Beta opens November 2026

RETO

Intelligent training.

A multi-sport training app that adapts to your body and your life, giving you the support to succeed, so hitting your goals never means missing out.

Why RETO? The name comes from Pareto: the curve above is a Pareto front, the best trade-off between progress and health, and Pareto’s 80/20 rule says most progress comes from a few things that really matter. Reto is also Spanish for “challenge”.

How it works

We model your body. Then we plan around it.

01 · Connect

Bring your real data.

Connect your watch or ring, and log your lifts and your period in the app. Every session, every night of sleep and every day of your cycle lands in one place, with nothing else to type in.

Connects with

Garmin
Oura

Coming soon

Apple Health
WHOOP
COROS

RETO's Today screen: this morning's sleep, HRV and resting heart rate, today's session and the week's targets

02 · Model

A model of your whole body.

RETO models you from your own data: your physiology, the load on your muscles and tendons, and your hormonal and metabolic health. It learns how your body responds, and what it can tolerate, rather than assuming you are average.

RETO's Body screen: today's state, cycle day and phase, and recovery against your baseline

03 · Plan

A plan that is solved, not guessed.

Mathematical optimisation, not AI guesswork, finds the week across every sport you do that maximises your progress and protects your health at the same time, around your cycle, your work and your weekends. It re-solves every night and after every session, from where you actually are.

RETO's Calendar: a week of planned sessions across strength and running with load and zone for each

From the founder

Elite athletes get a team. Everyone else gets a template.

At 24 I was training hard and building a career in London, and my body paid for it: severe period pain, exhaustion, low iron and one injury after another, on top of PCOS. Recovery took over two years. The warning signs were all there, but no doctor, device or app joined the dots.

I studied Mechanical Engineering at Imperial College London and started my career at a London startup. For the last three years I’ve worked in elite sport, first as a data scientist for the Great Britain Rowing Team, then building full-stack sports data products at Red Bull for teams around the world. I saw what elite athletes have: a whole team of coaches, scientists and doctors behind them. I left to build RETO, so everyone can have that support.

Jess

Jessica Eichel, Founder · Mechanical engineer, data scientist

Jessica Eichel on LinkedIn

Our mission

Progress shouldn’t cost you your health.

Women spend around 25% more of their lives in poor health than men, and part of every month managing symptoms they’re told are normal. Sleep, iron, hormones and fatigue all shape what your body can take on, yet most training apps chase one number and miss the warning signs, so women push through until something breaks.

More than half of that gap falls in women’s working years, exactly when they’re chasing goals and building careers. Much of it is preventable.

RETO gives you that understanding: the power to train with confidence, protect your health and chase every goal.

Source: McKinsey Health Institute and World Economic Forum, Closing the Women’s Health Gap, 2024.

Our vision

Close the gender research gap in sports science and health.

RETO will become the leading training and health platform built around women’s physiology, while serving everyone who trains. Built with women, it will help create the largest picture yet of how women’s bodies train, adapt and recover, and use it to support research, so guidance for women is finally based on women.

The impact: a world where women understand their bodies instead of fearing them. Where symptoms aren’t dismissed as normal, warning signs are caught early, and no woman has to choose between her health and her goals, at any stage of life.

Frequently asked questions

01 Who is it for?

Anyone training for a goal, or several: a first 5 km, a marathon, a triathlon, a strength target.

It is also for anyone who trains and wants to understand their body: how their cycle, sleep and recovery change what they can take on from week to week.

02 How is RETO different from asking ChatGPT or an AI coach?

A language model generates a plausible plan from a summary of your history. It can answer the same question differently twice, and nothing guarantees its plan respects your limits.

RETO solves the plan with mathematical optimisation over your full history. Every constraint, such as load caps, recovery gaps and fatigue limits, holds at once, the same inputs always give the same plan, and the rules can be reviewed by specialists.

AI is the interface, not the planner: you can describe a niggle or a busy weekend in plain language, and it explains the plan back to you.

03 How is it different from other training apps?

Most apps scale a template for one sport. RETO models four kinds of load separately: low intensity, high intensity, anaerobic, and muscular load per muscle group from your logged sets. Each has its own fatigue and recovery, so the plan balances all four across every sport, and strength and endurance are planned together instead of competing.

04 How does RETO handle my menstrual cycle?

RETO builds a model of your own cycle from your inputs: the periods and symptoms you log, and overnight temperature when your device records it. Ovulation is confirmed from a sustained temperature rise and predicted from the length of your past cycles, so the model fits you, not a 28-day template, and sharpens with every cycle.

The plan uses your phase when placing sessions, so the hardest training does not have to land on your hardest days.

05 Why build for women first?

Most sports science and training tech were built on male data. Cycle phase, iron, energy availability and hormonal health all change how much training your body can absorb, and ignoring them is how warning signs get missed until injury or RED-S.

RETO treats them as planning inputs, and the same model works for everyone who trains. More in our vision.

06 Is my data safe?

Your data is stored in the EU and handled under the GDPR. It is used only to plan and explain your training, and never sold or shared for advertising.

Cycle and other health data are processed only with your explicit consent and erased if you withdraw it. Anonymised research use needs a separate opt-in. You can export, correct or delete your data at any time; details in the privacy policy.

07 When does it launch, and what does the waitlist get me?

The iPhone beta opens in November 2026 with limited spots. Waitlist members are invited first, by a single email.

Train with us first.

Beta spots are limited. Join the waitlist and we will tell you when it is your turn.