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Latissimus Dorsi Length Test (Muscle Length Test)
The Latissimus Dorsi Length Test is a muscle length test that evaluates the flexibility of the latissimus dorsi muscles, which are the large back muscles responsible for shoulder and arm movement. The test measures and compares the distance between the highest point (acromion process) and the lowest point (spine of scapula) of the latissimus dorsi muscles with the opposite side and with the average values. The test can be used to assess muscle imbalances,
Transcript
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This is Brent of the Brookbush
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Institute, bringing you another muscle
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length test. In this video we're going to do the lat length test.
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Now the lat length test we use to determine if the latissimus dorsi is one
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of the muscles restricting shoulder flexion. I'm then going to show you some
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of the if-then scenarios, that will help you determine whether the lats, the
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shorter internal rotators of the shoulder, or both are involved. I'm going
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to have my friend Melissa come out, she's gonna help me demonstrate. So what the
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lat length test really is, is a shoulder flexion test. It's just a very quick
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shoulder flexion test, just like shoulder flexion goniometry. Alright so what I'm
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gonna have you do, sorry start here, laying flat. I'm going to have you try to
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bring this part of your forearm back to the table in front of you. Alright
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there you go, so you guys see. We know that normal shoulder flexion is between
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100 and 185 degrees, so she's missing some shoulder flexion right.
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The lat length test part comes in and it goes, if you really push it, can you
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push it, just go all the way down to the table, go for it. Alright she pushes
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her arms down and does this, did you guys see all this lumbar extension. I have to
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start thinking to myself all right the muscles that could restrict shoulder
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flexion, I got the teres major, subscapularis, the latissimus dorsi
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pectoralis major probably not likely in this position. Of those muscles, which one
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crosses the lumbar spine, well the lattisimus dorsi crosses the lumbar
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spine. Not only does it cross the lumbar spine, but it will cause lumbar extension,
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which is exactly what I saw. So when I told Melissa to go ahead and push it, or
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I could even add a little overpressure, obviously you wouldn't want to do that to a
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painful shoulder. But if you added a little overpressure and it pulled her into
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lumbar extension, I know that she ran out of room from her lats, and had to shorten
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it somewhere else. So this would be a positive lat length test. I know that the
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lats are one of the structures that could be restricting her shoulder
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flexion. There's another way to go about this,
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we'll start over. This time we'll put her in a hook lying
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position. Now hook lying position posteriorly tilts the pelvis a little bit,
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flattens up the lumbar spine and it kind of anchors the pelvis
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a little bit, so that lumbar extension is not as easy to get in this position. Now
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I have her go ahead and pull this way, and usually what you'll have is in that
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same individual, somebody will actually look like they're even more restricted
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and shoulder flexion. I could test to see how much the lats are contributing to
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this by going okay, let's go ahead and bring your legs up, push you into a
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posterior tilt, and you guys see how when I pushed her into a posterior tilt her
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arms came up a little bit. That's a pretty good sign that her lats are
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contributing to the restriction on her shoulders. So that's all the lat length
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test does. Is the lat one of the muscles restricting shoulder flexion, the problem
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with that is, is it doesn't do all that much for us from a practical application
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standpoint. I still don't know if it's subscapularis and teres major
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contributing to this. So how would I figure that out? Well I could go back to
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my goniometry, if you guys remember shoulder external rotation is done here.
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Alright, why shoulder external rotation? Well subscapularis, teres major,
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latissimus dorsi are all internal rotators. But if i go and put the arm
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back in ninety degrees of shoulder abduction, i just shortened the lats a little
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bit right. It's like halfway through a lat pulldown. So these structures that
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are more likely to restrict this range of motion in this position are the
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shorter external rotators. So if I had positive lat length tests, and then I did
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external rotation and she had full 95 degrees, I might be able to deduce that
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it's the lats restricting her shoulder flexion, and
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the short internal rotators, teres major and subscapularis. If I had a
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positive lat length test and she only had 85 or 80 degrees of shoulder
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external rotation, then I know it's probably teres major, subscapularis and
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latissimus dorsi. If I had a negative lat length test right, so that's
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I did those lat length tests, she had restricted shoulder flexion but
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pulling you into a posterior pelvic tilt, or laying your legs flat didn't change
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anything. So pulling your legs this way didn't cause your arms to come up, laying
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your legs flat didn't cause your lumbar spine to go into extension right, that's
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a negative lat length test. But I came over here and she was still restricted
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in internal rotation, then I know it's not my latissimus dorsi but my short
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internal rotators that are causing a restriction in shoulder flexion. You
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guys catch all that. So let me review this a little bit. If I had positive lat
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length test, negative shoulder external rotation. So somebody had normal external
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rotation, then it's probably just the lats. If I had positive lat length test, and
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somebody had reduced shoulder external rotation, they had a limit in external
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rotation, then it's probably not only the latissimus dorsi, but the subscapularis
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and teres major. If I didn't get a positive lat length test, but I have a
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restriction in external rotation, then it's probably the subscapularis and teres
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major, and not the lats. Now on a side note, if we take this back to movement
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impairment, generally speaking the only time I find
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that the lats are tight without the subscapularis and teres major coming along
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for the ride, is when latissimus dorsi over activity is not stemming from upper
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body dysfunction, but from lumbo-pelvic hip dysfunction.
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In other words somebody has an anterior pelvic tilt maybe with some low back
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pain, and you notice limited shoulder flexion, however that limited shoulder
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flexion is caused from over activity of the latissimus dorsi as a lumbar
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extensor, and your intervention, your corrective exercise, your physical
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therapy, your therapeutic modalities should be focused on trying to fix an
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anterior pelvic tilt, not this. I'm willing to bet that if it's upper-body
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dysfunction that's causing the limit in shoulder flexion, but not only will your
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lats be tight, but so will your teres major, and your subscapularis along with
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potentially your anterior tippers of your scapula. Now if you guys want to
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know how to differentiate between lumbo-pelvic hip complex and upper body
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dysfunction, go check out the videos on the overhead squat assessment,
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particularly the overhead squat assessment sign clusters. You'll see one
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for upper body dysfunction, one for lumbo-pelvic hip dysfunction, one for
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lower leg dysfunctional, one for asymmetrical weight shift. Go over the
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ones for upper body and lumbo-pelvic hip. I think you'll be able to differentiate
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those two dysfunctions, go back and start thinking about the lat length test
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versus external rotation goniometry, and think about how those play out positive
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or a negative lat length test, restricted or normal external rotation. I think
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before you know it you'll have a shorter list of muscles that could be
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restricting this motion. Which means less release techniques, less lengthening
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techniques, and less mobilization techniques that you'll need, which means
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a more refined program, a more effective program, a more efficient program and
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hopefully better results. I'll talk with you guys soon.
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