Softball players pitch underhand because the sport’s rules require it, and those rules exist because softball was designed from the start as a distinct game from baseball. The underhand (windmill) delivery defines the sport’s identity, creates a different competitive dynamic on a smaller field, and places a different set of physical demands on the pitcher’s body.
Softball Was Built Around the Underhand Pitch
Softball traces its origins to 1887, when it emerged as an indoor alternative to baseball. The smaller playing field (60 feet from the pitching rubber to home plate, compared to 60 feet 6 inches in baseball) meant an overhand fastball would give batters almost no time to react. The underhand delivery was the natural solution: it kept the game competitive by limiting pitch speed while opening up a completely different style of play. By the time rules were unified at the first national tournament in Chicago in 1933, underhand pitching was firmly codified as a core rule of the sport.
Today, the official rules are clear. The pitcher must release the ball with an underhand motion, keeping the hand below the hip and the wrist no farther from the body than the elbow. The windmill technique, where the arm makes a full circle before releasing the ball, became the dominant style in fast-pitch softball because it generates the most speed within those constraints.
How the Windmill Motion Works
In the windmill pitch, the pitcher’s arm swings in a complete 360-degree circle, building momentum before releasing the ball near the hip. This is fundamentally different from an overhand throw, where the arm cocks back behind the head and snaps forward. The windmill keeps the arm moving in one continuous plane rather than forcing the shoulder into extreme external rotation.
That circular motion still generates serious force. Research published in the Journal of Orthopaedic & Sports Physical Therapy found that peak compressive forces at the elbow and shoulder during a windmill pitch reach 70 to 98 percent of the pitcher’s body weight. Shoulder torques equal roughly 9 to 10 percent of body weight multiplied by height. These are not trivial numbers, and they help explain why the windmill pitch, despite its reputation as “safer,” is more physically demanding than many people assume.
Why Underhand Is Easier on the Elbow
The biggest biomechanical advantage of pitching underhand is what it does not do to the elbow’s inner ligament, the ulnar collateral ligament (UCL). In overhand throwing, the arm cocks back and then whips forward, creating enormous outward stress on that ligament. This is why UCL tears (and “Tommy John” surgery to repair them) are so common in baseball. A University of Wisconsin study comparing high school baseball and softball pitchers found that while both groups averaged under 100 newton-meters of elbow torque, baseball pitchers consistently showed higher average arm stress, higher arm speed, and a more extreme arm angle. The researchers attributed this to the reduced shoulder abduction and external rotation involved in the windmill delivery.
In practical terms, the underhand motion doesn’t force the elbow into the vulnerable position that tears ligaments in baseball pitchers. The stress is distributed differently, loaded more through compression than through the sideways pulling force that damages the UCL.
The Shoulder Tells a Different Story
While the underhand pitch spares the elbow’s ligament, it creates its own set of demands on the shoulder and upper arm. One key finding: the biceps muscle works significantly harder during a windmill pitch than during an overhand throw. Research measuring muscle activation found that peak biceps activity during the windmill pitch was roughly double that of an overhand throw (38 percent versus 19 percent of maximum contraction). The hardest moment comes at the “9 o’clock” position, when the arm is roughly horizontal and pointing forward during the circle. At that point, the biceps contracts eccentrically, meaning it’s lengthening under load, which is the type of contraction most associated with muscle strain and tendon irritation.
This helps explain a pattern that sports medicine clinicians see regularly: elite windmill pitchers frequently develop anterior shoulder pain, the dull ache at the front of the shoulder caused by repetitive stress on the biceps tendon and surrounding structures. Among softball athletes overall, about 50 percent of shoulder injuries and 49 percent of elbow injuries are classified as chronic or overuse injuries rather than acute events.
Why Softball Pitchers Can Throw More Often
One of the most visible differences between softball and baseball is how often pitchers are used. In baseball, starting pitchers typically rest four or five days between outings. In softball, a single pitcher may throw multiple games in one day across two or three consecutive days, especially in youth tournament play. This convention developed because the windmill pitch was long perceived as fundamentally safer than overhand throwing.
That perception is only partially correct. A study published in the American Journal of Sports Medicine tracked youth fast-pitch softball pitchers through multi-day tournaments and found clear evidence of progressive fatigue. Shoulder and elbow strength declined after a single day of competitive pitching and continued dropping over consecutive days. Critically, pitchers did not recover to their baseline strength by the following morning, meaning they started each new day already weakened. Pain and subjective fatigue also increased steadily throughout the tournaments.
Despite this evidence, softball has no equivalent of baseball’s pitch count rules. There are no universal limits on how many pitches a softball player can throw in a game or how much rest is required between appearances. This gap between the sport’s tradition and the emerging science is an ongoing point of discussion among coaches and medical professionals.
Unique Pitches Only Underhand Can Create
The underhand release doesn’t just change the stress on the body. It creates a completely different set of pitch options. Because the ball leaves the hand near the hip with the fingers underneath or behind it, pitchers can generate spin orientations that are impossible in overhand throwing.
The rise ball is the most distinctive example. A pitcher snaps the wrist upward at release, putting strong backspin on the ball. The spinning ball generates a Magnus force (the same aerodynamic effect that makes a curveball curve) pushing upward against gravity. The ball doesn’t actually rise in an absolute sense, but it drops far less than the batter’s brain expects, creating the illusion of a rising pitch. This effect is unique to underhand delivery because an overhand pitcher releasing the ball above the shoulder can’t produce the same backspin orientation relative to the ball’s trajectory.
Drop balls, screwballs, and changeups all exploit the underhand release point in similar ways, using different wrist angles and spin directions to manipulate the ball’s path. On a field where the pitcher stands just 43 feet from the batter (in college and professional play), these movements are devastating. The batter has roughly the same reaction time as in baseball, around 400 milliseconds, but the visual angles and pitch behaviors are entirely different.
The Short Field Makes It All Work
Everything about underhand pitching connects back to the dimensions of the field. A 43-foot pitching distance with a ball that can reach 70-plus miles per hour in elite play gives the batter a challenge comparable to facing a 90-mph fastball from 60 feet in baseball. If softball pitchers threw overhand from that distance, the game would be virtually unhittable. The underhand rule keeps pitch speeds in a range that allows genuine competition between pitcher and batter while creating a sport with its own tactical depth, physical demands, and signature style of play.