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In baseball, milliseconds can mean the difference between a home run and a strikeout.
For over a century, pitchers have pushed the limits of human performance, throwing baseballs at speeds once thought physically impossible.
Behind these extraordinary feats is a combination of biomechanics, physics, and a long history of innovation that has transformed the game.
Learn more about the history and science of the fastball, and the legendary pitchers who perfected it, on this episode of Everything Everywhere Daily.
In a previous episode, I discussed the knuckleball, the rarest and most confounding pitch in baseball that only a small number of pitchers have ever mastered.
In this episode, I want to go in the opposite direction and talk about one of the most common, straightforward pitches: the fastball.
The strategy behind the fastball is very simple. Throw the ball as hard as you can and try to not give the batter much time to react and swing.
When organized baseball began developing its rules in the mid-nineteenth century, pitching was very different from what it is today.
Under the Knickerbocker rules of 1845, pitchers had to deliver the ball underhand. They were not supposed to whip their arms forward using a modern throwing motion. The pitcher’s original function was largely to put the ball into play.
In 1883, pitchers were permitted to deliver the ball with their arms above the waist, and in 1884, restrictions on overhand pitching were removed.
This was a revolutionary change.
Pitchers could now use their entire bodies to generate velocity, with their arms moving in a manner resembling the modern pitching motion.
The results were dramatic. Pitching velocity increased, strikeouts became more common, and baseball’s rules increasingly had to account for the pitchers’ growing advantage.
In 1893, the pitching distance was standardized at 60 feet, 6 inches, where it remains today. The pitching box was also replaced by a pitching rubber.
One of baseball’s first legendary power pitchers was Amos Rusie, who earned the nickname Hoosier Thunderbolt. He was particularly dominant during the early 1890s, when he played for the New York Giants.
Walter Johnson, nicknamed the Big Train, became the dominant fastball pitcher of the early twentieth century and one of baseball’s greatest pitchers.
Johnson was unusual because he used a low three-quarter, almost sidearm delivery. Instead of throwing over the top of his shoulder, he delivered the ball with a sweeping motion that batters found exceptionally difficult to track.
His contemporaries frequently described his fastball as the fastest they had ever seen.
Every generation had one or more pitchers widely considered the hardest-throwing of their era.
One of the most celebrated fastball pitchers of his generation was Satchel Paige, whose extraordinary career largely took place in the Negro Leagues because of baseball’s racial segregation.
Bob Feller was perhaps the first baseball pitcher whose fastball became a scientific curiosity. His remarkable velocity made him a national celebrity and inspired attempts to measure exactly how fast a human could throw a baseball.
Nolan Ryan is probably the most famous fastball pitcher in baseball history. His remarkable velocity, extraordinary longevity, and unparalleled strikeout totals made him synonymous with the power fastball.
In more recently, the number of dominant fastball pitchers has increased. Randy Johnson, Roger Clemens, Rob Dibble, Aroldis Chapman, and Jacob Misiorowski were all known for their fastballs.
Usually, anything above 90 mph is considered a typical major league fastball, and anything over 100 mph is considered an elite-level fastball. For those outside the US, I’ll use imperial units for the rest of the episode, but 100 mph is 160.9 kph.
So why can some pitchers throw a ball so fast? It all comes down to biomechanics.
A fastball isn’t just about arm strength. It results from a carefully coordinated sequence of movements involving almost the entire body, with energy transferred from the ground through the legs, hips, torso, shoulder, and finally into the fingertips.
The fundamental principle behind pitching is called the kinetic chain. This describes how different parts of the body accelerate in sequence, transferring energy from larger, heavier body segments to smaller, lighter ones.
A useful analogy is cracking a whip. The handle moves relatively slowly, but a wave of motion travels along its length, accelerating the tip to extraordinary speeds.
Something similar happens with a fastball.
The process begins with the pitcher pushing against the pitching rubber and the ground. Newton’s third law states that every action produces an equal and opposite reaction. As the pitcher pushes against the ground, the ground pushes back. This helps accelerate the pitcher’s body toward home plate.
As the pitcher moves forward, the leading leg strides toward the plate. Research on pitching mechanics suggests a stride length of about 85% of the pitcher’s height is common in efficient throwing mechanics, though the ideal stride varies by individual. The front leg then braces against the ground, redirecting forward momentum into rotation.
The pelvis begins rotating toward home plate while the shoulders initially remain turned away. This separation between hip rotation and shoulder rotation stretches muscles and connective tissues through the torso, allowing them to contribute to a powerful subsequent rotation.
As the torso turns, the throwing arm initially rotates backward relative to the upper body, reaching extreme external rotation. The shoulder then rapidly rotates forward internally. In elite pitching, shoulder internal rotation can reach approximately 7,500 degrees per second, making it one of the fastest measured joint movements in the human body.
As the shoulder accelerates, the elbow extends rapidly, and the hand moves forward. The wrist and fingers contribute to the final release and impart spin to the baseball.
At release, a typical 95 mph pitch carries about 128 joules of kinetic energy. A 100 mph pitch carries about 142 joules.
One interesting consequence is that kinetic energy increases with the square of velocity. Increasing a fastball from 90 to 100 mph requires about 23% more kinetic energy, even though the speed increases by only 11%.
This helps explain why gaining the last few miles per hour is so difficult. The faster you throw, the more energy it requires.
The human body also pays a price for producing these velocities. The shoulder and elbow undergo tremendous rotational forces. The ulnar collateral ligament, or UCL, resists stress on the inside of the elbow, which is why UCL injuries and Tommy John surgery are such prominent issues in professional baseball.
It is also one of the most remarkable things about Nolan Ryan’s career. He was not only one of the hardest-throwing pitchers in history, but he also had one of the longest careers.
Height provides several advantages for fastball pitchers. Many of the greatest fastball pitchers have been well over 6 feet tall.
The first is leverage. Taller pitchers generally have longer arms, which can create higher hand speeds at the same angular velocity. However, longer arms also create greater rotational inertia, so the relationship between height and throwing velocity isn’t as simple as a longer lever.
The second advantage is a longer stride. A taller pitcher can cover more ground during the delivery, bringing the release point closer to home plate.
The third advantage is release height. Taller pitchers often release the ball from a higher position, giving the batter a different angle of approach.
From the batter’s standpoint, more speed equals less time. The difference between a 90 mph pitch and a 100 mph pitch is only about 50 milliseconds. That might not seem significant, but for a batter, it means less time to identify the pitch and prepare a swing.
Swinging a baseball bat takes time. Research places the forward-swing phase at about 130 to 280 milliseconds, depending on the hitter and how you define the start of the swing. The nervous system also needs time to process visual information and initiate the swing.
Consequently, a batter facing a 100 mph fastball often has to form a prediction and commit to the swing during roughly the first 150 to 200 milliseconds after the ball is released.
One of baseball’s biggest questions is who the fastest throwing pitcher of all time is.
Until recently, this has been a difficult question to answer because there hasn’t been a reliable way to measure a baseball’s speed.
One of the first attempts was to measure Walter Johnson’s speed. Researchers conducted experiments at the Remington Arms factory in Bridgeport, Connecticut, using equipment normally used to measure projectile velocity.
Historical accounts describe tests in 1912 and 1917, although details of these early experiments have sometimes been conflated. One widely cited figure places Johnson’s fastball at 122 feet per second, or about 83.2 miles per hour.
That might not seem like much, however, the measurement was taken beyond where home plate would have been, after the baseball had already slowed considerably.
By the late 1930s, Bob Feller of the Cleveland Indians had developed a reputation as baseball’s fastest pitcher. Feller’s velocity became a major attraction, and promoters looked for ways to dramatize his speed.
One of the most famous demonstrations took place in 1940, when Feller threw a baseball as a motorcycle raced past him.
A much more serious attempt occurred on August 20, 1946, when Feller participated in a speed test at Griffith Stadium in Washington, D.C.
Feller threw a baseball through the testing apparatus, which measured how long the ball took to travel between two detection points. Feller’s fastest recorded pitch was 98.6 miles per hour.
However, the apparatus measured the ball near home plate, not at its release point. This actually makes an enormous difference in speed.
In 1974, the Angels contacted Rockwell International, an aerospace company, and developed an instrument that used reflected infrared radiation and the Doppler effect to determine the ball’s speed.
On August 20, 1974, Ryan hit 100.9 mph during a game against the Detroit Tigers. However, the instrument measured the ball about 10 feet in front of home plate, after it had already slowed substantially.
From 2006–2014, the PITCHf/x was used, which was much better as it used multiple high-speed cameras. However, PITCHf/x initially reported velocity at a point 50 feet from home plate, rather than precisely at the pitcher’s release point.
On September 24, 2010, Aroldis Chapman threw a fastball originally recorded at 105.1 mph. The pitch was subsequently recalculated at 105.8 mph.
In 2017, MLB standardized its reported pitch velocity to the ball’s speed at release, making measurements more representative of the initial speed generated by the pitcher.
Another major advance occurred in 2020, when MLB replaced its original radar-based tracking hardware with a system developed by Hawk-Eye. The new system uses 12 cameras positioned around each ballpark, several of which are specifically dedicated to tracking pitches. The pitch-tracking cameras were upgraded from 100 to 300 frames per second in 2023.
Aroldis Chapman is still credited with the record at 105.8 mph, but with the new equipment, Jacob Misiorowski and Ben Joyce are tied at 105.5 mph.
It is entirely plausible that Bob Feller or Nolan Ryan might have hit 106 to 108 mph, but we don’t have the evidence.
I want to end with the pitcher who might have been the fastest of all time, but he never made it to the major leagues: Steve Dalkowski.
During the late 1950s and early 1960s, Dalkowski developed a reputation as perhaps the hardest-throwing pitcher anyone had ever seen. Some observers believed he threw well over 100 mph, with estimates occasionally reaching 110 mph or higher.
Hall of Famer Ted Williams, who faced Bob Feller, said that Dalkowski was the fastest he’d ever seen. Manager Early Weaver, who faced Nolan Ryan, said Dalkowski was the fastest he’d ever seen. Manager Davey Johnson, who played with Dalkowski and saw Aroldis Chapman pitch, said that Dalkowski was the fastest he’d ever seen.
Sadly, he had very poor control, had an extremely low IQ, and a drinking problem, and never made it to the majors. The character Nuke LaLoosh in Bull Durham was modeled after Steve Dalkowski.
The fastball is one of the purest expressions of human athletic ability.
Yet despite all the advances in biomechanics, training, and technology, the fundamental challenge remains the same. A pitcher has to throw a five-ounce ball past someone standing just 60 feet away, and a batter has only a fraction of a second to do something about it.