Serve 2.0: Biomekanik och dataanalys bakom en snabb och skadefri tennisserve

Serve 2.0: Biomechanics and data analysis behind a fast and injury-free tennis serve

September 10, 2025

Introduction: Speed without damage

The tennis serve has evolved into a powerful weapon in modern tennis, but with higher speeds comes the risk of overload. Today's elite players are therefore looking to optimize every link in the body's movement chain – from footwork to wrist flick – to maximize speed without increasing the risk of injury. In this post, we delve into Serve 2.0 : how advanced biomechanics, data analysis and evidence-based training are helping elite players hit harder serves safely. We review the kinetic chain of the serve, current research findings on shoulder and back strain, expert quotes on technique and injury prevention, as well as concrete prehab and training routines both on the court and in the gym. Finally, we also compare the serve styles of different top players (e.g. Zverev vs. Alcaraz, Sabalenka vs. Swiatek) to highlight that there are multiple paths to an effective and healthy serve.

The kinetic chain in the serve

Image: Illustration of the three phases of the serve (preparation, acceleration, completion) and a total of eight sub-moments [1] Each sub-moment builds on the previous one, and energy is stored in the preparation phase and then released in the acceleration phase [2] [3] .

A tennis serve is a complex movement that involves the entire body in a sequence of segmental rotations – often called the kinetic chain [4] . Power generation begins in the legs and travels up through the hips and torso to the shoulder, arm and finally into the racket head and ball [4] An effective serve utilizes synchronized movements in all body segments , where major muscle groups are activated in the correct order to sum forces from the ground up. [4] [5] If any link in the chain is mistimed or weak, the result can be suboptimal – either lost speed or increased load on other links [6] .

Research shows that the legs and torso are the “engine” of a serve. By pushing off the ground and twisting the torso upwards, over half of the energy is generated and ultimately transferred to the racket [7] In fact, the legs+torso can account for about 51–55% of the total kinetic energy in a maximal serve [7] These large muscle groups also provide a stable base (proximally) that allows for rapid movement distally in the arm with control [7] Conversely, this means that if the lower body contributes less, the arm must compensate – one study using mathematical modelling found that a 20% reduction in energy contribution from the torso would require a 34% higher swing speed in the arm (or 70% more mass) to achieve the same ball speed [8] In other words, strong leg and core support is crucial both for performance and to relieve shoulder/arm strain.

Kinetic chain connection to injury risk: An effective technique where the force comes from the ground reduces stress on the shoulder and elbow. Studies have shown that elite players who use an optimal “leg rattle” (properly bent front knee joint >15° in the jump) experience lower stress on the anterior shoulder and inner elbow when hitting the ball [9] The benefits of a well-coordinated kinetic chain include a reduced risk of injury in a high-performance serve [10] Conversely, a weak link or lack of technique can increase the load: For example , 17% higher shoulder load and 23% higher elbow load occur if a player does not bend their knees enough in the upstroke phase of the serve (“cocking”), to still achieve the same ball speed [11] . This is because more of the work is then forced to be done by the upper body. As a coach and player, you should therefore strive to activate the entire body chain – from the foot strike and the squat, via the rotation of the hips and torso, to the shoulder/arm snap – for maximum effect per risk.

Shoulder and back strain: research and risk zones

The serve is the stroke in tennis that places the greatest strain on the lower back , through a powerful combination of rotation, hyperextension, and lateral bending of the spine [12] . Measurements in a laboratory environment have found that the lateral bending forces in the back during a serve can be up to 8 times greater than the forces that occur when, for example, running [13] These peak forces occur simultaneously as the player pushes off the ground and extends/rotates the trunk explosively [13] . Especially with kick serves, where the back is bent and twisted even more to generate topspin, the back can be exposed to extra stress – biomechanical analyses suggest that kick serves with the racket head further behind the body increase the risk of both shoulder and back injuries compared to flatter serves [14] .

A common overuse injury to the lower back in young tennis players is a stress fracture of the vertebral arch (spondylolysis), often caused by repeated hyperextension and lateral rotation in the serve position. In the worst case, this can lead to a slipped vertebra (spondylolisthesis). The extreme range of motion required by the serve explains why back pain is the most common injury among tour players, according to ATP medical director Todd Ellenbecker: “There’s so much rotational stress in the lower back… the torso is the hub that funnels the force from the legs to the arm, and that’s why the lower back is often affected,” says Ellenbecker [15] . Researchers and clinicians therefore recommend training that increases core stability and controls spinal mobility to withstand the load of the serve. For example, EMG studies find that players during the serve activate the core muscles strongly in several directions – both the deep back extensors and the lateral abdominal muscles contract to stabilize the spine [16] [17] At the same time, elite players tend to develop an imbalance between stronger abdominal muscles (forward flexion) and relatively weaker back extensors [17] , which emphasizes the need to train both sides (both trunk rotation in both directions and back extension) for injury prevention purposes [17] .

Shoulder challenges: The shoulder joint is exposed to extreme ranges of motion and forces during the serve. In the so-called cocking phase (when the racket is brought far back and up before impact), elite players reach a maximum outward rotation of the shoulder joint of about 170–180° – similar values to those of professional baseball pitchers [18] This large outward rotation, combined with the arm being lifted to the side (~100° abduction) and slightly pulled backward, creates a potentially exposed position for the soft tissues of the shoulder [19] [20] Cadaver studies have shown that such a hyperabducted and externally rotated position increases contact between the rotator cuff tendons (primarily supraspinatus/infraspinatus) and the posterior aspect of the scapular fossa – a phenomenon known as internal impingement [20] . In throwing athletes, this posterior impingement is a known risk factor, which can lead to irritation and minor injuries to tendons and labrum. If the serving technique is faulty – e.g. the player drops the throwing arm too early and rotates the hip/torso too early forward – the arm can end up too far behind the body (so-called “arm lag”), which further increases the risk of pinched structures in the back of the shoulder [21] .

In addition, at the moment when the shoulder is maximally externally rotated, the anterior structures are subjected to great stretch. The muscles in the rotator cuff and around the scapula must work hard to stabilize the shoulder joint in this phase. Measurements of muscle activity show moderate to high activation (approximately 40–70% of maximum) in, among others, supraspinatus, infraspinatus, subscapularis, biceps brachii and serratus anterior during the cocking phase [22] – all of which contribute to keeping the ball of the shoulder centered and controlling movement. This data underscores the importance of strong rotator cuff and shoulder stability for a safe serve [22] A weakness in these stabilizers, or a lack of power transmission from the legs, forces the shoulder joint to endure more wear and tear to generate speed [11] This is consistent with the injury profile: among the most common overuse injuries in elite players are internal impingement of the shoulder, rotator cuff tendinopathies, and SLAP injuries (injuries to the labrum of the shoulder joint) [23] . Back and hip problems can also arise as a result of imbalances in power transmission. Overall, epidemiology shows that the shoulder and lower back are among the most vulnerable areas in professional tennis [24] [25] – especially for server specialists who perform thousands of explosive upper arm movements per year.

The expert's words: “Proper technique is one of the single most important factors in preventing injury,” emphasizes Todd Ellenbecker [26] , physiotherapist and medical director on the ATP tour. He reminds us that even with perfect technique, excessive amounts can still cause injuries – it’s about finding the balance between training and recovery [27] [28] But an efficient, well-coordinated serve that avoids unnecessary strain on the shoulder and back is a big step towards both maximizing performance and minimizing the risk of injury in the long run.

Prehab and training: building a sustainable serve

To be able to serve hard without wearing out the body, elite players and their teams place great importance on prehab – preventive training and proper warm-up – as well as continuous physical training aimed at the demands of serving. Here we break it down into work on the court and in the gym , focusing on a few key areas and exercises.

On the court: technique exercises and warm-up

Before your first serve in practice or a match, pros make sure your shoulders, back, and hips are properly warmed up. A typical on-court serve warm-up might include:

· Dynamic mobility: arm circles, windmills and scapular wall slides to activate the shoulder blade muscles. Also trunk rotations (e.g. standing rotation with medicine ball without throwing) to soften the spine and hips.

· Shadow serves: Many players do some mimed serve movements without the ball, perhaps with a light racket or just their arm, to wake up the nervous system and instill rhythm into the serve. The focus is on rhythm (“dip and drive”) rather than power.

· Medicine ball throws: A popular drill is explosive medicine ball throws that mimic the motion of a serve. For example, the player can do an overhead slam into the ground or against a wall, which trains the connection between leg thrust, hip/torso rotation, and arm flick in one complete movement.

In addition to the warm-up, coaches often work with technique drills to improve the biomechanics of the serve. This can involve isolating certain parts of the movement, e.g.: kneeling and serving (to focus on the shoulder and arm movement), or conversely practicing only leg presses against a medicine ball without hitting, to enhance the feeling of the legs' contribution. Another exercise is serves with delayed arm swing – the player pauses in the trophy position (backswing with the racket up) before hitting – which can help find the right sequence (that the hip and torso rotate before the arm hits, not the other way around). Through video analysis, the coach can provide feedback on whether the player, for example, drops their throwing arm too early or if the squat is insufficient – factors that, as mentioned, affect both speed and injury risk [20] [11] .

In the gym: strength, stability and mobility

Off-court strength and mobility training is equally important for Serve 2.0 . Here, efforts are focused on both improving power generation (e.g. explosive leg strength) and strengthening the small, stabilizing muscles that protect the shoulders and back. ATP physiotherapist Ellenbecker points out that modern players “need to get fit to play tennis, not play tennis to get fit” – i.e. preparing the body physically for the demands of the sport [29] Especially for the shoulder, this means preventive strength training .

Some cornerstones of gym prehab for serve:

· Rotator cuff and scapula: Elite players perform daily exercises with rubber bands or light weights for external rotation, internal rotation, scaption / “Y-raise”, as well as scapular exercises such as “prone T's/Y's” (lying on your stomach and raising your arms in a T and Y shape). The goal is to build endurance in the small muscles . “Most tennis players do too much pressing exercises for the front – muscles that are already strong – but neglect the small muscles that hold the scapula in place,” says Ellenbecker [30] He instead recommends light loads and high repetitions (e.g. 3×15–20) for muscles such as the rotator cuff, trapezius, rhomboids, and serratus anterior [31] These durable stabilizers help the shoulder joint withstand serve after serve without collapsing.

· Shoulder mobility: Repetitive serving can lead to increased external rotation but decreased internal rotation of the dominant shoulder (GIRD – glenohumeral internal rotation deficit) [32] To counteract this, mobility exercises such as cross-body stretches (pulling the arm across the chest to stretch the posterior shoulder capsule) and “sleeper stretches” (internal rotation of the shoulder in a side-lying position) are often included – exercises Ellenbecker believes “should be done by every serious tennis player” [33] [34] They help maintain normal mobility and prevent impingement.

· Core: A strong and balanced core is critical for transferring power from the legs and protecting the lower back. Players perform everything from anti-rotation exercises (e.g. , Pallof press , side planks) to explosive rotational exercises (sidewall medicine ball throws, Russian twists) to both stabilize and generate rotational power. It is important to train the core symmetrically —i.e., including the non-dominant side—to counteract imbalances that can lead to back problems [17] .

· Hips and Legs: Hip mobility and leg strength are the foundation of the entire serve chain. Deep lunges, hip flexor stretches, and 90/90 rotations improve hip range of motion so the player can descend and rotate without restriction. For explosiveness, leg curls, jumps, and lunges are practiced—often with a focus on unilateral variations since serving is a unilateral movement. For example, a player can do Bulgarian lunges or one-leg hops to mimic the leg kick of the serve. Studies have shown that good front-leg drive is associated with lower shoulder strain [9] , so there is also an injury prevention aspect: strong, explosive legs can take a greater share of the force requirement so that the shoulder is not overloaded.

Finally, the pre-hab session is wisely planned into the training schedule. One tip from physiotherapists is not to do tiring shoulder exercises right before tennis practice – exhausting your rotator cuff with band exercises before serving a hundred balls is like running the mile right before a marathon, which increases the risk of injury [35]. [36] . Instead, the heavier shoulder strength is added after the tennis session or with a good margin of time before, so that the muscles have time to recover. Warming up with bands before a game is still good, but then with light resistance and a focus on activation, not exhaustion.

Data analysis: from force plates to smart sensors

Another hallmark of Serve 2.0 is that the elite are using objective data and new technology to fine-tune their technique. High-tech training centers around the world are using 3D motion analysis, high-speed cameras, force plates and sensors to understand exactly what a player's serve looks like biomechanically.

Traditionally, much research on the serve has been done in a lab environment with marker-based motion capture and force platforms under the feet [37] . This has enabled us to measure joint angles, time sequences and ground forces – for example, how much energy each segment contributes, or how much load a certain movement pattern places on the joints. As we mentioned earlier, we can quantify things like 55% of the energy coming from the legs/torso, or that incorrect knee use increases shoulder load by double-digit percentages [7] [11] . Thanks to the technology, coaches can identify “leaks” in the kinetic chain: Perhaps the player generates good power in the legs, but loses it due to poor core stability? Or the arm moves too early before the hip has fully rotated, which makes the shoulder work extra hard (a potential “pathomechanical” pattern according to the researchers) [38] By identifying inefficient movements that increase joint stress without increasing speed, technique can be adjusted to both increase speed and reduce injury risk [38]. .

Nowadays, technology is also starting to move out of the lab and onto the tennis court. Wearables and markerless systems enable analysis in more natural environments. For example, researchers have tested inertial measurement suits (IMUs) to measure serves on the court – with small motion sensors on the body, 3D data on joint angles and segment movement can be obtained in real time, without cameras [39]. [37] In a case study with such an IMU suit (Xsens), it was shown that two different players (a man and a woman) had very similar movement sequences and energy contributions in their serves, which suggests that the technology provides reliable data [40] [41] . Such wearable technology opens the door for coaches to provide direct feedback on a player’s serve on the practice court – one could imagine sensors vibrating or giving a signal when, for example, hip rotation is too slow or if the center of gravity is not moving correctly. Smart racket sensors are also available: they measure swing speed, angle and ball strike and can give a player statistics about their serve (e.g. maximum racket speed, location of the impact point on the strings, spin, etc.). Such data, combined with video, provides a rich picture of the serve as a whole.

At the highest level, systems such as Hawk-Eye and video analysis of matches are also used to see trends. One can analyze serve speed vs. placement, the effect of kick serve vs. slice, how fatigue affects serve technique over time [42] , etc. During a match, coaches can see if the first serve percentage drops or if the second serve becomes too cautious under pressure – then they know what needs to be honed in training. Overall, they use both biomechanics experts and “big data” to drive serve development forward. A telling example is Aryna Sabalenka, a top-ranked WTA player, who in 2022 had major serve problems (a stream of double faults) but hired a biomechanics specialist to analyze and rebuild her serve [43] [44] . Through video reviews they discovered technical flaws – “He was just showing what's not really right about my serve” , Sabalenka said [44] – and then they changed her movement pattern. Her previous choppy movement with a “hitch” was replaced by a smoother and more compact swing [45] She also reduced the raw power a little and increased the percentage of topspin, to get better margins [45] The result was not long in coming: Sabalenka went from 56 double faults in four matches at the 2022 Australian Open to just 11 double faults during the same stretch at the 2023 Australian Open [46] – and won the title. Her first serve is still XL at speed (she often serves over 190 km/h) but thanks to data analysis and technical adjustments, it is now significantly more reliable and less prone to damage.

Different serve styles: examples from ATP and WTA

Despite common biomechanical principles, serve technique can vary greatly between players. Individual factors such as body height, mobility, timing and tactical preferences mean that “one size does not fit all” when it comes to the serve. Here we briefly compare some contrasting serve styles of today’s stars and how they all benefit from kinetic chain and technique training:

Explosive power vs. reach (Zverev vs Alcaraz): Alexander Zverev (198 cm tall) illustrates how a tall player can deliver enormous serve power relatively “easily” thanks to leverage and reach. Zverev’s first serve averaged ~208 km/h in 2024 (about 129 mph) – significantly higher than the tour average [47] – and his average second serve of around 169 km/h is also a tour top [47] . Much of this comes from his explosive legs and high contact point: he has a deep squat and extends high at impact, which gives him a steep angle and speed. Carlos Alcaraz, on the other hand, is ~185 cm (6 ft 11 in) tall and needs to maximize his explosiveness to keep up with his serve speed. At Wimbledon 2024, Alcaraz's fastest serve was measured at ~217 km/h (135 mph) and his average was around 187 km/h (116 mph). [48] – a clear improvement after he and coach Juan Carlos Ferrero focused on the serve. They changed Alcaraz's technique by going from two stops to one on the backswing, for a smoother rhythm and more efficient power transfer. [49] The result has made his serve both faster and more reliable under pressure, according to Alcaraz himself. [50] [51] . Zverev's serve is characterized by a fluid " down-up-hit " rhythm and takes full advantage of his length, while Alcaraz's serve demonstrates how an optimized chain and explosive training can give a relatively shorter player an elite serve. Both players, of course, work with their physical teams to keep their shoulders and backs healthy despite the high speed - the key is that their technique lets the legs and core do the work, rather than overloading the arm.
Redesign for stability (Sabalenka vs. Swiatek): Aryna Sabalenka and Iga Swiatek are two top women’s players who have recently reworked their serves with great success, but for different reasons. Sabalenka, known for her raw power, had a serve that collapsed in 2021 with a huge number of double faults. Through biomechanical analysis, she discovered that the problem was technical: “Even when my serve worked, it wasn’t quite right,” Sabalenka admits. [52] She mustered up the courage to change her practiced movement pattern and made the serve more compact and topspin-oriented [45] . Now she still has one of the hardest serves on the tour, but the movement is easier to repeat under stress. Iga Swiatek, for her part, didn’t have a bad serve – but as world number one she was still looking for improvement. For 2024 , “we changed the whole movement before the shot, basically,” Swiatek said. [53] Her new serve is shorter and softer in the approach; she holds her arms higher initially and eliminated an unnecessary chop at the beginning of the swing. [54] [55] The goal was to make the serve more consistent and stress-resistant – “we make it smoother and shorter, so I don’t have time to hesitate under pressure,” says Swiatek [56] The change paid off: Swiatek increased his first serve percentage and saved more break points than anyone else in the first half of 2024 [57] . Mary Carillo, a commentator and former professional, noted during Roland Garros that Swiatek's new serve looked "very controlled", while fellow player Elena Rybakina (known for one of the WTA Tour's most beautiful serves) has a more relaxed, natural swing. [58] [59] . It shows that there is no one right way – Sabalenka and Swiatek have different physiques and styles, but both found their solutions through technical analysis: one to tame their explosiveness, the other to get more out of their potential. Both examples highlight the importance of being open to change even at the highest level: small technical adjustments, supported by biomechanical data, can make a big difference to both serve quality and injury prevention.

Conclusion

Serve 2.0 is about combining science and sport : by understanding the biomechanics of the serve in minute detail, players and coaches can find ways to increase speed while relieving the body. A well-coordinated kinetic chain – from strong legs and mobile hips, through a stable and explosive core, to a powerful but controlled shoulder/arm movement – is the foundation of an elite serve. Modern research warns of risk zones such as lumbar rotation/extension and extreme external rotation of the shoulder, but it also shows the way to counteract injuries: through pre-game exercises (e.g. rotator cuff, core stability, mobility) and through technique adjustments based on data.

Finally, we see that even among the world stars there are different serving styles – the important thing is not to copy a certain player’s technique, but to make the most of one’s own strengths and avoid unnecessary stress. As Ellenbecker puts it: overexertion is the tennis player’s worst enemy [60] , but with the right training and smart use of biomechanics, you can push the boundaries of serve speed without paying the price in injury. Serve 2.0 is here to stay – harder, smarter and more durable than ever.

Important biomechanical checkpoints and prehab tips

Checkpoint in the serve	Key points & tips
Footwork & balance	Stable basic position. Balance between front and back foot in the throw; good balance reduces oblique strain. Practice landing in a controlled manner in the finish to protect your back.
Squats & leg extensions	>15° bend in the front knee is recommended for good leg drive [9] Deeper squats (especially with foot-up technique) provide higher jumps and more upward force [61] . Practice explosive jumps and single-leg exercises.
Hip & trunk rotation	Maximum separation between hips and shoulders (“X-factor”) in the upstroke stores energy. The torso should rotate and flex appropriately – excessive hyperextension can strain the back. Train the torso in rotation (medicine ball throws) and anti-rotation (Pallof press).
Shoulder joint cocking (straightening)	The shoulder is externally rotated ~170° just before ball impact [62] . Full range of motion is good for speed, but requires stability. Important: avoid placing the shoulder too far back/up (risk of impingement [20] ). Prehab: Sleeper stretch for internal rotation, band exercises for rotator cuff.
Arm and racket acceleration	The arm strikes forward with elbow extension, internal rotation of the shoulder and pronation of the forearm. Timing is critical – the arm should come like a whiplash after the hip/torso has started the rotation. Technique drill: “sequence serves” (focus on the order).
Wrist flick & pronation	After hitting the ball, the forearm pronates and the wrist flicks, which increases speed and creates spin. A relaxed wrist gives the best effect – avoid convulsively “musing” the racket. Exercise: Serve at half speed and feel the pronation clearly.
Follow-up & recovery	A complete movement where the arm sweeps down to the opposite side ends the serve chain and helps to gently slow the arm down. An abrupt stop increases the risk of injury. Practice “throwing through the target” – let the arm go naturally to the final position. After serving session: do a light stretch of the chest muscles and shoulders to recover.

Pre-hab favorites: After tennis practice, many players do their shoulder routines : 3×15 external/internal rotation with rubber bands, scapula push-ups , and 2–3×30 seconds sleeper stretch and cross-body stretch for the shoulder [63] [34] . Hip/back prehab can include cat-camel and the world's greatest stretch (for mobility), plus side planks and bird-dogs (for core stability). By ticking off these checkpoints and exercises, coaches and players can ensure that the serve is not only fast – but also sustainable over time.

Sources: This review is based on current research articles and expert opinions in tennis medicine and biomechanics. All references are listed in the text in the format 【 number† row-row 】 for in-depth reading. Thanks to scientific insight, we can continue to develop the tennis serve with both speed and health intact – something that benefits both professionals on the ATP/WTA tour as well as coaches and players at all levels.

[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [16] [17] [18] [19] [20] [21] [22] [32] [33] [61] [62] [63] An 8-Stage Model for Evaluating the Tennis Serve: Implications for Performance Enhancement and Injury Prevention - PMC

https://pmc.ncbi.nlm.nih.gov/articles/PMC3445225/

[11] [23] Current Sports Medicine Reports

https://journals.lww.com/acsm-csmr/fulltext/2020/10000/common_and_less_well_known_upper_limb_injuries_in.9.aspx

[12] [13] [14] Aspetar Sports Medicine Journal - Low back pain in the young tennis player

https://journal.aspetar.com/en/archive/volume-3-targeted-topic-sports-medicine-in-tennis/low-back-pain-in-the-young-tennis-player

[15] [24] [25] [26] [27] [28] [29] [30] [31] [34] [35] [36] [60] Todd Ellenbecker- Injury Prevention and Recovery for Tennis - Athletic Performance Academy