Supplements for tennis players
I spend most of my working life taking supplements away from people. Fighters arrive with a bag of them, we throw out most of the bag, and performance does not drop. That is the honest starting position for anything written on this subject, including this.
Before any of that I ran an online supplement shop for 7 years, which is an odd thing to admit at the top of an article that recommends buying less. It is also why I trust batch certificates rather than brand names. I have seen how the supply chain actually works and how a label gets written, and neither has as much to do with what ends up in the tub as a customer would assume.
Tennis has one genuine advantage over the sports I usually work in, and almost nobody uses it.
The one your sport lets you keep
Creatine monohydrate has by far the strongest evidence base of anything on the shelf. It raises intramuscular creatine, speeds phosphocreatine resynthesis between efforts, and shows up most clearly where efforts repeat with short recoveries. In a repeated sprint running protocol, mean power and speed in the second half of the session improved by around 4 to 5 percent, and the drop-off within each sprint was blunted.
Read that description again and think about a third set.
It comes with about a kilogram of extra body mass, most of it water drawn into muscle. In combat sport that single fact ends the conversation: my fighters stop creatine 4 to 6 weeks before a weigh-in because a kilogram is a division. In tennis there is no weigh-in and no division. The cost that makes creatine unusable in my normal work does not exist in yours.
Creatine monohydrate, 3 to 5 g a day, taken continuously rather than cycled. Loading with 20 g a day for 5 to 7 days fills the muscle faster if you want the effect sooner, and is not necessary otherwise. Monohydrate, not one of the expensive variants, which exist to be different rather than to be better.
One honesty note. Creatine is not a recovery aid in the general sense. A trial in professional cyclists through a heavy training camp found no consistent benefit to recovery, body composition or performance markers. It does one job well. It does not do all jobs.
Caffeine, where the problem is timing
Caffeine works, at doses people already use, and nobody disputes it. The difficulty in tennis is that you do not know when you are playing.
Take it for a 1 pm start and walk on at 4:40 and you have taken it at the wrong end of the delay. The rule I use is to hold it until the match before yours reaches its final set, an imprecise rule that still beats a clock that has already been wrong twice. The full version of that problem is set out here.
Certified tablets at a dose you already use in training. Never a blended pre-workout, which is the single most contaminated category in the industry.
What is sold to you that does not do the job
Magnesium for cramping. There are no randomised controlled trials supporting it for exercise-associated cramps, and the tennis market for it is large. The evidence on cramping points at neuromuscular fatigue rather than mineral status, which is also why the potassium explanation for the banana does not hold.
Magnesium itself has a use: it makes sense if intake is low and sleep is poor, at 200 to 300 mg of elemental magnesium in the evening. Note the word elemental: magnesium bisglycinate is only about 14 percent magnesium by weight, so a capsule marked 1,000 mg of glycinate delivers around 140 mg of the thing you wanted. Most labels do not make this easy.
Testosterone boosters and fat burners. Two categories, one answer, which is no. They are among the most frequently adulterated products in the industry and they buy you nothing that food and sleep do not.
BCAAs, if protein intake is adequate. Which for a tennis player eating properly it is.
The part that actually threatens a career
Everything above is about performance. This part is about eligibility, and it is why I would rather a player took nothing than took something unverified.
Supplements are not regulated as medicines. The contamination numbers are not marginal. A 2017 review reported rates between 12 and 58 percent across the 23 studies that met inclusion criteria. An international analysis of 634 nutritional supplements from 13 countries found that around 15 percent of non-hormonal products, ordinary things including vitamins, minerals, protein and creatine, contained anabolic steroid-like compounds or prohormones that were not on the label.
Not a fringe brand. A range that included the categories every player already owns.
From the retail side this is less shocking than it reads. Most sellers do not manufacture, most manufacturers share equipment between products, and the certificate a distributor shows you is frequently for the ingredient rather than for the batch in your hand. None of that requires anybody in the chain to be dishonest. It only requires everybody to assume somebody else checked.
And tennis has an exposure that most sports do not: you buy in a different country every fortnight. Contamination rates differ sharply by market, and the product you have used safely for 2 years is a different product when the tub was bought in a different jurisdiction.
The thing that is not a supplement at all
Food travels too. After the Asian swing, a study of athletes returning from trips to China found clenbuterol in the urine of 22 of 28 volunteers, at low concentrations, consistent with contaminated meat rather than with anything anybody chose to take.
Clenbuterol is prohibited at all times. Strict liability does not distinguish between a decision and a dinner.
The answer is to keep eating while knowing which destinations carry the risk, being deliberate about where meat comes from during those weeks, and keeping a record of where you ate, which sounds paranoid until the day it is the only thing standing between you and a charge.
The protocol, which is short
Buy only batch-tested products. Informed Sport and NSF Certified for Sport test individual batches and publish the results. A trusted brand without batch certification is not the same thing.
Keep a log. Product, manufacturer, lot number, dose, dates. Photograph the label and the batch code, and keep the empty tub. This costs nothing and it is the difference between an explanation you can evidence and one you can only assert.
Check every medication on Global DRO before the first dose, not after. Cold remedies are the classic route into trouble, and in several markets over-the-counter painkillers are sold combined with substances prohibited at all times.
Know who touches your skin. Creams, sprays and treatments applied by other people have produced findings. If the person cannot tell you what is in it, the answer is no.
The programme itself, who tests you and what happens if something goes wrong, is written out separately.
What I would actually have a player take
Creatine monohydrate, daily, all year, because your sport does not make you give it up.
Vitamin D through a northern winter of indoor training, when the sun is not supplying it. Outside those conditions, food and the recommended daily allowance are the default.
Magnesium in the evening if intake is low or sleep is poor, at an elemental dose, and not for cramps.
Caffeine on match days, from certified tablets, timed off the match in front of you.
Electrolytes during play in heat, for fluid balance rather than for cramp prevention, because that distinction is the whole argument.
The same list with doses, timings and the elemental-versus-compound distinction set out in a table is in the Tennis Competition Guide.
That is a short list and it is meant to be. Everything on it is certified, logged, and defensible. Most of what is missing from it is missing because the evidence is thin, not because I have forgotten it.
Common questions
There is a good case for it. Creatine monohydrate has the strongest evidence base of any performance supplement and shows its effect most clearly in repeated efforts with short recoveries, with mean power and speed in the second half of repeated sprint protocols improving by around 4 to 5 percent. It brings roughly a kilogram of extra body mass, mostly water in muscle, which is why athletes in weight-category sports stop it before a weigh-in. Tennis has no weigh-in, so that cost does not apply. A dose of 3 to 5 g a day taken continuously is the usual approach.
No randomised controlled trials support magnesium for exercise-associated muscle cramps. It may be worth taking if dietary intake is low or sleep is poor, at 200 to 300 mg of elemental magnesium in the evening, but not as cramp prevention. Note that magnesium bisglycinate is only about 14 percent magnesium by weight, so a capsule marked 1,000 mg of glycinate delivers around 140 mg of elemental magnesium.
A 2017 review reported contamination rates between 12 and 58 percent across the 23 studies that met its inclusion criteria. An international analysis of 634 nutritional supplements from 13 countries found around 15 percent of non-hormonal products, including vitamins, minerals, protein and creatine, contained undeclared anabolic steroid-like compounds or prohormones. Rates differ substantially between markets, which matters for players buying in a new country every fortnight.
It can. A study of athletes returning from trips to China found clenbuterol in the urine of 22 of 28 volunteers at low concentrations, consistent with contaminated meat rather than deliberate use. Clenbuterol is prohibited at all times and strict liability does not distinguish between a decision and a meal. The practical response is to know which destinations carry the risk, be deliberate about where meat comes from in those weeks, and keep a record of where you ate.
A short list: creatine monohydrate daily throughout the year, vitamin D if testing indicates a need, magnesium in the evening if intake is low or sleep is poor, caffeine on match days from certified tablets timed off the preceding match, and electrolytes during play in heat for fluid balance rather than cramp prevention. Everything on that list should be third-party batch tested and logged with lot numbers.
Two complete sample documents are free to read before you buy anything.
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Educational material, not medical advice. Supplement decisions should be individualised and checked against the rules of your own federation and anti-doping organisation.