Treadmill Performance Predicts Mortality | Hacker News Reader

Treadmill Performance Predicts Mortality

hopkinsmedicine.org

66 pointsforloop25 comments

I am really interested in how this is measured. I have found this info on free sources so far

"The FIT Treadmill Score, calculated as [percentage of maximum predicted heart rate + 12(metabolic equivalents of task) – 4(age) + 43 if female]"

And this from another interview.

"In addition to age and gender, the formula factors in peak heart rate reached during intense exercise and the ability to tolerate physical exertion as measured by so-called metabolic equivalents, or METs, a gauge of how much energy the body expends during exercise. More vigorous activities require higher energy output (higher METs), better exercise tolerance and higher fitness level. An activity such as slow walking equals two METs, compared with eight for running."

If anyone has access to the paper and could better show the algorithm I would be super thankful.

EDIT: I think I figured out more but still not positive about MET unless the 2 for if heart rate hit max walking and 8 for if heart rate hit max with running. [(Measured Heart Rate Max/(220-age))100 + 12MET - 4*age + (43 if female)]

So basically the closer your actual maximum heart rate when excersising vs your age estimated maximum heart rate[0] the healthier you are.

[0] http://www.runningforfitness.org/faq/hrmax

I'm confused though because as you increase your endurance your heart is able to get more oxygen to your body while beating slowing. For example the heart rate of a marathon runner's first mile might not look much different than you or I going on a walk.

They stress you to the point of maximal exertion. This will favor fit people for a couple of reasons.

1. The fitter you are the more experience you have working through the pain of maximal exertion and the closer you can get to your true max

2. The fitter you are the better shape your heart is in and the easier it is to break your age estimated max heart rate

When I was 25 I rode competitively for my university in grad school. Max heart rate prediction is 220 - age so my theoretical max was 195 but I routinely saw numbers above 200 and occasionally above 205 and a few times over 210.

Further the metabolic equivalent is what really does the correction. If your heart rate hit max at a brisk walk you don't get very many bonus points; if it hits max at a run you get a lot of bonus points (past your heart rate) and your score goes up considerably.

That's interesting. I always figured the max heart rate by age was just a recommendation. But you're saying the max heart rate actually decreases as you age? What would cause that?

So I guess it's good I can get 5 bpm above my age max but bad that a 6MPH jog for 5 minutes is all it takes?

My guess is that the heart is a muscle and just like other muscles it tends to not have as much output as you age.

I actually suspect that it has less to do with your heart and more to do with your fitness. People generally get less fit as time goes on and thus the target heart rates reflect that. I rode with one guy who was in his 50s and could still hit 190ish no problem (while outriding us college kids), mostly because he was monstrously fit.

If your muscles are able to do less as you age (and that I definitely believe!) then it's easy to see that it's harder to produce the same amount of power. As the power requirements on your heart decrease it slows down. So for a younger guy who can make 1000 watts peak his heart rate might be 210 to do so. An older guy might only be able to make 800 watts peak and have a heart rate of 180 for that amount of power.

you mention: "Further the metabolic equivalent is what really does the correction"

The formula given above MPHR + 12 x METS -4 x age +(female factor) is correct.

however it doesn't seem to NORMALIZE for METs as you indicate. what you imply is more of a ratio: MPHR / METs. This is not the case, so this "FIT" treadmill test metric does not care how easily you reach your MPHR, UNLESS, it is all variables entered at the moment of MPHR.

don't worry: METs help increase the score for O2 intake. see my below post.

If I'm reading it correctly, it's actually the higher your maximum heart rate is, when compared to your age estimate. If your percentage is over 100, it would give you a higher score, even as your number gets less 'close'.

Compare with:

Prognostic Value of Treadmill Exercise Testing http://circ.ahajournals.org/content/98/25/2836.long

Maximal Exercise Testing Variables and 10-Year Survival Fitness Risk Score Derivation From the FIT Project http://www.mayoclinicproceedings.org/article/S0025-6196(14)0...

Also, from the Christmas edition of the British Medical Journal (where somewhat serious articles with a funny side are a tradition):

*"How fast does the Grim Reaper walk? Receiver operating characteristics curve analysis in healthy men aged 70 and over"

(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3240682/)

"What does it say Moss, does it say I'm already dead?"

"Oh, no, that'd be terrible."

"Oh thank--" "It's Thursday."

"The results are in. Yep, you're mortal."

Does anyone have a link to the chart described at the bottom of the article?

http://www.mayoclinicproceedings.org/article/S0025-6196(14)0...

It'll cost you $31.50 to rent for 24 hours. Elsevier thanks you for your custom.

Or, hypothetically, an unscrupulous person could go to r/scholar, check the right sidebar for the link to libgen, and search by the DOI, which in this case is 10.1016/j.mayocp.2014.12.013 ...but I'm sure nobody here would stoop to such things.

Not sure if it's globally visible, but the paper is here:

http://www.sciencedirect.com/science/article/pii/S0025619614...

Figure 1 is the money plot. In short, FIT scores below 0 show survival percentages that drop roughly linearly from ~90% down to 25% at a FIT of -200. Above a FIT of 0, survival percentages rise roughly linearly to near 100%.

TL;DR: you want your FIT score to be better than 0.

FIT Treadmill Score = MPHR + 12(METs) - 4(age) + (43 pts bonus for being female).

Note if you are 50 years old male, your age docks you 200 points off the top! so you start at -200, then assume you "DO" reach your maximal heartrate (acc to "220-age" ) then you are still at -100 for mortality. Only your METs, can then push your FIT number to a value greater than zero (if the MET number is > 9).

Does anyone know what unit the METs are measured in for this "FIT" metric? wikipedia indicates MET values of activities range from 0.9 (sleeping) to 23 (running at 22.5 km/h or a 4:17 mile pace). I have never run at a 4:17 pace. So it is these elite athletes whose MET numbers (times 12) enable them to score so high on this "FIT" metric. The average joe will only get a MET around 7 i'd imagine, bringing the MET contribution to around 84 points only.

having said that, the survival curve FLATTENS out above zero "FIT" score. so elite/high METs contributions to the "FIT" score beyond zero will not necessarily increase survival, but it does imply less chance of cardio being cause of death.

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http://www.pdf-archive.com/2015/03/04/article/

Correlation is not causation. since this study is not experimental we can't assume that increasing your FIT score will improve mortality.

Completely correct.

"Correlation" and "causation" are spelled differently, and have different numbers of letters.

There are probably a ton of confounding variables at play here that aren't being accounted for.

damn straight. take this "paper" with a pinch of salt!

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