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Slow running builds endurance and improves adaptation to fatigue.
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Prolonged workouts strengthen the body and mind.
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Alternate low and high intensity to optimize your running program.
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et’s start with a caveat: no training plan should rely exclusively on low-intensity exercises, no matter how appealing it may sound to train while putting in (relatively) less effort. More intense workouts—whether at moderate or high intensity—are essential for making real progress, especially if you’re already in decent shape.
Low-intensity training does have its place, though, as it helps you balance intensity and duration effectively. The key is in how long you run. Short, easy sessions won’t cut it; running slowly for just 20 minutes won’t offer the same benefits as a longer workout. At that point, you’re better off resting or committing to a longer session to see real gains. So, let’s explore how to make the most of low-intensity training.
Why run (more) slowly?
Endurance over the long haul is built by gradually getting your body used to longer periods of exertion (i.e., greater distances). Extending the duration of slow running helps improve endurance through biochemical adaptation: your muscles produce interleukin-6, a substance that manages your perception of fatigue. The more consistently your body produces it, the better it adapts, reducing the amount needed for the same level of effort. This makes you more resilient and able to tolerate prolonged physical activity.
The difference between slow, steady runs and fast, intense workouts comes down to stress. Low-intensity workouts generate less physical and mental strain. Think about your weekly routine: doing more than three high-intensity sessions can lead to overtraining, which brings on fatigue, loss of motivation, and stalling progress. To avoid burnout, it’s best to stick to one or two intense workouts per week.
The mental benefits
Slow running doesn’t just help your body adapt; it also has a mental impact. Long workouts train your brain to manage fatigue and maintain focus for extended periods. In endurance events like marathons, success isn’t just about bursts of speed but about sustaining effort over the long haul. A sprint is fine for the last few hundred meters—assuming you have the energy left—but maintaining a maximum workload for a long stretch is much tougher and, for many, simply not feasible. Running builds patience and helps you handle fatigue better, skills that come in handy in everyday life.
So, what’s the point of training your brain for long periods of exertion? It’s not necessarily about boosting speed but about improving your ability to tolerate fatigue and keep a steady pace over longer distances.
Building endurance in zones 1 and 2
The first two training zones (Z1 and Z2) encompass the low-intensity range, covering everything from a leisurely warm-up pace to marathon speed. Here’s how to recognize them:
- Zone 1 (50-60% of max heart rate): This is a very light pace, perfect for warm-up or recovery. You should be able to chat easily, like talking on the phone with a friend. Breathing is steady, and your heart rate remains moderate.
- Zone 2 (60-70% of max heart rate): This is a comfortable yet sustained pace, ideal for improving aerobic endurance. You can still talk, but your sentences are shorter, and you’ll naturally pause for breath. Your breathing is deeper and more frequent, but you’re not struggling.
What’s it for?
- Zone 1: Ideal for active recovery, helping eliminate fatigue from previous workouts. At this intensity, your body mainly burns fat for energy, aiding muscle oxygenation and flushing out toxins. It’s best used after competitions or intense workouts to rebuild energy and repair muscles.
- Zone 2: You’ll want to get familiar with this zone because it’s where most of your training should take place. It optimizes fat burning and builds a solid aerobic base. While these sessions need to be longer to be effective, they do wonders for endurance without overtaxing your muscles.
Training tips
Organize your routine by mixing low-intensity sessions with some medium or high-intensity workouts. Here’s a useful trick: use high-intensity training sparingly to make it more challenging. The “polarized” approach—80% of your training at low intensity (Z1/Z2) and 20% at high intensity (above the anaerobic threshold, in Z4 or Z5)—is a great way to blend different intensities.
Try this: alternate 4 minutes in Z1 with 1 minute in Z5, repeated 10 times, for a total workout of about 50 minutes (not counting warm-up). This “4+1×10” formula gives you a balanced ratio of light to intense training (80/20 split), allowing you to enjoy the benefits of slow running while still getting muscular and metabolic stimulation. It helps you avoid overloading the body, as you’ll work at both low and high efforts, reaping the rewards of both.
If you always train in Z1 or Z2, you’ll build endurance but not speed. On the other hand, always pushing in Z4 or Z5 can lead to excessive fatigue or even injury. We definitely want to avoid that, right?