Level Up Your Stretching With PAILs And RAILs

February 21, 2022 | Assessments

Level Up Your Stretching With PAILs And RAILs

PAILS & RAILS: It’s A mouthful.

If you’ve ever been to our gym or done one of our KINSTRETCH classes, you know we do these things called PAILs and RAILs.

PAILs and RAILs are acronyms we use to describe a method of stretching from Functional Range Conditioning (FRC). And as you’ll see, it makes a lot more sense to abbreviate this method versus calling it its full name.

PAILs stands for Progressive Angle Isometric Loading.

RAILs stands for Regressive Angle Isometric Loading.

We use PAILs/RAILs to create permanent changes in a given joint, improving range of motion, tissue architecture, joint control, and more. In other words, PAILs & RAILs are the bee’s knees.

Progressive and regressive angle.

The progressive and regressive angle refers to the joint itself.

The progressive side of the joint is the one that is undergoing length because the angle is increasing; this is the same side that is being stretched.

The regressive side of the joint is shortening because the angle is decreasing; we also call this the closing side of the joint.

Let’s use ankle dorsiflexion as an example. The progressive side of the ankle is the calf because it is undergoing length; the regressive side is the shin because the angle is closing.

Ankle Dorsiflexion PAILs RAILs positioning
Dan setting up Mike for Ankle Dorsiflexion PAILs/RAILs
The PAILs RAILs angles illustrated

Isometric loading.

An isometric contraction happens when a joint creates force, but there is no motion. And although the fitness industry doesn’t often use isometric contractions, they are an instrumental tool you should be putting in your arsenal. For instance, isometric contractions are:

  • Safe. They allow us to create extremely high magnitudes of force with little risk because the load (resistance) does not exceed the capacity of the joint you’re working on. So, for instance, if you push up against a brick wall as hard as you can, there’s a small risk for injury; the joint is more likely to yield to the wall from contractual, neurological, or biological failure versus injury.
  • Scalable. You can dictate how much effort and intensity you want to put into an isometric contraction.
  • Controllable. You can choose what lines of tissue you want to focus on (i.e., different muscles or connective tissues in a given joint).
  • Repeatable. Isometrics generally allow faster recovery times because the subsequent muscle damage tends to be less than conventional full range of motion exercises (1).

The law of irradiation.

Sherrington’s Law of Irradiation goes something like this,

‘A muscle working hard recruits the neighboring muscles, and if they are already part of the action, it amplifies their strength. The neural impulses emitted by the contracting muscle reach other muscles and ‘turn them on’ as an electric current starts a motor’ – Quote pulled from FRC.

Simply put, if we’re attempting to work a muscle or tissue with the appropriate intent, effort, and intensity, it behooves us to create irradiation (systemic tension). For example, if we’re attempting to stretch the tissue that moves the ankle, it may be useful to create full-body tension to innervate the work we’re doing at the calf/ankle.

This is why you’ll see us recommending irradiation/tension when we’re doing pretty much anything related to FRC; it allows us to put our energy into the right places.

the protocol.

The PAILs/RAILs protocol can be done in a lot of ways, but there are a few key points that are worth highlighting. We’re going to continue using the ankle as our example since you already have the visual.


First, we want to isolate the tissue we’re targeting and put it under as much passive length as we can muster. This often requires patience and time, which is why the general recommendation is to sit in the stretch position for at least two minutes. Furthermore, stretching for longer durations will yield better tissue architecture changes that you’re likely seeking anyway. (2)

That being said, you can sit in the stretch position for as long as needed (e.g., three to five minutes).

To keep yourself focused and occupied, we recommend focusing on your breath. You can breathe in for a 4-count and exhale for a 4-count over and over again.


Once we’ve sat in the stretch for a long enough duration, we irradiate and create body tension. You can isometrically engage muscles surrounding the joint or the entire body. The more things we lockdown, the better results we will get from the joint we’re working on.

Keep breathing. Don’t hold your breath; instead, take shallow breaths (think belly breathing, but not as deep).


MVC is a scale we use to gauge and direct effort and intensity; think of it like slowly turning a dial if you were turning up the volume in your car.

The MVC Scale illustrated

Once we’ve sat in the stretch for at least two minutes, we’re going to start to engage the progressive (stretching) tissue slowly. To err on the safe side, we start at a low MVC (usually less than 10%) and work our way toward our maximum safest contraction.

For the ankle, we would slowly gas pedal the foot (without moving anything), trying to get the tissue on the back of the calf to fire up. Then, as we build tension, we increase the amount of force going into the ankle and calf, going from 10% to 100% as slowly as needed.

Editor’s Note: You don’t always have to work to 100% MVC. Sometimes, 50% is all you need to get the desired result.


The PAILs contraction is our maximum safest contraction; we’re trying our very hardest to get the calf muscle to lengthen under as much isometric load as we can manage.

We hold this contraction for 15 seconds.


The RAILs contraction is our maximum safe contraction but on the closing angle side of the joint. So now we’re trying to get the shin muscles to pull us into the deepest stretch position we can manage.

We hold this contraction for 15 seconds.

Editor’s Note: Like everything else, the PAILs/RAILs contractions at the end can be shorter or longer depending on what is needed. 15 seconds is a general recommendation.


Let all the tension go. Relax. Try to find the stretch again. Sit here as long as you’d like and try to gently relax into it.


Okay, so this might seem like a lot to take in, but it’s a simple concept.

  1. We find lines of tension in a tissue and put them under length. For ankle dorsiflexion, we’re looking to stretch the back of the calf for time.
  2. We slowly start to engage the lengthened tissue (calf muscles). We use a term called maximum voluntary contraction, or MVC. Think of this as a sliding scale from 0 to 100%; you can voluntarily contract a muscle gently or hard as hell, depending on how much effort you put in. Generally, we work from 0% to 100% MVC, as you’ll see next.
  3. We build to a max-effort contraction (i.e., you’re going to try to engage the muscle we’re stretching fully) and hold it for some time. This is PAILs.
  4. We eventually shift and try to maximally engage the opposite muscles (e.g., if we’re stretching the calf, we will switch to trying to engage your shin muscles) for some time. This is RAILs
  5. Boom! Improvements in how the joint works.

Here’s a quick demo of me setting up for ankle dorsiflexion PAILs/RAILs to tie it all together.

I hope this sheds more light on the PAILs/RAILs process. However, no amount of written text is going to help you feel what it’s like to go through your first PAILs/RAILs. If you have joints that don’t work right, achy or painful body parts, or simply want to learn how to move with purpose, I highly suggest you reach out to us today.

We’ll bring new meaning to the word “stretching.”


  1. Muscle damage produced by isometric contractions in human elbow flexors

Written by:

Motive Training StaffMotive Training Staff

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