Arms under chest in tummy time

my 5mo certainly can prop on his elbows during tummy time, but for whatever reason he is now refusing to. Unless there’s a toy in front of him that he can grab, he puts his arms out to the side then fussed (elbows still bent, not arms straight out like an airplane) & won’t bring them back under. He does this even if propped on something under his chest. I repeatedly move his arms back under for him, but if I don’t keep my hands on lightly on him like a boundary, he doesn’t hold the position.

Is there anything else I can be doing to help him? I’m really trying to get him to start pushing up on extended arms by doing baby planks to strengthen his arms. I hold his arms straight during the planks but he fights me. He just wants to grab whatever is in front of him even if it’s things he “can’t” grab like high contrast cards, a mirror, etc.

(On a similar note, he refuses to practice tripod sitting. He’ll push is arms back when I try to get him to bear weight & push off his feet)

He has mild hypertonia in his arms but with stretches we’ve done since he was 2mo, he’s actually pretty limber now

I know this can be so frustrating! I have a highlight about propping and pushing up. Prone Propping and Push Up
I found that being on the ball helped with this some. I also just switched things up and wouldn’t work on it all the time but would intermittently block the arms like you talk about doing. Also making sure that there are different items around on the floor that they might be interested in. Maybe consider bringing out the activity center so they have to reach up to hit the dangling toys.

In terms of tripod sitting, you almost have to block him some. So get him in tripod and you hover behind and around him so that if he pushes back you are there. The mild hypertonia is contributing to this some, but also the fact that he is figuring out how to grade his muscles. I’ve had some questions about sitting that I will try to address in one of my upcoming stories. Happy to come up with more ideas for you as well.

This is a great question. I like the ball idea above too.

Another idea is to maybe try positioning him differently so that his arms stay forward and you can give him a little more support through extended arms. Try placing him like this
(link below) over your leg. If he’s too far off the ground over your thigh try it over your shin. You can give him a little nudge by rocking his weight forward into his extended arms by shifting your leg a little. Let me know how it goes, happy to keep problem solving.