Terra Research

Uncovering groundbreaking insights from the world's health data. Led by 2x Olympic champion Alistair Brownlee.

Research Mythbusters Report

All research articles

Here you can find all articles published by the Terra Research team. All articles consist of original findings.

Marathon Series

The Data Behind the London Marathon

While Sabastian Sawe was busy breaking the two-hour marathon barrier in London, the watches of 571 amateur runners told…

April 27, 2026

London Data

Tube Strikes Made Londoners Active

During the April 2026 Tube strikes, Londoners adapted by cycling more—activity tripled, e-bike commutes rose 13%, and…

April 24, 2026

Endurance Training

Running Is The Hardest Endurance Sport? Not so Fast

Which sport is hardest on the heart? We ran the question through hundreds of thousands of sessions across nine activity…

April 23, 2026

Heat Exposure

Cold Plunging Might Make Your Biomarkers Worse

We analyzed large-scale wearable data to understand what cold exposure actually does to your body. Sporadic plunges act…

April 14, 2026

Winter Training

How The Fittest Do Winter

We analyzed 856,000 exercise sessions from Europeans across 20 countries to find out how people really train across the…

April 9, 2026

Period Tracking

Your Breathing Changes a Week Before Your Period

We often hear that our hormones make us unpredictable, but the data tells us otherwise: its a subtle but shockingly…

April 7, 2026

Alcohol Effects

Alcohol Doesn't Ruin Your Sleep The Way You Think

We analyzed 15,000 nights of sleep data to uncover what drinking before bed actually does to your rest. Using a mixed…

March 30, 2026

Sauna

Saunas Lower Your Heart Rate More Than Exercise

We analyzed 59,000+ daily records from 256 sauna users to quantify what saunas actually do to your body. Using paired…

March 26, 2026

Peptides

What GLP-1s are Really Doing to Your Training

We analysed over 70,000 activities from 305 GLP-1 users to understand how these medications alter physiological…

March 23, 2026

Supplement Tracking

Caffeine Kills Your Deepest Sleep First

We analyzed 37,000+ nights of wearable data to understand how caffeine really affects your sleep. The results? Caffeine…

March 17, 2026

Peptides

GLP-1s: The Real Tradeoffs Nobody Tells You About

We studied 500+ users. Notable side effects are activity drops, resting heart rate rises, and HRV drops well below…

March 12, 2026

Supplement Tracking

Melatonin’s Real Effect Peaks on Day 4 - And It's NOT Sleep

Most people take melatonin expecting to fall asleep faster or sleep longer. We analyzed over 200,000 sleep records from…

March 5, 2026

Cycle Tracking

Can We Predict Cycle Phase Without Temperature?

Temperature has long been the go-to for tracking the menstrual cycle with wearables, but it turns out your body offers…

February 27, 2026

Winter Olympics

The Secret Behind Norway's Olympic Dominance

Norway claimed 41 medals at the 2026 Milano-Cortina Winter Olympics, more than any nation in a single Winter Olympic…

February 23, 2026

Marathon Training

Simulate Your Next Marathon Race Pace

This week's research blog dives into a data-driven model that unlocks marathon potential by explaining 79% of finish…

February 20, 2026

Marathon Training

How To Train For Your Next Marathon

Instead of treating training like a simple “more in = faster out” equation, we tested where the curve bends using six…

February 12, 2026

Academic Research

Seasonal Effects on Sleep Performance

We used a large anonymized dataset to track nights of sleep from people across hundreds of countries to understand how…

February 11, 2026

Marathon Training

The Easier You Train The Faster You Finish

We analyzed training data from 425 verified marathon runners to figure out what actually makes people faster. The…

February 5, 2026

Women's Health

How Temperature Predicts Women's Cycle Phases

We analyzed ~3 million nights of wearable sleep data to see whether the menstrual cycle leaves a measurable signature in…

January 29, 2026

Sleep Tracking

Sleep Metric Variation Across Wearables

We analyzed sleep data from 77,000+ nights across six major wearables, then zoomed in on same-person, same-night…

January 22, 2026

New Year Resolutions Cliff

The January Activity Spike: A two-day Story

We analysed wearable data from over 3,000 users to measure the New Year's resolution effect on physical activity. The…

January 15, 2026

Sleep Tracking

Sleep Patterns Across the World

We analyzed 8,298 sleep records from October 2025 across wearable users in North America, Europe, and beyond, linking…

January 6, 2026

New Year Resolutions Cliff

New Year’s Resolutions Cliff

Every January, millions pledge to sleep more along with their New Year's Resolutions. But does it work? Analyzing more…

December 31, 2025

Sleep Tracking

How HRV Actually Works

We unpack what HRV really is and how it actually works to demystify the data from Apple Watch, Fitbit, and Garmin. Some…

December 17, 2025

Sleep Tracking

How Do People Really Use Wearables?

We analyzed 93 days of continuous sleep data across Fitbit, Apple Watch, and Garmin users to answer a simple question:…

December 9, 2025

Sleep Tracking

Benchmarking Wearable Sleep Data Reliability

We analyzed sleep data from over 5,000 real-world nights across Apple Watch, Fitbit, and Garmin users. Garmin delivered…

November 28, 2025

Sleep Tracking Series

Is Consistency Actually More Important Than Intensity?

In this report, we reveal why high-step users averaging 11,500+ daily steps succeed: consistency. Their 36% activity…

October 23, 2025

Sleep Tracking Series

Which activity metrics actually matter? 28,000+ days analysed

Smart rings track five different activity metrics, but they don't always align. Drawing on nearly 28,000 days of user…

October 9, 2025

Sleep Tracking Series

Burn More Calories, Sleep Like a Log?

An analysis of 1,000+ ring users examined the relationship between daily calorie expenditure and sleep metrics. Active…

October 2, 2025

Sleep Tracking Series

GAMM analysis – can complexity tell us anything we don’t already know?

Based on an analysis of nearly 90,000 nights, the connection between sleep duration and next-morning HRV is minimal for…

September 25, 2025

Sleep Tracking Series

Think a good HRV score follows a good night’s sleep? Think again!

Despite their perceived link, sleep and HRV are only weakly correlated. The analysis of nearly 90,000 nights showed that…

September 20, 2025

Sleep Tracking Series

Descriptive HRV using Z scores

Based on an analysis of nearly 100,000 HRV records, this report reveals that most daily HRV changes are small, but…

September 19, 2025

Sleep Tracking Series

Why Mondays Might Be Your Healthiest Day: What 1,000+ Sleepers Taught Us About Recovery

At Terra, we recently ran an analysis on wearable data from over a thousand users, focusing on two key metrics: sleep…

September 18, 2025

Meet the Research Team

A team of scientists, engineers, and athletes working to make sense of the world’s health data.

Alistair Brownlee

Head of Research

Alistair Brownlee is Head of Research, where he leads large-scale analysis of wearable health data to better understand sleep, recovery and human performance, translating these insights into products that help people live healthier lives.

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Faraaz Akhtar

AI and Health Researcher

Faraaz Akhtar is an AI & Health Researcher at Terra API, where he develops statistical and machine-learning methods to extract insights from large-scale wearable health data.

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Rocio Mexia Diaz

AI and Health Researcher

Rocio Mexia is a Biomedical Engineer and AI & Health Researcher at Terra API, where she applies machine learning to wearable and health record data to uncover insights about human health.

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