Conner Mantz crushed the 2025 Boston Marathon with a personal best time of 2:05.08—just off the podium in fourth place! Meanwhile Jess McClain, the top American woman, came in at 2:22:43 for seventh overall.
miles at goal marathon pace 4-5 RPE lactate threshold workouts. While you likely can’t mimic their blazing speeds, you can adapt their workouts for your pace, which may help you PR in your next race.
Here’s everything you need to own the lactate threshold run.
How to Find Your Lactate Threshold
Lactate is a byproduct of intense exercise. During tougher efforts, it accumulates in your blood faster than your body can get rid of it. Workouts run at a relatively comfortable hard pace elevate both the body’s capacity to hold lactate as well as its ability to remove it, resulting in faster runs over longer periods of time.
You know it when you feel it: you are pushing yourself, but not so much that you need to immediately stop. You also don’t feel like you can’t breathe. The pace is a challenge, but a challenge that doesn’t make you want to quit…at least, not right away. Essentially, practicing it during your endurance training makes harder run efforts feel easier over time.
There a few ways to find your lactate threshold, but existing research has found that the majority of seasoned runners who undergo lactate threshold testing hit the mark around a sustained 5K pace. So, to find your lactate threshold pace, try to run your best 5K (either in a real race or a test run), exercise physiologist Kaitlyn Baird, C.S.C.S., the coordinator for running and metabolic services with the Hospital for Special Surgery in New York told Runner’s World. Training Tweaks That Will Get You to a BQ.
Mantz, as you’ll see below, ran a little faster than his overall marathon pace (4:44) during one of his later workouts in prep for the marathon.
How the Pros Train at Threshold
A few weeks before Boston, McClain showed signs of a great marathon ahead, according to her coach, David Roche.
“[McClain’s] final threshold workout 2.5 weeks out is a good one that works for any distance from the mile to ultramarathons,” Roche told Runner’s World.
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- 5 x 1-mile at threshold effort (5:10 min/mile or so) with 90 seconds recovery
- 3 minutes easy
- 5 x 30 seconds fast/1-min slow (think mile to 800 meter effort)
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“Throughout the training build, [McClain] did a few sessions of mile intervals at threshold or harder efforts, followed by fast 200s,” Roche said.
Similarly, Mantz, according to a previous Runner’s World story, does lactate threshold workouts, among other high-effort runs, on Tuesdays and Thursdays. According to his Strava data, he did 4 x 3 miles at threshold pace (his best mile split was 4:36/mile) with rest between each set on March 27, totaling 18 miles when factoring in the warmup.
Can’t keep a 4:37/mile pace? Hardly anyone can! That’s okay. We’re going to explain exactly how to run like the pros at your own speed.
How to Train at Threshold
First, the parameters for mere mortals, i.e., runners who want to push themselves and are comfortable with intervals: Threshold workouts should consist of 20-30 minutes of hard running at a RPE of between 7-8. You are pushing yourself, but you don’t need to stop immediately. It is as if you are running at your best 5K pace, give or take a few seconds.
Below are two excellent threshold workouts designed to replicate those used by McClain and Mantz in their Boston training.
15-Plus-Mile Progression Run
This workout, created by Alex Morrow, RRCA- and USATF-certified run coach and founder of Resolute Running in Birmingham, Alabama, will hit multiple paces and includes a steady tempo run in the middle, perfect for simulating fatigue in the later miles of your marathon.
- 3-4 miles at easy pace (3-4 RPE)
- 3-4 miles at goal marathon pace (4-5 RPE)
- 20 minutes at lactate threshold pace (7-8 RPE)
- 3-4 miles at goal marathon pace (4-5 RPE)
- 3-4 miles at easy pace (3-4 RPE)
2-Mile Repeats
Hitting almost three straight 5Ks at threshold pace like Mantz did in his workout, even for advanced marathon runners, may wind up being almost an hour of effort, which is about double the recommended time. Instead, cut down the distance of your intervals while retaining the same amount of threshold effort. Try this workout designed by Tia Accetta, Run Tuscon cofounder and RRCA-certified run coach.
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Make Sure You Recover From Lactate Threshold Runs
Look, these workouts are tough, and in order for them to do their job, i.e., improve your pace and endurance, you need to give your muscles time to recover. Do not do them on consecutive days, and do them only once or, at most, twice a week. Your pace improvements will be small and incremental, which is fine. The goal is to be consistent with the small pushes so that, over time, your marathon pace not only improves, but also feels more comfortable.
Matt Rudisill is an Associate Service Editor with the Hearst Enthusiast Group. A Nittany Lion through-and-through, Matt graduated from PSU in 2022 with a degree in journalism and worked in communications for the university's athletic department for the past 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 the Penn State football team’s 2024 College Football Playoff run as well as the Nittany Lion men’s basketball team’s 2023 NCAA Tournament appearance. In his role with Hearst’s Enthusiast Group, Matt contributes to both Runner’s World and Bicycling magazines, creating service content to benefit runners and cyclists of all ages. When he’s not out jogging, Matt can be found tweeting bad takes about the Phillies or watching movies.
