Even in anime, strength and skill don't appear out of the blue. In fact, many anime characters start off as weak or undisciplined and only reach their full potential later. How do characters like Vegeta, Guts, and Izuku Midoriya gain the strength they display? With some of the most intense training experiences of all time, that's how.
Training from hell scenes in anime are fascinating because they show the process of learning the skills that define the character undergoing them. These scenes also offer a great opportunity to develop relationships with mentors, as well as to show character growth over time. Sometimes the training sessions are brutal but humanly possible, as with Saitama's daily routine of doing 100 squats, 100 sit-ups, and 100 push-ups followed by 10km of running. At other times, they're only possible with superhuman strength - as with Vegeta's attempts to train in 450x the gravity he's used to.
These training scenes will either inspire you to amp up your own workout or make you never want to move again.
Vegeta is serious about his goal to surpass his rival Goku. When he realizes that Goku has been able to achieve the Super Saiyan state that he himself has yet to unlock, he undergoes intense training at 450x normal gravity in order to dramatically increase the effectiveness of his workouts. This process makes him so strong that he's able to survive a meteor shower, but his failure to actually allow himself time to recover ultimately stunts his physical potential.
A lot of people in Hunter X Hunter undergo rigorous training, but few of them literally train for 50 years straight. Already at the peak of his physical abilities, Netero wanted to show gratitude by throwing 10,000 punches a day. At first it took him nearly the entire day to finish, but after years of punching he could eventually finish the drill in an hour or two. This allowed him to unlock a ridiculously strong ability we see him use against Meruem during their fight.
Izumi Curtis might look like a simple housewife, but she's a beast when it comes to training budding alchemists. After accepting two small children - Edward and Alphonse Elric - as her pupils, she immediately makes them survive on their own for a month on a desert island with only a knife and a proverb they were responsible for decoding. Later training involved a ton of physical violence when her students displeased her.
The training she puts herself through is no less rigorous - Izumi once survived in the frigid wilderness for a month, all while fighting off angry bears.
Before Izuku Midoriya can take on All Might's incredible quirk, he has to improve his physical strength and stamina to the point where he can use it without tearing his body apart. To accomplish this, he's placed on a strict diet and exercise regimen that he isn't allowed to deviate from, which includes lifting heavy weights and cleaning up an entire beach covered in debris.
Even after all that training, Izuku still injures himself - to the point of completely destroying his limbs - nearly every time he uses his quirk until he gets the hang of it.