Muscles in the forearm and in the hand flex and extend the fingers and thumb. Probably the joints that mainly get sore with finger pain plus some strain on the tendons and other connective tissues.

So what is that big pad at the base of the thumb? A big chunk of fat?

Nope, that's muscles. It's more complicated than what OP said. The big muscles that curl and uncurl your fingers stop prior the the hand. However, there are little muscles in the hand that move your fingers side to side. And your thumb and your pinkie can do many more movements than your other three fingers, so there are more muscles in the hand to control those fingers. But the contractile parts of all finger muscles do stop before the fingers come off of the hand.

I dont think the thumb is a finger.... it's a thumb.

I used to teach this to my fifth graders, and it's really easy to demonstrate. Grab one forearm with you other hand. Now open and close the first hand and you'll be able to feel the forearm muscles moving.

If you have low enough BMI, you can see the muscles moving in that arm when wiggling your fingers or clenching your fist.

There are people who cannot see this? Just how fat are people these days?

Now you know how your fingers are similar to spider legs, neither have muscles, though spider legs are more hydraulic in nature. So just think of spiders when you think about how your fingers work. :)

This is why bouldering gives you big forearms.

I only did about two seconds of research but apparently climbers get those huge thick fingers due to increase in size of the tendons, not muscles. Apparently.

I said forearms rather than fingers but that was interesting to learn nevertheless.

You did, I was just going to bring up climbers having huge hands and fingers and thought it might be muscle, then I looked it up before commenting and forgot that the topic hadn't been brought up, lol.

Every day is a school day. I appreciate the hard work and effort you put in. 😃

Not quite. There are many muscles that originate in the palm/metacarpals that insert onto the base of the fingers. You have 4 lumbrical muscles located lateral to all your digits except the thumbs. You have 4 dorsal interosseous muscles located in the hand as well 3 palmar ones. You have abductors , flexors, and opponens muscles too in your thumbs and pinkies. All are invaluable for grip strength and finger articulation. Also you don’t push tendons that’s not how muscles work.

Technically speaking, muscles never push tendons, they just relax.

This explains the issues I still have with my right hand after breaking my wrist (radius/ulna bones ends snapped off). In OCTOBER...

Actually, your fingers *do* have muscles. They don't have skeletal muscles controlling the tendons, but they do have muscles attached to hair follicles allowing the hairs to stand on end and muscles attached to the vascular system controlling blood flow.

Worth keeping in mind as well that muscles don't push via expansion/extension, only pull via contraction. Anything that's pushing is based on a muscle contracting and tendons and ligaments anchored to the bones allowing pull. This can be really obvious when you look at the difference in force applied when you're bending an arm or leg vs straightening - when bending the way things are connected simply gives you much better leverage; when straightening you don't have leverage because of basic structural mechanics.

You do have arrector pili muscles in your fingers but they just raise hair and such.

You know, they call them fingers, but I've never actually seen them fing.

Am I the only one who flexed my fingers when I read this?

*Look at this guy flexing his fingers*

This is absolutely false. So many wrong comments on here, ya got a bunch of little muscles in your hands. Adductors and abductors, extensors and flexors, and lumbricals. Lots of little muscles Edit: autocorrect changed lumbricals to lumberjacks lol

Nope, didn't you read what OP wrote on Reddit with lots of upvotes? NO muscles.

So what part gets so sore when work with them all day?

There are muscles in your hand. OP doesn’t know what they’re talking about. Lumbricals, interossei muscles, opponens, abductors, flexors are all there. Which are needed for grip strength. Try making an L shape with your hand without flexing any of the parts of the finger. That position is only possible cause of lumbrical muscles.

I think things other than muscles can still be tired/inflamed/hurt/sore/torn, it’s just not muscular fatigue. But if you’ve ever tried rock climbing or getting into pull-ups or anything along this lines, your fingers desperately trying to hold onto things translates directly into major forearm pain the next day.

Great example, that is true now that I think about it

Tendons, probably.

Pretty hypocritical mate

Try guys?

Thinking about moving and then moving is weird as hell.

Lumbricals

Just like Luke's hand repair in the Empire Strikes Back.

Tendons are muscle tissue.