This Simple Tip Helped Me Understand the Purpose of Threshold Training. Here’s How It Made Me a Better Runner.

The difference between finishing a hard run strong and watching my pace unravel often comes down to something I learned in high school: The moment a comfortably hard effort tips into a heavy-legged struggle, I know I’ve pushed too hard.Once I understood what was happening—and how to stay just shy of that line—I became better at controlling my effort and sustaining faster paces for longer. That lesson began with a simple analogy from my high school cross-country coach.His explanation of lactate threshold turned an intimidating exercise-science concept into something I could feel and apply on the run, ultimately changing how I paced workouts and races.Nearly a decade later, it remains both a practical guide for controlling my effort and one of the early lessons that sparked my connection to running.Lactate threshold is the exercise intensity level at which lactate—a byproduct of exercise created when cells break down glucose for energy without sufficient oxygen—accumulates in the blood faster than the body can remove it. It’s the border between aerobic and anaerobic exercise (and sometimes known as anaerobic threshold).Runners of all levels seek to boost this metric because it improves speed endurance—the ability to run faster for longer—which is the best indicator of long-distance performance, says Alabama-based RRCA Level II- and USATF-certified run coach Alex Morrow, founder of Resolute Running.How I Learned About Lactate ThresholdBack in high school, I started running cross-country simply to condition for basketball in the winter and baseball in the spring. At that point in my life, even the above simplified explanation of threshold training flew way over my head. I just assumed—like I did with every cross-country workout—the training would help me feel fresh during the second half of my basketball games. And truthfully, I couldn’t care less how it did so at the time.But every cross-country practice, we would gather as a team to go over our workout for the day. At one of these meetings, my coach brought out a 16-ounce plastic water bottle, a larger refillable water jug, and a pair of scissors to use as props for a demonstration. As a visual learner, I was intrigued.He started by using the scissors to poke an opening a bit bigger than a pinhole in the bottom of the plastic bottle, letting water slowly leak out. As the water spilled, he began to pour more from the refillable jug into the plastic bottle to keep the water level.After noting the equilibrium, he wrapped up the presentation by pouring more and more water into the plastic bottle until it overflowed.He used this guide to explain the science behind our upcoming workout:Water represents lactate. In the demonstration, the volume of water being poured into the plastic bottle is the lactate produced during exercise, where the amount coming out of the plastic bottle represents the lactate cleared by the body during the same exercise.The point where the water pouring into the plastic bottle is equal to the water coming out represents your lactate threshold.The overflow symbolizes the moment when your body worked too much above its lactate threshold and produced more waste than it can clear, hence the spillage.The volume of the plastic bottle itself represents your body’s capacity to tolerate lactate buildup during high-intensity exercise. A smaller bottle represents a lower capacity.The hole in the plastic bottle represents your body’s ability to clear lactate during exercise.Finally, he laid out the two results that come from threshold workouts—which we were about to do—following the logic of the analogy:It makes the plastic bottle bigger, which means that your body has an increased ability to tolerate lactate buildup before it affects performance.It makes the hole at the bottom of the bottle larger, meaning your body can clear that lactate buildup faster.Both of these factors allow you to run at a higher intensity for longer periods of time before exhaustion sets in.Although I don’t remember exactly what our workout was that day, it likely consisted of a warmup jog, dynamic stretching, and mile repeats at threshold pace (a.k.a. cruise intervals—more on this later). Coach said that during the workout, if your legs start to feel heavy or sluggish at any point, you went out too fast and that feeling was your metaphorical water bottle overflowing.With that, the analogy really clicked: I’d experienced the sluggish feeling before, and I finally knew exactly what it was, why it happened, and how to solve (or at least improve upon) the problem.You’ve likely encountered this overflow feeling firsthand, too.“We’ve all done it—you bolt off the starting line, feel great for the first mile, and then you completely fall apart,” Morrow says. “That’s because you zoomed right past your lactate threshold, and your body couldn’t clear the waste fast enough.” When a runner finally recovers and can run steady again, Morrow says their new pace tends to be below threshold.Hearing the last little nugget, I became fascinated by threshold training all over again nearly 10 years after I heard about it for the first time. I thought back to all the races where my legs gave out far too early. Did I finish those races? I sure did, but it was at a slower pace because my body had already tried—and failed—to maintain an effort above my threshold.How Learning to Hold Threshold Pace Changed My WorkoutsWhen you do threshold workouts—and all running workouts for that matter—you shouldn’t simply go through the motions. Every step is an opportunity for you to become more in tune with your body. “Learning more about your running isn’t so much about paying more attention to your watch, it’s about knowing what it feels like at those certain paces, in those certain zones,” says Morrow. “You should be able to recognize how fast you’re going without ever looking down.” Achieving this, he says, requires solid training.I put this into practice in my own running using the water bottle analogy. When I start to feel that sluggish feeling in my legs during a threshold workout, I visualize the bottle overflowing and I back off the intensity. I know that I pushed too far past my own lactate threshold into the wrong training zone. When I reach a comfortably hard intensity (around 7 to 8 out of 10 RPE) but still feel good, I know that my metaphorical bottle is level and I’m training right at my lactate threshold.Over time, I started learning to pace myself using this visual, not only in threshold training, but in nearly every run I did. My strategy involved sticking to the same loops and running the same paces for a few weeks in a row until I didn’t need to check my watch anymore to tell how fast I was going—I could feel the rhythm in my breathing and the turnover in my legs.I was noticing the difference between easy, comfortably hard, and way too fast in long runs, easy recovery days, and races in addition to my threshold work. Bit by bit, I learned how to improve in multiple aspects of my training, and that made me proud of how far I’d come since high school.Perfect Your Lactate Threshold Training With This Workout ProgressionFor me, threshold training started in high school with cruise intervals, which included threshold pace mile repeats (typically four reps) with short breaks in between (60 to 90 seconds). This worked out to running threshold pace for about 20 to 30 minutes. This isn’t a short sprint workout, but it’s also not about running at a tough pace for an hour. You’re just doing enough to bump up that boundary between aerobic and anaerobic effort.Morrow uses the RRCA concept of I.I.P. (introduce, improve, perfect) to guide athletes through threshold training for the first time. Coaches, including Morrow, generally recommend threshold training once per week in a training plan. The goal is to steadily progress from cruise intervals to a steady-state workout by eliminating recovery segments as tolerated. But really it’s about doing 20 to 30 minutes of threshold effort during a workout to gain the benefits, Morrow says.Cruise IntervalsWhy it works: “Cruise intervals make the workout more manageable as runners learn effort and pace,” says Morrow. This workout allows you to learn from each rep, which is why my high school coach started us out with this workout. If you mess up one rep, that’s okay! Figure out what you did wrong and fix it in the next one.How to do it:1-mile warmup jog at easy pace3 x 1 mile at threshold pace with 800-meter recovery jog in between1-mile cooldown jog at easy paceLong Threshold IntervalsWhy it works: In this stage of the progression, runners have a better understanding of their pacing but still may not be able to handle a full 30 minutes of comfortably hard running. You’ll hold your threshold pace for longer, but get a break before the final interval.How to do it:1 mile warmup jog at easy pace2 miles at threshold pace1 mile recovery jog1 mile at threshold pace1 mile cooldown jog at easy paceSteady-State Threshold RunWhy it works: Eliminating all breaks with a steady-state workout helps runners push through the low-grade discomfort that distance running is all about, says Morrow.How to do it:2-mile warmup jog at easy pace3 miles at threshold pace1-mile cooldown jogThe beauty of threshold training—specifically for distance running—is that it doesn’t matter what your top speed is; it’s about extending the time you can sustain your own challenging pace without falling apart.“If my athlete can run longer at a higher intensity without accumulation forcing them to slow down,” Morrow says, “they will be much more successful as a distance runner.”Looking back, that water bottle demonstration was just one piece of advice, but it completely reframed how I think about running. Morrow believes every runner has moments like this. “If you want to be a great runner, it takes a long time,” he says. “Everybody wants a quick fix, but that’s not what running is all about. It’s about building training on training, year after year. When you do that, you reach your true potential.”Sometimes all it takes is one lesson, one workout, or one coach’s advice to change the way you run—and once it sticks, it can guide you for years.Matt Rudisill is an Associate Service Editor who has been with Runner's World since 2025. A Nittany Lion through-and-through, Matt graduated from Penn State in 2022 with a degree in journalism and worked in communications for the university's athletic department for three years as the main contact and photographer for its nationally-ranked cross country and track & field teams. Matt was also heavily involved in communications efforts for Penn State football, men's basketball, and women's gymnastics. In his role with Runner's World, Matt has interviewed Olympians, world champions, and countless experts in the field to create service content that helps runners of all ages and experience levels train smarter and race faster. When he’s not out jogging, Matt can be found tweeting bad takes about the Phillies or watching movies.