Any exercise physiologists in the house?

[Neil]

Ok chaps, riddle me this - hardware issue or Neil issue?

Here's todays long, slow run (https://www.strava.com/activities/521749547) (featuring an initial 10k, then some sightseeing, then me eventually running on to hit two hours/a half marathon distance):

https://c2.staticflickr.com/2/1614/25904006516_101c1db090_b.jpg

This is showing SMO2, essentially the oxygen saturation in the muscle, in this particular case my right calf. Here are the traditional metrics:

https://c2.staticflickr.com/2/1540/25809134522_39518e4ce6_b.jpg

As I said at the top, initial 10k then some dicking around, as you can see.

What I'm wondering about is the first quarter of an hour:

https://c2.staticflickr.com/2/1547/25629339370_ffa3c20030_o.png

Which (if accurate) shows my SMO2 trending down very sharply pretty much as soon as I set off, hitting ~30%, then slowly coming back up. This is repeated in another run I did in January:

https://c2.staticflickr.com/2/1662/25301188853_61ef3a03a4_o.png

It's a shorter run so less compressed, but you have the time stamp at the bottom. The whole run actually follows a very similar pattern:

https://c2.staticflickr.com/2/1496/25297193104_aeb52763fe_b.jpg

Ultimately my question is are these graphs an accurate representation of what my body is doing (start from cold, massive drop in SMO2, eventually comes back up during exercise) or is the sensor likely to be borked?

If the former this indicates that it's essential for me to warm up for at least 15 minutes before a race, and also might explain why I have a "3k of pain" at the start of every run I do, during which my legs feel like sticks, but then come back to me after (strangely, or maybe not so strangely) 15 minutes of running.

If the latter then I need to get a new unit I guess.

Over to you, Internet experts!

[malcolm]

First off take my response with a massive dump truck load of salt.
If you are talking about oxygen saturation in a given muscle, in this case I assume your calf, I don't think you can extrapolate that data to the body overall. Blood flow with shift based on the needs of various capillary beds. It would not surprise me if flow decreased in the calf at the beginning of a run especially if you start off hard as larger muscles groups are getting initiated and demanding increased flow. As you reach steady state, working pace and heart rate you may see flow increase in some of the accessory groups.
If this is complete nonsense please forgive me as I'm reaching way back to undergrad and grad physiology and well thats been a while and with the physiology of the brain being what it is my rememberer may not be as good as it once was

[illuminaught]

^ definitely can't extrapolate to whole body.

How did you measure it. Oxygen tension is usually a direct measure... Did you puncture your calf ;)?

[Neil]

I used NIRS:

http://www.dcrainmaker.com/images/2016/01/IMG_4926_thumb.jpg

http://www.dcrainmaker.com/2016/01/insight-depth-review.html

[numbskull]

I hesitated to respond to this but decided there was a small chance this could be something important so here you go.

First, the device looks like a glorified high power oximeter and percutaneous oximeters often give inaccurate readings for all sorts of reasons so quite possibly this all is nothing. That said, it sounds like you think you have long standing symptoms that fit the data and suggest a possible muscle perfusion problem that improves during exercise and is not limiting (since you can complete a marathon).

The pattern of symptoms and test data suggesting initial under-perfusion that improves during exercise is not unusual in patients with mild large vessel vascular disease. Typically this would be atherosclerotic and related to HTN, DM, and smoking. I'd not expect those people to be able to run a marathon, however.

There is a form of congenital large vessel vascular disease that might act like what you are showing/experiencing. That would be a mild or moderate aortic restriction. Most commonly that would be from a condition called aortic coarctation. This usually results in high blood pressure (at least in the right arm) and a heart murmur although the milder the condition the less reliable these signs are. Even in mild forms it can be important to diagnose since it may be associated with weakening of the proximal aorta and increased risk of aortic dissection (particularly during exercise). Less commonly people can have a congenital malformation/stenosis (or acquired narrowing after blunt abdominal trauma) of the abdominal aorta. In both situations blood pressure to the legs is lower than it should be. As BP raises during exercise perfusion improves and symptoms subside.

Odds are you don't have this, but a GOOD physical exam including listening carefully (bare chest, quiet room, experienced MD) for a heart murmur (including using the stethoscope in your left arm pit and upper left back), accurately measuring BP in BOTH arms and in a leg (this means not a cuff over a shirt and the use of an appropriate sized leg cuff +/- using a doppler), and listening to your abdomen for bruits would go a long ways towards eliminating the diagnosis. A formal non-invasive arterial study might or might not (particularly if mild) pick it up.....although such a study, if done with exercise, should confirm your oximeter findings. An echocardiogram can be used to look for coarctation........but tends to be operator dependent and somewhat unreliable. The gold standard is a CT angiogram or MRA/MRI of the thoracic aorta.....which involve dye and cost plenty.

So there you go......a lot more, I'm sure, than you want to hear or think about.
But again, if you have a mild aortic coarctation it would not be the first one missed into adulthood, it might present as you describe, and it certainly would be worth knowing about so you might want to discuss the possibility with your MD.

[Neil]

Well, that would be sub-optimal.

I checked synchronisation of radial and femoral pulses (on the advice of a friend who is a junior doctor) and as far as I can tell they're all firing at once.

It's hellish getting a doctors appointment here due to our current government doing their damnedest to destroy the NHS, any other simple tests I can do to work out whether I need to get a private appointment?

[numbskull]

Your best bet is probably just to make a routine NHS appointment and wait.
If you have an obstruction (and odds are you don't) it likely has been there all your life, is obviously fairly mild (given your ability to run long distances) and any short term risk from it is very, very small.

The problem is that when a vascular obstruction is mild it may not have much in the line of findings on physical exam and only become significant as blood flow tries to increase during exercise. A GOOD exam (not easy to get these days) is helpful since if it finds abnormalities such as a murmur or discrepant BP arm to leg the likelihood of disease increases.........but the lack of findings does not rule out a mild issue that might cause symptoms with exercise.

In this country most MD's would likely just bite the bullet and do a MRA to settle the question. Alternatively, you could do a formal non-invasive arterial study (NIAS) WITH EXERCISE (the standard NIAS for more severe disease is done only at rest). This test just involves accurate simultaneous BP measurements and vascular wave forms of both arms and both legs before and immediately after treadmill exercise. If your leg symptoms are from restricted blood flow the latter measurement should be abnormal..........in which case the next step would be a MRA (MR-angiogram). One other caveat to keep in mind, BP with a coarct can sometimes be reduced in the left arm so the "normal" reference BP number used when looking for a coarct is the RIGHT arm.

Again, all this is predicated on your symptoms.....not the new fangled oximeter data. You face an uphill battle sorting this out because your functional class is good (most doctors will mistakenly assume if you can run long distances everything must be fine), your own inability to tell whether what you feel in your legs is the same as others feel or something abnormal (since if it is a coarct you will have had it all your life and not know anything different), and the abnormal "test" you've got involves a technology that is new and unstudied for this condition. Given what you describe I think it worth checking eventually but I'd not obsess or worry too much over it in the meantime since most likely you don't have it.

[soulspinner]

One of the reasons I get on this board so often is because I almost always learn something.

[jimcav]

It mirrors my "empty mile" feeling--which as I hit 40 (now 46) takes more like 15-20 minutes to resolve

Now, are you 20? your HR seems WAY high for what would be a LSD run?

[Spdntrxi]

I use the cycling version and see a drop at the start as well.. I think you just need to warm up


Sent from my iPhone using Tapatalk

[Neil]

It mirrors my "empty mile" feeling--which as I hit 40 (now 46) takes more like 15-20 minutes to resolve

Now, are you 20? your HR seems WAY high for what would be a LSD run?

I am 40 in a couple of months

[flydhest]

For those with actual knowledge, if the readings are correct, is it consistent with those of us who need a long time to warm up before putting in a real effort?

[benb]

I am 40 in a couple of months

I am a crap runner, super crap, but I'll be 39 in a few months and my HR is even higher running, and like I said I am terrible. Really really poor cadence and I barely get down to 9 minute miles but I'll be in the 170s at least in the summer. Longest I ran last summer was about 5k.

My threshold HR is way up around 170 cycling.

It doesn't seem to matter.. it's always been about that. (It's maybe dropped 2-3bpm since I was 25) Doesn't necessarily help me or hurt me. Nothing has ever come up on any of my physicals. I've and an EKG or some other heart workup at one point as well in my late 20s when I was racing, they didn't find anything.

[jimcav]

I am 40 in a couple of months

that looks like near 85% of Max HR, which is not close to what zone you should do for a long slow run

[benb]

that looks like near 85% of Max HR, which is not close to what zone you should do for a long slow run

Isn't that only if you were going off 220-Age?

[Neil]

This is (the very edge of) aerobic threshold for me:

https://c2.staticflickr.com/2/1452/25872354892_6ea1315c7c_b.jpg

(taking out the initial ramp I'm averaging around 178 for most of that 5k).

[giverdada]

i don't know anything about your data or those weird numbers, but that's a killer 5k! sweet. and, i'm 35, and i think my strava file would parallel your numbers for a training/tempo 5k. my long run pick-ups sections dip into that pace, and my heart rate averages 165-168 during those pick-ups. nice.

[numbskull]

It seems very unlikely to me that you would be able to maintain that pace from the outset (even with a preceding warm up) if you had blood flow problems to your legs sufficient to cause symptoms and low O2 sat readings.

If you look at your HR data it rises gradually in response to your pace (which is steady and high from the start).
If you had a circulation problem of the degree the initial data suggested I'd think you would need to increase your HR (and thereby cardiac output) significantly before your legs would receive enough blood to let you go fast. Your peak speed would also be impaired to some degree.

I suspect the O2 sat monitor is not giving an accurate initial reading .

[Neil]

Ok, that's reassuring.

One data point that might help here I have been thinking was ambient temperature - it was ~3 degrees centigrade when I left the house, which for the benefit of time travellers and Americans would be ~37 degrees F.

Total guesswork on my side, but the device measure muscle oxygenation by shining an LED laser into the calf, would said calf have dramatically reduced capillary blood flow in response to the cold, and only increase it again when body temp got back to/beyond a certain point?

i.e. I needed a very literal warm up period?