When Data Tells the Story Before You Feel It
On an 88°F September day in Texas—not extreme by local standards, this athlete's HeatSense sensor tracked heat strain climbing from moderate (1.5) to high (3.1) to critical (4.0) over the course of an afternoon workout.
Symptoms were invisible until they were not
At strain level 3.1, HeatSense sent SMS alerts warning that core body temperature had crossed her set threshold. The athlete felt fine and kept pushing. After taking a few breaks and continuing the workout, heat strain level reached 4.0 and the symptoms finally caught up—fatigue, higher perceived effort, declining motivation.
With visible symptoms, she had to stop the workout. Her core temp stabilized. She felt better after rest.
The insight
Now this athlete knows her limit. She can train right at the edge of her personal zone—maximizing adaptation without crossing into symptom territory where performance drops. As she becomes more heat-acclimated, that threshold will shift. But she'll always have visibility into where she actually is—not where weather guidelines assume she should be.
One hour outdoor workout
1:02 PM. Building Heat Strain
1:15 PM. high heat strain
Alerts via SMS as Thresholds crossed
See Alerts in app + check weather
Symptoms visible with rising heat strain
Continued Heat Strain but Now With Symptoms
(Shortness of breath, nausea)
Slow down to cool off
Stabilize rising core body temp
See how your athlete responds to heat—in real time. Shop the HeatSense sensor kit and start training smarter. Shop HeatSense
The HeatSense App Experience
Heat strain and envirnoment
Alerts and ensuring cool off effective
Understanding Core Body Temperature Zones
Optimal Range
Normal: 97.7°F–99.5°F (36.5°C–37.5°C)
Normal, healthy body temperature. The body is well-regulated.
Elevated: 99.5°F–101°F (37.5°C–38.3°C)
Early heat stress is possible. Stay hydrated and monitor for symptoms.
High Range
Caution: 101°F–103.1°F (38.3°C–39.5°C)
Heat exhaustion risk increases. Drink water, take breaks, and cool down with shade or cold towels.
Critical Range
Alarm: 103.1°F–104°F (39.5°C–40°C)
Heat exhaustion risk is high. Stop any physical activity and remove extra clothing and sports gear. Drink water and cool down with shade or cold towels.
Danger: Above 104°F (40°C)
Severe risk of heat stroke and organ damage. Seek immediate cooling (ice packs, cold water immersion) and medical attention.