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Human Physiology · Internship 2026

How hot do AirPods Max get
during a workout?

A study measuring the thermal comfort, sweat, and fit of over-ear AirPods Max across a full exercise session — pairing continuous ear-cup temperature with participants' own subjective ratings.

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Why This Project

This one is personal. I've used AirPods Max for years and love them everywhere — except the gym. They heat up, get sweaty, and slip off when I lift. That everyday frustration is exactly what I turned into this study.

Stone at Apple as a Human Physiology intern
Summer 2026 — Human Physiology intern at Apple.
Training with AirPods Max on
Where it started — the heat, sweat & slip I kept hitting mid-lift.
Background & Research Questions

Background

  • Evaluate AirPods Max thermal comfort, stability & fit during exercise.
  • Quantify ear-cushion heat / sweat and link it to perceived comfort.
  • Exertion capped at RPE ≤ 6 (1–10 perceived-exertion scale).

Research Questions & Hypotheses

  • RQ1: How does ear-cup heat build across the workout?
  • RQ2: Does perceived comfort track the measured temperature?
  • H1: Ear-cup temperature rises across sets, discomfort with it.
  • H2: Hotter temperatures → lower comfort & fit ratings.
Study Design

One structured session per participant; cardio & weight-lifting order is counter-balanced. Hover a phase for detail.

Room BL
Room baselineDevice off. ~2-min ambient reference before the headphones go on.
Put on
Put on deviceParticipant dons AirPods Max (Transparency); ear-cup temperature starts to climb.
Worn BL
Worn baseline3-min seated hold with the device on — the settled worn baseline.
Warm-up
Warm-upLight warm-up, 40s work / 20s rest.
Cardio
Cardio · randomizedTreadmill or stair climber, ~15 min — the machine is randomly assigned.
Weights
Weight-liftingBench, shoulder press & squat — 3 sets each (15 / 12 / 8 reps), 9 sets total.
Recovery
Recovery3-min seated hold after exercise — cool-down.
Room BL
Room baseline (final)Device off. Final ambient reference after removal.
⇆ order randomized
RPE · rate of perceived exertion (1–10) — hover a level
1
2
3
4
5
6
7
8
9
10
shaded 7–10 = above our cap
Our study keeps every participant at RPE ≤ 6 — if it climbs above 6 we lighten the load or stop the set. Hover a number to see what each level feels like.

Protocol

  • Exercise: Weight Training & Cardio — block order counterbalanced (50/50).
  • ~70 min worn session, room-temperature references at both ends.

Participants

  • AirPods Max users, or people who use overhead products during exercise.
  • Collected: N = 17 so far; target N = 20.
Gender — 10 Male / 7 Female
10 Male
7 Female
Prior AirPods Max use — 50 / 50
Used before
First time

Data Collected

  • Objective: Left & Right ear-cup + ambient temperature (thermocouple logger).
  • Subjective: comfort, thermal, instability & satisfaction (ASK survey each phase).
  • Adjustment counts, phase timestamps (Tagger), and baseline / final photos.
Equipment

Hardware

  • AirPods Max
  • Thermocouple logger
  • iPhone camera
  • iPad mini

Exercise gear

  • Bench
  • Dumbbells (2.5–20 lb)
  • Treadmill
  • Stair climber

Capture

  • Tagger app
  • ASK survey
  • Apple Music
Set Up

How a session is run — a screened-off room, standardized equipment, and AirPods Max instrumented with thermocouples.

Cardio zone with stair climber and treadmillStair climberTreadmillBlackout curtains
Cardio zone — stair climber & treadmill, screened off with blackout curtains.
Weight-lifting zoneLogging deskAdjustable benchDumbbells
Weight-lifting zone — adjustable bench, dumbbells, and the logging desk.
Headphone set-up kitWaist beltLabQuest 2 loggerThermocouple leadsAirPods Max
Headphone set-up — LabQuest 2 logger, thermocouple leads, waist belt & AirPods Max.
Thermocouples taped inside the ear-cupsThermocoupleThermocouple
Sensor placement — a thermocouple taped inside each ear-cup, under the cushion.

Controlled environment — ambient temperature averaged the room baseline of ~73°F (23°C) at 52–59% relative humidity (kept below the ~60% skin-comfort threshold), so every ear-cup rise reflects the device warming, not the room. The AirPods Max themselves weigh 13.6 oz (385 g).

Tools I Built

Every step — running the session, cleaning messy sensor logs, visualizing the survey — is a small, offline, local-first tool. Click any card to open it live.

Momentum

Workout interval timer — voice-guided reps, exportable timer video.

Open →Download ↓

Face Blur

Batch photo anonymizer — auto-blur faces, per-participant ZIP. 100% local.

Open →Download ↓

Thermocouple Analyzer

Aligns ear temp to the Tagger timeline — auto sections, cleaning, per-phase stats, compare.

Open →Download ↓
At a Glance

Numbers that came out of the data so far — measured or observed across the sessions (N = 17).

Who we tested — sample so far (N = 17)

10/1759%
Male · 10 of 17 (7 Female)
8/1747%
Had used AirPods Max before
8/1747%
Train 5 or more times a week
5/1729%
Train at vigorous intensity
10/1759%
Had the device fall off — mostly on the bench press
10/1759%
Wouldn’t reuse for workouts (probably / definitely not)
73°F
Ambient room temp (71–74°F)
55%
Ambient relative humidity (52–59%)
+8°F
Heat added just by donning — in the first 3 min
90°F
Avg peak ear-cup temp · range 86–94°F
+16°F
Total rise, room → worn peak
4.4/10
Avg overall session RPE (≤ 6 cap)
Results

Ear-cup temperature (°F): Room BL is ambient (device off); PT BL & Recovery are the value at the end of each 3-min seated hold; Cardio & Weight-lifting are the block peak.

ParticipantRoom BLPT BLCardioWeight-liftingRecovery
MD1053667178848388
MD1125027380868888
MD1467577379848385
MD1608807384919093
MD1218157379878184
MD1533407480878489
MD7675287481868989
MD1795397280898692
MD7364607380868786
MD1834177179858288
MD1316717482899090
MD1364097381929190
MD2127867386929090
MD9661877481888586
MD8202467382888885
MD8566647181878684
MD7155447182888987
Caveat: pilot data (N = 17); some self-reported warmth scales were used inconsistently — directional findings, not conclusions. Where the two ear-cup sensors disagreed by >4°F (2 participants), the higher reading is used.
Key Findings

It heats fast and stays hot · people reject the trapped sweat more than the degrees · and the fit won't stay put. Pilot data, N = 17.

Temperature

Donning is the big jump — the ear-cup spikes into the 80s within minutes, then climbs to a ~89°F peak and holds in the high-80s until removed. At ≈31°C that sits at the upper edge of the skin–cushion comfort zone (≈31–33°C, RH <60%), so a full 30–90 min session is spent in a near-uncomfortable microclimate (Y. Li 2001; Fukazawa & Havenith 2009).

Ear-cup temperature across session phases (cohort mean, 95% CI)

Ear-cup heat jumps on donning, then holds in the high-80s until the device comes off.

Room · 0–6 minAmbient tempPT · 6–12 minPT tempWarm-up · 12–20 minWarm-upExercise 1 · 20–40 minExercise 1Exercise 2 · 40–57 minExercise 2Recovery · 57–62 minRecoverybeyond measured↑ headphone on73°F79°F85°F91°F0 min153045607590≈89°F peak ~55 min · stays high-80s through recoveryshaded = 95% CI (N = 17)

Ear-cup heating rate by worn phase (°F/min)

Nearly all the heat arrives in the first few minutes — then it plateaus.

00.511.522.5+2.13Donning+0.23Warm-up+0.15Ex 1+0.10Ex 2°F / min

Perceived warmth & sweat (0–10) by phase, with measured temperature

Felt warmth & sweat rise right along with the measured heat behind them.

02468100–1082°88°89°4.45.86.40.83.55.1BaselineEx 1Ex 2WarmthSweatTemp (bg)

Perceived exertion (RPE) vs. ear-cup temperature, by phase

Temperature climbs into the high-80s while effort stays at/under RPE 6 — the heat isn’t from working harder.

0246810RPE ≤ 6 cap3.4Warm-up4.9Cardio3.9Weight-lifting4.4OverallRPE 0–1084°89°88°RPE (bars, 0–10)ear-cup temp (°F)

Prior work That ~88°F (≈31°C) sits at the upper edge of the skin–cushion “microclimate” comfort zone (≈31–33°C, RH <60%), where discomfort is driven more by trapped moisture / skin wettedness than by temperature itself — and the head is among the body’s most heat-sensitive regions. Y. Li, The Science of Clothing Comfort, Textile Progress (2001); Gagge, Stolwijk & Hardy (1967); Fukazawa & Havenith, Eur J Appl Physiol (2009); Arens, Zhang & Huizenga, J Therm Biol (2006).

In their words — thermal discomfort

Very hot ears. Feel like a swamp.
When I started to sweat, my ears got a little hot.
It got worse through the session — general stickiness as I got sweaty.
The occasional adjustment and the warmth wouldn’t be a good trade-off for me.
It feels like warmth is trapped near my ears.
Around the ear cup, extremely warm and sweaty after about 5 minutes.

Fit & wearing

The failure is stability, not comfort: 10 of 17 had it fall off — almost all on the bench press — as the band slides back and down off the head during supine lifts. Pressure and material comfort stayed fine throughout.

Device re-adjustments by activity block (proctor-logged)

Nearly every adjustment — and every fall — lands in weight-lifting.

020406080Warm-up21Cardio20Weight-lifting73re-adjustments logged (Tagger, total across 17)

Per-participant re-adjustments vs. peak perceived instability

Logged adjustments track how unstable the fit felt.

051015MD13167117MD96618716MD17953914MD1053668MD1834178MD7155448MD1533407MD1467576MD2127866MD8202466MD8566646MD1364094MD1608803MD1218153MD7675281MD7364601MD1125020Felt:NoSlightModerateSevere

Peak-rated stability, mechanical & material comfort (N = 17)

Instability is the real failure — 10 of 17 peaked moderate-or-severe; pressure & material stayed fine.

1655Stability710Mechanical161Material
NoSlightModerateSevere

Peak perceived instability by hair length (exploratory)

Shorter hair sat more stably — exploratory, small n.

NoSlightModerateSevere0.5Very shortn=21.7Shortn=32.1Medium+n=12

Prior work Headphone comfort has mostly been studied as clamping pressure & cushioning (Sapiejewski 1990), and head-worn fit depends on head/face form (Bredenkamp 2024); helmet studies show fit quality governs stability & retention under movement (Yu et al. 2018). Over-ear headphone retention during exercise is largely unstudied — the gap this pilot addresses. Sapiejewski, J. Acoust. Soc. Am. (1990); Bredenkamp, in Product Fit & Sizing (2024); Yu et al., J. Biomech. Eng. (2018).

In their words — instability

When lying down and getting up for bench press, it fell off.
Very unstable when lying down — not really suitable for that exercise.
The headphones fell off too many times to use reliably.
Headphone slipped off my head when I lay down — need to adjust it.
They shouldn’t move around this much just walking around.

Overall

10 of 17 wouldn’t reuse them for workouts, and rejection concentrates in the people who’d use them most — 6 of the 8 who train ≥5×/week said no. It’s the trapped sweat they reject more than the degrees, and prior AirPods Max experience didn’t change that.

Reuse acceptance by weekly training frequency

6 of 8 frequent trainers wouldn’t reuse — the people who’d use them most reject them most.

1–2×/wk13–4×/wk345–6×/wk24Daily2
AcceptableUnacceptable
Limitations & Next Steps

An ongoing pilot — N = 17 of a target N = 20. What limits today's read, where we go next, and the design direction it points to.

Limitations

Light load

Weights capped at ~20 lb / RPE ≤ 6 — so the heat & slip here are a lower bound.

Small, short pilot

N = 17, directional only — and sessions ran ~60 min with temperature still rising at the end, so the true plateau isn't captured.

Cavity air, not skin

We log only the ear-cup air temperature — no humidity or skin-contact temp.

One device, lab only

A single AirPods Max, one cushion colour, in a fixed indoor lab (no sunlight).

Next steps

Heavier, harder training

Push past 20 lb toward the RPE cap — see if heat & slip scale with effort.

More PTs, longer wear

Reach N = 20 and run longer sessions to capture the true plateau / ceiling.

Add humidity + skin sensor

Log humidity and skin-contact temp to find the real driver of discomfort.

Test colours & environments

Try other cushion colours and run sessions outdoors in sunlight.

Future direction

A cooling, breathable sport cushion

Mesh vents + moisture-wicking, quick-dry fabric + cooling-gel / phase-change padding & washable covers pull trapped heat & sweat out — with a higher-grip, supine-stable seal so it stays put through bench lying↔upright transitions.

A headphone people can actually train in — cool, dry & stable.

Concept: cooling, breathable sport ear-cushion

A cushion re-imagined for cooling, airflow & grip — drag to compare with today’s knit.

current cushion
CurrentConcept

Tap each upgrade to see what it does

  • Blunts the donning heat spike.
  • Lets trapped heat & sweat escape.
  • Airflow across the ear.
  • Swappable & washable.
  • Keeps it put on the bench.
Timeline

A glowing marker tracks today's position across the project.

May 27 – Jun 13

Scope & Research

Confirm direction; literature & competitor review; define questions.

Jun 16 – Jul 4

Design & Plan

Study protocol; session checklist; recruit participants; build tools.

Jul 7 – Aug 8

Data Collection & Analysis

Run pilot sessions; align & clean data; cross-link subjective vs. measured.

Aug 11 – Aug 21

Finalize & Present

Final technical report, polished demo & presentation.