DexaFit visit

[NHAero]

On Tuesday I went to DexaFit Boston (actually in Cambridge) and got three tests - a Dexa scan, VO2 Max, and Metabolic (supposed to assess basal metabolism calorie requirement). I don't know how accurate any of their devices are and how well/often they are calibrated, but I found this to be an interesting experience and I hope the numbers I received aren't nonsense. Here's what I learned (or didn't):

VO2 Max
Because of my loss of nerve/muscle in my lower left leg, I had to use an AirDyne bike vs. the usual treadmill. If i do this again I'll bring my leg brace (duh, i forgot to) and my own toe straps since the ones on the bike were crappy and slipped and I had to pay attention to keeping my left foot from slipping out. They strap a mask on your face so they can measure O2 and CO2, and use an armband HR monitor (which I understand is less good than a chest monitor - next time I'll bring my Polar H10.) The way the test works is that a constant resistance is used and they start you riding at 35-40 rpm then every minute tell you to up that by 5 rpm. I stopped at the point where I couldn't raise my cadence above 60 rpm, and unfortunately I should have ridden a little bit longer to get complete results. There is only a tech there, and she is very good at getting you set up for the tests and running them, but info like this doesn't occur to her to tell you.

I watched the HR on the screen and i'm pretty sure I saw 178 bpm which I have never seen on my H10 (I'm 70). The results on the graph they gave me showed a max of 173 bpm. VO2 Max with 39.6 ml/kg/min, based on the weight I gave them, they don't weigh you. In season I'm a touch lighter, so maybe round up to 40. Greg Lemond is not shaking in his biking shoes But I think it's acceptable for my age, especially given that I just ride and don't do training (maybe I should some intervals?)

DexaScan
This surprised me. Most people would call me skinny at 140 pounds and 5'9". Based on a body weight of 143 pounds (I have no idea why this is different on their output from the 142 pounds I gave them, maybe the DexaScan table weighs me, and I was wearing light clothing?). My body fat % was 20.2%. Visceral (organ) fat was 0.76 pounds, or 2.6% of total fat. The results say I have 13.1 pounds of fat in my legs! This is the one result in this metric where I am over the average for my peer group! The most pertinent result for me and maybe for other PLers is that my Appendicular Lean Mass Index and my Fat Free Mass Index are Below Average. These metrics are lean mass based on my height. I do know that I have lost upper body muscle, and this has been exacerbated these past 4 months with tendinitis or similar in my shoulder. I've started PT for the shoulder recently and also found a trainer i like and have started the long path towards building strength. FWIW my BMI is 21.

My bone density T Score was positive which surprised me because the one scan I have had at the hospital diagnosed me with osteopenia. I'm going to ask my PCP about this at the next appointment.

Resting Metabolic Rate
If I do absolutely no physical exertion this is 1,703 kcal/day. Not much more info on this test. I'm not getting fatter so whatever I'm eating seems to balance out OK with my level of exertion as far I can see.

I'm open to anyone's contributions about what any of this means and what I should do with it. My conclusions are what I knew about getting my shoulder working right, and then working to build upper body strength. But I might look into some occasional bits of interval training to maintain VO2 Max.

Finally, this is a national chain so many people would have access to the same testing. I got a package deal and paid $291.

[kppolich]

No hiding from the DEXA scan.

[benb]

Your #s are exceptional for a 70 year old... stuff to be proud of.

[NHAero]

Originally Posted by kppolich

No hiding from the DEXA scan.

That's funny!

[NHAero]

Originally Posted by benb

Your #s are exceptional for a 70 year old... stuff to be proud of.

Thanks Ben, but I think only in comparison with my American peers who are working the remote while eating Mickey Ds

[Likes2ridefar]

Interesting; thanks for sharing the experience!

[mjf]

Originally Posted by NHAero

I watched the HR on the screen and i'm pretty sure I saw 178 bpm which I have never seen on my H10 (I'm 70). The results on the graph they gave me showed a max of 173 bpm. VO2 Max with 39.6 ml/kg/min, based on the weight I gave them, they don't weigh you

Caveat: Optical arm bands are sub standard and are not as accurate or precise as the gold standard of an EKG or Polar H10. If it's a random spike in reading it's not a ton to worry about. Outside of that speaks to the quality of the equipment and the interpretation from the person running the test.

As a physiologist, there's some tolerance in your heart rate, but hitting 178bpm (118% of your predicted max of 150) is out of the range of what I'd consider safe and I would have stopped your test before you got close to that number.

Broad HR things when equipment is known to be working, accurate, and used correctly.

• Outliers should be filtered out from the report as abnormalities in readings.
• Consistent out of bounds numbers generally indicate 1 of 2 scenarios
  1. Equipment is failing to read properly and may need to be resecured, relocated, or replaced.
  2. HR is actually going that high above predicted max
     • **Stop test**
     • Sending you to the hospital if you have any symptoms
     • Otherwise cardiologist for a proper workup

Complaint: They don't weigh you? For a measure that relies on weight as a defining factor? What?

As someone in the field, reading some of their reviews and your experience, that place sounds like a mess.

[weiwentg]

Originally Posted by mjf

...

As a physiologist, there's some tolerance in your heart rate, but hitting 178bpm (118% of your predicted max of 150) is out of the range of what I'd consider safe and I would have stopped your test before you got close to that number.

Broad HR things when equipment is known to be working, accurate, and used correctly.

• Outliers should be filtered out from the report as abnormalities in readings.
• Consistent out of bounds numbers generally indicate 1 of 2 scenarios
  1. Equipment is failing to read properly and may need to be resecured, relocated, or replaced.
  2. HR is actually going that high above predicted max
     • **Stop test**
     • Sending you to the hospital if you have any symptoms
     • Otherwise cardiologist for a proper workup

...

220 minus age is an estimate of the average max HR for a given age.

First, it's not the best estimate, there are other formulas out there.

Second, individual max HRs vary. After all, it's the nature of averages that some people will be above average and some will be below. A few will be way above or below.

Third, the sample of people they based that formula on was, I believe, drawn from the general US population. That is, they're generally not athletes and aren't used to pushing themselves to the max. That introduces the possibility of measurement error. I suspect that in general, athletes are going to be above the max HR formula.

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?

[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.

[Louis]

Originally Posted by mjf

As a physiologist, there's some tolerance in your heart rate, but hitting 178bpm (118% of your predicted max of 150) is out of the range of what I'd consider safe and I would have stopped your test before you got close to that number.

In a related matter, I have a stress test on Monday to see if they can tell me anything about the > 200 bpm I saw while rowing the other day. It occurred immediately after I completed my row, where my peak HR was 171 bpm. (I'm guessing that my nomal max HR is in the low to mid 170's)

I'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?

(Since the "problem" row, I've done 5 additional workouts, and trying to be careful limited myself quite a bit. My max HRs were 150, 157, 155, and 157, with no problems.)

[Dave]

I'll soon be 71 and I can still hit 178 bpm, but I try not to. Still 135 pounds at 66 inches tall. I do enough weight lifting so I don't have a cyclist body. I recently got back into doing chin-ups and it revived my chest muscles pretty quickly. Body fat is down, based on the midsection muscle that I've exposed. I'm just starting to use perfect amino brand amino acids to see if it helps reduce recovery time.

In the summer, my regular ride is 52 miles with 3600 feet of climbing to 8000 foot elevation. I only do it every other day to allow adequate rest. This winter I did a lot of 35-40 mile routes with around 2000 feet of climbing and did up to 6 days in a row to take advantage of limited good weather.

I'm trying to get the most out of my old body.

[superbowlpats]

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.

That formula seems to be a better estimate, maybe? Using it my max would be 170 (I'm 64). Measured during racing it is 182, and during a CX race I will typically be above 170 for 30+ minutes.

But then again I know a guy in his 50's who is a very good racer and his max is only 155.

[Spaghetti Legs]

The DEXA is a very cool test. I’m curious in your case if the percentiles they quoted you were age matched, whole population matched? At any rate, it’s not terribly surprising that a skinny cyclist would have below average muscle mass. Everyone will lose muscle mass with aging, so it will be important to get back into the strength training(with flexibility exercises too!) to maintain the muscle mass and mobility as you get older. The visceral fat numbers are really good - higher levels of that are related to fatty liver, insulin resistance and diabetes.

I did a VO2 max test last year and my max HR was higher than the simple calculated prediction as well.

The resting metabolic rate is a pretty simple calculation with age, height and weight but the body fat # from the DEXA will make it a little more accurate.

I was in Cambridge visiting friends last week and the weather was atrocious; hope it was better for you! Despite the weather we had a great time.

[weiwentg]

Originally Posted by superbowlpats

That formula seems to be a better estimate, maybe? Using it my max would be 170 (I'm 64). Measured during racing it is 182, and during a CX race I will typically be above 170 for 30+ minutes.

But then again I know a guy in his 50's who is a very good racer and his max is only 155.

Yeah, my understanding is that some people have higher max HR but lower stroke volume (the volume of blood the heart can pump with each beat), and some have the reverse. To some extent, there's two roads to the same destination.

But still, that formula is an estimate of the average max HR for a given age. We would generally assume that the distribution of max HRs is normal, centered on the prediction. Entering my age into that formula gets 183, so they're assuming that people fall in a normal-ish distribution around that. Most people are close enough to the average. Some people are not that close to the average. I recently got up to 189, which is not terribly far off. So, it's not unreasonable for you to use the average max HR as your own predicted max HR, but again, you may be far off the prediction and you will need to watch for that.

Realistically, if there is some physiological limit to max HR or max stroke volume, the distribution of max HRs may not exactly be normal. I generally use regression for inference, not for prediction. There may be more advanced methods to handle cases like that. But this is likely good enough.

[NHAero]

Originally Posted by mjf

Snip

As someone in the field, reading some of their reviews and your experience, that place sounds like a mess.

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.