THE KICK, SLICE-KICK & SLICE SERVES

A Modern Biomechanical Guide to Serve Shape, Spin and Contact

The ACE System: Preparation • Hitting Zone • Ending

SERVE FAMILY VISUAL

A visual introduction to the serve variations examined in this article.

The Four Serve Profiles

The serve can be shaped along a spectrum rather than treated as four completely separate strokes. The ACE System uses four practical categories: the flat serve, the slice serve, the slice-kick serve and the kick serve. The important distinction is not simply the name of the serve, but the direction of racquet-head velocity, racquet-face orientation, contact location and the resulting combination of ball speed, spin, trajectory and bounce.

A first serve is commonly built around a higher speed-to-margin trade-off. A second serve normally accepts less linear ball speed in exchange for greater spin and a steeper, more predictable trajectory over the net. The exact balance is individual: elite players can use slice, kick or hybrid serves in both first- and second-serve situations.

Modern biomechanics also cautions against treating one set of angles or positions as universal. Research comparing serve types has found meaningful differences in the direction of racquet velocity and some joint motions, but results are not completely consistent between studies. Much of the research has also concentrated on flat first serves, leaving the kick and slice less extensively studied.

The ACE System

The serve will be organised into three practical phases:

• Preparation — ball toss, body organisation and the transition into the upward drive.

• Hitting Zone — the racquet and hand pathway approaching contact, the contact location and the direction of racquet-head velocity.

• Ending — the post-impact movement of the racquet and forearm, allowing the stroke to dissipate its rotational energy safely and naturally.

These phases provide useful coaching reference points without suggesting that every elite server must reproduce an identical joint angle, toss distance or swing path.

1. Preparation — The Toss

The toss is not simply the act of putting the ball into the air. It establishes the spatial and temporal conditions from which the rest of the serve is organised. A reliable toss allows the player to arrive at an appropriate contact location without having to make large compensations with the trunk or hitting arm.

For a right-handed player, the general tendency is for a first serve to be released more to the right/front of the body than a kick serve. A kick serve normally requires the ball to be positioned further to the left and often slightly behind the first-serve contact location. For a left-handed player the directional relationship is reversed.

The important coaching principle is therefore not a fixed distance such as ten or twelve inches. The useful question is: where must the ball be so that the player can swing upward and across the intended contact trajectory while maintaining balance and racquet-head speed? The required position varies with body proportions, serve direction, stance, ball toss height and individual technique.

Recent work also reinforces the importance of the tossing arm. Changes to the timing of the tossing arm can alter toss location and the subsequent serve trajectory, demonstrating that the toss is integrated with the whole-body movement rather than being an isolated hand action.

RODDICK — FIRST- AND SECOND-SERVE TOSS COMPARISON

The original visual sequence compares the release and subsequent ball trajectory.

TOSS DISPLACEMENT SEQUENCES

The second-serve toss moves further toward the left side of the server's hitting space for a right-handed player.

Tossing Arm — A Functional Reference

A useful cue is to keep the tossing arm organised long enough to help establish the intended contact window, rather than collapsing it early. The arm, trunk and head form a coordinated reference system for locating the ball. The goal is not to hold a rigid pose but to give the hitting system a stable spatial target.

• First serve: establish a contact window that supports a more direct upward-and-forward racquet trajectory.

• Kick serve: establish a contact window that permits more upward and lateral racquet-head motion around the ball.

• Slice-kick: occupy the middle ground between these two intentions, combining meaningful forward velocity with a stronger spin component.

2. Hitting Zone — Contact

The major technical difference between serve types is created during the approach to impact. Spin is produced by the relationship between racquet-head velocity, racquet-face orientation and the ball's contact with the strings. The post-impact finish is an outcome of that interaction; it is not the mechanism that keeps the ball on the strings or creates the spin.

For coaching, the path of the hitting hand and racquet can still provide an excellent kinesthetic reference. The original sequences in this article show that the hand approaches the ball along a somewhat different three-dimensional pathway in the first and second serves. Modern analysis supports the broader principle: kick serves tend to have a greater lateral component of racquet velocity, while flatter serves tend to emphasise the forward and vertical components more strongly. However, the exact path varies between players.

SAFIN — FIRST-SERVE HAND PATHWAY

Original eight-frame hand-path sequence.

SAFIN — SECOND-SERVE HAND PATHWAY

Original eight-frame hand-path sequence.

RODDICK — FIRST-SERVE HAND PATHWAY

Original eight-frame hand-path sequence.

RODDICK — SECOND-SERVE HAND PATHWAY

Original eight-frame hand-path sequence.

The 'Hammer Position' — A Useful Cue, Not a Universal Angle

The ACE System uses the term 'hammer position' for the racquet-hand organisation immediately before the final acceleration to the ball. It remains a useful coaching image because the hand and racquet appear organised to accelerate upward toward the contact zone.

The original article used specific forearm angles to distinguish slice, slice-kick and kick serves. Modern evidence suggests that these should be treated as approximate visual tendencies rather than fixed technical rules. Different players can produce the same ball characteristics using somewhat different segment orientations and timing.

A more useful continuum is:

• Slice — greater emphasis on a cutting, lateral component of racquet-head motion, producing sidespin with a relatively direct trajectory.

• Slice-kick — a blend of lateral and upward racquet-head motion, producing both sidespin and meaningful topspin.

• Kick — a stronger upward/lateral component, producing greater topspin and a higher-bouncing ball.

FOREARM APPROACH — FIRST SERVE

Original visual examples of the forearm/racquet approach before impact.

FOREARM APPROACH — SAFIN

The original sequences illustrate the different approach orientations used across serve types.

3. Contact — Direction Rather Than a Clock Face

The 'imaginary clock' remains a useful coaching visual, but it should be understood as a representation of the intended racquet path around the ball rather than a universal contact law. A flatter first serve is commonly contacted with a more forward-directed racquet path. A kick serve requires the racquet to move more upward and laterally across the ball. A slice serve sits between these extremes depending on the desired amount and direction of sidespin.

For a right-handed player, a useful starting image is that the kick contact is located somewhat to the left of the first-serve contact. The exact position should be individualised according to serve direction and the player's natural swing path. The objective is to create the intended ball-flight conditions rather than to hit a predetermined clock number.

RODDICK — CONTACT COMPARISON

First- and second-serve contact comparisons from the original visual material.

MOYA — CONTACT COMPARISON

The same comparison using Moya's serve.

Contact Height and Body Relationship

The contact point is high because the server is reaching into the ball with an extended hitting arm, but 'higher' does not automatically mean 'better'. The player must be able to reach the ball with sufficient stability and without excessive spinal extension or lateral collapse.

The first serve generally uses a contact location that is further forward and more directly aligned with the intended ball trajectory. The kick serve typically places the ball more to the left and slightly further back for a right-handed server, allowing the racquet to travel upward and across the ball. These relationships should be coached as functional windows rather than exact coordinates.

SAFIN — FIRST- AND SECOND-SERVE CONTACT

Original contact-point comparison.

RODDICK — FIRST- AND SECOND-SERVE CONTACT

Original contact-point comparison.

4. Ending — Forearm Rotation and Racquet Release

The modern interpretation of the serve finish is particularly important. The racquet does not create spin because it 'stays on the ball' after contact; ball-racquet contact occurs over only a few milliseconds. Instead, the ball's spin is determined by the racquet's velocity vector, face orientation and the relative motion at impact.

Forearm pronation is a rotation of the forearm in which the radius crosses relative to the ulna. It is not simply a wrist flick. Ulnar deviation is movement of the hand toward the ulna side of the forearm. Both motions can occur around the impact and follow-through, but their timing and magnitude vary with the serve type and individual technique.

For coaching purposes, a second serve can often benefit from a feeling of maintaining the racquet's upward/lateral trajectory through the contact zone before allowing the forearm and racquet to rotate naturally into the follow-through. On a slice serve, the racquet may rotate into its post-impact position sooner. These are movement cues rather than instructions to force a particular wrist action.

ULNAR DEVIATION — ANATOMICAL REFERENCE

Ulnar and radial deviation of the wrist/hand.

POST-IMPACT RACQUET MOVEMENT

Original visual sequences illustrating the post-impact racquet and forearm action.

SLICE-KICK POST-IMPACT EXAMPLE

The original sequence highlights the immediate post-impact racquet position.

The Serve Spectrum

The most useful way to understand these serves is as different solutions to the same biomechanical problem: how to direct the racquet-head velocity into the ball so that the resulting combination of speed, spin, trajectory and bounce serves a tactical purpose.

Serve	Primary ball characteristic	Racquet-path emphasis	Typical tactical use
Flat	High linear speed; comparatively low spin	More forward/direct	High-speed first serve; pressure through pace
Slice	Sidespin with some forward speed	More lateral/cutting component	Wide angles, movement, changing direction
Slice-kick	Sidespin + meaningful topspin	Upward + lateral blend	Second serve with pace, clearance and movement
Kick	High topspin; pronounced bounce	Strong upward/lateral component	Second serve, height over net and high bounce

Practical ACE Coaching Progression

• Preparation: establish a repeatable toss and a stable spatial relationship between the ball, head and hitting shoulder.

• Hitting zone: first identify the intended ball trajectory, then organise the racquet path that can create it.

• Slice: feel more lateral movement around the ball while maintaining forward racquet speed.

• Slice-kick: blend upward and lateral racquet-head motion rather than trying to 'add' spin with the wrist.

• Kick: prioritise a reliable upward/lateral racquet path and sufficient net clearance.

• Contact: use the clock-face concept only as a visual cue; individualise the actual contact location.

• Ending: allow pronation and wrist motion to emerge naturally from the acceleration and racquet path rather than forcing a post-impact position.

• Progression: develop the movement at submaximal speed first, then increase racquet-head speed while preserving the intended contact window.

Modern Technical Checklist

• Can the player reproduce the toss without significant lateral or backward correction?

• Does the toss create a usable contact window for the intended serve rather than a predetermined number of inches?

• Does the racquet approach the ball with the intended combination of forward, upward and lateral velocity?

• Is the kick serve actually producing topspin and a higher bounce, rather than simply being hit higher over the net?

• Is the slice serve producing meaningful sidespin without sacrificing unnecessary ball speed?

• Can the player produce a slice-kick by blending the two movement intentions rather than manipulating the wrist?

• Is the contact location stable enough to allow the intended ball trajectory?

• Does the racquet and forearm rotate naturally after impact rather than being forcibly 'flicked'?

• Can the player repeat the serve under pressure without excessive compensatory trunk or wrist movement?

Biomechanical Context

Contemporary serve research supports a flexible, individualised approach. Studies comparing flat, slice and kick serves have found differences in the direction of racquet velocity and selected joint motions, but findings are not completely consistent across studies. A 2023 systematic scoping review identified substantial methodological variation and noted that most available serve research still focuses on flat serves. A 2024 systematic review similarly found wide variation in reported serve kinematics. More recent work also demonstrates that the tossing arm can influence the timing and trajectory of the whole serve.

The coaching implication is straightforward: use biomechanics to understand the purpose of a movement, then use visual and kinesthetic reference points to help the player reproduce that purpose. The reference points in this article are therefore best treated as adaptable guides rather than rigid positions that every player must copy exactly.

References

• Lambrich, J., & Muehlbauer, T. (2023). Biomechanical analyses of different serve and groundstroke techniques in tennis: A systematic scoping review. PLOS ONE, 18(8), e0290320. DOI: 10.1371/journal.pone.0290320.

• Jacquier-Bret, J., & Gorce, P. (2024). Kinematics characteristics of key point of interest during tennis serve among tennis players: a systematic review and meta-analysis. Frontiers in Sports and Active Living. DOI: 10.3389/fspor.2024.1432030.

• Reid, M., et al. / related serve-type literature summarised in Lambrich & Muehlbauer (2023): differences in racquet-velocity direction and selected upper- and lower-body kinematics between flat and kick serves.

• Whiteside, D. et al. (2012). Review of tennis serve motion analysis and the biomechanics of three serve types with implications for injury. Sports Medicine.

• Biomechanical analysis of three tennis serve types using a markerless system (2012), PubMed PMID 22936411.

• Recent tossing-arm research (2025): The Hidden Link in the Kinematic Chain: The Influence of the Tossing Arm on Head and Serve Kinematics in Tennis, PMCID PMC12294548.