Why Your Aerobic Base Matters More Than High-Intensity Intervals

A new paper in the Strength & Conditioning Journal recommends prioritizing high-volume, low-intensity work over HIIT for building aerobic capacity. According to the authors, HIIT still has a role — but only when layered into a polarized or pyramidal structure.

The Core Finding

The recommendation is blunt: more easy miles, fewer intervals. The study, indexed on ResearchGate and titled "Beyond High-Intensity Interval Training: Optimizing Endurance Training Intensity Distribution to Enhance Warfighter Aerobic Fitness," argues that endurance gains are driven by accumulated time below the first ventilatory threshold. HIIT, in this framework, is a supplement — not the foundation.

Polarized vs. Pyramidal

Two distribution models surface as the viable frameworks:

• Polarized: roughly 80% low-intensity / 20% high-intensity. Hard days stay hard. Easy days stay easy. No junk middle.
• Pyramidal: a graded approach where intensity bands taper — a large base of easy work, a middle zone of moderate effort, and a small peak of high-intensity output.

Either model accepts the same premise: Zone 2-style volume does the heavy lifting for VO2 max development over time. HIIT sessions sharpen the top end but cannot compensate for a missing aerobic base.

What This Means for Home Training

For HIIT-focused athletes working without a gym, the practical translation is straightforward:

• Most sessions should feel easy enough to hold a conversation. Heart rate stays in the low-to-moderate band.
• Reserve 1–2 sessions per week for genuine high-intensity intervals — sprints, bike efforts, or bodyweight circuits pushed to near-max.
• Skip the gray-zone "moderate-hard" steady-state work. It accumulates fatigue without the metabolic payoff.

The verdict: do HIIT — but build the base first. Skip the all-HIIT-every-day programming.