Sports Medicine: Heat Acclimatization & Sickle Cell Trait

Length of heat-acclimatization period

14 consecutive days of preseason practice.

Maximum length of an individual practice on Days 1-5

3 hours.

Maximum walk-through duration per day

1 hour.

Recovery period between practice and walk-through on Days 1-5

3 hours.

Protective equipment allowed on Days 1-2

Helmet only.

Protective equipment allowed on Days 3-5

Helmet and shoulder pads.

When full contact and all protective equipment may begin

Day 6.

When double-practice days may begin

Day 6.

Maximum total practice time on a double-practice day

5 hours.

Minimum separation time between two practices on a double-practice day

At least 3 continuous hours.

Scheduling rule following a double-practice day

Must be followed by a single-practice day (unless separated by a rest day).

Rest day requirement after consecutive practices

1 complete rest day after 6 consecutive days of practice.

Rule for days missed due to illness, injury, or scheduled rest

They do not count toward the 14 acclimatization days.

Walk-through equipment restriction

Athletes should not wear protective equipment.

Genetic basis of sickle cell trait

1 sickle hemoglobin gene plus 1 normal hemoglobin gene.

Exertional sickling onset time

Can begin in only 2 to 3 minutes of all-out exertion.

Four forces that promote sickling (H-M-H-R)

Severe hypoxemia, metabolic acidosis, muscle hyperthermia, and red-cell dehydration.

Timing of sickling compared to typical heat collapse

Often occurs early in exercise, within the first half hour.

Sickling muscle presentation vs. heat cramps

Muscles look and feel relatively normal, unlike rock-hard contracted muscles in heat cramps.

Sickling risk factors

Heat, dehydration, altitude, asthma, illness, and intense exercise.

Recommended emergency response for sickling collapse

Check vital signs, provide oxygen, cool athlete, activate 911 if worsening, and get to hospital rapidly.

First known college football sickling death

1974 (defensive back collapsed during a conditioning test at altitude in Colorado).

Rice University sickling case details

Fall 2006, a freshman defensive back died after 16 x 100-yard sprints.

Relative risk of exercise-related death with sickle cell trait in military research

Approximately 30 times.

Relative risk of exertional rhabdomyolysis with sickle cell trait

Approximately 200 times.

Definition of rhabdomyolysis

Breakdown of skeletal muscle fibers releasing contents into the bloodstream.

Definition of ischemia

Insufficient blood flow to tissue.

Definition of hypoxemia

Low oxygen content in arterial blood.

Definition of hyperthermia

Elevated body temperature.

Definition of metabolic acidosis

Blood becomes too acidic due to increased acid production.