In the book, Science and Practice of Strength Training, the authors write “The
heaviest weight that is lifted through a full range of motion cannot be greater
than the strength at the weakest point”, meaning that one is limited to how much
weight they can lift by the amount of strength that they have at the most
disadvantageous position of a lift.
Advantageous vs. Disadvantageous
The most advantageous position of a lift is the one where the least amount
of effort/strength is needed to lift a given weight. Therefore, the most
disadvantageous position of a lift is the one where the greatest amount of
effort/strength is needed to lift that same amount of weight. Generally the
most advantageous point of a lift is when the prime movers are in a shortened
state, and the most disadvantageous point is when the prime movers are in a
lengthened/stretched state, and if one wants to increase their 1 rep max (1RM),
they need to increase the amount of weight that they can lift in the most
disadvantageous position of a lift.
While it is accurate to say that one is limited to how much weight they
can lift by how strong they are at the weakest point of the range of motion, it
is incomplete by not accounting for (metabolic) fatigue, which accumulates the longer
the time under tension, and can influence just where that weakest point is.
The Limiting
Factor Principle As It Relates To Time Under Tension
The longer a muscle, or group of muscles, is under tension for, the more
it will become a limiting factor.
Exercises are generally looked at in terms of which muscle groups they are
‘supposed’ to target. But, what a lot of people fail to realize is that, just
because an exercise is supposed to target a specific area, does not mean it is
limited to that area only, even if it is an ‘isolation’ exercise, as the all
the muscles of the body work in unison to perform a given task (some more so
than others, obviously, depending on that task). Only when you breakdown a
movement, and consider what other muscle groups are indirectly, but highly
involved, do you begin to see what will ultimately become a limiting factor the
longer a set, or workout, goes on.
The muscle(s) that are under constant tension during the course of a set
are the ones that will become a limiting factor either acutely (during that
set) or chronically (during the workout, or from one workout to the next), so
it’s important to know what those muscles are so you can program accordingly to
get the best return per investment of time/effort.
Single-Joint vs. Multi-Joint
With most single joint exercises, the limiting factor will almost always
be the primary muscle group being trained, since it will be the one placed
under the most amount of tension. There are instances though, when a muscle
group that isn’t being directly trained will be the limiting factor.
Multi joint exercises on the other hand involve an assortment of muscle
groups to a much greater degree, which means you may in fact be limited by
muscle groups that aren’t ‘supposed’ to be worked with that specific exercise.
The Most Common Limiting Factors That Affect Performance
The Lower Back
Any axial loaded movement not only compresses the spine, but requires the
lower back to maintain continuous tension just to keep you erect/upright (hence
the name of the muscles responsible for this being called the erectors).
Therefore, fatigue of the lower back due to constantly being engaged during a
set could ultimately affect ones performance during exercises like squats,
lunges, split squats, step-ups (which are movements no one would prioritize if
their goal was specifically to strengthen their lower back).
Squats, Lunges, Split Squats, Step-Ups
If one chooses to perform a squat, lunge, split squat, or step-up, it’s
likely that they do so with the goal of targeting the quads, glutes, and
hamstrings.
As far as the most advantageous and disadvantageous positions are
concerned, the most advantageous would be when the knees, hips, and ankles, are
optimally extended and the individual is standing erect, and the most
disadvantageous is that in which the knees, hips, and ankles are optimally flexed.
Therefore, in these cases one is limited to how much weight they can attempt to
lift for one rep by how strong their quads, glutes, and hamstrings are in their
most disadvantageous (stretched/extended) position.
However, if one was to perform a set of 20+ reps in a set, or even a high
volume workout in which you performed 10 sets of 10, fatigue would alter what the
limiting factor is.
With squats, lunges, split squats, and step-ups, you can choose to
deliberately keep tension on the targeted muscles by performing your reps
rhythmically, in a ‘pumping’ fashion, until lactic acid accumulates within the
muscles to the point that it impairs their ability to contract, in which case
tension must be temporarily removed to allow for the metabolic waste to flush
out of the muscle so it can continue contracting.
The two ways this tension can be removed to allow the muscles to
immediately regenerate ATP is by simply ending the set, or for those who want
to get as many reps as possible by any means necessary, do what most people do
(whether they realize it or not), and remain as upright as possible for a few
seconds with the bar resting on your back. When the knees, and hips, are
extended at the top of a squat/lunge/split squat/step-up, the tension in the
quads, glutes, and hamstrings is dramatically reduced, which allows for the
instantaneous replenishment of ATP for those muscle groups.
The erectors of the lower back however, don’t have the luxury of relaxing
between reps to allow for ATP to be replenished, as they have to remain under
constant tension just to keep you from falling on your face with a loaded
barbell on your back. This ongoing tension leads to the accumulation of metabolic
waste, ultimately impairing muscle function/contraction.
On top of that, with uni-lateral exercises like lunges, split squats, and
step-ups, the lower back is doing double the amount of work with each set. While
each leg has the opportunity to rest while the other leg is working, the lower
back has to remain engaged for the entire duration of the set.
By taking into consideration that the lower back can very often become a
limiting factor with axial loaded movements, especially as the volume is
increased, you can effectively plan your workouts, and warm-ups, accordingly.
If your lower back is limiting how much weight you can lift for exercises that
are specifically designed to target other muscle groups, it will be a daunting
task to make improvements in those exercises.
The Arms (Triceps
and Biceps)
Pretty much every single upper body exercise can be classified under one
of two categories:
A) Pushing/Pressing
B) Pulling
Regardless of whether you are pushing/pressing, or pulling, or if the
exercise is a single joint, or multi joint movement, the weight that you are
lifting is transferred through the elbow joint on its way to the intended
muscle group that attaches in the shoulder joint. Therefore, if the muscles
responsible for extending (triceps), and flexing (biceps, brachialis, etc.) the
elbow are not strong enough to provide the force, or stability, necessary to
handle the weights that the larger muscles of the torso (pec, lats, etc.) are
capable of handling, you will be limited to how much weight you can attempt to
lift.
With both pushing/pressing, and pulling movements, the most advantageous
position is when the elbow is optimally extended, and the most disadvantageous
position is when the elbow is optimally flexed. The greater the bend in the
elbow, the more force that is required to move a given weight, but the greater extension
in the elbow, the less force that is required to move the same amount of weight.
Therefore, one is limited to how much weight they can attempt to lift for one
rep by how strong their pecs, lats, delts, etc, are in their most
disadvantageous (stretched/extended) position. This holds true for nearly all
upper body movements.
For example, with both the bench press and the pull-up, a much greater
amount of weight can be used to perform only the first ¼ of the movements range
of motion in which the arms go from fully extended, or locked out, to minimally
flexed, but a greater amount of force is required to press that same amount of
weight off the chest, or lift the same amount of weight up till your chin
clears the bar. In both cases, the amount of force required increases in direct
proportion to increases in the range of motion.
However, as with the example above regarding the lower back, if one was to
perform a set of 20+ reps in a set, or even a high volume workout in which you
performed 10 sets of 10, fatigue would once again, alter what the limiting
factor is.
Muscles are gradually smaller and weaker by comparison, the further away
from the midline of the body that they’re located. Logic would then dictate
that the relatively smaller muscles are subject to greater levels of fatigue
per repetition performed. In the case of the bench press, and the pull-up,
because the tension passes through the elbow joint on its way to the shoulder
joint, the muscles responsible for extending, or flexing the elbow, are likely to
become ones limiting factor, the more reps they choose to perform. Whether they
realize it or not, this is why lifters have difficulty locking out the elbows
to rack the bar at the end of a set of bench presses, and why they can’t pull
themselves all the way up to the bar at the end of a set of pull-ups.
By taking into consideration that the muscles responsible for extending,
and flexing the elbow, can very often become a limiting factor with pretty much
every single upper body exercise, especially as the volume is increased, you
can effectively plan your workouts, and warm-ups, accordingly. If your triceps
or biceps are limiting your ability to complete reps through a full range of
motion, your results will be compromised while the risk of injury is elevated.
Grip Strength
Grip strength is a no brainer as far as limiting factors are concerned in
that, if one cannot hold onto weight, then nothing can be done with it. This
doesn’t apply to pushing/pressing movements as much as it does to pulling, because
with pushing/pressing movements the weight simply needs to be supported by the
hand, whereas with pulling movements the hand needs to be tightly clasped
around the weight.
Because the muscles of the hand are as far away from the midline of the
body as can be, they are the smallest muscles from a relative perspective, that
are heavily involved in most upper body movements in which the weight needs to
be held tight by the hands, and therefore the first to fatigue. Very often a
lifter will fail during a high volume set/workout of deadlifts, pull-ups, etc,
because their grip ‘gives out’ before the primary muscle group(s).
This is the sole purpose for wrist straps having been created. The straps
enable a lifter to strap weights to their arms that they otherwise wouldn’t be
able to hold onto, so they can direct greater levels of tension onto the
primary muscle group(s). The use of straps however, will come at the expense of
one’s grip strength, as the muscles responsible for gripping don’t need to
create much tension at all if an external piece of material is doing the work,
and therefore have no need to adapt by getting stronger.
Combine all this with the fact that the muscles responsible for gripping a
weight are called upon every single time you pick something up, and not just in
the gym, and it’s easy to see how grip strength can easily become a limiting
factor.
Warm-Up
One of the biggest mistakes that most people make is performing too many
warm-up sets/reps before using their working weight. The purpose of a warm-up
is to rehearse the movement pattern, and pump a little blood into the primary musculature
to warm it up (hence the term ‘warm-up’), not to fully exhaust the smaller
muscles that become limiting factors as the volume placed upon them increases.
Very often people will wonder why they have not been able to make progress, and
why their strength levels aren’t going up, without taking into consideration
that by the time they attempt to break a personal record, they’ve already
lifted several thousand pounds!
An effective way to warm up that is sure to have a positive impact on
performance, without exhausting the most common limiting factors talked about throughout
this article, is to ‘overreach’ during the warm-up. For example, on your way up
to your working weight, you actually attempt to lift more than your working
weight for one rep, to reap the benefits of what is called ‘post-tetanic facilitation’.
That way, when you move onto your working weight, it will feel lighter by
contrast.
Training Split
Which muscle groups are worked or which days can indirectly affect
performance as well. Using the examples above, if one were to do a high volume
back workout, with some direct work for the lower back, and followed that a day
or two later with a leg workout, in which they intended to perform one, or multiple,
axial loaded movements, the lower back could easily limit the amount of work
they could perform.
Performing some direct work for the elbow extensors, flexors, or even some
grip work, a day or two before performing a workout in which the muscles
responsible for extending, or flexing the elbow, or gripping a weight are of
primary importance (presses, pulls, curls, as well as the other examples above)
could easily limit the amount of work one could do.
It is for these reasons that knowing which exercises take priority in a
routine should dictate which muscle groups are trained on what days. An ill
advised training split can not only limit your ability to perform the amount of
work necessary to get the best result per time of investment, but can lead to
overtraining, and increase the risk of injury.
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