DM a group with my friends and my friend is a 9th Lv Dwarf Ranger/1 Lv Rogue Multiclass and he wanted to jump across a 20 ft. gap. He has a Str score of 13 which means he can jump 13 ft. with a 10 ft. running start using long jump rules. He argued that because he Expertised into Athletics, giving him a +9, he could attempt to kick off a wall to make the other 7 ft. I told him kicking off of a wall mid jump would be an Acrobatics check but I was fine with him attempting it. He thought kicking off the wall mid jump would be Athletics, so first question would be: Kicking off a wall mid jump, Athletics or Acrobatics?
2nd he Argued that because he had a +9 into Athletics from Expertise he could roll Athletics to attempt to jump the 20 ft gap because he has trained so much into Athletics. I was fine with it, but the DC would be relatively high due to it being out of his capabilities. His movement speed max is 25, meaning with a 10 foot running start, max distance he could jump would be 15 with an Athletics check. I ruled he wouldn't be able to make this jump, but he could attempt with a near impossible success chance, DC 25-30. Second question would be: How would you rule this situation?
Would increasing your movement speed increase your jumping distance? Was another topic brought up, as stated your jump distance is equal to your Str score given you have 10 ft. to run and jump and each ft. traveled jumping is equal to a ft. of movement meaning you cannot jump farther than your movement would allow you.
Long Jump. When you make a long jump, you cover a number of feet up to your Strength score if you move at least 10 feet on foot immediately before the jump. When you make a standing long jump, you can leap only half that distance. Either way, each foot you clear on the jump costs a foot of movement.
If he is doing a 10ft run up, he would only have 15ft movement left so could not make it across even if he had a Str of 20.
Other than that, we are in the realms of DM fiat, rule of cool, and general homebrew. I know many DMs would allow a check to try something like this, with a fairly high difficulty and the risk that, on failure, the PC would not make it, fall and take appropriate damage.
Yea exactly, i was telling him that with a movement speed of 25 ft. and needing a 10 ft. running start the max he could clear would be 15, which would be feasible even with a 13 Str with a 20 ish DC.
What about the last question, if say he used Zephyrs Strike and had a movement of 55 ft. now, could he then jump 45 ft. with the 10 ft. running start?
If he had a strength score of 45, sure. With a strength of 13, he can jump 13ft RAW, and maybe a little extra with a clever description and a good roll at the DMs discretion.
Oh look, a player trying to use "rule of cool" to circumvent rules that are hard and fast. Tell the player "no".
To be fair, it sounds more like a player proposing an improvised action to his DM and asking for advice on whether/how it would work.
However, even if he is using the rule of cool, there's nothing wrong with doing that. It can be a lot of fun to leave the rules as rough guidelines and just enjoy yourself. Not everything needs doing inside the strict written rules, especially on a game where it specifically allows the DM to change and improvise things as and when they wish.
DM a group with my friends and my friend is a 9th Lv Dwarf Ranger/1 Lv Rogue Multiclass and he wanted to jump across a 20 ft. gap. He has a Str score of 13 which means he can jump 13 ft. with a 10 ft. running start using long jump rules. He argued that because he Expertised into Athletics, giving him a +9, he could attempt to kick off a wall to make the other 7 ft. I told him kicking off of a wall mid jump would be an Acrobatics check but I was fine with him attempting it. He thought kicking off the wall mid jump would be Athletics, so first question would be: Kicking off a wall mid jump, Athletics or Acrobatics?
2nd he Argued that because he had a +9 into Athletics from Expertise he could roll Athletics to attempt to jump the 20 ft gap because he has trained so much into Athletics. I was fine with it, but the DC would be relatively high due to it being out of his capabilities. His movement speed max is 25, meaning with a 10 foot running start, max distance he could jump would be 15 with an Athletics check. I ruled he wouldn't be able to make this jump, but he could attempt with a near impossible success chance, DC 25-30. Second question would be: How would you rule this situation?
Kicking off a wall fights gravity and requires strength, thus it is an athletics check in my opinion. Most physical checks are athletics when it comes down to it, they're rarely acrobatics.
You can never jump further than your movement speed. This is a function of ingame time. Assuming that the jump distance would not violate the movement speed limitation, I would give this a moderate difficulty of 15 DC vs Athletics. It's a bit more than he can do 100% of the time, so not unreasonable that it's a moderate difficulty to do it. The fact that he's an expertise in athletics makes it an easy jump for him, and I think that's 100% fair.
Would increasing your movement speed increase your jumping distance? Was another topic brought up, as stated your jump distance is equal to your Str score given you have 10 ft. to run and jump and each ft. traveled jumping is equal to a ft. of movement meaning you cannot jump farther than your movement would allow you.
I would say yes, movement speed is more momentum, so more air time.
Oh look, a player trying to use "rule of cool" to circumvent rules that are hard and fast. Tell the player "no".
To be fair, it sounds more like a player proposing an improvised action to his DM and asking for advice on whether/how it would work.
However, even if he is using the rule of cool, there's nothing wrong with doing that. It can be a lot of fun to leave the rules as rough guidelines and just enjoy yourself. Not everything needs doing inside the strict written rules, especially on a game where it specifically allows the DM to change and improvise things as and when they wish.
The rules dictate a 13 foot distance. The player is saying "but I want to parkour the gap, even though the rules state I can't do this".
Next step by the player: "I want to grab my Pole of Collapsing get a running start, jam the Pole into the ground just before the edge of the drop, then as the Pole has traversed about 70% of the arc, and on the way down, I will use my Acrobatics and Athletics both to contort my body, and using my initial momentum, plus the extension due to the Pole, clear the gap."
And when the DM says "no", the player says "but wait, 2 sessions ago you let me parkour the 20 feet. Why not let me use rule of cool in this manner?" At which point the game devolves into a 3-4 minute discussion on why one rule of cool using some kind of quasi-physics worked before, and but this instance is a bridge too far.
Would increasing your movement speed increase your jumping distance? Was another topic brought up, as stated your jump distance is equal to your Str score given you have 10 ft. to run and jump and each ft. traveled jumping is equal to a ft. of movement meaning you cannot jump farther than your movement would allow you.
I would say yes, movement speed is more momentum, so more air time.
By using this statement, you are totally erasing the jumping limitation rules that exist, and are completely into Homebrew. There is a sub-channel for Homebrew rules. This is not that sub-channel.
You can argue that the rules do not reflect reality. Olympic long jumpers are generally very good sprinters (Carl Lewis is an extreme example), but I can not see any of them excelling at weight lifting.
Having said that the rules are there to avoid debates about how far a character can jump so I would go with them.
25ft movement speed is a minor constraint. By giving up an action the player can dash allowing to move 50ft. The long jump distance is a hard constraint, a str 13 character an not jump more than 13ft.
The player can run 20ft and jump 13ft but as that involves at least 33ft of movement to make a 13ft jump he would need to dash.
Oh look, a player trying to use "rule of cool" to circumvent rules that are hard and fast. Tell the player "no".
To be fair, it sounds more like a player proposing an improvised action to his DM and asking for advice on whether/how it would work.
However, even if he is using the rule of cool, there's nothing wrong with doing that. It can be a lot of fun to leave the rules as rough guidelines and just enjoy yourself. Not everything needs doing inside the strict written rules, especially on a game where it specifically allows the DM to change and improvise things as and when they wish.
The rules dictate a 13 foot distance. The player is saying "but I want to parkour the gap, even though the rules state I can't do this".
Not really. The rules say that you can cover 13ft with a running start. They do not say that you cannot jump further. There is a big difference.
Next step by the player: "I want to grab my Pole of Collapsing get a running start, jam the Pole into the ground just before the edge of the drop, then as the Pole has traversed about 70% of the arc, and on the way down, I will use my Acrobatics and Athletics both to contort my body, and using my initial momentum, plus the extension due to the Pole, clear the gap."
And when the DM says "no", the player says "but wait, 2 sessions ago you let me parkour the 20 feet. Why not let me use rule of cool in this manner?" At which point the game devolves into a 3-4 minute discussion on why one rule of cool using some kind of quasi-physics worked before, and but this instance is a bridge too far.
It is better to say "no" in the first place.
Better for who?
As a DM, I always state that on-the-spot rulings are one-time events, and may change later. I even clarify that any house rule may be modified later if it is found to be overpowered or otherwise unwanted. It may be slightly easier to just say no to anything which isn't strictly defined in the rules, but IMHO it is far less fun (for both me and my players) and far too restrictive.
In this case, when the player questions it (assuming I do disallow pole-vaulting as you suggest), I would refer them to my previous statement: I made that ruling on the spot because it would be fun, but feel it should be handled differently now. My players are always made aware of my stance on on-the-spot rulings, so would expect that it may not be possible or may be handled differently a second time. Mostly they appreciate it, because it does allow them to get away with some quite ridiculous things every so often, even if only once, and that is a lot of fun for everyone involved. It makes for some really interesting stories.
The full answer is that we don't know how jumping works. We do know that movement speed only raises your maximum jump - within that limit, jumping is set strictly by your strength score, your strength modifier, and your athletics. Here's the closest we have to rules for jumping farther than your strength score (for a long jump) or modifier + 3 (for a high jump):
In some circumstances. your DM might allow you to make a Strength (Athletics) check to jump higher than you normally can. (rules entry for high jumps)
You try to jump an unusually long distance or pull off a stunt midjump. (rules entry for Athletics)
So, again, movement speed raises your maximum jump distance, strength and athletics raise your base jump distance (i.e. you determine base, then reduce to maximum). Do not let movement speed impact the calculation of the base.
Since there's basically zero guidance on how to apply athletics to jumping, here's a way to do it that's at least consistent with the RAW:
Long Jump: Roll an Athletics check, then (after modifiers) force it to be at least your strength score - this is how far you can jump.
High Jump: Roll an Athletics check with a -4 to the roll, then divide by 2. Then force the result to be at least strength modifier plus 3. This is how high you can jump.
(Note: -4 is the result of -10 to match the rules for mapping a number to a modifier, and then +6 so after division you're adding +3).
Would increasing your movement speed increase your jumping distance? Was another topic brought up, as stated your jump distance is equal to your Str score given you have 10 ft. to run and jump and each ft. traveled jumping is equal to a ft. of movement meaning you cannot jump farther than your movement would allow you.
I would say yes, movement speed is more momentum, so more air time.
By using this statement, you are totally erasing the jumping limitation rules that exist, and are completely into Homebrew. There is a sub-channel for Homebrew rules. This is not that sub-channel.
This may be the "rules and game mechanics" forum, but the OP came here asking how we would rule, not what the latter of the rule was. Maybe the question should have been posted in the other forum, but criticising somebody for answering a question honestly asked doesn't seem the right way to go.
The full answer is that we don't know how jumping works. We do know that movement speed only raises your maximum jump - within that limit, jumping is set strictly by your strength score, your strength modifier, and your athletics. Here's the closest we have to rules for jumping farther than your strength score (for a long jump) or modifier + 3 (for a high jump):
In some circumstances. your DM might allow you to make a Strength (Athletics) check to jump higher than you normally can. (rules entry for high jumps)
You try to jump an unusually long distance or pull off a stunt midjump. (rules entry for Athletics)
So, again, movement speed raises your maximum jump distance, strength and athletics raise your base jump distance (i.e. you determine base, then reduce to maximum). Do not let movement speed impact the calculation of the base.
Since there's basically zero guidance on how to apply athletics to jumping, here's a way to do it that's at least consistent with the RAW:
Long Jump: Roll an Athletics check, then (after modifiers) force it to be at least your strength score - this is how far you can jump.
High Jump: Roll an Athletics check with a -4 to the roll, then divide by 2. Then force the result to be at least strength modifier plus 3. This is how high you can jump.
(Note: -4 is the result of -10 to match the rules for mapping a number to a modifier, and then +6 so after division you're adding +3).
As usual, jumping costs movement.
That's not a bad system, I may use that (or something similar) in the future.
I think, if I did, it would be rolled after the player declared they were going to jump. They would not be able to roll, see if they could make it, then decide not to. You declare you are jumping, and then your jump distance comes from the roll. If you don't make it far enough, you fall. The player has the chance to make their character do something amazing, but there are consequences if they fail.
I mean, pole vaulting feels like a good, solid use of a Pole of Collapsing. If a player said to me "I use my Pole of Collapsing to try and pole-vault the gap", with my DM Hat on I'd give it to him as an Athletics check, DC dependent on the ground he's trying to pole-vault off of. The key there is whether he has the strength to generate the raw force needed and whether the ground is going to properly catch the end of the pole. Acrobatics would, in no way, be involved - they literally call this "Athletics" in sporting competitions.
Now, if a player said all that shit Vince said about describing how they wanted their action to resolve, I'd step in and remind that player that they are a player, not the DM. It is the player's job to describe the actions their character takes, and the DM's job to resolve those actions. What some people forget in their constant snarling about how Rule of Cool Destroys D&D Forever(TM) is that a player can take any action they can describe. The player can do anything, they can state anything to the DM, and a good DM will say "Okay." Good DMs may offer reminders on how their world works and what sort of results an action might have, offer an 'are you sure?' warning to players who may not have thought something through, but a DM should do their best to never just outright say "No."
That does not mean a player's action will always succeed. That does not mean they even get a roll, if they choose an exceptionally poor action - a player can absolutely state an action that the DM then narrates the failure of without bothering to touch the dice, such as "I use my cape to try and Batman-glide across the gap". A player can choose an action the DM narrates the success of without bothering to touch the dice, such as "I cast Fly and just fly over the gap". But if you are playing actual, for-real D&D - or any other properly built and run TTRPG - then you can take any action it is physically within your character's power to take.
A good DM is a DM that resolves the actions the players take as fairly as possible. An overly punitive DM that constantly auto-fails a player who dares to declare any action not listed in the "Actions in Combat" section of the Player's Handbook is just as bad as an overly permissive DM that lets anybody get away with whatever Loony Tunes nonsense they want, and only slightly better than a DM who shows outright favoritism at the table.
5e was built under the core assumption that a DM would make rulings. Not every possible action a player can declare can be covered by RAW, so the edition is designed to allow the DM to rule as they see fit. If a DM refuses to so rule and instead declares that players cannot take any action which is not clearly defined and recorded by the edition's overly-thin and scant base rules? They are not playing 5e properly.
* * *
Now. All that said? To the originally posed scenario: Walljumping/wallrunning is a parkour technique primarily intended to redirect momentum, not to generate more momentum. It's a method freerunners use to avoid losing momentum as they bounce around an environment. I would not allow it to add seven feet to a long jump, nor would I classify it as Acrobatics. That said, I'm not the DM at this table - if you'd like to classify parkour techniques as acrobatics, no issue.
I will note that the "you can jump a number of feet equal to your Strength score" figure is assuming that landing safely and stably on their feet on the other side of the jump is desired. If the player said "I want to try and jump far enough, hard enough to try and catch the other side with my hands and pull myself up", that would add a few feet - and an Athletics check - to the attempt. I don't know as I'd allow it to add seven feet to the attempt, and if I did that would be a very stiff DC, but given that the character has Expertise in Athletics indicating an effectively Olympic level of training and conditioning? I might let them try it, as dazzling feats of athleticism is that character's explicit forte. If they could find a means of boosting their jump, I'd lower the DC. Depends in part on how willing that player has historically been to play ball with me and roll with it when I make rulings. If they're likely to argue and disrupt my session, they don't get the attempt. If they're a good sport and accept their failures along with their successes - and are willing to plummet into the depths of whatever this gap holds if the dice say so - I'd consider letting them have the roll.
That's fair, but the Angry GM offered a very good piece of advice once for resolving where a given skill check belongs if multiple skills could all be said to apply, such as this wallrunning example. To paraphrase:
"Many ability checks can be argued to involve multiple skills, such as Athletics vs. Acrobatics. Elements of each skill contributes to the check. But one element has to contribute the most to that check. One of those elements is the one all the others are there to make the best of, or to interfere with. Identifying that key make-or-break factor is what tells you which ability to use, and once you've identified it, the player doesn't get to hornswoggle their way into using a different ability."
His example was actually, quite specifically, long jumps. The key factor for long jumping is Strength - the ability to generate enough raw force with your li'l Adventuring feeties and the fancy meat sticks they're attached to to get your great galumphing corpus across a given distance. if you don't have the ability to generate enough force to clear the distance, no amount of gymnastics training is going to help. Save maybe at the bottom, if the drop isn't too terrible.
You could make the argument that this wallrunning thing is an Acrobatics check, sure. If the player is good at talking up their game, I could see letting them have it. It would be a Strength (Acrobatics) check though, not a Dex (Acrobatics) check, to try and actually clear the gap. Because as you've pointed out yourself, you're actually increasing the amount of distance you have to clear using this method and requiring more total force/momentum to do it. Dexterity, in this instance, could help you get better positioning to make the most of your leg strength, but if you don't have the raw leg strength to clear the gap? No amount of ballet training is getting you across that twenty feet of nofloorium. It is the price one pays for dropping Strength on absolutely every single character in D&D that isn't a barbarian.
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DM a group with my friends and my friend is a 9th Lv Dwarf Ranger/1 Lv Rogue Multiclass and he wanted to jump across a 20 ft. gap. He has a Str score of 13 which means he can jump 13 ft. with a 10 ft. running start using long jump rules. He argued that because he Expertised into Athletics, giving him a +9, he could attempt to kick off a wall to make the other 7 ft. I told him kicking off of a wall mid jump would be an Acrobatics check but I was fine with him attempting it. He thought kicking off the wall mid jump would be Athletics, so first question would be:
Kicking off a wall mid jump, Athletics or Acrobatics?
2nd he Argued that because he had a +9 into Athletics from Expertise he could roll Athletics to attempt to jump the 20 ft gap because he has trained so much into Athletics. I was fine with it, but the DC would be relatively high due to it being out of his capabilities. His movement speed max is 25, meaning with a 10 foot running start, max distance he could jump would be 15 with an Athletics check. I ruled he wouldn't be able to make this jump, but he could attempt with a near impossible success chance, DC 25-30. Second question would be:
How would you rule this situation?
I agree, follow up question:
Would increasing your movement speed increase your jumping distance? Was another topic brought up, as stated your jump distance is equal to your Str score given you have 10 ft. to run and jump and each ft. traveled jumping is equal to a ft. of movement meaning you cannot jump farther than your movement would allow you.
A jump still uses your movement.
If he is doing a 10ft run up, he would only have 15ft movement left so could not make it across even if he had a Str of 20.
Other than that, we are in the realms of DM fiat, rule of cool, and general homebrew. I know many DMs would allow a check to try something like this, with a fairly high difficulty and the risk that, on failure, the PC would not make it, fall and take appropriate damage.
Yea exactly, i was telling him that with a movement speed of 25 ft. and needing a 10 ft. running start the max he could clear would be 15, which would be feasible even with a 13 Str with a 20 ish DC.
What about the last question, if say he used Zephyrs Strike and had a movement of 55 ft. now, could he then jump 45 ft. with the 10 ft. running start?
I would say no.
If he had a strength score of 45, sure. With a strength of 13, he can jump 13ft RAW, and maybe a little extra with a clever description and a good roll at the DMs discretion.
Thanks for the replies
Oh look, a player trying to use "rule of cool" to circumvent rules that are hard and fast. Tell the player "no".
To be fair, it sounds more like a player proposing an improvised action to his DM and asking for advice on whether/how it would work.
However, even if he is using the rule of cool, there's nothing wrong with doing that. It can be a lot of fun to leave the rules as rough guidelines and just enjoy yourself. Not everything needs doing inside the strict written rules, especially on a game where it specifically allows the DM to change and improvise things as and when they wish.
Kicking off a wall fights gravity and requires strength, thus it is an athletics check in my opinion. Most physical checks are athletics when it comes down to it, they're rarely acrobatics.
You can never jump further than your movement speed. This is a function of ingame time. Assuming that the jump distance would not violate the movement speed limitation, I would give this a moderate difficulty of 15 DC vs Athletics. It's a bit more than he can do 100% of the time, so not unreasonable that it's a moderate difficulty to do it. The fact that he's an expertise in athletics makes it an easy jump for him, and I think that's 100% fair.
Altrazin Aghanes - Wizard/Fighter
Varpulis Windhowl - Fighter
Skolson Demjon - Cleric/Fighter
I would say yes, movement speed is more momentum, so more air time.
Altrazin Aghanes - Wizard/Fighter
Varpulis Windhowl - Fighter
Skolson Demjon - Cleric/Fighter
The rules dictate a 13 foot distance. The player is saying "but I want to parkour the gap, even though the rules state I can't do this".
Next step by the player: "I want to grab my Pole of Collapsing get a running start, jam the Pole into the ground just before the edge of the drop, then as the Pole has traversed about 70% of the arc, and on the way down, I will use my Acrobatics and Athletics both to contort my body, and using my initial momentum, plus the extension due to the Pole, clear the gap."
And when the DM says "no", the player says "but wait, 2 sessions ago you let me parkour the 20 feet. Why not let me use rule of cool in this manner?" At which point the game devolves into a 3-4 minute discussion on why one rule of cool using some kind of quasi-physics worked before, and but this instance is a bridge too far.
It is better to say "no" in the first place.
By using this statement, you are totally erasing the jumping limitation rules that exist, and are completely into Homebrew. There is a sub-channel for Homebrew rules. This is not that sub-channel.
Try to be more positive tbh.
Altrazin Aghanes - Wizard/Fighter
Varpulis Windhowl - Fighter
Skolson Demjon - Cleric/Fighter
You can argue that the rules do not reflect reality. Olympic long jumpers are generally very good sprinters (Carl Lewis is an extreme example), but I can not see any of them excelling at weight lifting.
Having said that the rules are there to avoid debates about how far a character can jump so I would go with them.
25ft movement speed is a minor constraint. By giving up an action the player can dash allowing to move 50ft. The long jump distance is a hard constraint, a str 13 character an not jump more than 13ft.
The player can run 20ft and jump 13ft but as that involves at least 33ft of movement to make a 13ft jump he would need to dash.
Not really. The rules say that you can cover 13ft with a running start. They do not say that you cannot jump further. There is a big difference.
Better for who?
As a DM, I always state that on-the-spot rulings are one-time events, and may change later. I even clarify that any house rule may be modified later if it is found to be overpowered or otherwise unwanted. It may be slightly easier to just say no to anything which isn't strictly defined in the rules, but IMHO it is far less fun (for both me and my players) and far too restrictive.
In this case, when the player questions it (assuming I do disallow pole-vaulting as you suggest), I would refer them to my previous statement: I made that ruling on the spot because it would be fun, but feel it should be handled differently now. My players are always made aware of my stance on on-the-spot rulings, so would expect that it may not be possible or may be handled differently a second time. Mostly they appreciate it, because it does allow them to get away with some quite ridiculous things every so often, even if only once, and that is a lot of fun for everyone involved. It makes for some really interesting stories.
The full answer is that we don't know how jumping works. We do know that movement speed only raises your maximum jump - within that limit, jumping is set strictly by your strength score, your strength modifier, and your athletics. Here's the closest we have to rules for jumping farther than your strength score (for a long jump) or modifier + 3 (for a high jump):
So, again, movement speed raises your maximum jump distance, strength and athletics raise your base jump distance (i.e. you determine base, then reduce to maximum). Do not let movement speed impact the calculation of the base.
Since there's basically zero guidance on how to apply athletics to jumping, here's a way to do it that's at least consistent with the RAW:
Long Jump: Roll an Athletics check, then (after modifiers) force it to be at least your strength score - this is how far you can jump.
High Jump: Roll an Athletics check with a -4 to the roll, then divide by 2. Then force the result to be at least strength modifier plus 3. This is how high you can jump.
(Note: -4 is the result of -10 to match the rules for mapping a number to a modifier, and then +6 so after division you're adding +3).
As usual, jumping costs movement.
This may be the "rules and game mechanics" forum, but the OP came here asking how we would rule, not what the latter of the rule was. Maybe the question should have been posted in the other forum, but criticising somebody for answering a question honestly asked doesn't seem the right way to go.
That's not a bad system, I may use that (or something similar) in the future.
I think, if I did, it would be rolled after the player declared they were going to jump. They would not be able to roll, see if they could make it, then decide not to. You declare you are jumping, and then your jump distance comes from the roll. If you don't make it far enough, you fall. The player has the chance to make their character do something amazing, but there are consequences if they fail.
I mean, pole vaulting feels like a good, solid use of a Pole of Collapsing. If a player said to me "I use my Pole of Collapsing to try and pole-vault the gap", with my DM Hat on I'd give it to him as an Athletics check, DC dependent on the ground he's trying to pole-vault off of. The key there is whether he has the strength to generate the raw force needed and whether the ground is going to properly catch the end of the pole. Acrobatics would, in no way, be involved - they literally call this "Athletics" in sporting competitions.
Now, if a player said all that shit Vince said about describing how they wanted their action to resolve, I'd step in and remind that player that they are a player, not the DM. It is the player's job to describe the actions their character takes, and the DM's job to resolve those actions. What some people forget in their constant snarling about how Rule of Cool Destroys D&D Forever(TM) is that a player can take any action they can describe. The player can do anything, they can state anything to the DM, and a good DM will say "Okay." Good DMs may offer reminders on how their world works and what sort of results an action might have, offer an 'are you sure?' warning to players who may not have thought something through, but a DM should do their best to never just outright say "No."
That does not mean a player's action will always succeed. That does not mean they even get a roll, if they choose an exceptionally poor action - a player can absolutely state an action that the DM then narrates the failure of without bothering to touch the dice, such as "I use my cape to try and Batman-glide across the gap". A player can choose an action the DM narrates the success of without bothering to touch the dice, such as "I cast Fly and just fly over the gap". But if you are playing actual, for-real D&D - or any other properly built and run TTRPG - then you can take any action it is physically within your character's power to take.
A good DM is a DM that resolves the actions the players take as fairly as possible. An overly punitive DM that constantly auto-fails a player who dares to declare any action not listed in the "Actions in Combat" section of the Player's Handbook is just as bad as an overly permissive DM that lets anybody get away with whatever Loony Tunes nonsense they want, and only slightly better than a DM who shows outright favoritism at the table.
5e was built under the core assumption that a DM would make rulings. Not every possible action a player can declare can be covered by RAW, so the edition is designed to allow the DM to rule as they see fit. If a DM refuses to so rule and instead declares that players cannot take any action which is not clearly defined and recorded by the edition's overly-thin and scant base rules? They are not playing 5e properly.
* * *
Now. All that said? To the originally posed scenario:
Walljumping/wallrunning is a parkour technique primarily intended to redirect momentum, not to generate more momentum. It's a method freerunners use to avoid losing momentum as they bounce around an environment. I would not allow it to add seven feet to a long jump, nor would I classify it as Acrobatics. That said, I'm not the DM at this table - if you'd like to classify parkour techniques as acrobatics, no issue.
I will note that the "you can jump a number of feet equal to your Strength score" figure is assuming that landing safely and stably on their feet on the other side of the jump is desired. If the player said "I want to try and jump far enough, hard enough to try and catch the other side with my hands and pull myself up", that would add a few feet - and an Athletics check - to the attempt. I don't know as I'd allow it to add seven feet to the attempt, and if I did that would be a very stiff DC, but given that the character has Expertise in Athletics indicating an effectively Olympic level of training and conditioning? I might let them try it, as dazzling feats of athleticism is that character's explicit forte. If they could find a means of boosting their jump, I'd lower the DC. Depends in part on how willing that player has historically been to play ball with me and roll with it when I make rulings. If they're likely to argue and disrupt my session, they don't get the attempt. If they're a good sport and accept their failures along with their successes - and are willing to plummet into the depths of whatever this gap holds if the dice say so - I'd consider letting them have the roll.
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That's fair, but the Angry GM offered a very good piece of advice once for resolving where a given skill check belongs if multiple skills could all be said to apply, such as this wallrunning example. To paraphrase:
"Many ability checks can be argued to involve multiple skills, such as Athletics vs. Acrobatics. Elements of each skill contributes to the check. But one element has to contribute the most to that check. One of those elements is the one all the others are there to make the best of, or to interfere with. Identifying that key make-or-break factor is what tells you which ability to use, and once you've identified it, the player doesn't get to hornswoggle their way into using a different ability."
His example was actually, quite specifically, long jumps. The key factor for long jumping is Strength - the ability to generate enough raw force with your li'l Adventuring feeties and the fancy meat sticks they're attached to to get your great galumphing corpus across a given distance. if you don't have the ability to generate enough force to clear the distance, no amount of gymnastics training is going to help. Save maybe at the bottom, if the drop isn't too terrible.
You could make the argument that this wallrunning thing is an Acrobatics check, sure. If the player is good at talking up their game, I could see letting them have it. It would be a Strength (Acrobatics) check though, not a Dex (Acrobatics) check, to try and actually clear the gap. Because as you've pointed out yourself, you're actually increasing the amount of distance you have to clear using this method and requiring more total force/momentum to do it. Dexterity, in this instance, could help you get better positioning to make the most of your leg strength, but if you don't have the raw leg strength to clear the gap? No amount of ballet training is getting you across that twenty feet of nofloorium. It is the price one pays for dropping Strength on absolutely every single character in D&D that isn't a barbarian.
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