Tips for Coaches and Players
TennisBPM | Coach Ran
Almost three decades working with juniors, professionals, federations, and national teams globally there is one piece of serve advice I hear more than any other: work on your core. The serve is slow, or the shoulder is sore, so the session finishes with planks, crunches, band rotations and a few Russian twists, and everyone feels something useful was done.
Sometimes it was. Often, it was not, or not for the reason people think. So, I went through the research and linked them below to see what it really says as many in this decade is all about what is trending on social media rather than the reality. This article is my practical answer for coaches and players, from U14 to the pro tour with scientific base.
How the serve really gets its speed.
The serve is not an arm action. It is a kinetic chain, and the arm is the last link attached to the racket. Kovacs and Ellenbecker describe the legs and trunk as the engine, producing roughly 51 to 55 percent of the kinetic energy and force that reaches the hand [2]. Ben Kibler puts the shoulder’s share at only about 13 percent of the total kinetic energy of the serve [3]. The arm mostly passes on what the ground and the trunk have already built.
This is where the trouble starts. In the modelling quoted by Kovacs and Ellenbecker, a 20 percent loss of trunk energy would need about a third more shoulder velocity to deliver the same energy to the hand [2]. The shoulder is already one of the busiest joints in tennis. I do not want to ask it to cover for a weak link below it.
So yes, the core matters. Nobody seriously argues otherwise. The real question is a different one: does training the core make the serve faster?
How the core responds when you serve
The trunk works hardest now the racket accelerates. In a surface EMG study of 19 male players, every lower trunk muscle recorded its highest activity in the acceleration phase [5]. The abdominals at the front and the muscles of the lower back were firing together, with a lot of co-activation [5].
My take is that the trunk is bracing and rotating at the same time. It is not one muscle doing one clean job. It must keep the spine steady while the body twists and folds through the hit.
What the evidence says. That load comes with a price. A review of rectus abdominis strains in tennis players describes the late cocking phase, when the lower back arches and the shoulder go back, as the point where the abdominal muscles take a heavy eccentric load. It names that overload as the accepted injury mechanism for these strains [6]. In the EMG study, the lower-skilled group showed more trunk hyperextension, and the authors linked that to a higher risk of back injury [5].
So, the core has two jobs in the serve. It helps produce speed, and it protects the spine while doing so. Any core plan must cover both.
Speed is a whole-body coordination, not one muscle.
A 2024 motion-capture study tracked flat serves four ranked players with 82 body markers, 10 infrared cameras and two force plates [7]. Eleven measures showed very large, almost perfect correlations with racket speed. The list reads like a walk up the chain: vertical force through the back foot, back and front knee flexion, hip and shoulder rotation, trunk rotation in the loading phase, then trunk rotation and flexion again in the acceleration phase [7].
Trunk rotation appears twice. The legs appear several times. That matches what I see on court: a fast serve is about timing and sequence across the whole body, not one segment doing the work.
Take note: The study analyzed five serves from four players, so treat it as a description of patterns, not a rule [7]. And it measured movement and force, not muscle strength, so it cannot say how strong a trunk needs to be. It does say the trunk is one link among several. Hence isolation of core training is bad method instead of having a long-term S&C periodize plan.
What the research says:
Deng and colleagues combined 16 randomized trials, picked from 271 papers, which looked at strength and conditioning and serve speed in tennis players [1]. Three results matter here:
- Resistance training: significant effect (ES = 0.53, p < 0.001)
- Multimodal training: significant effect (ES = 0.79, p = 0.001)
- Core training: effect not significant (ES = 0.32, p = 0.231)
Read that last line carefully. “Not significant” does not mean “does nothing.” It means the data could not separate the effect from zero with confidence. The number leans positive, but it is smaller and less certain than the others, and the authors themselves ask for more high-quality studies [1].
My take: core training on its own is not the strongest edge for serving speed, and nobody can promise it is a reliable one. Training plans that combine several qualities did best, which fits a movement that needs the legs, trunk and arm working in sequence.
Why core work on its own may fall short.
The meta-analysis shows core training lagging behind other methods, but it does not say why [1]. I see three reasons. None of them is proven by the data.
- Speed. The trunk peaks in the acceleration phase of the serve [5]. A plank is slow and static, so the muscle is asked to do something quite different from what it does at the hit.
- Direction. The serve uses rotation and flexion after lumbar extension to build force [6]. Many popular core exercises train the trunk to resist movement, or to flex under light load.
- Dose. Core exercises are often done for time and rarely get heavier. Leg and upper-body strength usually progresses in load, which may be part of why those methods showed clearer effects.
What the evidence says. The better evidence comes from programmes that put the trunk inside a bigger plan. In one randomized trial, 30 nationally ranked 13-year-old boys were split into a training group and a control group. The training group did three sessions of 60 to 70 minutes a week for six weeks, made up of core strength, elastic resistance, and medicine ball exercises [8]. Serve velocity improved significantly in the training group (p = 0.0001) and did not change in the control group (p = 0.29). Serve accuracy was not affected, and shoulder internal and external rotation range improved [8].
That programme included core work, so it does not prove core work alone does anything. It does show that a trunk trained alongside rotational throws and shoulder work can move the serve in the right direction.
One more study answers a practical coaching question: will this kind of training spoil tomorrow’s serve? Ten competitive juniors aged 14 to 18 did either medicine ball throws (3 sets of 6 with a 2 kg ball at maximal speed) or resistance training (3 sets of 6 at 75% of one-repetition maximum, lifted fast). Serve, forehand and backhand speed and accuracy showed no significant drop 3 minutes, 24 hours or 48 hours later [9]. The sample was small and tested in the off-season, so use it as a guide, not a guarantee.
Core stability and core exercise are not the same thing!
A trunk that passes force along efficiently is one thing. A trunk that has survived 200 crunches is another. The first is the job of the core in the serve: a stable base that lets the segments above it move fast [3, 4]. The second is just a repetition count.
That is why I would never tell a player to drop core work. If the trunk is in the middle of the chain, a leak there is expensive. But a better plank is unlikely to add miles per hour by itself. As this is common topic, I have done few presentations on Core at World Tennis (ITF) World conference and WT (RCC) please refer to their web site for the links on this topic.
4 Task for the trunk, and how to train.
The trunk does four different things in a serve, and each call for a different kind of work. The right-hand column comes from my own coaching practice, not from study. Note: These are fine tuning combined with proper S&C, Nutrition, and recovery plan with LTAD.
| Job in the serve | What the research points to | How I would train it |
| Pass force from legs to arm | Legs and trunks produce about 51 to 55% of the energy and force reaching the hand [2] | Rotational medicine ball throws, step-and-rotate throws, band, or cable chops from a split stance |
| Keep the spine steady | Front and back trunk muscles co-activate through the acceleration phase [5] | Anti-rotation presses, side planks, loaded carries, dead bug progressions |
| Absorb load in late cocking | Eccentric overload of the abdominals in late locking is the accepted mechanism of rectus abdominis strains [6] | Slow, controlled lowering work such as rollouts and leg lowers, built up gradually |
| Rotational power | A program with core strength, elastic resistance and medicine ball work raised serve speed in 13-year-olds [8] | Medicine ball throws at full intent, with the load and distance progressed over weeks |
Core and serve training by age group.
Research specific to age groups is limited here, so this section is based on my coaching practice. Always consider chronological age, biological age, and training age together. My articles on LTAD for tennis players and weight and resistance training cover the bigger picture.
U14: build the base.
What I see: Players want a faster serve long before the body is ready to produce one. The technique is still changing, and many have never trained the legs or trunk in any structured way.
What to do:
- Teach jumping, landing, throwing, and rotation first. Light medicine ball throws are a useful tool.
- Keep core work playful and short. Learn the movement before adding load.
- Do not chase serve speed. Chase a clean, repeatable motion.
U16: growth spurt, higher risk
What I see: Serve speed often rises faster than trunk strength, and the lower back takes the strain, especially in extension. Coordination can drop for a while during fast growth.
What to do:
- Strengthen the trunk, glutes, and hamstrings together, not the trunk alone.
- Watches serve volume during growth spurts. If the back complains, reduce volume, not just intensity.
- Teach serve mechanics that share the load through the legs and trunk, not the lower back.
U18: ITF juniors and the schedule problem
What I see: Higher serve power, heavy match volume, and constant travel. Lower back, abdominal and shoulder complaints grow with serve counts.
What to do:
- Keep two short, sharp strength sessions a week, even in tournament weeks.
- Add rotational power work and controlled lowering work for the abdominals.
- Track serve counts, and warm up the trunk and shoulder properly before the first serve.
Pro tour: protect what you have built.
What I see: Accumulated wear and tears. Back, hip, and abdominal strains show up when fatigue builds across the calendar.
What to do:
- Keep the trunk work going all year. Cut the volume at events, but not to zero.
- Make mobility and activation a daily habit, not a reaction to pain.
- Work as a team: coach, physio, doctor, and S&C coach on the same page.
Boys and girls differ in growth timing, injury patterns and fueling needs, so individualize every plan. My article on training load for tennis players explains how to manage the volume side.
How I would use this with players
In my 6-point check (Monitor, Load, Strength, Recover, Fuel, Mind), core work sits under Strength. It is part of the strength programme, not a separate modality. What follows is my coaching practice, not a study result.
For coaches
- Screen first. Kibler suggests checking hip and trunk flexibility, core strength, and glute and hamstring strength to find where the chain breaks down [3]. Fix the real deficit.
- Give the legs and hips the biggest primary focus. Squat and hinge patterns, jumps and rotational throws build the force the serve starts with.
- Make core work look like the serve in anatomical planes, axis of rotation. Anti-rotation holds, rotational medicine ball throws and loaded carries train the trunk to transfer force, to endure.
- Judge by more than one number. Track serve speed but also ask how the shoulder and back feel after a serving block.
For players
- Keep your core work, but do not expect it to be your serve speed programme.
- Put your effort into leg strength and jump power first with foundational strength.
- If your serve feels like all arm, ask your coach to check your leg drive and trunk rotation before adding more reps.
A 6-week sample block
This is basic plan so that coaches and players will get the base idea and rational, not one size fit all types of plan. Every real plan must be individualized for age, training history, injuries, and the match calendar. A qualified coach should supervise juniors. 2-3 sessions a week, alongside normal tennis, is a reasonable starting point.
| Weeks | Legs and hips | Trunk power | Trunk control |
| 1 to 2: Base | Squat and hip hinge | Light rotational medicine ball throws | Pallof press, side plank, dead bug, |
| 3 to 4: Build | Heavier squats and hinge, jump squats | Step-and-rotate throws with a heavier ball | Loaded carries, anti-rotation with a step |
| 5 to 6: Convert | one heavy lift adds countermovement, broad jumps at low volume | Throws that copy the serve pattern, full intent | Controlled lowering work; keep earlier drills |
How to check progress
Use the same conditions every time and measure a few things together. Serve speed with a radar gun is the obvious one. Add a rotational medicine ball throw for distance, a vertical jump, and shoulder internal and external rotation range. The junior study tracked serve accuracy and shoulder rotation alongside speed, and both mattered to its conclusion [8].
Retest every six weeks. If serve speed has not moved but the shoulder feels better and the jump and throw numbers are up, you have still built something worth keeping.
Red flags: stop and get medical assessment.
- Lower back pain appears with serving and does not settle after a few days.
- Sharp pain in the abdominal or side area after serving, or pain that gets worse when you rotate or reach up.
- Pain that wakes the player at night or sits on one spot of a bone.
- A sudden drop in serve speed, or a changed serve action
- Swelling, instability, or a joint that gives way.
These are signals to involve a doctor or physiotherapist quickly, not to push through.
The limits
The meta-analysis comes from a limited number of trials, and the authors call for further high-quality research [1]. Core training programs also differ a lot from study to study, so one number cannot describe all of them. Treat this article as a direction, not a final ruling.
Each source also carries only so much. The meta-analysis reports the overall pattern, while the design of each core-training trial sits in the full paper [1]. The junior programme study had 30 boys and compared a combined programme with a control group, so it cannot isolate the core [8]. The medicine ball study had 10 players tested in the off-season [9]. The motion-capture study looked at five serves from four players [7]. The EMG study measured male players only [5]. In the sources used here, the evidence for girls and women is thin.
None of these tests have the exact question in this article: does adding core training to an otherwise identical programme change serve speed? That is the study the field still needs. Until it exists, my position is the one above. Keep core work in the plan and spend your biggest effort where the evidence is stronger.
Key takeaway for players and coaches
The core is the link between the ground and the racket, and it deserves respect. But the evidence says serve speed responds best to strength and multimodal training, with core work as one part of the package, not the whole plan. Build the legs, convert that force into fast rotation, protect the spine, and look after the shoulder.
That is how we build players whose serves are fast at 18 and who are still healthy and competing years later.
This article is for general education and is not medical advice. Players with pain, injury or health concerns should consult a qualified doctor or physiotherapist.
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References
- Deng N, Soh KG, Xu F, Yang X. The effects of strength and conditioning interventions on serve speed in tennis players: a systematic review and meta-analysis. Front Physiol. 2025;15:1469965. doi:10.3389/fphys.2024.1469965
- Kovacs M, Ellenbecker T. An 8-stage model for evaluating the tennis serve: implications for performance enhancement and injury prevention. Sports Health. 2011;3(6):504-513. PMC3445225
- Kibler WB. Understanding the kinetic chain. Aspetar Sports Medicine Journal, Volume 13 (Sports Medicine in Tennis). See also: Kibler WB. The kinetic chain in tennis: do you push or pull? Aspetar Sports Medicine Journal.
- Kibler WB, Press J, Sciascia A. The role of core stability in athletic function. Sports Med. 2006;36(3):189-198.
- Chow JW, et al. Lower trunk kinematics, and muscle activity during different types of tennis serves. Sports Med Arthrosc Rehabil Ther Technol. 2009;1:24. doi:10.1186/1758-2555-1-24
- Maquirriain J, et al. Rectus abdominis muscle strains in tennis players. Br J Sports Med. 2007;41(11):842-848. PMC2465294
- Gorce P, Jacquier-Bret J. Are there kinematic and kinetic parameters correlated with racket velocity during the tennis serve? Front Sports Act Living. 2024. doi:10.3389/fspor.2024.1451174
- Fernandez-Fernandez J, et al. Effects of a 6-week junior tennis conditioning program on service velocity. J Sports Sci Med. 2013;12(2):232-239.
- Terraza-Rebollo M, Baiget E. Acute and delayed effects of strength training in ball velocity and accuracy in young competition tennis players. PLoS ONE. 2021;16(12). PMC8659664