Improvised Training

"If you can dodge a wrench, you can dodge a ball!"

—Patches O'Houlihan, Dodgeball

So you have a Ragtag Bunch of Misfits from the Wrong Side of the Tracks who want to win a contest or sporting event. Well, they get a trainer, but have no money or equipment, what are they supposed to do? Get creative! Their trainer will think up Wax On, Wax Off techniques, the players will jury rig ingenious improvised training equipment, and get a lighter form of The Spartan Way / Training from Hell.

You can tell a group got Improvised Training because they will absolutely marvel at the luxury of well funded professional teams and arenas.The richer, posh kids will sneer at them, while these kids will reply they didn't need sissy advantages or buy success with money.

Despite the zero budget and dubious training methods, it turns out the rougher and unconventional training pays off and helps them win. The more traditional (especially the ultra well funded prep or snooty Legacy Team that always wins) will have such rigid and inflexible mindsets that the rag tag team keeps catching them by surprise. Be it with creative plays or enduring more pain, or outperforming them. Occasionally, the training itself may even give them comparable or superior physical performance, at times bordering on Charles Atlas Super Powers.

Not to be confused with Poor Man's Substitute about dealing with actors.

Examples of Improvised Training include:

Anime and Manga

Subverted in Rurouni Kenshin where Sano (a brawler) attempts to train while traveling to Kyoto by knocking down trees with his bare hands. Eventually however he admits, that this isn't really training and he's not learning anything useful by doing it. At least while he's lost in the forest he does meet a mentor who does train him and show him new techniques.
Eyeshield 21 had this trope going in the beginning. Ojou was so luxurious they owned a castle in Germany for the sole purpose of training in it. Deimon? They pushed a truck half way across the US in a month (part of the reason was also because they didn't have enough money for more gas).

Film

A Knight's Tale They used jury rigged contraptions to teach William to joust. Plus he had to wear a dead guy’s armor.
Cool Runnings has the story of the first Jamaican bobsledding team. With such gems as "sliding" on a cart down rocky hills, and locking players in an ice cream truck to acclimate them to the cold.
Shaolin Soccer, a washed up pro soccer trainer converts a team of washed up kung-fu trained brothers into a team of Super Soccer Kung Fu Monks. With such feats as eggs tossing and catching, and pitting them against a team that uses metal hand tools to bludgeon their opponents.
In Lagaan the new Indian cricket team chases chickens and the like. Half of their special skills originate from ordinary tasks that they do in their day jobs too.
The little league baseball team in The Perfect Game. They're poor, have no advantages, and actually have to clean up a church yard of brush, tires, and rocks to get a ball field. Their training consisted in a lot of running, cutting their own bats from wood, and hitting balls made of rubber bands/wire. They do eventually get real bats and balls, though they never see cut grass fields until they start competing.
Rocky does a version of this in every movie, chasing chickens, using whole cows as heavy bags, lifting logs, etc. Usually done to an 80's Sports Montage and juxatposed with his opponent's high-tech training.
- The opponents high-tech training was only really done in Rocky IV, where the contrast between Rocky lifting boulders and chopping wood and Drago using high-tech equipment with dozens of scientists surrounding him was played up to the extreme
- In Rocky III, this was done with Rocky's opponent ~~Clubber Lang~~ Mr. T, whos training montage was supposedly based on Mr. T's real life training.
  - Clubber Lang's workout is more like self-imposed Training from Hell and his "gym" has been compared to a dungeon.
A variant in Major League sees the ball players improvising ways to recover from the exertions of training, after the team's hostile owner takes away all their equipment. One player is seen lying in an improvised whirlpool bath made up of an aluminium horse trough, a garden hose, and an outboard boat motor.
Dodgeball parodies this while playing it straight.
X-Men: First Class has Charles Xavier using anything he can find on or around his estate to train young mutants.

Literature

The old children's book A Brother for the Orphelines by Natalie Savage Carlsson is about a bunch of girls in an orphanage where this turned up—the girls are able to beat the other local kids at marbles because they can't afford marbles themselves and so they always play with walnuts.
Sort of subverted in Unseen Academicals, in that Trev Likely can manipulate a kicked tin can six ways from Sunday, yet has never actually kicked a soccer ball in his life. When he finally does join a game, he's terrible at it until a friend engineers a "lost" ball and tosses a tin can onto the field as a substitute.

Real Life

While not truly a common rich vs. underdog example, one common way for Mixed Martial Artists to compensate for their ability is to train entirely in defending a person's strengths even though they might not be glass cannons.
- Made famous by Alan Belcher who trained with the best leg lock masters to defend against Rousimar Palhares the leglock master. While Belcher's JJ is highly respected, many broken fanbase considered Palhares to be so great at leg locks that once you go to the ground with him, it's pretty much over. Belcher did not only initiate the ground but defended multiple attempts of leglocks (which on the ground is less move per move but more like combos that can only work if the person getting hit blocks the attack)
- Modern MMA lay and pray could be said as this. Where in the past, LNP is basically staying on top of your opponent, the new rules forces fighters on top to stay active but if the bottom player tries a submission or a transition and the fighter on top defends it, it is counted as active. The combination led to such famous fighters as Jon Fitch calling the guard dead.