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Do Marathoners Need Short Intervals?

Short reps can improve speed reserve and running economy, but only when they solve the problem your marathon training actually has.

By Miles Rowan Updated Aug 31, 2026 3 min read
A runner accelerating along the curved lanes of a red athletics track
AI-generated original for The Steady Split

Marathon training is mostly aerobic, but that does not make short intervals irrelevant. Repetitions of 30 seconds to roughly three minutes can improve oxygen uptake, neuromuscular coordination, and speed reserve. They can also become an expensive distraction from the long runs, threshold work, and fueling practice that decide most amateur marathons.

The useful question is not “Do marathoners need speed?” It is “What is currently limiting this runner?”

Diagnose the missing quality

You may benefit from short intervals when:

  • your 5K and 10K performances are weak relative to your marathon goal;
  • marathon pace feels mechanically awkward rather than aerobically hard;
  • you have spent months doing only easy and steady running;
  • you recover well from long runs but lack leg speed.

You probably need more endurance, not short reps, when:

  • your 5K predicts a much faster marathon than you actually run;
  • pace falls sharply after 18–20 miles (29–32 km);
  • long-run fueling is inconsistent;
  • weekly volume is unstable;
  • threshold work already leaves you depleted.

That second profile is common. More 400-meter repeats will not repair under-fueling or missing long-run durability.

What short intervals can and cannot do

Systematic reviews in recreational runners find that high-intensity interval training can improve maximal oxygen uptake, running economy, and performance when combined with continuous running. Elite-distance reviews also show short intervals in many programs.

But marathoners still perform the great majority of training at low intensity. Race-specific work grows as the race approaches. Short intervals are a supporting tool, not the center of the plan.

One controlled session

Use this session in an early or middle marathon block:

12 × 1 minute fast / 1 minute easy, after 15 minutes easy and four relaxed strides. Run the fast minutes around current 3K–5K effort, not an all-out sprint. Cool down for 10–15 minutes.

The effort should remain repeatable. The final two reps can be hard, but cadence and posture should look like the first two. If pace drops sharply, the session was too fast.

After two or three exposures, progress to 10 × 75 seconds or 8 × 2 minutes. Do not increase pace, rep count, and rep duration at once.

Where it belongs in the cycle

Eight to sixteen weeks before a marathon, short intervals can restore speed and make later threshold work feel smoother. Closer to race day, reduce them to maintenance: short hills, strides, or a few quick reps after easy running.

The final specific block should prioritize long runs, marathon-pace work, fueling, and recovery. A runner who can hit every 400 but cannot complete a steady 18-mile (29 km) long run has optimized the wrong test.

Use one demanding run every three or four days, not on consecutive days. If you already have a threshold session and a hard long run, short intervals may fit only as six to eight relaxed strides.

Keep the fast running economical

Short reps invite stopwatch racing. Avoid it. Choose level terrain, stop before form deteriorates, and use effort when conditions are hot or windy. Above 75°F (24°C), a fixed pace can turn a controlled session into an excessive one.

For many marathoners, the best version feels almost too easy for the first third and exactly right by the last third.

The decision rule

If shorter-race ability is the bottleneck, use a small dose of short intervals. If durability, fueling, or volume consistency is the bottleneck, address those first. Your marathon does not award points for the fastest workout posted during the build.

Sources

marathon trainingintervalsspeed reserve