i The Direct Answer
The NATA heat acclimatization guidelines — formally the Preseason Heat-Acclimatization Guidelines for Secondary School Athletics, published in 2009 by the Inter-Association Task Force for Preseason Secondary School Athletics with NATA’s Secondary School Athletic Trainers’ Committee — define a 14-day progressive introduction to preseason practice in the heat.
The core structure: Days 1–5 permit only one practice per day, with no practice exceeding 3 hours. Helmets are the only protective equipment allowed on days 1–2; helmets and shoulder pads on days 3–5; full equipment and full contact beginning day 6. From day 6 through day 14, double-practice days are permitted but must be followed by a single-practice day, with no more than 5 total hours of practice and at least 3 continuous hours of rest in a cool environment between sessions.
Two rules are most often missed: days an athlete misses for rest, injury, or illness do not count toward the 14 days — that athlete resumes where they left off, not where the team is. And every athlete follows the full 14-day plan regardless of offseason conditioning or when they join, including athletes who arrive after the first day of practice.
The guidelines are a consensus statement, not federal law. But they have been adopted in some form by most state high school athletic associations, and they represent the recognized standard of care for preseason heat safety in secondary school athletics.
This article is written for certified athletic trainers, athletic directors, head and assistant coaches, school administrators, and anyone responsible for preseason practice planning in secondary school athletics. It covers the complete text of the NATA guidelines, the definitions that determine whether a session counts against the 3-hour limit, the provisions most commonly misapplied in the field, how WBGT monitoring fits alongside acclimatization, and what a defensible compliance program looks like.
⚠ Why This Matters: The Evidence Behind the 14-Day Period
Exertional heat illness affects roughly 9,000 high school athletes annually — a rate of 1.20 per 100,000 athlete-exposures. Football’s rate of 4.42 per 100,000 is 11.4 times that of all other high school sports combined, and 60.3% of all cases occur in August.
The strongest evidence that the guidelines work comes from Kerr et al. (2019), published in Environmental Health Perspectives. Across an estimated 2,697,089 athlete-exposures spanning 455 state-years in 48 states, state-mandated guidelines consistent with the NATA-IATF recommendations were associated with a 55% reduction in exertional heat illness incidence during preseason football practices. The EHI rate was 0.42 per 10,000 athlete-exposures in state-years with mandates versus 0.72 without.
Exertional heat stroke is one of the three leading causes of death in sport, and NATA states that death from EHS is 100% preventable when proper recognition and treatment protocols are implemented. From 1980 through 2015, 44 secondary school football players died during preseason practices from exertional heat stroke. Linemen account for approximately 97% of football EHS fatalities.
The NCAA, which adopted comparable guidelines in 2003 — six years before NATA’s secondary school version was modeled on them — has seen an approximately seven-fold reduction in preseason exertional heat stroke deaths since implementation.
The risk is concentrated in a narrow window. NATA’s Exertional Heat Illnesses position statement notes that the first two to three weeks of preseason practice present the greatest risk of exertional heat illness, particularly in equipment-intensive sports. That window is precisely what the 14-day period is built to cover.
The Definitions That Determine Compliance
Most compliance failures are not deliberate. They happen because a session was classified wrongly — a walk-through that included equipment, or conditioning that wasn’t counted against the practice clock. The guidelines define four terms precisely, and those definitions do the real work.
The heat-acclimatization period
◆ Verbatim — NATA/IATF Consensus Statement (2009)
“The heat-acclimatization period is defined as the initial 14 consecutive days of preseason practice for all student-athletes. The goal of the acclimatization period is to enhance exercise heat tolerance and the ability to exercise safely and effectively in warm to hot conditions. This period should begin on the first day of practice or conditioning before the regular season. Any practices or conditioning conducted before this time should not be considered a part of the heat-acclimatization period.”
Practice
A practice is any coach-supervised, school-approved, sport- or conditioning-related physical activity. Each individual practice may last no more than 3 hours — and critically, warm-up, stretching, and cool-down all count inside that 3 hours. The guidelines also state that regardless of ambient temperature, all conditioning and weight-room activities count as practice.
That last clause is the one most often overlooked. An indoor lifting session on a cool day is still practice time under the guidelines. A program that runs a 3-hour field practice and then a 45-minute lift has exceeded the limit.
Walk-through
A walk-through is a teaching opportunity in which athletes wear no protective equipment (helmets, shoulder pads, catcher’s gear, shin guards) and use no sport-related equipment — the guidelines specifically name footballs, lacrosse sticks, blocking sleds, pitching machines, soccer balls, and marker cones. A walk-through may last no more than 1 hour per day, does not count against the 3-hour practice limit, and may not include conditioning or weight-room activity.
! The Walk-Through Trap
If athletes handle a football, set up marker cones, or put on shoulder pads, the session is no longer a walk-through by the guidelines’ own definition — it is practice, and it counts against the 3-hour limit.
This is the single most common way programs exceed the daily cap without realizing it. A 3-hour practice plus a ‘walk-through’ in which athletes throw a ball is a 3-hour-plus practice, not a practice plus a permitted walk-through.
Recovery period
The recovery period is the time between the end of one practice or walk-through and the beginning of the next. During recovery, athletes rest in a cool environment with no sport- or conditioning-related activity of any kind — the guidelines explicitly exclude speed and agility drills, strength training, conditioning, and walk-throughs. Treatment with the athletic trainer is the one permitted activity.
The 14-Day Progression, Day by Day
This table consolidates the equipment, practice-count, and contact provisions into a single reference. It reflects the guidelines as written; where your state association imposes stricter requirements, the state rule governs.
| Period | Practice Structure | Equipment | Contact |
| Days 1–2 | One practice, max 3 hours | Helmet only, for sports requiring helmets or shoulder pads. Goalies (field hockey and related sports) should not wear full protective gear or perform activities requiring it. | No contact |
| Days 3–5 | One practice, max 3 hours | Helmets and shoulder pads only | Football only: contact with blocking sleds and tackling dummies may begin |
| Day 6 | May begin double practices | All protective equipment permitted | 100% live contact drills may begin — no earlier than day 6 |
| Days 6–14 | Double-practice days permitted, but each must be followed by a single-practice day or a rest day | All protective equipment | Full contact permitted |
| Any day | Max 3 hours per practice; max 5 total hours on a double-practice day | — | Walk-through of up to 1 hour permitted, separated from practice by 3 continuous hours of rest |
| After 6 consecutive practice days | 1 day of complete rest required — no conditioning, walk-throughs, or practices of any kind | — | — |
The Double-Practice Rules
From day 6 onward, double-practice days carry their own constraints, all of which must be satisfied simultaneously:
- Neither practice may exceed 3 hours
- Total practice time across both sessions may not exceed 5 hours — and warm-up, stretching, cool-down, walk-through, conditioning, and weight-room time all count toward that 5 hours
- The two practices must be separated by at least 3 continuous hours in a cool environment
- A double-practice day must be followed by a single-practice day. If a double-practice day is followed by a rest day instead, another double-practice day is permitted after that rest day
- On single-practice days, one walk-through is permitted, separated from the practice by at least 3 hours of continuous rest
Four Provisions Programs Get Wrong
1. Missed days do not advance an athlete’s acclimatization
The guidelines are explicit that the 14-day period is tracked per athlete, not per team. Days on which an athlete does not practice due to a scheduled rest day, injury, or illness do not count toward that athlete’s heat-acclimatization period.
◆ Verbatim — NATA/IATF Consensus Statement (2009)
“For example, an athlete who sits out the third and fourth days of practice during this time (eg, Wednesday and Thursday) will resume practice as if on day 3 of the heat-acclimatization period when returning to play on Friday.”
This creates a real administrative burden: on any given day, different athletes on the same roster may be on different acclimatization days, with different equipment and practice-count entitlements. A team-wide calendar does not satisfy the guidelines. Programs need per-athlete tracking.
2. Offseason conditioning does not count
The guidelines state that regardless of the conditioning program and conditioning status leading up to the first formal practice, all student-athletes must follow the 14-day plan. A well-conditioned athlete who trained all summer starts at day 1 alongside everyone else. Summer workouts conducted before the first official practice are not part of the acclimatization period.
3. Late arrivals start at day 1
Athletes who arrive at preseason practice after the first day of practice are explicitly included in the requirement to follow the full 14-day plan. A player who joins on team day 5 is on their own day 1 — helmet only, single practice, 3-hour maximum — while teammates around them are on day 5.
4. The six-day rest rule is absolute
If practice occurs on 6 consecutive days, athletes must have 1 day of complete rest. The guidelines specify no conditioning, no walk-throughs, no practices. A ‘light’ optional session on the seventh day defeats the provision.
The Seven Formal Recommendations
For reference, the consensus statement’s recommendations for the 14-day period, summarized in order:
- Days 1 through 5 consist of the first 5 days of formal practice; athletes may not participate in more than 1 practice per day.
- If a practice is interrupted by inclement weather or heat restrictions, it may recommence once conditions are deemed safe — but total practice time still may not exceed 3 hours in any one day.
- A 1-hour maximum walk-through is permitted during days 1–5, with a 3-hour recovery period inserted between the practice and the walk-through in either order.
- Equipment progresses by phase: helmet only on days 1–2; helmets and shoulder pads on days 3–5; all protective equipment and full contact beginning day 6. Football may use blocking sleds and tackling dummies on days 3–5. Full-contact sports begin 100% live contact drills no earlier than day 6.
- Beginning no earlier than day 6 and continuing through day 14, double-practice days must be followed by a single-practice day; when a double-practice day is followed by a rest day, another double-practice day is permitted after that rest day.
- On a double-practice day, neither practice may exceed 3 hours, total practice may not exceed 5 hours, and the two practices must be separated by at least 3 continuous hours in a cool environment.
- Because exertional heat illness risk during this period is high, the task force strongly recommends that an athletic trainer be on site before, during, and after all practices.
Why Acclimatization Works — and Why It Expires
Heat acclimatization is a genuine physiological adaptation, not simply getting used to discomfort. NATA’s Exertional Heat Illnesses position statement describes it as a response to repeated heat exposure during exercise over the course of 10 to 14 days, producing measurable changes:
- Increased plasma volume and stroke volume, so the cardiovascular system moves blood to both working muscle and skin more efficiently
- Increased sweat rate, and sweating that begins at a lower core temperature — cooling starts earlier and runs harder
- Decreased sweat sodium concentration, conserving electrolytes
- Lower heart rate, core body temperature, and skin temperature at the same workload
One practical corollary: during rest breaks, removing helmets and loosening or removing shoulder pads meaningfully improves evaporative cooling. Equipment interferes with cooling by covering skin surface area and trapping a layer of warm humid air against the body, and a break taken in full pads delivers much less recovery than the same break taken with equipment off.
The progression matters as much as the total duration. The guidelines note that progressive acclimatization is especially important during the initial 3 to 5 days of summer practices — which is exactly why the equipment restrictions are front-loaded into days 1 through 5 rather than distributed evenly.
! Acclimatization Decays in About Three Weeks
NATA’s position statement notes that if heat acclimatization is not maintained, the physiologic benefits decay within three weeks.
The practical implications: an athlete returning from a three-week injury absence, a mid-season break, or a move from an air-conditioned environment has lost much of the adaptation. A team that acclimatizes in August and then faces an unseasonable September heat wave after two cool weeks is not as protected as the calendar suggests.
The guidelines mandate the preseason period specifically, but the physiology does not stop applying on day 15.
Who Is Most at Risk During the Acclimatization Window
The 14-day period applies uniformly, but risk does not distribute uniformly across a roster. Knowing which athletes need closer observation during days 1 through 5 is where an athletic trainer’s judgment adds the most value on top of the protocol.
Intrinsic factors
- Low fitness or recent detraining — athletes who arrive out of condition acclimatize more slowly and carry higher risk throughout the period
- Higher body mass and adiposity — larger athletes generate more metabolic heat and shed it less efficiently relative to body mass. This is why linemen account for roughly 97% of football exertional heat stroke fatalities despite being a minority of the roster
- Prior history of exertional heat illness or exertional collapse
- Sickle cell trait, which carries its own exertional collapse risk profile and can complicate presentation
- Medications that impair thermoregulation — diuretics, antihistamines, and stimulants including ADHD medications
- Recent illness, particularly with fever, vomiting, diarrhea, or any dehydrating course in the preceding days
- Inadequate sleep, poor nutrition, or arriving already dehydrated
Extrinsic factors
- High WBGT, especially during late-morning and mid-afternoon sessions
- Heavy or dark-colored equipment, which both traps heat and absorbs radiant load
- Limited access to shade, cooling, or unrestricted fluids at the practice site
- Gaps in medical coverage or delayed recognition of early symptoms
⚠ Never Use Conditioning as Punishment
Punitive conditioning — extra sprints or gassers added at the end of practice, often in the hottest part of the day, often targeting athletes who are already struggling — is a documented contributor to preventable exertional heat stroke deaths in secondary school athletics.
It inverts every principle the acclimatization guidelines are built on: it adds unplanned volume outside the practice structure, it applies maximum thermal load to the athletes least able to tolerate it, and it discourages symptom reporting because athletes learn that showing difficulty produces more work rather than care.
This belongs in writing in any program’s heat policy, and it is a conversation worth having with coaching staff before the first day of preseason rather than after an incident.
Exertional Heat Stroke: Recognition and the Cool First, Transport Second Protocol
Acclimatization reduces the probability of an exertional heat stroke. It does not eliminate it, and the guidelines’ recommendation that an athletic trainer be on site for all preseason practices exists precisely because the response window is measured in minutes.
Recognition
Exertional heat stroke is defined by two findings together: a core body temperature above approximately 105°F (40.5°C) and central nervous system dysfunction. CNS involvement is the distinguishing feature versus heat exhaustion — confusion, disorientation, irrational or combative behavior, staggering, collapse, seizure, or loss of consciousness.
Skin condition is not diagnostic. An athlete with exertional heat stroke may still be sweating heavily, and the common belief that hot dry skin is required has contributed to missed diagnoses.
◆ NATA Position: Rectal Temperature Is the Standard for Assessment
NATA’s Exertional Heat Illnesses position statement strongly advises the use of rectal temperature for assessment of body temperature in a suspected exertional heat stroke patient. Oral, aural, axillary, and temporal measurements are not valid in an exercising, hyperthermic athlete and can produce dangerously falsely reassuring readings.
This has staffing and policy implications: the capability needs to exist before the season, and the protocol should be written into the emergency action plan rather than improvised.
Treatment: cool first, transport second
NATA’s position statement is explicit that a patient suspected of having exertional heat stroke must be cooled via cold-water immersion for the full treatment time before being transported to a hospital — and that this must be stated in the school’s emergency action plan. The National Association of EMS Physicians endorses the same approach.
| Element | Protocol |
| Cooling target | Reduce core body temperature below 102.5°F (39.2°C) within 30 minutes of collapse |
| Method | Whole-body cold-water immersion — the most effective modality available. Immerse from the neck down in a tub of ice water, with enough ice to keep water cold |
| Expected cooling rate | Approximately 0.37°F per minute, or roughly 1°F every 3 minutes across the full immersion period |
| Monitoring | Leave the rectal thermometer in place for continuous monitoring throughout cooling |
| Transport | Only after the athlete has been cooled to target. Cool first, transport second |
| Alternative if no tub | Tarp-assisted cooling — athlete on a tarp with ice water, edges held up, water agitated continuously by responders |
! The Equipment Is Cheaper Than Programs Assume
A livestock stock tank from a farm supply store, typically under $100, functions as an effective cold-water immersion tub. It needs to be staged at the venue with a water source and ice available before the first preseason practice — not ordered after an incident.
The gap in most programs is not budget. It is that the tub exists somewhere in a storage room, unfilled, and no one has rehearsed who fills it, who takes the temperature, and who calls 911. Drill it before the hottest part of the season.
Where WBGT Monitoring Fits Alongside Acclimatization
Acclimatization and environmental monitoring are complementary controls addressing different parts of the same risk, and neither substitutes for the other.
The 14-day period is a fixed, calendar-based control. It reduces risk by limiting exposure and equipment load during the window when athletes are least adapted — but it is blind to the actual conditions on any given day. Day 7 is day 7 whether the WBGT reads 76°F or 92°F.
WBGT monitoring is the variable control. Wet Bulb Globe Temperature combines ambient temperature, humidity, radiant heat load from the sun, and wind into a single figure, and it is the metric NATA’s Exertional Heat Illnesses position statement specifies for making activity modification decisions. It tells you what today actually requires: work-to-rest ratios, equipment removal, practice duration limits, or cancellation.
| 14-Day Acclimatization Period | WBGT Monitoring | |
| What it controls | Exposure and equipment load during the least-adapted window | Activity intensity and duration based on conditions today |
| Basis | Calendar — practice day 1 through 14 | Measurement — current WBGT at the activity site |
| Adjusts to weather | No. Day 6 permits full equipment regardless of conditions | Yes. That is its entire purpose |
| Applies after day 14 | No, as a mandated period | Yes — every practice, all season |
| Governing NATA document | Preseason Heat-Acclimatization Guidelines (2009) | Exertional Heat Illnesses position statement |
| What it cannot do | Cannot tell you whether today is safe | Cannot substitute for progressive adaptation in unadapted athletes |
✓ The Strongest State Policies Require Both
States rated highest for athlete heat safety — including Florida, Georgia, Louisiana, New Hampshire, New Jersey, and North Carolina — receive full marks both for requiring an acclimatization period at the start of formal practices and for mandating activity modifications based on wet-bulb globe temperature readings.
That pairing is the current best-practice standard. A program running the 14-day progression without on-site WBGT measurement has implemented half the framework.
→ Why On-Site WBGT Measurement Matters for Athletics
WBGT incorporates solar radiant load and wind, which means it varies far more across a single campus than air temperature does. A shaded practice field, an open turf field with radiant heat coming off the surface, and a stadium with restricted airflow can produce materially different WBGT readings at the same moment.
A regional forecast or an airport reading cannot resolve those differences, and the modification thresholds most state associations use are tight enough that a few degrees changes the required work-to-rest ratio.
cyclonePORT measures WBGT directly at the activity site with a black globe sensor, natural wet bulb, and dry bulb sensor, and delivers threshold alerts to the athletic trainer, coaching staff, and administration simultaneously — with automatic timestamped logging of every reading and every alert.
State Adoption: Where the Guidelines Are Actually Mandated
The NATA guidelines are a consensus statement issued by a professional association, not a regulation. Their legal weight comes from state adoption — and adoption is uneven.
New Jersey became the first state high school athletic association to adopt heat acclimatization policies in May 2011. Georgia followed in March 2012 and Arkansas in June 2012, the latter through state legislation. Adoption has expanded substantially since: the Korey Stringer Institute reports that states have collectively adopted nearly 200 heat illness prevention policies since 2017.
But adopting ‘some variation’ of the guidelines is not the same as meeting them. KSI’s evaluations have consistently found a gap between the number of states with some acclimatization policy and the smaller number whose policies meet the full NATA minimum standards. NATA’s own educational materials noted that as of August 2022, 14 states mandated all best-practice heat acclimatization standards at the high school level.
! Check Your Own State Association Before Building a Policy
Requirements vary considerably, and some states impose provisions stricter than the NATA minimum. The consensus statement itself describes its recommendations as minimum standards.
Where a state association rule and the NATA guideline conflict, the state rule governs your compliance obligation. Where the state is silent, the NATA guideline is the recognized standard of care — which matters in any review following a heat illness incident.
The Korey Stringer Institute maintains state-by-state policy evaluations and is the most reliable current source for where a given state stands.
Preseason Heat Acclimatization Compliance Checklist
Use this to audit a program against the NATA guidelines. Items marked (S) should also be checked against your state association’s specific rule, which may be stricter.
| Program Element | What to Confirm | ✓ | ✗ |
| Per-athlete tracking system | Acclimatization day is tracked individually, not team-wide, so missed days correctly pause an athlete’s progression (S) | ☐ | ☐ |
| Preparticipation exams complete | All athletes have a preparticipation medical examination by a physician or as required by state law before the first practice | ☐ | ☐ |
| Day 1–5 single practice enforced | No athlete participates in more than one practice per day during days 1–5 | ☐ | ☐ |
| 3-hour practice cap tracked correctly | Warm-up, stretching, cool-down, conditioning, and weight-room time are all counted inside the 3-hour limit (S) | ☐ | ☐ |
| Equipment phasing documented | Helmet only days 1–2; helmets and shoulder pads days 3–5; full equipment from day 6 — with a documented check at each transition | ☐ | ☐ |
| Contact restrictions enforced | No 100% live contact before day 6; football blocking sleds and tackling dummies not before day 3 | ☐ | ☐ |
| Walk-throughs correctly classified | No protective or sport-related equipment used; maximum 1 hour; 3-hour separation from practice; no conditioning included | ☐ | ☐ |
| Double-practice rules enforced | Not before day 6; followed by single-practice or rest day; neither session over 3 hours; 5-hour daily total; 3 continuous hours of rest between in a cool environment | ☐ | ☐ |
| Six-day rest rule scheduled | A complete rest day is scheduled after any 6 consecutive practice days — no conditioning, walk-throughs, or practices | ☐ | ☐ |
| Recovery environment available | A genuinely cool indoor space is available for the between-practice recovery period, with no activity permitted beyond athletic training treatment | ☐ | ☐ |
| Athletic trainer on site | An athletic trainer is present before, during, and after all preseason practices as the task force strongly recommends | ☐ | ☐ |
| WBGT monitoring in place | On-site WBGT measurement at the activity location, with documented modification thresholds and a defined decision authority (S) | ☐ | ☐ |
| Emergency action plan rehearsed | Venue-specific EAP covering exertional heat stroke, with cold-water immersion capability available on site and staff rehearsed in its use | ☐ | ☐ |
| Cold-water immersion tub ready | A tub, water source, and ice are staged and accessible at the practice venue before the first preseason session | ☐ | ☐ |
| Rectal thermometry capability | Rectal temperature assessment capability exists on site with a written protocol in the EAP, since oral, aural, and temporal readings are invalid for suspected EHS | ☐ | ☐ |
| No punitive conditioning policy | A written policy prohibits the use of conditioning as punishment, communicated to coaching staff before preseason | ☐ | ☐ |
| High-risk athletes flagged | Preparticipation screening identifies prior heat illness, sickle cell trait, thermoregulation-affecting medications, recent febrile illness, and low fitness — with individualized observation for those athletes | ☐ | ☐ |
| Records retained | Practice times, equipment phases, WBGT readings, modifications made, and per-athlete acclimatization days are logged and retained | ☐ | ☐ |
Frequently Asked Questions: NATA Heat Acclimatization Guidelines
What are the NATA heat acclimatization guidelines?
Why is heat acclimatization important?
Why is building up to full uniform and padding gradually a good idea for preventing heat illness?
Do missed practice days count toward the 14-day acclimatization period?
Does summer conditioning count toward heat acclimatization?
When can full contact begin under the NATA guidelines?
What counts as a walk-through under the NATA guidelines?
How does WBGT monitoring relate to the acclimatization guidelines?
Are the NATA heat acclimatization guidelines legally required?
What is the proper treatment for exertional heat stroke?
How do you recognize exertional heat stroke versus heat exhaustion?
How long does heat acclimatization last if training stops?
Additional Resources
- NATA — Preseason Heat-Acclimatization Guidelines for Secondary School Athletics (2009), Journal of Athletic Training 44(3):332–333 — nata.org
- NATA Position Statement — Exertional Heat Illnesses — nata.org
- Korey Stringer Institute — state-by-state heat acclimatization policy evaluations — ksi.uconn.edu
- NFHS Sports Medicine Advisory Committee — Heat Acclimatization and Heat Illness Prevention Position Statement — nfhs.org
- Your state high school athletic association’s current preseason practice regulations
Related cyclonePORT resources:
- WBGT Monitor & Heat Stress Sensor — Instrument Guide — cycloneport.com
- WBGT Calculator — cycloneport.com/wbgt-calculator-wet-bulb-globe-temperature/
- Weather Monitoring for Schools, Universities & Athletic Programs — cycloneport.com
- NFHS Lightning Safety Policy Explained: The 30-Minute Rule and What It Actually Requires — cycloneport.com
