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Most good running plans are built around different types of runs, and each one has a purpose.
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If you're a runner, you've probably been there. Lacing up full of energy, thinking, "Today I'm going to smash it!" And you do, for a few kilometres, only to feel exhausted, sore, or even injured the next day. It's a common trap. Running too fast all the time. Even seasoned runners can fall into the mindset that faster always equals better.
The truth is, running in what coaches call the "grey zone" (not quite hard, not quite easy) is one of the fastest ways to build fatigue without getting the full benefits of either speed or endurance work. You don't recover properly, and when race day (or a key workout) arrives, you have nothing left to give.
Don't get me wrong. There's absolutely a time and place to run hard. But it's not every day. The key to effective, sustainable training is variety. Most good running plans are built around different types of runs, and each one has a purpose. Let's break them down.
Easy runs: the unsung hero
Easy runs are the foundation of most running programs. They build your aerobic base, support recovery, and help you handle more training over time. The simplest way to judge an easy run is by feel. You should be able to hold a conversation comfortably, your breathing should be steady, and you should finish feeling like you could keep going.
Easy running is where your body builds the engine. It's where you develop endurance, improve aerobic efficiency, and build the kind of fitness that carries you through longer efforts. Just as importantly, easy runs give your muscles, joints and tendons time to adapt without constantly being under high stress.
For newer runners in particular, higher-intensity running without enough recovery is linked to increased injury risk. It's not that speedwork is "bad". It's that too much of it too soon can overload the system (Buist et al., 2010). A useful mindset shift is this: easy runs are not "wasted" runs – they're the runs that allow the harder sessions to actually work.
Tempo runs: speed endurance
Tempo runs help you build the ability to hold a strong, steady effort for longer. This is the kind of controlled discomfort that shows up in races like 10Ks, half marathons, and for parts of a marathon. A tempo run should feel "comfortably hard". You can speak in short sentences, but you can't chat the whole way.
The goal is to sit right on the edge of discomfort without tipping into an all-out effort. That's what makes tempo work so valuable. It builds speed endurance and helps you learn pacing discipline. Tempo runs are also a great confidence builder because you get used to holding a higher effort without falling apart.
A simple way to use this in training is to include 15 to 30 minutes at tempo pace inside a longer run, with an easy warm-up and cool-down around it (Seiler & Tønnessen, 2009; Casado et al., 2023).
Intervals: short, fast, powerful
Intervals are where you build speed, improve how efficiently you move, and challenge your cardiovascular system. They're hard, but they can also be one of the most time-efficient ways to develop fitness, especially if you don't have hours to train.
Intervals work best when the efforts are strong and controlled, rather than a sprint. A common mistake is going too hard on rep one, then spending the rest of the session trying to survive. Ideally, your pace should be repeatable across the set so you can keep form, stay relaxed through the shoulders and jaw, and finish the session feeling like you worked hard but didn't blow up.
Intervals can range from short bursts (like 30 to 60 seconds) to longer efforts of a few minutes. Either way, the recovery matters. Rest or easy jogging between reps is what allows you to run the next rep well and actually build the intended adaptation (Tschakert & Hofmann, 2013).
Fartlek: the flexible one
Fartlek is the fun, unstructured cousin of intervals. It's a mix of faster and easier running, but without strict timing or track-style structure. It's ideal if you want the benefits of speedwork without being glued to your watch or stressing about splits.
Fartlek is also great for learning how to change pace smoothly, which matters in races with hills, surges, or changing terrain. You can base your faster efforts on landmarks (like running faster to the next lamp post), or on time (like 30 seconds on, 60 seconds easy). You still get the challenge of speed and the benefit of recovery, but it often feels less mentally intense than formal intervals.
How to structure these runs into your week
The exact mix depends on your experience level, but as a general rule, most runners benefit from a lot more easy running than they think. Many high-level endurance programs are built around a foundation of high-volume, low-intensity training, with smaller amounts of tempo and interval work layered on top (Seiler & Tønnessen, 2009; Haugen et al., 2022).
- If you're running three times a week, keeping most runs easy is usually the smartest move while you build consistency and resilience.
- If you're running five times a week, a common structure is four easy runs and one session (tempo, fartlek or intervals).
- If you're running six times a week, you might include two sessions, but the majority of your running should still stay easy enough that you can recover and stay healthy.
The key is that hard days should have a clear purpose, and easy days should actually be easy. That's how training stays sustainable, and that's how you keep progressing month after month.
What to try in your week
If you're not following a plan and you want something simple to guide you, try this.
Keep most of your runs easy and pick one day for a quality session. That might be a short tempo effort inside an easy run, a structured interval workout, or a playful fartlek based on how you feel. Once you've done that session, protect the days around it. Run easy, keep it conversational, and give your body the chance to adapt.
For beginners, the biggest win is consistency. For more experienced runners, the biggest win is balance. Training that feels good in the short term should still feel good after four, eight, or twelve weeks.
Easy runs are your secret weapon
Tempo, intervals and fartlek sessions are exciting. But easy runs are the glue that makes training work. They help you recover, reduce injury risk, and build the aerobic base that supports performance when it counts.
Running fast all the time might feel productive in the moment, but it's usually a shortcut to fatigue. A balanced program, where easy days stay easy and hard days have a clear purpose, is the real route to sustainable progress. If you take one thing away, let it be this: you don't need every run to feel like a workout, you just need your training to make sense as a whole.
Looking for more expert advice and running tips? Check out rebel RUN and level up your running game.
Disclaimer
The information provided in this article is of a general nature only and is not intended to replace professional medical, health, or fitness advice. It does not take into account your individual objectives, physical condition, medical history, or needs. Before acting on any of the guidance or recommendations provided, you should consider whether it is appropriate for you in light of your personal circumstances. You should always seek the advice of a qualified healthcare professional (such as a physiotherapist, podiatrist, dietitian, or medical doctor) before starting, changing, or relying on any exercise, training, or nutrition program. Rebel Sport accepts no liability for any loss, injury, or damage suffered by any person relying on the information provided.
References
- Buist, I., Bredeweg, S. W., van Mechelen, W., Lemmink, K. A., van Middelkoop, M., Diercks, R. L., & Verhagen, E. (2010). The NLstart2run study: Training-related factors associated with running-related injuries in novice runners. British Journal of Sports Medicine, 44(15), 1158–1163. https://doi.org/10.1136/bjsm.2009.059634
- Casado, A., Foster, C., Bakken, M., & Tjelta, L. I. (2023). Does Lactate-Guided Threshold Interval Training within a High-Volume Low-Intensity Approach Represent the “Next Step” in the Evolution of Distance Running Training? International Journal of Environmental Research and Public Health, 20(5), 3782. https://doi.org/10.3390/ijerph20053782
- Haugen, T., Sandbakk, Ø., Seiler, S., & Tønnessen, E. (2022). The Training Characteristics of World-Class Distance Runners: An Integration of Scientific Literature and Results-Proven Practice. Sports Medicine – Open, 8, 46. https://doi.org/10.1186/s40798-022-00438-7
- Seiler, S., & Tønnessen, E. (2009). Intervals, Thresholds, and Long Slow Distance: The Role of Intensity and Duration in Endurance Training. Sportscience, 13, 32–53. https://sportsci.org/2009/ss.htm
- Tschakert, G., & Hofmann, P. (2013). High-intensity intermittent exercise: Methodological and physiological aspects. Sports Medicine, 43(9), 313–338. https://doi.org/10.1007/s40279-013-0065-6
