The rule that moves the goalposts
Beginning in 2026 the ATP has standardized how heat will be managed across its events. The regulation uses wet bulb globe temperature (WBGT), a measure that blends air temperature, humidity, radiant heat and wind. When readings reach 30.1 degrees Celsius during the opening two sets of a best-of-three singles match, either player can ask for a 10-minute cooling break to be taken after the second set. If the WBGT exceeds 32.2 degrees Celsius, play stops entirely. The break allows supervised cooling, hydration, clothing changes, showers, and coaching. These are written into the competition rules, and the full language was published by the tour in December in ATP heat rule details.
Grand Slam tournaments set their own policies, and the Australian Open uses a five-point Heat Stress Scale that can trigger cooling breaks and suspend play. Even so, the ATP standard will shape how players build their January. Most will land in Melbourne having already competed under these thresholds during lead-up events and mixed-team play, which means their routines will be calibrated to the new rhythm of a potential second-set break and the possibility of full stoppages. For a broader context on how WBGT is changing January tennis, see how WBGT reshapes Australian summer.
As the sport gathers in Australia from January 18 to February 1, the heat rule is not just a medical guardrail. It changes incentives. It asks players and coaches to plan backward from a 10-minute intermission that can reset physiology and momentum, and to prepare for on-off play when temperatures cross a hard line. That reshapes preparation. For deeper programming details, explore our cooling breaks and wearables guide.
First principles: what WBGT means for tennis
Dry air at 35 degrees Celsius does not equal humid shade at 31 degrees. WBGT captures the combined load of heat and humidity plus sunlight and wind. Two practical implications matter for tennis:
- The same air temperature can produce very different heat stress. A cloudy, breezy 33 can be less punishing than a windless 30 in direct sun.
- Thresholds will be crossed more easily in still, humid conditions and on sunbaked outside courts. Players who track only the forecast miss the real risk window.
If you coach juniors, consider buying or borrowing a portable WBGT meter for practice weeks and match days. It gives objective feedback and teaches athletes to feel what the number means in their body.
How physical preparation will change
Heat is a trainable stressor. With the 2026 rule, top teams will treat January like a heat championship. Here is how programs are already adjusting.
1) Heat acclimation with a deadline
A well-run acclimation block takes 7 to 14 days. The aim is to increase plasma volume, improve sweat rate and distribution, and lower heart rate at a given work rate. A practical progression for a player arriving in Australia two weeks before main draw:
- Days 1 to 3: 45 to 60 minutes of steady work in the heat at easy intensity. Think 65 to 70 percent of max heart rate. Finish with 10 to 15 minutes of light on-court footwork or serves to maintain skill feel.
- Days 4 to 7: Extend to 75 to 90 minutes total with controlled set play. Insert short, high-intensity games to simulate hot-point bursts, but guard recovery windows.
- Days 8 to 10: Move toward full practice sets in time slots matching likely match times. If you draw midday, train midday. Protect volume if quality drops.
- Maintenance: Once acclimated, 2 to 3 exposures per week sustain adaptations.
A useful alternative when court time is tight is post-session heat exposure. A 20 to 30 minute hot bath or sauna after a normal practice can speed up acclimation. This works best after, not before, the main training so you do not blunt quality.
Safety note for juniors: watch for red flags such as dizziness, nausea, goosebumps in heat, sudden chills, or loss of coordination. Cut sessions short at the first warning sign and cool the athlete aggressively with shade, cold fluids, ice towels, and airflow.
2) Hydration that matches sweat rate
Hydration is not guesswork. Personalize it.
- Sweat rate test: Weigh the athlete nude before and after a one-hour practice in conditions similar to match time. Keep track of how much they drink during the hour. Each kilogram lost equals roughly one liter of sweat. Repeat this test at least twice, including a humid day.
- Sodium plan: Many tennis players lose between 500 and 1,000 milligrams of sodium per liter of sweat, and salty sweaters may exceed that. Start with 700 to 1,000 milligrams per liter during hot matches and adjust based on cramps, weight loss, and gut comfort.
- Pre-hydrate: 4 hours before match time, drink roughly 5 to 7 milliliters per kilogram body weight, then top up with 3 to 5 milliliters per kilogram 2 hours before if urine is still dark. Include sodium, especially for morning starts after air-conditioned sleep.
- Carbohydrate: Target 30 to 60 grams per hour during long matches. Split across bottles and gels to keep osmolality friendly on the gut.
Coach tip: pack two bottle types for the player. One is higher sodium and a bit more concentrated for sips during games. The other is lighter and colder for changeovers and the mandated break.
3) Cooling tools that travel well
The 10-minute break after set two will reward teams that can drop core temperature quickly and safely.
- Ice-slurry bottles: A semi-frozen drink lowers core more than cold water alone because some energy goes into melting. Practice with flavors and concentrations so the athlete tolerates it well.
- Ice towels and vests: Keep a small cooler with hand towels and an ice vest. Place towels on neck, groin, and underarms. A vest can be worn while walking to the bathroom and back to maximize exposure.
- Fans and airflow: A compact battery fan in the bag sounds trivial and is not. Evaporation is the main path to cooling. Airflow increases it.
- Wearables: Heart rate monitors and skin-temperature sensors help track strain. They are not magic, but they teach pacing. If you use them in training, you can make smarter choices on match day.
Big brands already market heat-ready fabrics and perforated, light-colored kits. The rule will accelerate adoption. The test is simple: does the kit enhance evaporation and feel comfortable at match intensity.
The mental game of a 10-minute stop
A mandated intermission is like a mini half-time in a sport that rarely pauses. That changes psychology.
- Expect the break. When the WBGT reaches 30.1 during set one or two, the option exists. Players who treat the second-set finish like a checkpoint will handle the moment better.
- Plan the reset. The most costly mistake is drifting through the 10 minutes. Use a script. Below is a template you can print and laminate.
Break Blueprint, minute by minute:
- Minute 0 to 2: Triage. Cooling towels on neck and underarms. Ice-slurry drink. Shoes untied to reduce foot pressure and allow heat dissipation. Quick bathroom if needed.
- Minute 2 to 5: Debrief. One or two coaching points only. What first serve pattern won free points. Which return position bit into second serves. What to try first two games of set three. Write the points on a small card.
- Minute 5 to 7: Breathe and reset. Five slow cycles of 4-second inhale and 6-second exhale, eyes half closed. Visualize the opening point. Pick a cue word.
- Minute 7 to 9: Fuel and kit. Electrolyte sips, a small carbohydrate bite if tolerated, new shirt, dry socks, fresh wristbands, new towel.
- Minute 9 to 10: Ramp-up. Mini activation in the hallway. Calf raises, open-chain hip swings, 10 light shadow swings. Walk to the baseline ready to serve or receive with a plan.
Because coaching is allowed during the break, decide in advance which voice speaks and how. In a junior setting, limit to one adult and one message. Overcoaching ruins the recovery.
Tactics that exploit the new rhythm
Heat rules create tradeoffs. Smart players will manage the clock and the scoreboard to enter the break with momentum or to buy time when needed.
Serve tempo and targeting
- If you are serving near the end of set two and expect to take the break, use your most reliable first serve pattern on big points to secure the set. Lock in a clear B-plan to start set three while your opponent is still adapting to the cooler feel.
- If you are receiving and the conditions are extreme, consider a return position that forces more second serves. Extra lift and depth can push rallies to the third or fourth ball, increasing heat strain in the final games before the intermission.
- Between points, slow your breathing, but keep your routine consistent. Umpires will be quick with the clock in heat. Discipline preserves energy without triggering a time violation.
Pattern changes around the break
- Last two games of set two: If you are trailing, extend rallies selectively. High, heavy crosscourt to the opponent’s backhand can lengthen exchanges and raise their core temperature before they sit down. If you are leading, shorten points. Serve and first forehand into open space. The aim is to finish the set efficiently and protect glycogen for set three.
- First two games of set three: Expect touch to feel different. After intense cooling, some players report a few minutes of slower feel and slight stiffness. Open with high-percentage patterns that get you in the match quickly. Quality crosscourt, then work the line only on short balls.
The threshold game
Because the break only applies when the WBGT reaches 30.1 during set one or two, players may try to influence timing.
- If the number is hovering near the trigger, a trailing player who is fitter might choose not to request the break and bank on the opponent fatiguing. A player who is overheating should request it with zero hesitation. This is strategy, not pride.
- When conditions breach 32.2 and play will be suspended, expect multiple warm-up cycles. Keep a small routine ready: band work for shoulder, 10-meter shuffles, 20 to 30 seconds of skipping, three short accelerations. Do not sit and scroll. Use the stoppage to prime again.
What we are already seeing in week one
At the United Cup, several sessions in Sydney were described as sweltering and humid. Athletes who managed changeovers with discipline and kept organized benches made cleaner transitions into third sets. For related routines and coaching cues under pressure, see our United Cup pressure lab.
This is not proof that the rule decided matches. It is early evidence that the combination of mandated breaks and hard suspension lines is already changing how teams script the day. That matters as Melbourne’s draw unfolds over two weeks with late-afternoon starts and roof decisions that can turn a match into two different sports.
Coaches’ checklist for Melbourne
- Build a heat profile for each athlete. Use at least two sweat-rate tests and rate of perceived exertion logs from hot practices.
- Pre-pack a break kit. Ice vest, three ice towels, two bottle types, a laminated Break Blueprint card, a clip-on fan, and a small trash bag to keep wet gear off the bench.
- Rehearse the 10-minute break. Run it in practice. Time it. Practice the walk to the locker room, the bathroom stop, the coaching talk, and the ramp back on court.
- Set string and tension contingencies. High heat softens stringbed feel. Have a second frame ready a pound higher if touch gets too springy. Note which ball change aligns with the break.
- Scout by physiology. Note opponents who slow visibly after 40-minute sets, those who dab at sweat, or who avoid the towel. Heat tolerance is a real edge in January.
For juniors and parents: safe progression, real gains
- Do not copy a professional volume in week one. Use the acclimation sequence and be conservative the first 3 to 5 days in Australia or any hot climate.
- Teach signs and decisions. A junior who recognizes dizziness or stop-start chills and speaks up will stay safer and compete more often through the summer.
- Emphasize cooling literacy. Show them where to place ice towels and how to sip rather than chug.
- Keep records. Simple habit trackers for sleep, morning weight, urine color, training quality, and perceived heat strain teach self-management.
If you want a structured plan built from match data and your current fitness, OffCourt can help. Off-court training is the most underused lever in tennis. You can build a heat plan with OffCourt in minutes and adapt it as the weather and your draw shift.
What to watch for during the Australian Open
- The break decision at the end of set two. Who asks for it first. Who returns sharper. Watch the first two games of set three.
- The serve-pace story. Radar speeds often drop in oppressive conditions. Players who maintain pace in the 85 to 90 percent range of their personal best will hold more often.
- Cooling competence on the bench. Quick towel placement, organized bottles, clear coaching, and no wasted movements are tells of a team that prepared.
- Suspension choreography. If the WBGT crosses 32.2 mid-session, track who keeps their body primed through the delay and who cools too far and starts stiff.
The bigger picture
The 2026 rule closes the gap between science and competition. It rewards teams that treat the environment as a skill rather than a nuisance. It invites tennis to learn from endurance sports that have long used objective heat measures and preplanned cooling. It also nudges equality across tournaments, making outcomes less about random toughness and more about organized preparation.
For coaches, the opportunity is clear. January is no longer a scramble through jet lag and sweat. It is a controlled build, a few decision points during matches, and a gear bag that reflects reality.
The takeaway and a next step
Set a date, write a plan, pack your break kit, and rehearse your 10-minute reset. The new heat thresholds are not a problem to endure. They are a tempo to master. If you want a ready-made template personalized to your athlete’s physiology and shot patterns, bring your match data and start with our cooling breaks and wearables guide. Melbourne rewards the prepared. So will the rest of the season.