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Research-informed writing on VO₂max, interval training, breathwork, and training for the long term. Written by spira.
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Breathwork for recovery after hard training
Slow breathing with extended exhales shifts the nervous system back toward recovery. The vagal mechanism, and the post-training protocols that use it.
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VO₂max and healthy aging: why it matters after 40
VO₂max declines roughly 10% per decade in untrained adults — but it responds to training at any age. Why aerobic capacity matters more, not less, after 40.
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How to measure VO₂max improvement without a lab test
You don't need a lab to know your training is working: heart-rate recovery, heart rate at a fixed workload, and standardised retests — tracked consistently, per modality.
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How to improve your VO₂max with interval training
What VO₂max is, why intervals raise it more efficiently than steady cardio, the protocols that work — 30/30, Norwegian 4×4, Billat — and how to structure them over weeks.
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Norwegian 4×4: how the protocol works and how to do it
The benchmark VO₂max interval session: four 4-minute efforts at 90–95% of max heart rate. The exact prescription, why it works, and the mistakes that blunt it.
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