The Cheetah man, PART 2: “Bird Dog”, again.

In last week Wednesday’s blog post (link) we discussed the video of this man running amazingly on all 4 limbs at an incredible speed. He was doing it beautifully, most people would have fallen flat on their face after the first leap forward. 

As we discussed on that day, and these 2 screenshot photos will prove, there is ipsilateral interference between the foot and hand in this quadrupedal gait. This is diagonal quadrupedal locomotion (QL); the forward moving lower limb is impaired from further forward progression by the posting up (contact) hand of the same side.  However, in his case, there is such quick removal of the leading hand/limb that he can advance the ipsilateral foot/leg as far forward as he is able without impediment from the same side hand contact. 

As we mentioned in the Bird Dog post last week, (see photo of lady on yoga mat above) the contralateral upper limb will be in the opposite phase of the contralateral lower limb. ie when the left lower limb is in extension, the right upper limb will be in flexion (this is the classic Bird Dog position).

In last weeks blog post (see photos above), the opposite is clearly happening. One can see in the first photo that bird dog is clearly not helping to train a gait pattern, and that is ok, it has other values at times. Rather, in this first photo we see left hip extension and right shoulder extension, just as we see in the baby photo. This contradicts Bird Dog but this does support bipedal gait patterns.  Think about gait. Your right leg and left arm flex until about midstance, when they start to transition into extension; the left leg and right arm are doing the opposite. At no point are the arm and opposite leg opposing one another as in Bird Dog.

As Ivo would say , “if you look at it neurologically, it is a crossed extensor reflex.  It is very similar to a protective reflex called the “flexor reflex” or “flexor reflex afferent”.

The principles remain intact.

More critical thinking today. Hope you enjoyed.

Shawn and Ivo,

The gait guys

A new twist on an old exercise

Do you know the the “Bird Dog” exercise? It looks like the picture above. The upper and contralateral lower extremities are extended, the the opposite ones are flexed. Seems to make make sense, unless you think about gait and neurology (yes, as you can see, those things seem to always be intertwined).

Think about gait. Your right leg and left arm flex until about midstance, when they start to extend; the left leg and right arm are doing the opposite. At no point are the arm and opposite leg opposing one another. Hmmm.

If you look at it neurologically, it is a crossed extensor reflex (see above); again, flexion of the lower extremity is paired with flexion of the opposite upper extremity. It is very similar to a protective reflex called the “flexor reflex” or “flexor reflex afferent”.

Wouldn’t it make more sense to do a cross crawl pattern? Or maybe like the babies shown above? Seems like if that’s the way the system was programmed, maybe we should try and emulate that. Don’t we want to send the appropriate messages to our nervous system for neurological re patterning? If you are doing the classic “opposite” pattern, what is your reasoning? Can you provide a sound neurological or physiological reason?

Think before you act. Know what you are doing.

The Gait Guys. Bridging the gap between neurology and gait, so you can do a better job.

Neuromechanics Weekly: PART 2:

Stretching increases strength in contralateral muscles?

Lots of cool links in this post. please try and find time to check them out.

Figure it out?  Ever wonder about some of the magic behind some of those manual therapy techniques that are out there ? Sometimes it is not magic at all !

There are 2 related reasons we can think of to cause this seemingly odd length-strength phenomenon (OK, there are more, but this is what we are going to cover today):

• Reciprocal Inhibition
• Crossed extensor reflexes/responses

We remember reciprocal inhibition (as demonstrated in LEFT picture above) is when we activate or stimulate a muscle, the Ia afferent from that muscle stimulates that same muscle to contract (this is how a simple reflex arc works) and, through an inhibitory interneuron, inhibits the antagonist muscle on the opposite side of the joint.

Remember, that Ia afferents go to muscle spindles (don’t remember? look here); they respond to LENGTH changes. Wouldn’t you say stretching affects length? If we were talking about the R tricep surae group, we would be inhibiting the R anterior compartment.

But wait, the article said it affects the opposite side….Of course, there is more…

The picture on the right shows the crossed extensor response or reflex (don’t remember? look here). In a nutshell, when you FIRE the flexors on one side, you INHIBIT the extensors on the same side (sound like reciprocal inhibition? It should… it is : ) You also FIRE the extensors on the opposite side while INHIBITING the flexors on the opposite side. (Yes, the opposite side extensors will inhibit the opposite side flexors as well. Yes, this is also reciprocal inhibition).

But wait, that means the opposite calf would be weaker, not stronger, right?

It would be weaker if being called upon to be used at that moment in time, BUT in the study, stretching increased ROM of the stretched calf 8%, with a 1% loss of ROM of the opposite calf (study summary).

Hmm… sounds like shortening to me. That would mean that those spindles (ie the opposite calf)  would be MORE RESPONSIVE to stretch (ie a change in length; and coincidentally, the Golgi’s more responsive to the tension change) . And what happens when we preload a neuronal pool? The likelihood of firing is increased (like doing a Jendrassik maneuver to increase a reflex). The rest is neural adaptation (strength gains initially are due to increased efficiency of the nervous system. For a review to see our video on this, click here)

Interesting that one of the comments on the article was “I don’t have the full text of the paper but a summary prepared by Chris Beardsley and Bret Contreras states that one of the mechanisms for crossover in the case of unilateral strength training is thought to be modulation at the spinal cord level.”   Could they be talking about reciprocal inhibition and crossed extensor responses?

Wow! Very cool! And to think, you knew the answer. We are proud of you!

Ivo and Shawn…Neuro Geeks too!  And applying it to gait, running and motor patterns of all types !

Neuromechanics Weekly: Gait and Running and the Crossed Extensor Responses

This week we discuss why upper and lower limbs are paired in gait, and the neuronal wiring that is involved.

Yup, this is pretty geeky stuff, but geez…isn’t it nice to know WHY something works? Think of the implications if YOU DON’T see the upper and lower limb pairing. Think of the implications during rehab. One limb SHOULD be doing the opposite of the other AND always look at the upper limbs and arm swing. Yes, the central  nervous system is involved. It is more than just biomechanics, perhaps this is why this stuff comes easier to us because of our deeper neurology background. The whole is greater than the sum of the parts….

Ivo and Shawn