This Speed Workout Tweak Can Help You Finish Strong Instead of Fading. Here’s How to Do It.
The end of a speed workout can get ugly fast. Your first few reps feel smooth and controlled, but somewhere in the back half, your form starts to unravel, your pace slips, and every interval becomes more about survival than speed.
Danny Mackey, head coach of the Brooks Beasts Track Club, says breaking the workout into manageable sets can help you preserve the quality of the workout.
“One of the training variables that’s very important [to actually seeing the benefits of a workout] is just maintaining speed,” Mackey says. “If you chunk the workouts, runners tend to be able to keep the speed up through the rest of the reps.”
A 12 x 400-meter repeat workout can become three sets of 4 x 400 meters, with short recovery between reps and a longer recovery between sets. The total interval volume stays the same, but the recovery structure changes. Longer set breaks give you a better chance to complete each rep strong, rather than watching the workout slowly fall apart, Mackey explains.
Here are Mackey’s recommendations on when to chunk your intervals, when not to, and what your recovery between sets should look like to get the most out of your speed workouts.
Benefits of Chunking Speed Workouts
Mackey describes two main benefits of this workout structure, both of which help you achieve the main goal of completing the workout as strong as you started.
Physical Benefit
Chunking workouts helps you maintain pace and form deeper into the session.
In Mackey’s workout examples, the recovery between normal speed interval reps is often short—about one minute for his pros and closer to two minutes for newer runners. The shorter rest controls the stress of the session, but as the reps pile up, runners may find themselves slowing down just to get through the full workout.
Mackey says three or four minutes of rest every few reps—with the actual number depending on the length of the interval (we’ll get into that later)—can help prevent fading by giving your body time to reset.
“That’s generally enough time for the heart rate to come back down,” Mackey says of a three- to four-minute set break. “But the lactate levels don’t change that much.”
Essentially, the longer break helps you feel more in control before the next set, while still maintaining the stress of the workout. You’re still carrying some metabolic load, which means you can keep building fitness while giving yourself a better chance to hit the next reps with the right pace, mechanics, and effort.
Longer set breaks can also create a natural window for fueling. Mackey mentions this as especially beneficial for marathoners, who should practice taking in fluids and gels during hard sessions. For non-marathon runners, the same idea still applies on a smaller scale: Use the set break to sip water, regroup, and get ready to run the next block well.
At the end of the day, the idea is getting better results (read: faster running) out of the same workout.
Mental Benefit
According to Mackey, the psychological benefits may be more important.
Simply, big workouts can feel intimidating. Breaking the session into more digestible chunks allows you to focus on just the next set.
“It’s a skill that psychologists talk about for anyone dealing with something that’s really stressful and long in duration,” Mackey says. “Just chunk it. Then you’re like, ‘Okay, I’m going to do what’s in front of me right now and not worry about what’s coming after.’”
In Mackey’s experience, athletes are actually able to conquer more intense efforts in these shorter bouts because they’re not worried about the next set. “[Athletes] just seem to be able to handle the entire workout better,” Mackey says.
When to Chunk Your Workouts
Chunking is most useful when a workout is long enough, repetitive enough, or fast enough where quality may fade. Essentially, Mackey explains, you can employ the strategy whenever you feel you need to.
If the number of reps feels overwhelming, sets can make the workout easier to process. For recreational runners, that may mean turning six consecutive 1,000-meter repeats (with 90-second rest breaks) into two sets of three reps, with a three- to four-minute break between sets.
Mackey even uses the strategy for mile repeats, but he notes the longer the interval, the smaller the set should be. So if you’re doing four reps of mile repeats at threshold pace with one minute of rest between, simply split them into pairs and add a three- or four-minute rest between those pairs to make the work more manageable.
Remember, chunking is simply a tool for interval workouts, not a rule. Some efforts are already short enough you can roll straight through. Mackey’s example is a really hard, low-volume workout for his 5K or 10K athletes—something like six to eight reps of 400s at nearly top speed—with one minute of rest between.
What to Do During Set Breaks
The normal short recovery breaks between individual reps should be active, Mackey says. Walk, lightly jog, breathe, and prepare for the next interval.
During the longer breaks between sets, the three to four minutes, refuel and reset for the next group. Sipping water or sports drink while continuing to walk around helps your body recover so you can tackle the rest of your workout.
What should you avoid? Mackey’s advice is simple: Don’t sit down.
“Walking around is so much better than just sitting down for recovery,” Mackey says.
Sitting or standing around too long can make you feel stiff and flat when the next set starts. The longer break should help you reset, not switch off completely—so keep moving, use the rest with intention, and let each break set up a better next rep.
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.