David Grey on Lower-Leg Dynamics, “Fatigue Contrasts”, and Rethinking the Term “Corrective Exercise”

Today’s episode features biomechanics specialist, David Grey.  David is the founder of David Grey Rehab, where he works with clients from all walks of life. David’s specialty is assessing his clients gait cycle in depth to develop a plan to help restore the movement or movements they struggle to perform.  David has learned under a number of great mentors in the world of human movement, athletic development, gymnastics, Chinese martial arts, and biomechanics, and is an expansive thinker, blending many elements of human movement together in a down to earth way we can all resonate with.

Humans absolutely love to categorize things, and put things in boxes.  For those in their initial learning stages, this can really be helpful to the learning process, but at some point, we need to see the grey, or continuum-like nature of things, and how training interacts on its different levels.  When we put things in the box of simply being a “corrective” exercise, for example, it loses touch with many of the helpful principles of training and overload that come in more “standard” training exercises.  When we can see things from an expansive viewpoint, we can start to gather the wisdom regarding how different pieces of training work together.

On today’s show David, puts many things together in regards to good functioning of the kinetic chain for not only knee health, but also better movement.  We talk about the muscles of the lower leg, where he stands (and how he has changed) on the level of more “bodybuilding” oriented training methods, keeping things simple in exercise progression (and how putting “corrective exercise” in a box is a bad idea), sensory awareness and fatigue contrasts, and finally, a ridiculously good summary on how David approaches knee rehab and health from a multi-factorial perspective.

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David Grey on Lower-Leg Dynamics, “Fatigue Contrasts”, and Rethinking the Term “Corrective Exercise”

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Timestamps and Main Points:

3:48 – David’s experience in his United States tour

11:56 – Discussing the muscles of the lower leg, and their importance in movement

21:16 – Simplifying some exercise methods that improve hamstring calf interaction

25:30 – Where muscles sit on the “joints act, muscles react” end of the spectrum in the sense of simply training a muscle to alleviate joint pain or optimize the kinetic chain

36:10 – How to keep things “simple” in a rehab and “corrective exercise” space, and the “sensory to intensity” scale

41:55 – David’s use of “fatigue contrasts” in training and working with longer-ground contact plyometrics

57:27 – David’s current multi-lateral keys to knee training and rehab as he sees it and summarizes it


“With movement, you can talk about it all you want, but they need a chance to experience it and feel it”

“Even with slower running, the soleus has a lot of load going through it”

“If you think going for a jog is easy, it’s easy for a lot of muscles, but it’s not easy on the soleus”

“The gastroc has a lot of pre-activation before the foot hits the floor, the soleus has very little.  But when the foot hits the floor, the gastroc cools down and the soleus goes through the roof”

“A muscle like the soleus and glute max takes time to produce force, because of the shape of the muscle, but they are way stronger… there are other muscles that can contract quicker, but they are not as strong”

“Those types of (roller bridge) exercises open you up to a lot of sensation”

“Before full body strength work, that’s where we start to isolate a lot of muscles (for those who have inhibited muscles)”

“I use the foam roller bridge as a test; if someone can’t hold that for 5 seconds, I look at them and say “your hamstrings should be stronger”

“I’m moving more towards the bodybuilding side of things with just getting the muscles working”

“I’m a big fan of drop jumps; especially in rehab because it’s very structured”

“I like to think of the scale of sensory to intensity; that’s what we are working towards”

“I will use fatigue contrast; it might be something like we do some leg extension, hamstring curl, calf raises, and then I do the hop, and then it feels better.  If you bring those tissues to quite a bit of fatigue; the brain or nervous system has to figure out a new way to bring those muscles together”

“When we get into plyometrics, it’s important to work with short ground contact times, but that doesn’t mean we can’t work with the spectrum of other joint ranges and ground contact times”

“We don’t just think of movement from slow to fast; you can have faster movement through a large range of motion in certain areas; you don’t have to wait for all the parts of your body to catch up as well”

“With a knee issue; I need people to be able to straighten their knee, and bend their knee, which involves rotations.  Those rotations involve motions at the foot and the hip”

“One of the earliest skills I teach in the workshop is transitioning from early stance to mid-stance, and that is, allowing the shin to drop forward”

“A lot of people with knee issues rush towards their toes, and don’t know how to stay in middle on a bent knee”

“A big skill is how to get an active hip extension; hip extension without knee extension”

“I want them to learn how to push their knees back without letting their knee fully straighten”

“Life just doesn’t feel as good if you can’t bend your knees”


About David Grey

David Grey is a biomechanics specialist and expert in injury rehabilitation and performance based in Ireland. He is the founder of David Grey Rehab, where he works with clients from all walks of life. David’s specialty is assessing his clients gait cycle in depth to develop a plan to help restore the movement or movements they struggle to perform. His work often starts with training the foot to re-experience the ingrained movements that it should access during every single footstep. David has learned under a number of great mentors in the world of human movement, athletic development, gymnastics, Chinese martial arts, and biomechanics. He is greatly influenced by the work of Gary Ward, the creator of “Anatomy in Motion.” He has developed a program called Lower Body Basics, designed to be a holistic lower-body strength and mobility program that helps his clients move efficiently and without pain.

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