When you connect Apple Health to REN, the app doesn’t just look at what you do from today onward. It also looks back.
REN automatically imports (or “backfills”) your last 90 days of activities from Apple Health. This helps REN build a training plan that starts from your real recent history, not from a generic assumption.
Here’s what that means and how it can affect your first weeks of training.
What happens when you connect Apple Health to REN?
Once you connect REN with Apple Health and grant permissions:
REN reads up to 90 days of past activity
It focuses on your running workouts and related training
It combines that history with your onboarding information (goals, experience, target race, preferred frequency, etc.)
Using all of that, REN estimates a safe starting point for your plan: how often you should run, how long, and how challenging sessions should be at the beginning.
Why 90 days?
Your last three months give REN a solid picture of:
How consistently you’ve been running
How much volume your body is used to
Whether you’ve been building up, maintaining, or barely running
This helps REN avoid two extremes:
Starting you too hard, which risks burnout or injury
Starting you too easy, which can feel like a waste of time
When the recent weeks have been quiet
Even though REN looks at 90 days, what you’ve done recently matters a lot—especially the last 30 days.
If the most recent month in Apple Health shows:
Very few workouts
Very short or infrequent runs
A complete break (holiday, illness, life happening)
REN will be cautious and may start more gently than you expect.
That can look like:
Shorter runs
Fewer or later-introduced intense sessions
A slower build-up than what you feel you can tolerate
From REN’s perspective, it’s simply responding to the story your Apple Health data tells: “This runner hasn’t done much lately; let’s protect them.”
Can I help REN “catch up” if it underestimates me?
Yes — REN adapts quickly based on what you actually do.
If you know that:
The last 30–90 days in Apple Health don’t reflect your true ability, and
The early weeks in REN feel very easy
…then you can gently signal to REN that you’re ready for more by:
Doing a bit more than prescribed on some easy days
Slightly extending easy runs
Adding a small amount of extra low-intensity volume
Still keeping efforts controlled and not turning everything into a race
When REN sees you consistently and comfortably handling more load than expected, it will start to build you up faster and adjust the plan to better match your real capacity.
Key idea:
The 90-day backfill is just REN’s starting guess.
Your training in the first weeks teaches REN who you really are right now.
Important: Don’t overdo it
Even though REN can adapt, your muscles, tendons, and joints still need time.
Only add more if you’re confident your body can handle it
Make small, gradual increases, not massive jumps
Watch for warning signs: persistent soreness, niggles turning into pain, unusual fatigue
If you’re unsure, it’s completely fine—and often smarter—to stick to the plan as written, especially early on. A slightly conservative start is far better than derailing your training with an injury.
What if the 90-day backfill doesn’t reflect my true level?
This is common if:
You’ve trained seriously for years, but the last 90 days were unusually quiet
You recently switched devices/apps and your Apple Health history is incomplete
You’ve just come back from a short break, but your underlying fitness is still decent
Even if the 90 days in Apple Health don’t fully capture your capabilities:
REN will start cautiously, based on what it can see and what you entered in onboarding
As you train and sync your new workouts, REN will update its view quickly
Within the first few weeks, your actual, current training begins to matter more than that initial snapshot
In short
Connecting Apple Health lets REN backfill up to 90 days of your past activity
Your starting point is based on those 90 days plus your onboarding info
If your recent weeks were light, REN may start slower than you’d expect—be mindful of that
Doing a bit more (carefully) in the first weeks can help REN ramp up faster, if you truly can handle it
Most importantly, REN will adapt quickly, even if the 90-day backfill didn’t give a perfect picture of what you’re capable of
Trust the process, listen to your body, and let REN learn from what you do now—not just what’s in your history.