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the25percent newsletter

by Alessandro Kraschewski

A science-backed longevity training app for enthusiasts ready to invest seriously in their healthspan. After over 15 years as a UX consultant, I realized that most fitness advice optimizes you for ages 25 to 30, not 60 and above. Now I'm building the demanding but achievable protocol I wish existed, backed by the latest longevity science. Join me for evidence-based insights on training, healthspan, habit formation, and the reality of bootstrapping a health-tech startup.

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Featured Post

Most people train at one speed. Here's why that limits your results.

the25percent Newsletter What actually works for healthspan. April 02, 2026 Last time I said Zone 3 was "not hard enough to push your ceiling." That framing needs a correction. It's true from an efficiency standpoint. But it's not the full picture. Quick primer: the three zones Familiar with heart rate zones? Skip ahead. Heart rate zones are ranges that describe how hard your cardiovascular system is working. Three matter most here: đź’š Zone 2 (65-75% of max heart rate) You can hold a full...

14 days ago • 3 min read

the25percent Newsletter What actually works for healthspan. April 02, 2026 Last time, I shared my VO2max number: 33.84. Below the 50th percentile for my age. Poor on my Garmin. Now the question that matters: how do I raise it? The answer has been studied for decades. And one protocol has the strongest evidence behind it. The Norwegian 4x4 Four intervals. Four minutes each. At 90-95% of your max heart rate. Three minutes of active recovery between intervals at around 70% HRmax. Ten minutes of...

27 days ago • 3 min read

the25percent Newsletter What actually works for healthspan. April 02, 2026 Last time we covered Zone 2: the base. The long, boring sessions that build your aerobic engine. Now: the ceiling. Why VO2max matters more than any other fitness metric In 2018, Mandsager and colleagues published a study tracking 122,007 patients over two decades. They measured cardiorespiratory fitness and followed who lived and who didn’t. The findings were stark. People in the bottom 25% of fitness had a mortality...

about 1 month ago • 3 min read
Fit woman in her sixties performing a deep goblet squat with a kettlebell while her partner rests beside her

the25percent Newsletter What actually works for healthspan. April 02, 2026 You signed up for the25percent newsletter. That tells me something: you’re not looking for “5 easy tips” or “transform in 30 days.” You want protocols that actually work, even if they’re demanding. Good. You’re in the right place. But before we start, let me be honest about something. This isn’t about biohacking or living to 120 I’m not a fitness influencer. Not a sixpack Bro. I’m not trying to optimize my way to...

about 2 months ago • 3 min read