Browse evidence-based analysis of health-related claims and assertions
Even though the triceps muscle only straightens the elbow, it still turns on when you twist your forearm — your body uses it for something other than just elbow movement.
Descriptive
Even when you’re just bending your elbow without twisting your hand, the muscle that normally turns your palm down still turns on — maybe to balance out other muscles that are pulling the wrong way.
When you bend your elbow and twist your forearm at the same time, your biceps work harder, but the muscles on the side of your arm work less — your body doesn’t just turn muscles on or off the same way every time.
The more osteocalcin in the blood of older adults with diabetes, the weaker their hand grip tends to be — and this pattern gets stronger as levels go up.
Correlational
In older women with diabetes, higher levels of a bone protein called osteocalcin are more strongly linked to weak hand grip than in men — especially when levels are above 15 ng/mL.
People with diabetes who have more osteocalcin in their blood tend to have weaker hand grip, especially women, but we don’t know if the hormone causes weakness or if weakness changes the hormone.
Your bicep gets stiffer as you bend your elbow — but only if your palm is up or sideways. If your palm is down, it gets looser the more you bend.
As you bend your elbow more and more, your forearm muscle gets looser — no matter if your palm is up, down, or sideways.
When your palm is facing down and you bend your elbow slightly, your forearm muscle (brachioradialis) works harder than when your palm is up — it’s like your body uses this muscle more to help when your hand is in a 'handshake' position.
When you bend your elbow with a light weight, your bicep works hardest when your palm is facing up and your elbow is halfway bent — and it works least when your palm is facing down.
Just asking older adults if they have trouble lifting, reaching, or gripping can help predict who’s at higher risk of dying from non-heart causes years later — it’s a simple way to spot hidden risk.
Quantitative
People with weak arms don’t die right away — the risk of dying goes up only after 5 or more years, which means it’s tied to slow aging, not sudden sickness.
Some older adults have weak arms but can still walk fine and think clearly — this means arm weakness isn’t always just a sign of overall aging or disability.
Having weak arms doesn’t make older adults more likely to die from heart problems — it’s linked to dying from other things like getting sick, not eating enough, or falling.
Older adults who have trouble using their arms to lift, reach, or grip things are more likely to die from causes other than heart disease over the next 20 years, even when you account for other health problems.
Your bicep works best at different elbow angles depending on whether your palm is up, down, or straight — it’s strongest at 45° if your palm is down, and 60° if it’s up.
Even when you're not trying to bend your elbow, the muscle on the outside of your forearm feels stiffer if your palm is facing up than if it's facing down or straight ahead.
No matter how you turn your hand, the muscle on the outside of your forearm gets less stiff the more you bend your elbow.
When your palm is up or straight, your bicep gets stiffest when your elbow is bent at 60 degrees — but if your palm is down, it gets less stiff the more you bend your elbow.
When your palm is facing down and you bend your elbow with a light weight, the muscle on the outside of your forearm works harder than when your palm is up.
When you bend your elbow with a light weight, your bicep works harder if your palm is facing up than if it’s facing down or straight ahead.
Squeezing hard might tell us something about how your wrist bones are built inside, but we don’t know yet if squeezing actually changes the bones.
How dense and complex your wrist bones are depends more on your bone’s internal structure than on how tall or heavy you are.
Even though people use one hand more and squeeze harder with it, their wrist bones don’t look noticeably different between the two hands—so using one hand more doesn’t make the bones look different in a big way.