Korfball Shooting Elevation: Testing Clearance Over the High Post

A shooter in your gym drills the same catch-and-shoot move near the post forty times a week, and against no defender the shot is money: smooth release, soft touch, a high make rate off a cone or a coach's hand. Put a defender at arm's length with one arm fully extended overhead, the shape everyone in korfball calls the high post, and the same shooter starts getting the ball altered or swatted on close to a third of attempts. The usual instinct is to blame footwork or a rushed release. Often the real problem sits upstream of both: the shot's flight path does not clear the defender's hand by enough margin, and no footwork cue fixes a trajectory peaking a few centimeters below where it needs to.

Shooting percentage against a live defender tells you a problem exists. It does not tell you where the ball's path sits relative to the block, which is what a coach needs to fix the right thing. The protocol below measures that directly, with equipment most clubs already own, and turns a vague 'keeps getting blocked' into a centimeter figure you can retest in four weeks.

Why Clearance Margin Tells You More Than Shooting Percentage

Korfball's post stands 3.50m off the floor, topped with a 39cm-diameter open basket, and the sport's defensive rule turns that fixed height into a moving problem for a shooter. A defender may only guard an attacker at arm's length, facing them, and is allowed to raise one arm overhead to block or intercept. That rule is why shooting over the high post means something specific here: the shooter is not just clearing the rim, they are clearing a human ceiling that changes with every defender's height and reach.

Two shooters can each convert six of ten contested attempts and still be solving different problems. One clears the block by a comfortable margin and loses points to touch or entry angle at the rim. The other clears by two or three centimeters on the makes and gets outright blocked on the misses, one bad matchup from a much worse night. Shooting percentage collapses both into the same number; clearance margin, measured off the release trajectory, tells you which shooter you have.

The margin also moves independently of the shot going in: a ball can clear a block by 40cm and still miss long because the arc overshoots the rim, a touch problem rather than an elevation problem. That is the reason to test clearance as its own number, not read it off a scoresheet.

Equipment and Test Zone Setup

The test needs a regulation post, a way to record a defender's block height, a way to capture the release point, and distances matching how attackers get contested near the post.

Block height is the variable most programs skip and instead assume. A 1.65m defender and a 1.90m defender do not present the same ceiling. Measure it for each defender used, and re-measure if defenders rotate between sessions.

Step-by-Step Testing Protocol

Total time per shooter, warm-up included, runs 12-15 minutes once markers and camera are set.

1. Log baseline numbers: shooter height, dominant hand, standing reach, and defender's measured block height at each test distance.
2. Warm-up (8-10 minutes): uncontested reps near the post, building to game intensity.
3. Fix the defender's block: defender stands at the marked distance, raises the arm to full extension before the shooter receives the ball, and holds it statically. This isolates the release adjustment rather than mixing in reaction timing.
4. Familiarization: one uncontested rep and one contested rep per test distance, not scored.
5. Scored trials: five contested attempts at 1.5m from the post, then five at 2.5m, full shooting intent on every rep.
6. Capture the release: side-on video or IMU trace marking the frame the ball leaves the hand, recording release height and angle at that instant.
7. Valid trial criteria: discard any rep with a travel violation, a defender's arm below the marked height, or a shooter redirecting the shot to avoid contact rather than shooting through the block.
8. Scoring: compute clearance margin per valid trial with the formula below, then average the five trials per distance separately, since the two zones ask for different release angles.

From a Release Trace to a Clearance Margin Number

You do not need a launch monitor to estimate clearance margin. Standard projectile motion gets you there with three numbers off the release trace: release height, angle, and velocity. Height (Hr) and angle (θ) come straight off the video frame at ball release. Velocity (v0) is estimated from the ball's displacement across two consecutive high-speed frames right after release, or read off an IMU trace.

The ball's height at horizontal distance x from the shooter follows y(x) = Hr + x·tanθ − (g·x²) / (2·v0²·cos²θ), with g at 9.81 m/s². Plugging in the defender's distance (x_d) gives trajectory height at the point the ball passes the block; clearance margin is that value minus the measured block height (Hb): margin = y(x_d) − Hb.

Worked example: a shooter releases at Hr = 2.15m with θ = 52° and v0 = 6.5 m/s, against a defender at x_d = 1.0m with Hb = 2.80m. tan(52°) ≈ 1.28 and cos²(52°) ≈ 0.379, so trajectory height at 1.0m is 2.15 + (1.0 × 1.28) − (9.81 × 1.0²) / (2 × 6.5² × 0.379) ≈ 3.12m. Margin is 3.12 − 2.80 = 0.32m, about 32cm. Recalculate separately for the 1.5m and 2.5m distances, since a shorter shot tends to show a tighter margin for the same release.

What the Research Actually Shows

Published biomechanics on korfball's own shot against a raised arm is thin, so this protocol draws on the closest body of work: basketball jump-shot kinematics against a contesting opponent, producing the same postural adaptation korfball's arm's-length rule demands. Rojas, Cepero, Oña, and Gutiérrez (2000), in Ergonomics, filmed experienced basketball players shooting jump shots both unopposed and against a real defender with a raised arm, digitizing release parameters from high-speed video. Shooting against the defender produced a significantly higher release point, steeper release angle, and greater vertical velocity than the unopposed condition, the same shift this protocol measures directly. The limitation is direct: the sport is basketball, rim height and ranges differ, and the sample was small and male-only, so the magnitude should not transfer one-to-one.

Okazaki and Rodacki (2012), in the Journal of Sports Science and Medicine, had collegiate players shoot from three increasing distances and found release angle decreased while release height and ball speed increased as distance grew, with accuracy dropping at the longest distance, confirmed by repeated-measures ANOVA. That matters here: release angle and velocity shift with distance rather than staying fixed to a shooter's technique, so this protocol scores 1.5m and 2.5m separately instead of averaging them. Its limitation matches the first study: no defender was present, and the players were college-level rather than elite, so it speaks to how release parameters move with range, not the exact margin a defended korfball shot should show.

Reading Clearance Margin: Practical Bands

No published dataset reports population norms for clearance margin in korfball; the metric is not standard in the sport's literature. The bands below are a practical starting point from the trajectory math above and general shot-blocking margins in the wider jump-shot literature, not a validated table.

Treat a shooter's own number as a baseline to retest against, not a cutoff to chase alone. A shooter in the adequate band against a 1.85m defender may drop into contact risk against a defender 10cm taller, which is why block height gets measured per session rather than assumed constant.

Mistakes That Skew the Clearance Number

Turning a Low Clearance Margin Into a Training Fix

A shooter in the contact-risk band usually has one of two problems, and the release trace tells you which. A low release height with a normal angle points to a timing issue: the shot leaves the hand too early relative to peak elevation, which responds well to overhead-target drills forcing a later release against a bar marked above the shooter's reach. A normal height with a flat angle points to a habit built from years of shooting against no resistance, which responds better to cued reps where the shooter is told the block height before catching the ball and must consciously steepen the release.

Keep the Okazaki and Rodacki (2012) finding in mind before changing anything off one distance: release angle and velocity shift with range on their own, so a fix raising the 1.5m margin can leave the 2.5m number untouched. Retest both zones together, four to six weeks apart, so a technique change has enough reps to show in the trace rather than a single lucky session.