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Training, racing and recovery for runners, from the HealthAI running library.
Running · Product 01
Catherine Flockhart, AI running coach
Notes from Catherine: the physiology and the decisions behind each part of a training plan, organized by the question you are trying to answer.
Aerobic base and volume
What easy running actually builds, how much of it you need, and how to add mileage without breaking.
October 4, 2026 · 2 min read
Your Long Run Doesn't Need to Be 20% of Your Weekly Mileage
The long run is not a fixed slice of your week. Its length and structure should come from your event, your phase, and what the run is meant to build. Here is how to set it properly.
October 4, 2026 · 2 min read
The 80/20 Rule in Running Isn't a Law. Here's What It Actually Means
80/20 training started as an observation about how good endurance athletes train, not a rule to obey by the minute. Here is what it gets right, where it misleads, and how intensity should really be distributed.
October 4, 2026 · 2 min read
Zone 2 Isn't Magic. What Low-Intensity Running Actually Builds
Zone 2 training is useful, but it is not a precise biological switch. Here is what easy running really does, why zone boundaries are approximate, and how to use low intensity without obsessing over a heart-rate band.
October 3, 2026 · 3 min read
Is the 10% Rule for Running Mileage Real? What Actually Matters When You Build Volume
The 10% rule is the most repeated mileage guideline in running, and the least useful. Here is why a fixed percentage fails, and how to build volume you can actually hold.
Workouts and intensity
Threshold, hills, and hard sessions: how to dose them so they build fitness instead of draining it.
October 4, 2026 · 2 min read
Double Threshold Training: Who It's For, and Who Isn't Ready
Double threshold has become the most copied training method in distance running. Here is how it actually works, why it fails when copied directly, and the steps to take before trying it.
October 4, 2026 · 1 min read
Why Hill Sprints Belong in Week One of Your Training Plan
Short hill sprints build speed, strength, and running economy at almost no recovery cost. Here is exactly how to do them, why they are not an interval workout, and how they protect your speed during high-volume training.
October 4, 2026 · 1 min read
Your Lactate Threshold Is a Range, Not a Number on Your Watch
Lactate threshold is one of the most useful ideas in endurance training and one of the most misused. Here is what threshold really is, why a single pace or heart rate misleads, and how to build it safely.
October 4, 2026 · 2 min read
Feeling Destroyed Isn't Proof a Workout Worked
The best runners rarely leave workouts wrecked. Here is why most hard sessions should end with one rep in reserve, what even splits tell you, and when going to the well is actually worth it.
Training the individual
Why the same plan fits two runners differently, and how to adjust when the week does not go to plan.
October 4, 2026 · 1 min read
Missed a Workout? Don't Make It Up
Doubling up after a missed or failed session is one of the most common training mistakes. Here is how to handle missed workouts, workouts that fall apart, and why consistency beats repayment.
October 4, 2026 · 2 min read
Are You a Speed Type or an Endurance Type Runner? How to Tell, and Why It Matters
Two runners with the same 5K time can need completely different training. Here is how to identify whether you are speed oriented or endurance oriented, and how that should change threshold work, intervals, easy pace, and your taper.
Recovery and fueling
Cold, cramps, carbohydrate, and the gut: what helps adaptation and what quietly costs it.
October 4, 2026 · 1 min read
Do Ice Baths Help Runners Recover? When Cold Can Cost You Adaptation
Ice baths feel like recovery, but using them right after training can blunt some of the adaptation you trained for. Here is how to time them, what cooldowns really do, and how to match recovery to the actual problem.
October 4, 2026 · 1 min read
Running Cramps Probably Aren't About Salt
Electrolytes are sold as the cure for muscle cramps, but cramping is more closely tied to neuromuscular fatigue. Here is what that means for prevention, and where sodium still matters.
October 4, 2026 · 1 min read
When Do Runners Actually Need Fuel? Gels, Hydration, and Training Your Gut
You do not need a gel on a 40-minute run, but you do need a plan for runs approaching two hours. Here is when fueling actually matters, how to hydrate without overdrinking, and how to train your gut for race day.