Intervals & VO₂max Workouts

What they are

An interval workout is a set of hard repetitions — typically around 5K effort or a touch faster — broken up by recovery jogs. Classic shapes are things like 5 × 1 km, 6 × 800 m, or 4–5 × 3–4 minutes. The recoveries are deliberate: they let you accumulate several minutes of genuinely hard running that you couldn't sustain in one continuous block.

Why they work

Time spent near your maximal oxygen uptake appears to be one of the most effective stimuli to raise it, and well-trained runners in particular likely need real time at high percentages of VO₂max to keep improving it¹. Intervals also sharpen running economy and turnover. Think of them as raising the ceiling that your threshold and endurance then let you use.

How to do them

Warm up thoroughly first (10–15 minutes easy plus a few strides) — you can't safely hit hard running cold. Then run the reps controlled-hard:

• Effort: hard but repeatable. The first rep should feel almost too easy; build into the set rather than emptying the tank on rep one.
• Recovery: take the full jog recovery — it's what lets the next rep hit the same quality.
• Quality over count: if you can't hold the effort with good form on the last rep or two, stop. A great 5 × 1 km beats a falling-apart 6 × 1 km.

Where they fit

Intervals are potent and stressful, so they're used sparingly — usually once a week at most, in the build and peak phases, on a foundation of easy volume. They come *after* you've built an aerobic base, not instead of it. For 5K–10K runners they're a peak-phase priority; for marathoners they're a sharpening tool rather than the main event.