What is a threshold run, and what heart rate is a tempo run?

What is a threshold run?

A threshold run is a run at your second lactate threshold. That is the hardest effort you can hold for a long time while your body keeps lactate steady. Part 1 of this series explains both thresholds and their many names in lactate threshold heart rate.

Runners use three main shapes for this work.

• The tempo run. You hold threshold effort in one unbroken stretch after a warm-up. Runners use the word tempo loosely, so one coach's tempo can be a different effort from another's.
• Threshold intervals. You run long repeats at threshold effort with short jogs between them. Some coaches call these cruise intervals.
• Double threshold. You run two threshold sessions on the same day. Some Norwegian runners made this method famous, and it gets its own section below.

All three shapes use the same effort. They differ in how the work is split up. A review of world-class distance runners gives typical sizes^[4]. Their threshold runs last 20 to 50 minutes at about half-marathon pace. Their threshold intervals last 3 to 15 minutes each, usually with a minute or two of easy jogging between them. The same review says repeats let a runner do more total time at threshold than one continuous run.

What heart rate is a tempo run?

Lab tests agree on the average. Blood tests on 165 recreational runners put the second threshold at 90.6% of max heart rate^[1]. In 22 well-trained distance runners the maximal lactate steady state came at 89% of max for men and women alike^[2]. In a threshold run you aim for that effort, which comes out near 90% of max on average.

Diastra's Threshold band runs from 87% of max up to one beat under 92%. For a runner with a max of 190 that is 166 to 174 beats a minute. The bands below show yours.

Single people spread out much wider than the averages. In 100 adults the maximal lactate steady state landed anywhere from 75% to 97% of max heart rate^[3]. Treat the band as your starting target and check it against how the effort feels.

Coaches do not all put the word threshold on the same heart rate. The review of world-class runners lists threshold runs and intervals at 83 to 87% of max heart rate^[4]. On Diastra's bands that is the gray band, just under Threshold. Diastra starts Threshold at 87% because blood tests put the second threshold near 90% of max. Gray minutes don't glow, and they are still real training.

A run that a plan calls a tempo can land in the gray band too. If the pace is closer to your marathon effort, your heart rate may stay between Easy and Threshold. That run is steady work. On Diastra's bands it is a different session from a threshold run.

How hard should a threshold run feel?

It should feel hard and steady. Runners at the second threshold rated their effort 15.4 on the 6 to 20 effort scale that labs use^[1]. At the first threshold the same runners rated it 12.5. In the same study, effort ratings were the least accurate way to find a runner's threshold. Feel helps you settle in, and heart rate is the better check once it catches up.

Coaches often call this effort comfortably hard. A common rule of thumb is that you can say a few words at a time but you cannot hold a conversation.

The review of world-class runners says a threshold run should not be extremely tiring^[4]. Well-trained runners in one study held this effort for about 80 minutes before they had to stop^[2]. So a threshold run of 20 to 50 minutes should end with some effort left. A threshold run that leaves you unable to run another minute was closer to a race.

Why does heart rate lag and drift on a long tempo?

Heart rate is slow to start. In a treadmill study of 24 men, heart rate made about two thirds of its change in about a minute after each change in speed^[5]. By that math it takes about 3 minutes to get most of the way to its new level. For those first minutes the number on your watch reads low even though your legs and lungs are already working at threshold.

That lag leads to a common mistake. A runner sees a low heart rate early and speeds up to push the number into the band. A few minutes later the heart rate catches up with the faster pace and climbs past the band, and the run turns into something harder than planned. Settle into the effort by feel and pace first, then let heart rate confirm it.

Heart rate also creeps up through a long steady effort. Fifteen trained young runners held one steady speed for 40 minutes in one study^[6]. At the end their heart rate was about 4 points of max higher than the same speed gave them in a lab step test. For one runner it was 8 points higher. A long threshold run can start low in the Threshold band and finish near its top or above it. When heart rate crosses into your VO₂max band late in a tempo, ease the pace a little. That keeps the run a threshold run.

How is a threshold session different from a VO₂max session?

The two sessions train different things. A review of champion endurance athletes names three main factors in performance. They are VO₂max, the lactate threshold and efficiency^[7]. VO₂max is your aerobic capacity. It is the most oxygen your body can use when you go all-out. VO₂max and your threshold together set how much oxygen you can keep using through a long effort. Efficiency then decides how much speed you get from that oxygen^[7].

In a VO₂max session you work close to your max. The repeats are shorter and harder, and in Diastra's bands they reach 92% of max and up. A well-known version is the Norwegian 4x4. Four 4-minute intervals at 90 to 95% of max raised VO₂max 7.2% in 8 weeks in a study of moderately trained men^[8]. A group in the same study ran the same total work at 85% of max and raised VO₂max less. The study called that group's training lactate threshold training. The Norwegian 4x4 workout has the full session.

Threshold work moves a different marker. In one small study, eight well-trained runners added one 20-minute run a week at about their threshold speed^[9]. After 14 weeks they ran faster before their blood lactate reached the same level. Their VO₂max stayed the same.

In a threshold session you run a lower effort for longer. Your heart rate stays mostly in your Threshold band. Late drift can push it a little over 92% on a long effort. The breaks between repeats are short compared with the work.

What is the Norwegian double-threshold method?

A 2023 review by Casado and colleagues describes the method^[10]. It is the training reported for some world-class Norwegian middle and long distance runners. Each week they run three to four threshold interval sessions and one VO₂max session. They often run two threshold sessions on the same day.

The pace is set by blood lactate. The runners test a drop of blood every one to three repeats and keep lactate at a target, usually between 2 and 4.5 mmol/L^[10]. That unit measures how much lactate is in the blood. The long repeats cover 2,000 to 3,000 m near half-marathon pace. The short repeats cover 400 to 1,000 m at a pace between 5K and 10K race pace. The breaks between repeats last from 20 seconds to a minute and a half.

Those lactate targets cover more than one of Diastra's bands. The zone table in the review of world-class runners pairs 2 to 3.5 mmol/L with 83 to 87% of max heart rate^[4]. It pairs 3.5 to 5 mmol/L with 88 to 92%. So the easier repeats on a double-threshold day would land in the gray band and the harder ones in Threshold.

All of this threshold work happens inside a very large week. Runners in this model cover 150 to 180 km a week, and most of that distance is low-intensity running^[10]. The review reports what these runners did. It does not test the method against another plan.

Where does threshold work go in a mostly Easy week?

Even at the top of the sport, most of the week is easy running. In a review of world-class distance runners, at least 80% of the running was low intensity all year^[4]. A recreational runner's week is far smaller, and the same shape still applies. Most running stays easy, and threshold work is one of the few hard pieces.

Studies that compared plans point the same way. One study of 30 recreational runners compared two 10-week plans^[11]. One plan kept about 77% of training easy. The other spent about 35% of its time between the two thresholds. Diastra draws that stretch roughly as the gray band. Both groups ran a faster 10K. The easier plan improved 5.0% and the other 3.6%, a gap too small to be sure of. A 5-month study of 12 sub-elite runners found a similar pattern^[12]. Both groups got faster, and the group with more easy running gained more.

People who start out inactive raise their threshold with easier training too. A review of 34 studies found large threshold gains in inactive people who began training, and the training intensity made no clear difference^[13].

Three habits keep that shape. Run your easy days in your Easy band. Easy is Diastra's name for the Zone 2 most runners know, and its top edge follows where blood tests on runners find lactate starts to rise^[1]. Put a threshold run after an easy day, so you start it fresh. Keep the hard days few, so each one gets your best effort. 80/20 running covers how the easy and hard parts of a week work together.

What are common threshold run mistakes?

1. Starting too fast. Heart rate lags at the start, so the first minutes feel easy. Runners who chase the number early end up above threshold within minutes.
2. Ignoring the late climb. Heart rate creeps up on a long effort. Easing the pace a little late in the run keeps you at threshold.
3. Using an interval session as your threshold test. The breaks let your heart rate run higher than you could hold without them. Your threshold number comes from one steady effort, as in the test in part 1.
4. Letting easy days drift into the gray band. A run that starts easy can creep up past the top of Easy without you noticing. Gray-band running is still real training. Gray minutes don't glow, though, and a week with threshold work is built on Easy days and Threshold runs.
5. Copying a world-class week. Runners in the double-threshold model do three to four threshold sessions on top of 150 to 180 km a week^[10]. A smaller week needs fewer hard sessions.

How does Diastra help with threshold runs?

Diastra reads every workout your Apple Watch saved in Apple Health. It finds your max heart rate from those workouts, a guided test or a number you type, and it says which one it used. Your Threshold band is drawn from that max. On a threshold run the watch holds you in the band with a tap when you drift out, so a late drift shows up while you can still ease off. Only the minutes that held in the band are credited. Over the weeks Diastra shows whether your training is working. Getting fitter. Holding steady. Slipping.