DexaFit visit

[mjf]

Originally Posted by weiwentg

I appreciate that you're a physiotherapist and not a cardiologist with an exercise testing lab and experience with older adults. So I can understand why you would not want to push someone beyond the average max HR for their age. The thing is, if you're not pushing them to their max, is there any point to measuring VO2max in the first place?

Your phrasing is throwing me off a bit here, but I think you're misunderstanding what I do.

I'm a physiologist, not a physiotherapist. These are two very different roles. As a physiologist, I am a scientist who works with people performing measurements to assess bodily function, for me, the cardiopulmonary system.

I work mainly in clinical research in a exercise lab and have extensive experience testing older adults in clinical cardiac testing. When I previously worked on the clinical cardiac side, I was the person who performed and interpreted the results of your cardiac or pulmonary stress tests prior to them being sent to a physician.

Cardiac stress testing

In a clinical cardiac environment 85% of max HR is considered to be diagnostic and where we'd typically expect to see heart abnormalities to make themselves known. In the clinic that I previously worked at, our cardiologists did allow tests to continue the testing past 85% to see if any abnormalities did manifest at a higher HR. Again, this only happened because it was in a clinical environment where the patient would be safe even if things happened to go sideways.
But, I'm not a fan of pushing older adults beyond 85% without having them hooked up to an EKG and having a clinical support staff for patient safety.

VO2max testing

To the average person VO2max is great at telling us about your overall health, because you're looking at the bodies ability to consume oxygen and produce energy. Most people aren't getting a VO2max for anything besides seeing a big number (me included), and that's obviously okay too!

On the measurement side, VO2max is the max sustainable amount of O2 that your body can consume during a maximal effort.

If your bodies ability to consume oxygen is impaired (low VO2) it may suggest a wide variety of issues such as reduced mitochondrial health (number, size, mutations, etc), impaired gas exchange or ventilation, reduced cardiac output, or a ton of other issues. During VO2max testing we are only getting into the what is happening by measuring VO2, and not the why, as that's a different type and part of testing.

Is there a point of VO2max testing?

In general I think testing and screening gives some peace of mind that everything is working as it should. In the small chance that you do have an issue, like an undiagnosed asthma, testing is one step that can lead you to being healthier and stronger in the long run.

Originally Posted by NHAero

I think the formula someone here posted in another thread a while back (211-0.64xAge) may be more accurate for me. It yields 166 bpm and I have seen low to mid 160s on my H10. I hit 161 riding with Sparky33 a few weeks ago.

Max HR is of course very individual, and in the context of athletic people, that can be a much wider range than the average. 220-age is used for the sake of simplicity in most cases.

Originally Posted by Louis

II've read that for stress tests they typically go to (220 - age)x85%. In my case that's ~135 bpm, which IMO is practically useless if I'm trying to see if I can duplicate something that occurred at 171 bpm. Unless they can see things at much lower HRs that allow them to predict what will happen at much higher HR, I'm concerned that the test won't tell me much.

>>>> How likely is it that they'll let me go well above 135 bpm?

85% is diagnostic and generally you're going to see most problems come up by that point, but that's obviously not always the case. As I mentioned above, Dr.'s have allowed us to continue past 85%, until the patient requested to stop or if there was a safety concern.

You'd have to chat with your cardiologist to determine whether it's reasonable or safe to continue to a higher HR during testing.

At the end of the day, a lot of these things are about liability, and the Dr. is the person to make those decisions since they'll be the person accepting responsibility if anything were to happen.

Originally Posted by NHAero

I'm beginning to think this is true. They didn't email me one of the three test PDFs, and one that they did email was all zeros for the values. Now I learn that there are different "corrected" calibrations for the DXA machines and if the machine uses the NHANES calibrations it over-estimates body fat % by 5%. I was pretty flabbergasted by the fat numbers they gave me, and particularly the fat number in my legs.

It's very hard to get info from this particular company, you can't get a person by phone, so it's all by email. I'm going to see if there's a more reliable test center where I might duplicate these tests.

My concern initially came from looking at the Dexafit Boston's instagram where they're making posts about low body fat % "records" as if that's something that indicates a healthy individual.

https://www.instagram.com/p/CuHkVvkNoMt/?hl=en One of the more recent posts that just leaves me a bit aghast because it's sending the completely wrong message about body composition and fats role in our health. This type of perspective alone would send me running in the opposite direction.

I'd do some more digging, but there's essentially no information on their website describing anyones background at the company to justify why this type of testing is important. Lots of the information is lacking specificity, and in general isn't satisfactory in my opinion.

https://www.dexafit.com/faq

Originally Posted by dexafit

A big part of what we do is help you hold yourself accountable. So we suggest you retest with us three months after your first visit. This way you’ll be motivated to improve on your numbers. We’ll help you determine how often you should return based on your results.

Their answer to how often you should be retested is counter to the recommendations of the international atomic energy agency, which specifically cites self referred sports clinics as problematic.

https://www.iaea.org/resources/rpop/...al%20exposures.

» Is there an upper limit on the number of DXA scans that can be performed on a person?

No, provided that each individual scan is medically justified.

There is no upper limit on the number of scans that can be performed, since there is no dose limits in the case of medical exposures. Instead, the radiation exposure for each patient and each scan must be justified in terms of the risk and benefit. The risk increases with the number of scans. If a number of repeat scans are required then the justification process must show that the benefit outweighs the risks for the total number of scans required. In addition, it must be borne in mind that DXA will not be sensitive to the small changes in bone density typically seen over short time periods. The real problems in this area arise when the justification is not strictly medical in the individual case involved. This may arise in unapproved screening programmes, sports clinics or with self-referral. In such circumstances special attention needs to be given to the justification protocol."

As far as finding testing for yourself moving forward, you're in a good part of the country to jump on any number of clinical trials at one of the many hospitals or universities who have programs related to physiology and have labs themselves. A few universities with physiology labs that I'm aware of in the Boston area

UMass Amherst
UMass Boston
UNH
Tufts
Springfield College

Some programs will offer testing for a fee if done outside of a research study, but sometimes there'll be a research study if you're lucky that'll have testing as a component. Not as convenient as going whenever you want, but you'll be working with a team whose main concern is getting the most accurate information possible.

[ridethecliche]

It’s generally frowned upon to trigger an arrhythmia and not be able to do something about it. I doubt they were acls trained or had a crash cart handy.

Pretty wild if you’re testing older athletes. Not common for endurance athletes to develop afib, though that’s usually an issue when your RHR lives on the super low end iirc.

I think lactate threshold HR is a more useful metric for older endurance athletes. I doubt you spend as much time in your VO2max range on the bike since it’s way more taxing and will hinder recovery.

Anyway. Not my area of expertise etc etc.

[m_sasso]

I know GCN, however he is doing it to, you might find his testing and progress interesting. https://www.youtube.com/watch?v=YIEjavvzCfU

[Louis]

Originally Posted by mjf

85% is diagnostic and generally you're going to see most problems come up by that point, but that's obviously not always the case. As I mentioned above, Dr.'s have allowed us to continue past 85%, until the patient requested to stop or if there was a safety concern.

You'd have to chat with your cardiologist to determine whether it's reasonable or safe to continue to a higher HR during testing.

Thanks for taking the time to reply - that's helpful.