Running News Daily

Run too fast some of the time, and you'll probably get slower all the time. Here's what aerobic threshold is, and how to train below it.

That is the running-training paradox- a paradox that has led to the downfall of countless motivated trail runners through injury, burnout and reduced aerobic efficiency.

How It Unfolds

The story plays out so often that it's like a horror movie running on a loop on a dysfunctional DVD player. A trail runner has success through consistent, moderately hard running. That trail runner thinks that his/her success comes from the moderately hard part, rather than the consistency. At that point, coaches and experienced runners usually start screaming "Don't run too hard!" and "Slow down!" just like a horror-movie watcher will scream "Don't go into that abandoned chainsaw warehouse!" But the trail runner keeps on pushing, venturing into the foreboding warehouse, oblivious to the chainsaws around the corner.

Often, that training horror movie does not have a happy ending. In the best cases, the trail runner starts stagnating. In the worst cases, the trail runner starts getting stress injuries or experiencing symptoms of overtraining syndrome.

Many times when professional runners reach out for coaching, they are at the inflection point, starting to feel run down and injury-prone from running a bit too hard, too often. But it's not just pros. Most trail runners seem to struggle with the running training paradox, especially early on in the running journey.

RELATED: Tempo Runs 101

Aerobic Threshold Defined

The most important physiological variable to understand to avoid being the star of your own training horror story is aerobic threshold. Aerobic threshold is the intensity range at which the body switches from primarily relying on fat oxidation for fuel to primarily relying on carbohydrates. Below aerobic threshold, the body has enough oxygen to function without producing significant amounts of lactate and other associated byproducts that build up with harder exercise. Above aerobic threshold, breathing rate increases and lactate levels begin to build up, plus there may be a bit more muscle damage. That is: above-aerobic-threshold training takes longer to recover from.

At even harder efforts, your body produces more lactate than it can use and waste products accumulate without being cleared. That tipping point is called Lactate Threshold.

For training purposes, it's not helpful to think of aerobic threshold as a specific point. Instead, think of it as a range of intensities that vary slightly over time, depending on age, psychological stress, weather and many other variables. Bottom line: it's when you transition from easy to moderate exertion, to a slightly harder effort with deeper breathing and a less-sustainable pace.

How to Figure Out Your Aerobic Threshold

The best way to calculate aerobic threshold is with a metabolic test in a lab. But there are a few other ways to approximate it. Coach Joe Friel estimates that aerobic threshold occurs at a heart rate of around 20 beats per minute below lactate threshold heart rate, which can be estimated easily (in my coaching experience, aerobic threshold is usually around 85 percent of LTHR, or 25 to 35 beats away, with the exception of very highly trained athletes or those 50+ years old, as discussed by Coach Gordo Byrn).

Dr. Phil Maffetone developed the famous (or infamous, depending on your perspective) maximum aerobic function (MAF) formula, which ballparks "MAF" heart rate at 180 minus your age. This often gets close to aerobic threshold. The exact heart-rate number is less important; what's important is figuring out what truly constitutes an easy or hard effort for your physiology and background. Aerobic threshold should be a five or six perceived exertion on a scale of 1 to 10, or a mostly conversational effort you could hold for an extended period of time.

Why Aerobic Threshold Matters

Training too much above aerobic threshold can be a ticking time bomb for health and long-term aerobic development. First, the increased stress of training above aerobic threshold often causes an increase in the stress hormone cortisol; second, it can cause higher levels of muscle breakdown and forces your body to absorb more impact forces.

If your stress levels-physical or psychological-are higher than they should be on easy days, the body won't be able to recover from hard days. If stress keeps piling up without adequate recovery, the body often breaks down through fatigue and injury.

Even if break-down doesn't happen, too much running above aerobic threshold can actually cause you to get slower. High-volume aerobic training leads to increased aerobic enzyme activity; it also spurs your body to grow more capillaries to transport oxygen and fuel to working muscles, and more mitochondria, the cellular power centers that convert oxygen and nutrients to energy.

Train too hard too often, and you're neglecting the aerobic base necessary for reaching your performance potential at all distances, including shorter trail races. To run fast when it counts, you need to get comfortable running slowly.

There's an added peril for trail runners: uphills. Most runners find it difficult to stay below aerobic threshold on climbs. As a result, runners who spend lots of time on steep or mountainous terrain might break down sooner than someone training without big climbs, if they aren't careful to take some days easier.

Think of training like a big salad, with time below aerobic threshold being the greens, time closer to lactate threshold being the dressing and time above lactate threshold and VO2 max being the bacon. A salad with just greens isn't going to get a five-star yelp review; likewise, a cup of dressing and bacon might taste okay, but it's not a well-balanced meal.

3 Tips for Putting Your Aerobic Threshold to Work

1. Get an understanding of what your aerobic threshold feels like.

You can approximate your aerobic threshold using a heart-rate monitor or perceived exertion. The MAF test works for many runners, though it can be off for physiologies that vary from average. I often coach the athletes I work with to do a Friel Lactate Threshold Heart Rate test-a 30-minute time trial, averaging your heart rate over the final 20 minutes to get LTHR. Multiply that number by 85 percent to roughly approximate an effort cap for easy runs (though adjusting to a different percentage if you feel like that's a bit too hard or too easy).

You can also use perceived exertion to determine what your "easy" should be. Remember, "easy" does not mean the fastest pace you can go while finishing your run intact; it means truly relaxed and comfortable, talking mostly in complete sentences, with no urge to stop.

The goal isn't to run at your aerobic threshold all the time, but to use it as a general guideline to prevent you from going too hard. It's okay (and recommended) to do easy runs well below that number; it's also OK to go above that number sometimes. But you shouldn't spend lots of time above aerobic threshold without a training goal in mind.

2. Hold yourself accountable to aerobic threshold for most of your running.

Most of your training should be below aerobic threshold. A typical week for an athlete I coach is:

Monday: rest 
Tuesday: Run below aerobic threshold (often with short, fast strides) 
Wednesday: Interval workout (with warm-up and cool-down below aerobic threshold)
Thursday: Run below aerobic threshold (sometimes with faster finishes) 
Friday: rest or run below aerobic threshold 
Saturday: Long run or workout with time spent above aerobic threshold
Sunday: Run below aerobic threshold (often with short, harder strides or faster finishes)

The two days in bold are the days to play with truly hard efforts. All the other days are below aerobic threshold, with variation depending on the athlete. This approach lets you build aerobic volume while minimizing injury risk.

3. Listen to your body.

The body sends stress signals in a lot of different ways, from persistent fatigue, injury or insomnia to abnormal changes in sexual function. If you notice yourself feeling a bit worn down, consider spending more time below aerobic threshold to allow your body to recover.

Most Olympic marathoners spend their youth focused on running. They join track clubs, compete in national championships, and pursue the sport from an early age.

Julia Mayer’s journey was very different.

Today, Mayer is Austria’s marathon record holder, a multiple national record holder on the roads, and an Olympian. Yet for much of her athletic life, running was not her primary sport.

For 16 years, she played soccer.

Then she discovered something that would change her life.

“I noticed that I was really fast in the fun runs and that it was really, really fun,” Mayer said when reflecting on her transition from soccer to distance running.

What began as curiosity quickly became a passion. She eventually made the bold decision to leave soccer behind and focus entirely on running. It was a move that surprised many people around her, but Mayer believed she had found her true athletic calling.

The decision proved to be the right one.

Within a few years, Mayer developed into one of Europe’s top marathon runners. Her steady improvement carried her from local races to the international stage, where she began rewriting Austria’s record books.

She now holds Austrian records in the marathon, half marathon, and road 10K. Her marathon best of 2:26:08 established her as the fastest female marathoner in Austrian history. Her performances in the half marathon and 10K have further cemented her place among the country’s all-time great distance runners.

Her rise culminated with qualification for the 2024 Olympic Games in Paris.

Competing in the Olympic marathon represented the realization of a dream. On one of the most challenging marathon courses ever used for the Olympics, Mayer ran courageously against the strongest field in the world and finished 55th in her Olympic debut.

Behind the scenes, success has come through extraordinary dedication. During marathon preparation, Mayer trains twice a day and covers approximately 200 kilometers, or 124 miles, each week. The workload demands discipline, patience, and a deep commitment to continuous improvement. 

What makes her story especially inspiring is not simply the records or the Olympic appearance.

It is the fact that she found her greatest talent later than many elite runners.

In a sport where athletes are often identified at a young age, Mayer’s journey serves as a reminder that potential does not always reveal itself early. Sometimes it takes years of experience, a willingness to try something new, and the courage to follow a different path. 

The former soccer player who once chased a ball across a field is now chasing history on the roads of Europe.

And according to those closest to her, her best performances may still be ahead.

For runners of every age and ability, Julia Mayer’s story delivers a powerful lesson: it is never too late to discover what you are capable of.

From soccer player to Olympian, her journey proves that remarkable achievements can begin when least expected.

Megan Keith produced the performance of her career in Oslo on Thursday night, shattering one of Scotland’s longest-standing distance running records and cementing her place among Britain’s greatest female 3000m runners.

The 24-year-old clocked a sensational 8:28.35 over 3000m, breaking the Scottish outdoor record that had stood for nearly four decades. In doing so, Keith eclipsed the previous mark of 8:29.02, set by Scottish legend Yvonne Murray back in 1988, ending a record reign that had lasted 38 years.

Keith’s breakthrough run was more than just a national record. The performance also propelled her to third on the UK outdoor all-time list, placing her behind only two of Britain’s most celebrated distance runners — Paula Radcliffe, who leads the rankings with 8:22.20, and Laura Weightman, whose 8:26.07 remains the second-fastest outdoor mark by a British woman.

The significance of Keith’s achievement is amplified by the calibre of athletes she now joins in the record books. For decades, Murray’s mark stood as one of Scottish athletics’ most untouchable records, surviving generations of elite competitors. Keith has now succeeded where many outstanding runners have fallen short, announcing herself as one of the leading distance talents in British athletics.

Her time also compares favourably with the best performances produced indoors. Olympic medallist Laura Muir ran 8:26.41 indoors in Karlsruhe in 2017, underlining just how exceptional Keith’s outdoor effort in Oslo truly was.

The run continues a remarkable rise for the Scottish star, whose progression over recent seasons has transformed her from a promising prospect into a genuine force on the international stage. Running with confidence and composure against elite competition, Keith demonstrated both the speed and endurance required to challenge the very best in Europe and beyond.

With the World Championship season gathering momentum, Keith’s record-breaking display sends a powerful message. Not only has she etched her name into Scottish athletics history, but she has also established herself as a serious contender in one of the sport’s most competitive events.

In Oslo, Megan Keith did far more than break a record. She ended a 38-year wait, climbed into the upper echelon of British distance running, and delivered a performance that may prove to be a defining moment in her career.

British middle-distance talent Phoebe Gill took another significant step forward in her return to top form, producing a determined victory over 800 metres at the Meeting de Marseille in France on Wednesday.

Competing in challenging, wind-affected conditions, the 19-year-old demonstrated both resilience and composure as she held off a late charge from Switzerland's Veronica Vancardo to secure the win in 2:00.81. Vancardo finished just three hundredths of a second behind in 2:00.84, underlining the fiercely contested nature of the race.

While the margin of victory was narrow, the result represented another encouraging milestone for Gill as she continues to rebuild momentum following her injury setback. The young Briton showed impressive race awareness and strength in the closing stages, maintaining her advantage despite the difficult conditions that made fast running a challenge throughout the evening.

The Marseille triumph adds to a growing body of evidence that Gill is steadily progressing toward her best form. Earlier in her comeback campaign, she clocked 2:01.50 for 800m in Bydgoszcz before demonstrating her versatility with a strong 4:05.53 performance over 1500 metres at the BMC Grand Prix meeting in Trafford.

Those performances have highlighted not only her improving fitness but also her ability to compete across multiple distances as she carefully builds her season. The Marseille victory now provides further confirmation that the European junior star is moving in the right direction.

Gill emerged as one of Britain's most exciting middle-distance prospects through a series of breakthrough performances as a teenager, earning widespread recognition for her fearless racing style and remarkable maturity. Injury temporarily interrupted that upward trajectory, but her recent results suggest she is steadily rediscovering the form that made her one of the sport's brightest young talents.

With each race, the signs of progress become increasingly evident. Winning in difficult conditions and under pressure from a quality field is often a stronger indicator than a fast time alone, and Gill's latest success demonstrated exactly those qualities.

As the summer season gathers pace, the Marseille victory offers another confidence boost for the British teenager, whose return continues to gain momentum. If her recent progression is any indication, Gill could soon find herself back among the leading names on the European middle-distance circuit. 

The NCAA Track and Field Championships delivered a moment few could have predicted as Ja’Kobe Tharp produced one of the most astonishing performances in the history of sprint hurdling, rewriting the record books in spectacular fashion.

Competing in the opening round of the men’s 110-meter hurdles, the Auburn star stunned the athletics world by clocking an incredible 12.75 seconds, becoming the first athlete ever to break the 12.80-second barrier. In doing so, he eclipsed the long-standing world record of 12.80 set by Aries Merritt in 2012, a mark that had stood as one of the sport’s most revered achievements for more than a decade.

What makes Tharp’s breakthrough even more remarkable is the scale of his improvement. Entering the championships, the defending NCAA and U.S. champion had recorded a season-best of 13.05 seconds. Yet under the brightest spotlight, he unleashed a performance that exceeded every expectation, slicing an extraordinary 0.26 seconds from his personal best in a race that instantly became one of the greatest ever run.

The achievement sent shockwaves throughout the track and field community. While Tharp arrived in Eugene as one of the leading contenders for the NCAA title, few envisioned a performance capable of redefining the limits of the event. Instead, the American hurdler delivered a race for the ages, combining flawless technique, explosive speed, and impeccable rhythm from the first hurdle to the finish line.

The historic run not only secured his place in athletics history but also transformed the outlook of the championship. With the world record now in his possession, Tharp advances to the final as the overwhelming favorite, carrying momentum that could make an already unforgettable weekend even more extraordinary.

For years, the 12.80 barrier appeared untouchable. On a stunning day at the NCAA Championships, Ja’Kobe Tharp proved otherwise, producing the kind of performance that reminds fans why sport remains so unpredictable. In a matter of seconds, he turned a routine qualifying round into a landmark moment that will be remembered for generations.

The world record no one saw coming is now a reality—and Ja’Kobe Tharp is the man who changed history.

A new chapter in middle-distance running may have begun in Oslo after American teenager Cooper Lutkenhaus produced one of the most remarkable performances of the season, narrowly defeating reigning Olympic champion Emmanuel Wanyonyi in a thrilling men's 800m contest at the Diamond League meeting.

The 17-year-old sensation shocked a world-class field by crossing the finish line first in a race that came down to the smallest of margins. After an intense battle over the final metres, Lutkenhaus held off Wanyonyi by just one hundredth of a second, producing a dramatic finish that left the packed stadium in disbelief.

From the opening lap, the pace was relentless as the leading contenders positioned themselves for a fierce showdown. As the athletes entered the home straight, Wanyonyi appeared poised to unleash his trademark finishing kick. However, Lutkenhaus refused to be intimidated, matching the Olympic champion stride for stride before producing a perfectly timed lean at the line to secure a historic victory.

The result marks a breakthrough moment for the young American, who continues to establish himself as one of the brightest talents in global athletics. Defeating an Olympic champion at a Diamond League event is a feat many athletes spend entire careers pursuing, yet Lutkenhaus achieved it before reaching adulthood.

For Wanyonyi, the narrow defeat does little to diminish his status as one of the world's premier 800m runners. The Kenyan once again demonstrated his exceptional class and competitiveness, pushing the race to a world-class standard and forcing his young rival to deliver the performance of a lifetime.

Beyond the result itself, the race offered a glimpse into what could become one of the sport's most exciting rivalries in the years ahead. With established stars and emerging talents now pushing each other to new heights, the men's 800m continues to evolve into one of athletics' most captivating events.

On a memorable night in Oslo, the spotlight belonged to Cooper Lutkenhaus. At just 17 years old, he stood toe-to-toe with an Olympic champion and emerged victorious, announcing himself to the athletics world in spectacular fashion.