Softball requires underhand pitching because the sport was invented as a safer, indoor version of baseball, and the rule stuck as the game evolved into its own distinct sport. The underhand delivery wasn’t an arbitrary choice. It was a practical solution to a real problem: people wanted to play baseball inside a gymnasium in 1887 Chicago, and throwing overhand in a confined space with a larger, softer ball was a recipe for injury. That origin story shaped every rule, field dimension, and piece of equipment that followed.
The Indoor Origins of Underhand Pitching
George Hancock is credited with inventing softball in 1887 as a way for people to play baseball indoors during harsh Chicago winters. The game needed to work in tight spaces, which meant a bigger, softer ball and a pitching motion that kept speeds manageable. Tossing the ball underhand gave players more control and reduced the risk of someone getting hurt by a fastball in a small room. The sport eventually moved outdoors, but by then the underhand rule was baked into its identity.
As softball grew through the early 1900s, organizers formalized the rules and kept the underhand requirement as a defining feature. It distinguished the sport from baseball and created a fundamentally different game, one with shorter base paths, a smaller field, and pitching mechanics that changed how hitters, fielders, and pitchers all interact.
How the Ball Changes Everything
A regulation softball is noticeably larger and heavier than a baseball. Softballs measure roughly 12 inches in circumference and weigh between 6.25 and 7 ounces, compared to a baseball’s 9 to 9.25 inches and 5 to 5.25 ounces. That size difference matters more than most people realize. Gripping and controlling a larger ball through an overhand throwing motion at high speed would be far more difficult and would place different stresses on the arm. The underhand motion works naturally with a bigger ball, allowing pitchers to generate speed and spin without fighting the equipment.
The Windmill Pitch Is Far From Slow
If you’ve never watched elite fastpitch softball, you might assume underhand pitching is casual or easy. It isn’t. The dominant technique today is the windmill pitch, where the pitcher’s arm makes a full 360-degree rotation before releasing the ball near the hip. Top college and professional pitchers throw in the mid-60s to low 70s mph. Given that the pitching rubber is only 43 feet from home plate (compared to 60 feet 6 inches in baseball), hitters have roughly the same reaction time as they would facing a 90-plus mph fastball.
The windmill wasn’t always standard. Older techniques like the slingshot pitch, where the arm swings back and then forward without a full rotation, were common through at least the 1980s. The slingshot is still legal and some coaches use it for batting practice, but the windmill dominates competitive play because it generates more speed and spin. The transition happened at different rates across the country, with the West Coast adopting windmill mechanics earlier than the Midwest.
Unique Pitch Movement
The underhand release angle creates pitch movement that’s physically impossible with an overhand delivery. The most famous example is the rise ball: a pitch that appears to defy gravity by climbing as it approaches the plate. This happens because of backspin. When a pitcher snaps the ball upward at release, the spin creates a force (the same aerodynamic principle that makes curveballs curve) pushing the ball in the direction of the spin axis. For a rise ball, that force points upward, counteracting some of gravity’s pull and causing the ball to drop less than the batter’s brain expects.
Softball pitchers also throw drop balls, curves, screwballs, and changeups, all shaped by the angle and direction of spin at the underhand release point. The combination of a large ball, short distance, and these movement patterns makes hitting in fastpitch softball genuinely difficult.
Arm Stress and Pitching Workload
A common belief is that underhand pitching is dramatically easier on the arm than overhand throwing. The reality is more nuanced. Research published in Sports Health found that windmill pitching produces high forces and torques in the upper arm, and those joint loads at the shoulder and elbow are actually similar to what baseball pitchers experience. Softball pitchers do get hurt, and shoulder and elbow injuries are well-documented at both the high school and college levels.
That said, the injury patterns differ in important ways. High school fastpitch softball players experience shoulder injuries at a rate of roughly 0.88 to 1.14 per 10,000 athletic exposures, with elbow injuries at 0.41 to 0.71. At the collegiate level, those numbers climb to 3.76 to 5.93 for shoulders and 1.5 to 3.39 for elbows. Collegiate baseball players see shoulder injury rates of 1.8 to 4.02 and elbow injury rates of 1.8 to 2.44 per 10,000 exposures. The numbers overlap more than most fans expect, though baseball’s signature injury, the torn ulnar collateral ligament requiring Tommy John surgery, appears less frequently in softball. Collegiate softball pitchers had a UCL injury rate of 1.9 per 10,000 exposures, while baseball pitchers face a broader pattern of elbow damage.
Where the underhand motion does offer a clear advantage is in recovery and endurance. Softball pitchers routinely pitch full games on back-to-back days during tournaments. About 43% of collegiate softball pitchers throw more than 100 innings per season, compared to just 7.35% of collegiate baseball pitchers. Softball pitchers also make significantly more game appearances per season. The underhand motion, while not injury-proof, allows a workload that would be impossible for an overhand pitcher. This is partly why softball rosters typically carry only two or three pitchers, while baseball teams need deep pitching staffs with strict rest schedules.
Why the Rule Will Never Change
The underhand pitching requirement isn’t just a leftover rule from 1887. It’s the foundation of everything that makes softball its own sport. The shorter distances, the larger ball, the field dimensions, the defensive positioning, the hitting strategy: all of it is calibrated around what an underhand pitcher can do. Change the pitching motion and you’d need to redesign the entire game. The 43-foot pitching distance only works because underhand deliveries top out around 70 mph. Allow overhand throwing and pitchers would be unhittable at that range, or the field would need to expand to baseball dimensions, at which point you’re just playing baseball with a bigger ball.
Softball’s underhand rule began as a practical safety measure for a winter pastime, but it created a sport with its own physics, its own athletic demands, and its own identity. The pitching motion that once made the game accessible in a Chicago gym now produces some of the most difficult-to-hit deliveries in any sport.