The Skeptical Cardiologist has always had a fondness for push-ups. Therefore I read with interest a recent study that looked at how many push-ups a group of 30- and 40-something male firefighters from Indiana could do and how that related to cardiovascular outcomes over the next 10 years. The article was published in JAMA Network Open, and is freely available to access online. The British National Health Service pointed out that "The UK media has rather overexaggerated these findings." "Both the Metro and the Daily Mirror highlighted the result of 40 push-ups being 'the magic number' for preventing heart disease, but in fact being able to do 10 or more push-ups was also associated with lower heart disease risk," it pointed out. What Was Studied? The study involved 1,104 male firefighters (average age 39.6) from 10 fire departments in Indiana who underwent regular medical checks from 2000 to 2010. At baseline the participants underwent a physical fitness assessment that included push-up capacity (hereafter referred to as the push-up number, or PUN) and treadmill exercise tolerance tests conducted per standardized protocols: "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). Numbers of push-ups were arbitrarily divided into 5 categories in increments of 10 push-ups for each category. Exercise tolerance tests were performed on a treadmill using a modified Bruce protocol until participants reached at least 85% of their maximal predicted heart rates, requested early termination, or experienced a clinical indication for early termination according to the American College of Sports Medicine Guidelines (maximum oxygen consumption [V̇O2max])." The main outcomes assessed were new diagnoses of heart disease from enrollment up to 2010. Cardiovascular disease (CVD) events were verified by periodic examinations at the same clinic or by clinically verified return-to-work forms. These events were defined as incident diagnosis of coronary artery disease or other major CVD event (e.g., heart failure or sudden cardiac death). Here's the graph of the probability of being free of a CVD event on the y-axis with time on the x-axis. The black line represents those 75 firefighters who couldn't make it into double digits, the green are those 155 who did more than 40 push-ups. Participants able to complete more than 40 push-ups had a significant 96% lower risk of CVD events compared with those completing fewer than 10 push-ups. It is surprising that the PUN seemed a better predictor of outcomes than the exercise test. This should be taken with a grain of salt, because the stress tests were not maximal tests even though the investigators report at VO2max. The firefighters with lower PUNs were fatter, more likely to smoke, and had higher blood pressure, glucose, and cholesterol levels. What's Useful From This Study? You definitely cannot say that being able to do more than 40 push-ups will somehow prevent heart disease. The PUN is neither causing nor preventing anything. The PUN is a marker for the overall physical shape of these firefighters. It's a marker for how these men were taking care of themselves. If you are a 39-year-old fireman from Indiana and can't do 11 push-ups, you are in very sorry condition and it is likely evident in numerous other ways. The <11 PUN crew were a bunch of fat, diabetic, insulin resistant, hyperlipidemic, out-of-shape hypertensives who were heart attacks in the waiting. Push-ups Are A Great Exercise Despite the meaningless of this study you should consider adding push-ups to your exercise routine. Doing them won't save your life but it will contribute to mitigating the weakness and frailty of aging. Don't obsess about your PUN. I've always liked push-ups and highly recommend them. They require no special equipment or preparation. It's a quick exercise that builds upper body muscle strength, adds to my core strength and gets my heart rate up a bit. For some reason, my office in O'Fallon is always cold so several times during the day when I'm there I'll do 100 jumping jacks and drop on the carpet and do some push-ups in an effort to get warm. I don't do them every day, but the last time I tried I could do 50 in less than a minute and that has me convinced I will live forever! In my post on mitigating sarcopenia in the elderly, I talked about the importance of resistance exercise: Americans spend billions on useless supplements and vitamins in their search for better health but exercise is a superior drug, being free and without drug-related side effects. I've spent a lot of time on this blog emphasizing the importance of aerobic exercise for cardiovascular health but I also am a believer in strength and flexibility training for overall health and longevity. As we age, we suffer more and more from sarcopenia -- a gradual decrease in muscle mass. Scientific reviews note that loss of muscle mass and muscle strength is quite common in individuals over age 65 and is associated with increased dependence, frailty, and mortality. Source
