the same as no moment arm: the axes are in line with the
weight. As you break lockout in the
squat, and your hips move back, it has the same effect as stepping to the side
on the seesaw. Instead of the weight
walking away from the axis (the seesaw), the axis is moving away from the
weight. Either way, a moment arm is
created, and the weight gets “heavier”.
The moment
arms in the barbell bench press are less visual, but as you lower, the weight
moves away from directly over the shoulders and elbows. It’s easier to see with dumbbells. Since hand width is fixed on a barbell, as
the elbows bend, they also move away, so you get moment arms created at both
sets of joints. With barbells or
dumbbells, the weights get harder to handle as they approach the bench presser.
This
easy-to-hard pattern is in play at all weight levels, but is obviously more of
a concern at maximum efforts. With a
light enough weight, you could conceivably throw the weight off or push it to
the side if you run into trouble. As you
approach your maximum, this becomes less of an option, and if you’re in a smith
machine, it’s not an option.
Practically, this means you could guess wrong about your capability, put
too much weight on the bar, start out ok, and then only realize, too late, that
it’s too heavy. So the conventional squat and bench press with a barbell moves
from easy-to-hard, mechanically.
There’s also a muscular aspect.
You
can lower more weight than you can lift.
Muscles are
commonly described as having three levels of strength. Positive strength comes from the shortening
of muscle (a “concentric contraction”); an example of which is lifting a
weight. A higher level of strength is
isometric (“static contraction”), where
the muscle exerts effort to hold its’ position.
The highest level is “negative” strength (“eccentric contraction”),
which comes from allowing the muscle to lengthen under control.
Practically,
in the gym, this has several applications.
Generally, if you’ve lifted a weight ten times, and can’t complete
number eleven, you could stop your set at ten.
Or, you could begin rep 11, stall during the rep, and hold that position
for as long as you can, extending your set.
And if you have attentive training partners, they can then lift the
weight for you, so you can lower it under control, extending the set even
further.
It
could also go the other way (“negative training”), where you deliberately pick
a weight heavier than you could lift and just do the lowering portion of the
set. If you can’t do a chin up, for
example, you could climb to the top, and only do the lowering portion of the
rep; which obviously allows you to work those muscles better than not doing any
chin ups.
The issue with the squat and bench
press, however, is if you don’t realize the weight is too heavy.
For
exercises where you lift, first, if you pick too heavy a weight, you know right
away that you can’t do the rep. Put 500
pounds on a bar and try to deadlift it.
Put 200 pounds on a bar and try to curl it. You’ll know right away that the weight is too
heavy, and generally stop before anything bad happens.
With the
squat and the bench press, you start at lockout, the mechanically easiest
part. You’re also starting with the
lowering phase, where you can handle more weight than you can lift or
hold. You might actually be able to
start the squat with the same 500 pounds you walked away from on the deadlift,
and you might be able to lower it under control; but if you realize it’s too
heavy, you may not be able to lift it, and you may not be able to stop it. The same aspects of muscle strength that
allow you to extend your set, and to practice chin-ups, even to walk down steps
with little effort, can cause real problems on the squat and bench.
Starting at
lockout and doing the negative first apply to both the squat and bench
press. The squat has the added
complication of involving the spine.
The
bones and muscles of the spine aren’t suited for top-heavy loads.
Take a look at the human skeleton, the spine in particular, preferably a
rear or side view. Starting at the
pelvis and looking towards the head, we see three sections of vertebrae: 5
lumbar, 12 thoracic, and 7
cervical. The size and shape of each is
related to their function. The lumbar
are the biggest and strongest of the column with interlocking processes,
preventing rotation. This stability is
to support the weight of the entire upper body.
Next up is
the thoracic. The lower vertabrae are
about the same size as the lumbar, but each next, higher vertebrae gets
smaller, as each supports less weight.
Each thoracic is not as locked in to the next, as the lumbar are, which
allows for rotation. We need more
general mobility in the thoracic, compared to the lumbar, because this is also
where the ribs attach, which have to accommodate breathing.
The top
section of the spine, the cervical, has the smallest vertebrae with the least
amount of interlock. These only have to
support the weight of the head, and require the most mobility (as a unit) of the three regions.
Generally,
the overall organization of the bones of the spine is a pyramid: stronger and
thicker at the bottom, supporting less weight towards the top. Practically, a pyramid provides stability: a
broader base of support with a lower center of gravity means you can stand,
walk, or sit with very little muscular effort.
Once you
move, however, the pyramid is disrupted, and the muscles have to provide more
stability. Let’s look at the muscles
around the spine, moving from deepest to most superficial.
The deepest
layer are the rotatores, each of which connect each vertebrae to the next
adjacent, running almost horizontally.
Visually, these are stacked from top to bottom, and each individual
muscle is very short. Next are the
multifidis, which connect each vertebrae diagonally to the next; also stacked
top to bottom, and individually not as short as the rotatores. Each individual muscle in these sets of
muscles only connects one vertabra to the next.
The shortness of these muscles suggests that their function is not so
much to twist the spine, as it is to hold the spine steady.
The
most superficial layers, the semispinalis and the erector spinae, are
individually longer, and connect over more than the next vertebrae. Part of the semispinalis connects the head to
different points in the thoracic; part of it connects the neck to different
parts of the thoracic; and part of it connects the upper portion of the
thoracic to the lower portion. Parts of
the erector spinae connect the pelvis and thoracic to higher points on the
thoracic and cervical spine. These sets
of muscles, which can contract over a greater distance, seem more suited to
moving the spine (although the functions probably don’t break up that neatly).
Compare
above the pelvis with below. The pelvis
itself is a pretty solid structure of few bones, each significantly bigger than
any of the vertebrae. On the back side,
a big superficial muscle, the gluteus maximus, connects the pelvis to the
femur, and the hamstrings (connect the pelvis to the lower leg. On the front side, part of the quads (rectis
femoris) connects the pelvis to the lower leg, while the rest connects the
femur to the lower leg.
The system
below the pelvis provides for speed and power: big, superficial muscles pull on
few, solid beams of bone, moving through large ranges of motion, in few
directions. Above the pelvis, there’s no
muscle match for the glutes or quads; and even if there were, the spine isn’t a
beam like the femur. With the spine,
many muscles only have to hold or move slightly, the next vertebrae. This system provides mobility, with stability,
for the overall spine.
What does
this suggest about putting a barbell on top of the spine?
With
bodyweight alone, the muscles and joints of the spine are fully capable of
holding the torso and head steady, while the bigger muscles (glutes, quads, and
hams) move the legs and propel the upper body.
In this example, the spine does function as a “column”. Manual laborers have known this for
years: “Lift with your legs, not your
back”, means “hold your spine steady, while you bend at your hips and knees”.
Put a
barbell across your shoulders, however, and the situation changes. Now, instead of a decreasing load from pelvis
to head, we have dramatically reversed the load: even just a bar at shoulder
level is significantly greater than the weight of the head. Neither the muscles nor the vertebrae are
structured to support this: the closer the vertebrae are to the head, the
smaller they are; and there is no single mass of muscle connecting the lower
vertebrae to the head and neck. The
same weight that is appropriate to challenge the glutes and quads, working
through the largest, strongest bones and muscles in the body, also has to be
supported by the dozens of smaller muscles around each individual vertabrae.
Practically,
if you squat with a barbell, your back muscles will get stronger, up to a
point. But the spine also has discs and
nerves that are being loaded with the bar on your back, which doesn’t apply to
the femur. As the glutes and quads get
stronger and need more weight to challenge them, your back is taking on more
strain in a variety of ways.
So the idea
of working your lower body, by loading a barbell on your shoulders, is limited
in several directions. Don’t worry; it
can get worse: put a barbell on your
shoulders and try to exercise one leg at a time.
Balancing
on one leg or a split stance relies on small muscles of the hip and deep
muscles of the spine.
A fundamental concept in biomechanics is relating your center of gravity
to your base of
support. You can stand
on two feet and maintain your balance pretty much without effort, because your
center of gravity falls within your base of support. Pick one foot up, i.e., remove a support, and
you should fall to that side, because now, your center is outside your single
support.
Generally,
though, we don’t, by unconsciously shifting our center of gravity away from the
foot off the ground, and directly over the foot on the ground. The function of the muscles on the side of
the hip (gluteus medius and minimus), in spite of what’s implied by hip
abduction machines, isn’t to pull the femur towards the outside of the pelvis;
it’s to pull down on the pelvis, shifting the center of gravity towards that
side.
It’s not a
dramatic shift; in fact, it’s barely noticeable. If you stand, put your thumbs on the sides of
your hip, and pick one foot up to balance on one foot, you can feel the muscle
tighten and (if you avoid falling) feel your balance shift. At the same time, the deep muscles around the
spine, rotatores and multifidis, tighten, so when the pelvis shifts, the torso
follows, maintaining the balance.
The
same shift has to happen with exercises.
Heel raises, split squats, lunge walking, reverse lunges, stepping up to
a bench are all common exercises that disrupt your base of support. Your performance of these exercises,
conceivably for the prime movers of the lower body, is going to be limited by
how well your side hips manage that shift.
This is not necessarily a bad thing, because aside from rowing and
weightlifting, few sports and physical activities use both legs together as in
a leg press or squat. Your inner thigh
and outer hip muscles will work extra to stabilize the femur, so the larger
muscles can drive the limbs. So you
might trade off some intensity for the prime movers, for more stabilization,
and in the long run it may even out. The
complications start when you try to add resistance.
Using a
barbell extends your mass so far to the sides that the normal shift of your
center of gravity gets magnified.
Instead of your center of gravity being connected to your body mass,
it’s now connected laterally to the ends of the bar. If the bar isn’t placed exactly centered, or
if the plates shift at all, or if the wind blows to one side, you don’t just
have to manipulate your bodyweight; it’s your bodyweight, plus the extra moment
arms created laterally. If you lose your
balance, you’re probably better off if the bar falls off than if you try to
re-balance, because the spine is going to be unavoidably involved. (Maybe not so good for other people in the
gym.)
The safest
way to load single-leg or split stance exercises with weight is by keeping the
weight close to your center. Weighted
vest, one dumbbell on the working side, dumbbells in each hand, weight plate
held across the chest, even a hip belt:
all these keep the weight closer to your center, and provide similiar
work for the lower body stabilizers and prime movers.
Putting
the weight back involves much smaller muscles than the ones that lifted it.
You have finished your set without incident. Your muscles might be burning, you’re
breathing heavier, you have barely locked out the last, most difficult
rep. Don’t relax yet: you have to maintain lockout until the bar is
physically supported by the rack. Your
prime movers are shot, so if the weight moves away from zero moment arm, that
load is going to have to be supported by much smaller, deeper muscles.
With the
squat, if you slouch, relax your gut, or bend forward to put the bar on the
stand, the weight moves off center, and the deep muscles of the spine discussed
above will try to hold things together. With any amount of weight on your shoulders,
this puts the spine in a vulnerable position, so a weight that challenged your
glutes and quads is especially dangerous.
You have to keep everything tight, walk as short a distance as possible
to the rack, position the bar directly over the rack, then set the weight
down. Now you can collapse.
The bench
press is a bit more complex. Many bench press stations have too much height
between the bench and the rack, so you either need a lift off from a partner or
you hunch your shoulders forward to get the bar. Bench pressers usually position themselves
away from the rack, so it doesn’t interfere with the path of the bar; but this
means the bar has to move over your forehead, face, jaw, and throat before
getting set to press.
This is
manageable at the start of the set, but when you’re done, you have to reverse
everything, and this is where the problems are.
At the end of the set, you’re locked out: the pecs and triceps are shot,
but you can still support the weight.
Since the rack is “overhead”, you have to move the bar away from
directly over your chest, towards the rack.
Even though your elbows are still locked, you create a new moment arm,
so again, the same weight gets “heavier”.
Only now, the weight is over your face, and your pecs and triceps are
spent.
At the same
time, you have to raise the bar to clear the rack. If you lift your shoulders off the bench
(protract the scapula), you use the serratus anterior and pectoralis
minor. Since both are deeper and smaller
than the pectorals, in order for them to move the same weight that exhausted
the pectorals, they probably have to heave, not lift under control. The combination of exhausted prime movers,
deep muscles trying to move big weight, a new moment arm, and being pinned in
place can be a disaster.
A single
human spotter may not be much help.
Usually the spotter stands centered between the stands, but away from
the path of the bar. If the bench
presser misses the rack, or gets stuck at the bottom, the spotter has to be
able to power clean or deadlift the bar, quickly. I especially like the 200 pound bodybuilder
being spotted by the 135 pound partner.
Unless that 135 pounder can clean 300 pounds, the best you can hope for
is the 911 call.
Ideally,
once you finish your set, you stay locked with the weight above your chest,
without trying to lift your shoulders or lean the weight towards the rack,
while spotters lift the weight to the supports.
The minimum setup is to have two, one at each end, to lift and place the
bar on the rack, or to hold it off you while you scramble. The best is to have a third, centered, who
can steer the bar.
Practical
steps to avoid barbell catastrophe
If your tool
of choice is the barbell, whether by necessity or preference, you have to take
precautions, especially with maximum efforts.
You may still get hurt with submax efforts, and you may still get hurt
with the precautions in place, but probably not with permanent, life-altering
injuries.
Center the bar, and always use collars. Deep muscles make small adjustments for
centering and balance. Extending the
weight laterally makes excessive demands on them, that will probably never come
up in any other context, and is too risky.
Use structural barriers
to avoid being pinned by the barbell. Horizontal rails
should be sturdy enough and set high enough to keep the bar off you. If you use a smith machine, the bottom stops
must be set no lower than the sticking point; don’t rely on the hooks.
Use a minimum of 2,
preferably 3, human spotters who are paying attention.
One at each end of the barbell, to catch and lift it off you, and a center one
to steer, either the barbell or you out of the way.
Stay tight at the end
of the set. Even with locked knees and elbows, you can
still make the weight “heavier” by accidentally creating a new moment arm,
which would risk straining the deep muscles and worse. Maintain your posture
until the bar is placed in the supports.
To load single-leg or
split stance exercises, keep the weight close to you, or use other techniques
for progression. Keeping the extra load close to the center
mimics the natural balancing more than the extended weight on a bar. You may choose less risk over more load, and use bodyweight
alone, for more reps and sets, and less rest.
Of course, the most direct way to avoid injury with a barbell
is: Don’t
put a barbell over your spine, face, jaw, and throat. If you’re open to the idea, that is.
For many
people, even if the barbell was capable of delivering unique, phenomenal
benefits, the risk simply isn’t worth it.
There are other, effective ways of working the same muscles, and safer,
more appropriate ways of loading joints than with the barbell squat and bench
press. The barbell is a perfectly
adequate tool, especially compared to what was available before it, but it’s
not magic or super-science.
“Conventional
wisdom” has created an aura around certain exercises and approaches that isn’t
necessarily supported by basic biomechanics.
Weights load limbs; deep muscles stabilize joints, so superficial
muscles can move the loaded limb; and bones at the joint move in relation to
each other. This happens whether you use
a barbell, bodyweight, a weight stack, or a rock. There’s no magic attached to one technique or
tool vs. the other. There are, however,
specific, documented ways that muscles and joints are supposed to function, and
walking into a gym doesn’t change that.
Avoiding
catastrophe is really the least you can get out of applying biomechanics to
weight training. You can also cut down
on unnecessary strain on the joints, and load the muscles more
effectively. Fortunately, the two go
together.
***
