A tempo run is a steady, sustained effort that is comfortably hard, usually at or a little below threshold. A threshold session is work deliberately placed at the boundary between steady effort and fatigue that keeps climbing, often broken into reps. Intervals are repeated faster efforts with recovery between them, usually aimed at VO2 max or race pace. The three overlap, and the label matters less than the quality each session is meant to build.
Why are these terms so confusing?
Because coaches, apps and magazines use them differently. "Tempo" can mean marathon pace to one runner and 10K pace to another. "Intervals" can mean 200 m repeats or 2 km repeats. Research does not settle it either: an influential review of interval training describes intervals as any repeated efforts at or above maximal lactate steady state, which means threshold reps technically count as intervals too.
Our coaching method avoids arguing about labels. Every session gets a clear purpose and a pace or effort described in race terms, such as "half marathon effort" or "5K pace," instead of a vague word like "hard."
What is a tempo run?
A tempo run is a continuous effort, typically 20 to 40 minutes, run at a pace you could hold in a race of roughly 1 to 2 hours. It feels steady and strong but not strained.
- Builds: aerobic strength, pace control, the ability to hold a rhythm when you are tired.
- Effort: around 6 to 7 out of 10. Short phrases are possible.
- Examples: 25 minutes steady; a 40 minute progression finishing near threshold; 3 x 10 minutes at half marathon to marathon effort.
Tempo runs fit well in base and early build phases, and they are especially useful for half marathon and marathon runners, for whom this effort is close to race pace.
What is a threshold session?
Threshold work targets the top of that steady range, the fastest pace your body can still hold in balance. It is usually a little quicker than most tempo runs and is often split into reps so you can control it.
- Builds: the pace you can sustain for long efforts, which supports every race from 5K up.
- Effort: about 7 out of 10. Controlled, rhythmic breathing.
- Examples: 5 x 6 minutes with 1 minute jog; 4 x 1 mile with 1 minute rest; 3 x 12 minutes with 2 minutes jog.
The full guide to pacing these sessions is in threshold runs: what they are and how fast to run them, and why the threshold itself is a range rather than one number is in lactate threshold is a range.
What are intervals?
In everyday running language, intervals usually means faster repeats with recovery: VO2 max reps, 5K or mile pace work, and speed endurance.
- VO2 max intervals: 3 to 5 minutes at roughly 3K to 5K effort, with recoveries of a few minutes. They push the top of the aerobic engine. A frequently cited randomized trial in moderately trained men found that 4 x 4 minute intervals at 90 to 95 percent of maximum heart rate raised VO2 max more than the same total work done at threshold or at an easy pace over eight weeks.
- Race-pace intervals: reps at goal 5K, 3K or mile pace. They teach the specific rhythm of the race.
- Short speed reps: 200 m to 400 m at mile pace or faster, with long rest, to build speed and economy.
See VO2 max for runners for how much that number really predicts performance.
Where do they overlap?
Plenty:
- A long tempo at the faster end and a continuous threshold run can be the same session.
- Short threshold reps with brief rest are, technically, intervals.
- Rep length, rest and pace together decide what a session trains. Lengthen the rest and a threshold session drifts toward VO2 max work at a faster pace. Shorten it and VO2 max reps start to behave more like sustained aerobic work.
A review of interval programming describes up to nine variables that change the stimulus, including rep intensity and length, recovery intensity and length, number of reps and sets, and rest between sets. Change one and the session changes.
When does each one fit?
The answer depends on your event and where you are in the season.
- Base phase: mostly easy running, the long run, strides and hill sprints, with tempo runs or gentle sub-threshold sessions as the main aerobic workout.
- Build phase: threshold becomes the backbone. VO2 max intervals appear in small doses.
- Specific phase: race-pace intervals take priority. Threshold drops to a smaller maintenance dose.
By event, as a rough guide:
- Marathon and half: more tempo and threshold, fewer short intervals.
- 10K and 5K: threshold and VO2 max work share the load, with race-pace sessions late.
- Mile and 1500 m: threshold is support, while faster intervals and speed work carry more weight.
A systematic review of highly trained distance runners found that elite runners used both a threshold-type session and a faster interval session at least once a week, with marathoners leaning toward a pyramidal pattern heavier in threshold work and 1500 m runners toward a more polarized one.
How many hard sessions should you do each week?
For most runners, one or two. A typical week might hold one threshold session and one interval or long run session, with easy days between. Stacking all three types every week is a common route to stale legs. Hard sessions should usually end with about one rep left in reserve. See how it all fits together in our pillar guide running workouts explained.
How your HealthAI coach applies this
Your coach labels every session by the quality it builds and the effort to run it, using race paces you understand rather than vague zones. Each two-week plan mixes tempo, threshold or intervals according to your event, your phase and the runs you have logged. If your splits drift or your check-in shows heavy soreness or poor sleep, your coach can shorten the session, change it or move it. See plans from $30 a month.
Your coach builds this around your training data. Start at HealthAI.coach.
Sources
- Billat LV, Interval training for performance: a scientific and empirical practice. Special recommendations for middle- and long-distance running. Part I: aerobic interval training. Sports Medicine, 2001. doi:10.2165/00007256-200131010-00002
- Helgerud J et al., Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine and Science in Sports and Exercise, 2007. doi:10.1249/mss.0b013e3180304570
- Buchheit M et al., High-intensity interval training, solutions to the programming puzzle: Part I: cardiopulmonary emphasis. Sports Medicine, 2013. doi:10.1007/s40279-013-0029-x
- Casado A et al., Training Periodization, Methods, Intensity Distribution, and Volume in Highly Trained and Elite Distance Runners: A Systematic Review. International Journal of Sports Physiology and Performance, 2022. doi:10.1123/ijspp.2021-0435