Increasingly, people are wearing smartwatches to track a variety of health concerns, from steps and heart rate to quality of sleep.

But in a new study published in the journal Sensors, researchers found that while the health information can be useful, it's often the result of algorithmic estimates rather than direct measurements of the body — and some outputs are more accurate than others.

"The most important takeaway is that not all smartwatch metrics should be interpreted the same way," said study author Adam Lepley at the University of Michigan School of Kinesiology.

"Some outputs are relatively close to what the device's sensor actually detects, while many others are estimates generated by combining sensor signals with proprietary algorithms, user characteristics and other assumptions. People shouldn't take these metrics at face value. In many cases, these devices are better suited to tracking trends over time, rather than as precise laboratory measurements."

Also, results may not be comparable across brands because manufacturers use different sensors, definitions and algorithms.

Body of Knowledge

The average American consumes 14,820 pounds of meat in a lifetime, or the equivalent of a large Minke whale.

Stories for the Waiting Room

Rockefeller University scientists report that three minutes of sprinting can have a bigger impact than 90 minutes of moderate running. They found that intense bouts of exercise dramatically reshape the molecular contents of the bloodstream, with more dramatic beneficial effect.

Doc Talk

Olecranon bursitis: Inflammation of the olecranon, the outside point of the elbow. It can be caused by nothing more than repeated pressure while leaning and resting your upper body weight on your elbows. Thus, its nickname: "student's elbow."

Phobia of the Week

Zelophobia: Fear of jealousy

Best Medicine

Girlfriend: When someone tells me I'm ugly, I get super sad and hug them.

Other girlfriend: Why do you do that?

Girlfriend: Because I know how tough life can be for the visually impaired.

Hypochondriac's Guide

Amnesic shellfish poisoning comes from consuming shellfish contaminated with domoic acid, a biotoxin produced by marine algae. Within 24 hours, symptoms can include diarrhea, abdominal cramps and vomiting. Within 48 hours, symptoms can include headaches, seizures and permanent short-term memory loss. Recovery is a few hours to a few days, after which you probably won't remember that you vowed never to eat shellfish again.

Listicle With a Twisticle

Little boys may be made of snips, snails and puppy dog tails, or so the nursery rhyme goes, while girls are sugar and spice and all things nice. But snails, tails, sugar and spice are all composed of basic elements.

Which means your body is, in fact, primarily composed of (by number of atoms):

— 62.91% hydrogen

— 24.003% oxygen

— 11.97% carbon for a total of 98.89%

The remaining elements are far less abundant. Nitrogen, calcium, phosphorus and sulfur make up another 1%, leaving just 11 one-hundredths of 1% for everything else, including a mere 0.00000000000000015259% radium, give or take.

That translates to about 7 octillion atoms (7,000,000,000,000,000,000,000,000,000), which sounds like a lot until you learn a single drop of water contains more than 5 sextillion atoms (5,000,000,000,000,000,000,000).

Observation

"Neurotic means he is not as sensible as I am, and psychotic means he's even worse than my brother-in-law." — American psychiatrist Karl Menninger (1893-1990)

Medical History

This week in 1983, David Vetter, the "boy in the bubble," underwent a bone marrow transplant operation in the hope that it could help him develop the immunity he had lacked all his life.

David was born with a genetic disease — severe combined immunodeficiency — that left him vulnerable to any infectious agent. He spent his life protected, but isolated, in a sterile plastic "bubble." The hope was that the bone marrow from his sister (four years older) would stimulate the growth of his immune system.

Doctors treated the marrow to eliminate potential pathogens and transferred it in a fluid through a vein into David's bloodstream. Unfortunately, it contained an undetected Epstein-Barr virus. By New Year's Day, David had a temperature of 99.5 F, indicating the onset of illness. Less than two months later, he died of Burkitt's lymphoma, a rare, fast-growing type of non-Hodgkin lymphoma that starts in B-cell white blood cells.

Cures for Boredom

In the 18th and early 19th centuries, European physicians used the tobacco smoke enema on drowning victims under the belief that tobacco smoke's warmth and stimulant properties could restart breathing and circulation.

The procedure involved using a leather bellows attached to a tube to pump tobacco smoke directly into the victim's rectum. Emergency kits with the necessary equipment were strategically placed along major waterways for public rescues.

Tobacco smoke enemas were abandoned when doctors realized nicotine was a toxic poison and likely harming or killing patients, but the practice may have provided inspiration for the longer-lasting idiom "blowing smoke up your arse" and its variations.

Med School

Q: Why do things taste weird after you brush your teeth, especially orange juice?

A: Chemicals in toothpaste, specifically sodium lauryl sulfate, which helps make toothpaste foamy, mess with your taste buds.

SLS suppresses tongue receptors that perceive sweetness while simultaneously breaking down the phospholipids (a kind of fat molecule) on the tongue that usually inhibit bitterness. Together, they accentuate bitter tastes while reducing perceived sweetness.

Curtain Calls

On June 20, 1991, Harry Collinson, chief planning officer for the Derwentside District Council in England, was supervising the demolition of an illegal structure built by Albert Dryden.

A BBC camera crew accompanied Collinson to film the demolition. Dryden produced an unlicensed handgun. Collinson asked the BBC crew to get a shot of the gun. Dryden took part by aiming the gun at Collinson and firing. Collinson was killed, and a BBC reporter and policeman were wounded. Dryden was subsequently convicted of murder and sentenced to life imprisonment.

To find out more about Scott LaFee and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

Photo credit: Amanz at Unsplash