What is Load Tolerance?

KEY CONCEPTS AND DEFINITIONS

Load Tolerance is the amount of pain-free force you can produce or absorb for a specific movement, over a specified period of time and still control the movement.

The most common movement we test is squatting – both a single leg squat and a squat using two legs (bilateral).

When your Load Tolerance is less than your bodyweight, symptoms – pain, aching, stiffness, swelling – usually show up.

The benefit of knowing your Load Tolerance is two fold. One, it helps create the proper loads for an exercise program designed to increase your Load Tolerance and two, it serves as a benchmark for measuring progress.

Without knowing your Load Tolerance, improving it is a guessing game.

We describe Load Tolerance as a percentage of bodyweight (for weight bearing joints) after conducting a Load Tolerance Test. For example, if you weigh 160lbs and we discover through testing that your Load Tolerance for a single leg squat is 55lbs, then from a percent of bodyweight perspective, we would report that test result as 34% (55 /160).

Keep in mind that, for most people, until you are close to 100%, you’ll likely be symptomatic. This is why periodic retests are important.

You might work diligently for 4 or 5 weeks yet still hurt when you do certain things. However, upon re-testing, we might find that your Load Tolerance increased from 34% to 58%. You still hurt because your Load Tolerance is still below your bodyweight.

A fringe benefit of this information is it helps you stay in the game. Remain committed and disciplined with your exercises. You can see the progress but have a ways to go. Without A Load Tolerance Test, how would you know you were actually improving?

You wouldn’t.

Imagine going to rehab, spending 4 or 6 months of time and yet you still hurt. Armed with the data from a Load Tolerance Test, you could actually feel good about having spent that time working so hard on yourself, Yes, you hurt but you can see the change that is happening.

To perform a Load Tolerance Test, we use a device called a Variable Incline Plane  (for weight bearing joints) to find the specific amount of pain-free force your painful leg can produce or absorb. You can learn more about the testing procedure by going here.

Pain-free force is the amount of physical load your body can withstand without feeling pain. This might seem straightforward and simple to apply but oftentimes, because many people have lived with chronic pain, their ability to identify a pain-free state is difficult to do. For many people, pain becomes like a backdrop to their life. It’s just always there.

I’ve had clients who have replied, after being asked if they hurt during a test, say things like, “Uh, it’s okay” or “It’s not that bad” or “I can manage” or “Not really”. All of those statements mean that the test was not pain-free.

Pain is binary. You either hurt or you don’t hurt. The feeling of pain is a gradation from minor to severe.

A response of “Not really” is not a binary response. It indicates some degree of discomfort but likely on the minor end of the scale.

If we accept a “Not really” response during a Load Tolerance Test, the exercise prescription – load, sets, reps – will be imprecise, progress could be slower than it needs to be and as a result, you might get too frustrated and give up.

For a Load Tolerance Test to be valid and useful, the test must be pain-free except in one situation.

For people who have had pain a long time or have difficulty identifying a pain-free state, sometimes the Load Tolerance Test procedure has to be modified. For example, you might be able to find a load level that decreases your feeling of pain and a level that makes it worse. This will be a range of load. On the lower end, the pain decreases but doesn’t go completely away and on the upper end, there’s a load level that increases pain. While this is less than an ideal result, we have used this kind of result successfully. Usually, on subsequent tests as the body improves, so does the Load Tolerance Test and people often experience a pain-free movement sometimes for the first time in a number of years.

In addition to being pain-free, you should also be able to control the movement. There might be a level of force that becomes non-painful yet your movement pattern is not well controlled. A valid Load Tolerance Test includes both a pain-free level of force and a controlled movement pattern.

Training Environment describes the amount of gravitational force that is used during an exercise session.

There are four Training Environments: sub-gravity, gravity, gravity-plus and super-gravity.

Sub-gravity is a training environment that includes forces that are below bodyweight loads. Gravity means bodyweight loads, gravity-plus means bodyweight plus a light additional weight and super-gravity includes bodyweight plus additional weight plus speed.

Movement from person to person varies such that defining one type of movement as “normal” is not very helpful. A Movement Pattern is the result of coordinating movement at different joints either simultaneously or sequentially or both.

Movement Patterns are instead often described as ideal or optimal. Some people can move with a less than ideal pattern and have no symptoms and function just fine. While others might hurt a lot yet have close to ideal movement patterns.

Movement Patterns become more of a concern when the Load Tolerance Test loads are in the gravity and gravity-plus range of forces. When the loads that are tolerated are sub-gravity, the movement pattern is much less of a concern.

The most common mistake people make is not noticing the onset of pain but waiting until they notice significant pain. The test stops when you notice any pain and sometimes that will reveal itself as just feeling different from the other leg or that it doesn’t “feel right”.

We can perform a Load Tolerance Test for practically any weight bearing joint – hip, knee, ankle, foot and even the spine. We also perform Load Tolerance Tests for the upper extremity (using a different device than that described for the lower extremity).

Keeping in mind that our definition of Load Tolerance is a pain-free level of force, as your body gets stronger your Load Tolerance will migrate into what many practitioners might consider as muscle strength testing. And this would not be wrong. I found it was easier to think of Load Tolerance since it’s applicable across the spectrum of training environments whereas muscle testing becomes invalid when pain is involved.

The prognosis for improvement is generally quite good if we can identify a person’s Load Tolerance. In the cases where we can’t, it doesn’t mean people won’t improve but, from our experience, the road back to a Load Tolerance of 100% is bumpier and longer.