You open your Runna plan and see “tempo” one day and “intervals” the next week. They’re both speed sessions… so what’s the actual difference? Why does one feel controlled and one sometimes feel much more intense? If you’ve ever felt unsure, you’re not alone, even the science behind these sessions can get blurry. We are here to break it down.
You'll notice Runna uses 'intervals' and 'tempo runs' rather than the word 'threshold'. That's deliberate – threshold is a physiological term, not a session structure. Both your interval sessions and your tempo runs can train your lactate threshold. The difference is in how they do it.
Intervals vs Tempo
Intervals
Intervals are shorter, harder efforts, typically run at, or just below, your lactate threshold, with a walking or static recovery between reps. Because the intervals are broken up with recovery, you’re able to run faster than you could continuously. This challenges your cardiovascular system, increases your speed, and helps raise your lactate threshold over time. Interval sessions often fall at an effort level of 8-9/10.
Although intervals are typically run at your threshold pace, some sessions, particularly when training for a shorter distance like a 5K, involve shorter reps (e.g. 200-400m) which increase intensity and move you above threshold pace.
You can check out this episode of Runna TV, where Coach Kayla guides Aisha through an interval workout and explains exactly how they boost performance.
Tempo Runs
Tempo runs are longer, sustained efforts performed below your lactate threshold, usually as one continuous block, or with short, steady jog recoveries after longer efforts. During these sessions, you spend extended periods running at a challenging but controlled pace. The goal isn’t to sprint, it’s to hold a "comfortably hard" pace. This improves your endurance, efficiency, and ability to maintain a strong pace over longer distances. Tempo sessions often fall at an effort level of 7-8/10 effort. If you push much harder, you’re likely drifting into interval effort territory.
That’s the simple difference – but if you’re curious about the different benefits and paces, the guide below breaks down the science in more detail.
Your Runna plan guides you though your interval and tempo sessions with personalized pace targets based on your fitness levels, making sure you are always training at the right effort.
| Interval Run | Tempo Run |
Effort level | 8-9 out of 10 | 7-8 out of 10 |
Most common pace | ~Threshold pace or 5k to 10k race pace | ~10k to half marathon race pace |
Rep length | Shorter (e.g. 400m–1.6km) | Longer (e.g. 2km–5km+) |
Recovery between reps | Full rest or walking | Steady jog, or no rest at all |
How it feels | Challenging effort that feels tough; you could hold it a little longer, but it would be uncomfortable | Comfortably hard – challenging but you can sustain it |
Primary benefit | Boosts speed, running economy, tolerance for high intensity and paces | Endurance at pace, lactate clearance |
Heart Rate During Tempo and Interval Runs
Typically, it's normal for tempo runs to sit between zones 3-4. You may find your heart rate reaches zone 4 during a shorter rep or in challenging conditions. Intervals typically sit in zone 4-5, depending on the distance of each rep. During shorter, faster reps, your heart rate may spike into zone 5 – that's also normal.
Heart rate varies hugely between individuals, by temperature, fatigue, hydration, and more, so don't panic if your zones don't match exactly. Most importantly, remember that wrist-based heart rate data is not completely accurate.
If your heart rate is consistently climbing into zone 5 and nearing its maximum on every tempo run – and the effort feels unsustainable – that’s a sign to reassess your pace targets. You may need to dial the pace back slightly to avoid overdoing the session. For more detail on understanding heart rate zones, check out the guide below.
Zone | Description | % of max HR | Duration you should be able to hold this HR for |
Zone 1 | Recovery | 0-65% | 6+ hours |
Zone 2 | Endurance | 65.1 - 81% | 1-3 hours |
Zone 3 | Tempo | 81.1% - 89% | 40-90 minutes |
Zone 4 | Threshold | 89.1% - 97% | 6-40 minutes |
Zone 5 | Anaerobic | 97.1-100% | Less than 5 minutes |
The line between tempo and threshold can be blurry because tempo pace is close to threshold pace.
Your running watch may label your interval sessions as a "threshold run" – this is just a labelling difference, not an error.
If your tempo pace regularly exceeds your threshold, it may be worth reviewing your pace targets in the app.
What to Do If the Pace Feels Wrong
If tempo pace feels too hard:
Try slowing down by 5–10 sec/km rather than taking a walking break, this keeps the aerobic stimulus alive.
Check whether your estimated race time in the app reflects your current fitness.
Switch to RPE (Rate of Perceived Exertion) mode if pace targets are consistently off.
If tempo pace feels too easy:
Stick to the prescribed pace – the goal is sustained speed, not maximum effort.
The adaptation happens over weeks, not in a single session.
If you're running on hills, in heat, or other challenging conditions:
Pace targets are calibrated for flat routes – on hilly terrain, switch to effort level (RPE) rather than hitting exact numbers.
Running uphill at tempo effort is perfectly valid even if your pace drops.
Final Thoughts
Your personal effort level is the clearest guide. Sometimes the pace numbers will look similar, but a small difference in pace between your tempo and interval targets isn't a mistake, it reflects a real but subtle physiological difference.
Your heart rate also doesn't have the final say: tempo runs pushing into zone 5, intervals spiking higher than expected, both are normal, especially in challenging conditions, early in your training, or if you're tired or stressed. Use heart rate for context, not as the defining metric.
Most importantly, both intervals and tempo sessions are teaching your body to run faster for longer. Runna's tempo and interval sessions include personalized pace targets that sync straight to your device of choice and pacing insights that