Push-up Exercise Capacity and Future Cardiovascular Events

[TomBAvoider]

This is a link to the full study, and it's interesting from many points of view. A few comments 

Association Between Push-up Exercise Capacity and Future Cardiovascular Events Among Active Adult Men

"Abstract

Importance  Cardiovascular disease (CVD) remains the leading cause of mortality worldwide. Robust evidence indicates an association of increased physical fitness with a lower risk of CVD events and improved longevity; however, few have studied simple, low-cost measures of functional status.

Objective  To evaluate the association between push-up capacity and subsequent CVD event incidence in a cohort of active adult men.

Design, Setting, and Participants  Retrospective longitudinal cohort study conducted between January 1, 2000, and December 31, 2010, in 1 outpatient clinics in Indiana of male firefighters aged 18 years or older. Baseline and periodic physical examinations, including tests of push-up capacity and exercise tolerance, were performed between February 2, 2000, and November 12, 2007. Participants were stratified into 5 groups based on number of push-ups completed and were followed up for 10 years. Final statistical analyses were completed on August 11, 2018.

Main Outcomes and Measures  Cardiovascular disease–related outcomes through 2010 included incident diagnoses of coronary artery disease and other major CVD events. Incidence rate ratios (IRRs) were computed, and logistic regression models were used to model the time to each outcome from baseline, adjusting for age and body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared). Kaplan-Meier estimates for cumulative risk were computed for the push-up categories.

Results  A total of 1562 participants underwent baseline examination, and 1104 with available push-up data were included in the final analyses. Mean (SD) age of the cohort at baseline was 39.6 (9.2) years, and mean (SD) BMI was 28.7 (4.3). During the 10-year follow up, 37 CVD-related outcomes (8601 person-years) were reported in participants with available push-up data. Significant negative associations were found between increasing push-up capacity and CVD events. Participants able to complete more than 40 push-ups were associated with a significantly lower risk of incident CVD event risk compared with those completing fewer than 10 push-ups (IRR, 0.04; 95% CI, 0.01-0.36).

Conclusions and Relevance  The findings suggest that higher baseline push-up capacity is associated with a lower incidence of CVD events. Although larger studies in more diverse cohorts are needed, push-up capacity may be a simple, no-cost measure to estimate functional status."

In the methodology section we have this for push-ups:

"For push-ups, the firefighter was instructed to begin push-ups in time with a metronome set at 80 beats per minute. Clinic staff counted the number of push-ups completed until the participant reached 80, missed 3 or more beats of the metronome, or stopped owing to exhaustion or other symptoms (dizziness, lightheadedness, chest pain, or shortness of breath)."

To me, this is somewhat unclear. It reads - to me - as if the idea was to complete 40 push-ups in 30 seconds. That means less than a second per push-up - that's a pretty brisk pace for a full push-up - a full push up would incorporate two stages, the move UP and the drop DOWN before you can move UP again; all this in less than a second? Btw., very quick push-ups are not the most challenging. It is much harder if you have to SLOWLY push up than if you push up explosively using momentum, and further, if you then have to use your muscles to SLOWLY get down controlling the rate of descent rather than using gravity. Meanwhile, with super fast push-ups, it is not really possible to control the rate of descent, and you are using gravity to just drop - much less exertion that way. 

The other thing that's unclear to me is the sensitivity of this test. What exactly are you measuring? If you take someone who is not used to doing push-ups, it is unlikely that the person in question will be able to deliver 40 chest-to-the-ground push-ups without training; in effect you are selecting for those who regularly do anaerobic exercise and training and incorporate push-ups into their regular exercise. Well, DUH. I mean, aren't you just saying "those who do anaerobic exercise/training regularly have better CVD health than those who don't"? In this case, the push-up test is merely a proxy or marker for a specific exercise status. 

But the sensitivity seems to me low. What if you have someone who does a lot of aerobic exercise, but not much in the way of push-ups - their CVD status is probably very good, even thought they'd fail this test. Meanwhile, you can have someone who constantly works out like many bodybuilders who could pass this test with flying colors who nonetheless have terrible CVD status (as many bodybuilders paradoxically have - see any number of them dropping dead from heart attacks). In other words, there is nothing that's particular to training your push-up muscles wrt. CVD health - it's all a marker, and a pretty fuzzy one at that. 

What is a more interesting question is whether there is an effect similar to what has been said about grip strength - what matters is your *un*trained grip strength, as that is a more accurate gauge of your physiological potential/health than a trained state that merely obscures the underlying condition.

Now I suppose these being firefighters, they are not exercise naive - isn't doing a set number of push-ups a requirement to get or stay on the job as a firefighter?

Any thoughts here? Can YOU do 40 push-ups in 30 seconds?

[Todd Allen]

Although it wasn't explicitly stated my expectation would be a metronome beat per movement up or down and thus a rate of 40 pushups per minute.  Seems much more reasonable to me. 

Clearly the test is imperfect, one can imagine a wide range of things that could impact pushup performance with minimal impact on cvd health such as injuries to wrists, elbows, shoulders or back.  My expectation is accurate measures of body fat %, resting pulse and blood pressure could better predict cvd risk.  The pushup test is appealing for not needing much in the way of equipment or expense.  But consumer grade pulse and blood pressure monitoring is very affordable and one can get a fair estimate of body fat % with a tape measure and scale weight.  I'd be interested to see how that stacks up against the pushup test and against the best measures of pulse, blood pressure and body fat.   I also expect for the roughly half of US adults that are prediabetic or diabetic that monitoring post prandial blood sugar could be a potent indicator of cvd risk and achieving stable moderate blood sugar is an important element of reducing cvd risk.

[Saul]

20 hours ago, TomBAvoider said:

But the sensitivity seems to me low. What if you have someone who does a lot of aerobic exercise, but not much in the way of push-ups - their CVD status is probably very good, even thought they'd fail this test

Yes.

For example,  I do vigorous aerobic exercise 30 minutes 6 days a week; my CVD health is great.  But I can't do a single pushup (rotator cuff sports injuries).

  --  Saul

[mccoy]

Yes, the push-ups proficiency level seems to have been adopted as a general qualitative proxy for a combination of aerobic plus resistance exercise.

Obviously, the conclusions are valid insofar as the proxy reflects accurtely the underliyng mechanistic principles. Which are?????

Proxy: Ability to keep the body rigid while doing brisk arm resistance exercise which imply some level of previous training and no upper-limb related injuries or inflammations....

Mechanistic principle: max VO2? tolerance to lactic acid? slow twitch fibers in upper arms?  Are they really the fundamental elements of CVD hazard?

[mccoy]

On 2/17/2019 at 2:07 AM, TomBAvoider said:

What is a more interesting question is whether there is an effect similar to what has been said about grip strength - what matters is your *un*trained grip strength, as that is a more accurate gauge of your physiological potential/health than a trained state that merely obscures the underlying condition.

 

That study to me appears too far-fetched.

Untrained grip strenght is a function among other things of genetic hand size and pattern of muscle and tendons insertions, plus the neurological genetic pattern (innervation and neurological recruitment of fibers), quantity and ratios of various muscle fibers....

How can the above genetic factors iunfluence CVD hazard? I can really find no logical answer to that.