Repetition Training: Purpose, Benefits, and How to Do It

Most runners structure their training around easy jogging and pace runs — but repetition training is one of the most overlooked tools for building real speed. In this article, I break down the purpose, physiological benefits, and how to implement it, based on Jack Daniels’ Running Formula and exercise science.

I personally include repetition training in my own program and have felt its effects firsthand. This type of workout delivers critical adaptations that jogging and pace runs simply cannot provide.

Below, I examine the benefits of repetition training through a physiological lens — so you’ll know not just what to do, but why it works.

What Is Repetition Training?

Repetition training in running means working at intensities at or above 1,500m race pace.

Expressed in terms of oxygen uptake, that’s 105–120% of VO2 max — corresponding to 800m–1,500m race pace.

Heart rate is not a reliable intensity marker for this type of training. Because each rep is short, heart rate doesn’t fully climb during the effort — so pace is the primary guide.

Jack Daniels’ Running Formula describes the purpose of repetition training as follows:

The primary goal of this training is to improve anaerobic capacity, speed, and running economy. Always keep in mind what you are trying to get from training. Of special importance is to allow adequate recovery between runs and to use good running mechanics.

Jack Daniels’ Running Formula, 4th Ed.

The specific pace targets and recovery guidelines from Jack Daniels’ Running Formula are as follows:

When using the VDOT Calculator to find your repetition pace, refer to the Repetition row.

In this example, the repetition pace works out to 4:50/mile (3:00/km). Enter your recent race time into the VDOT Calculator to find your personal R pace.

As Daniels emphasizes, the key to effective repetition training is taking full recovery between reps and maintaining good running form throughout. Struggling through the end of a rep is a sign the session isn’t working as intended.

From personal experience, breathing distress is relatively low during repetition training — the effort feels more manageable than you might expect given how fast you’re running.

The 2-minute per rep guideline is Daniels’ recommendation. Extending to around 1,000m can push beyond that limit, but if you can maintain the target pace with good form and some margin, that’s generally acceptable.

Keep total rep volume per session to 5% or less of your weekly mileage. This limit exists to prevent injury, so staying within it is strongly recommended.

Benefits of Repetition Training

Jack Daniels’ Running Formula lists the benefits of repetition training as “improving anaerobic capacity, speed, and running economy.” These terms are fairly abstract — so let me break them down from an exercise physiology perspective.

Enhancing the Glycolytic System (Anaerobic Power)

The “anaerobic capacity” mentioned in Daniels’ Running Formula refers to what exercise physiologists call the glycolytic energy system.

Repetition training primarily develops the glycolytic (anaerobic) metabolic system. Reps typically last 30–60 seconds, with a maximum of 2 minutes — a duration range where anaerobic glycolysis dominates energy supply.

Here’s an approximate breakdown of energy contribution by metabolic pathway during repetition-pace running:

The anaerobic glycolytic system provides the highest share of energy at repetition pace. In response, the body upregulates enzymes involved in anaerobic glycolysis — including phosphofructokinase and lactate dehydrogenase — improving the glycolytic system’s overall capacity. A 7-week sprint interval training study reported statistically significant increases in these glycolytic enzyme activities.※1

However, as the graph below illustrates, with repeated repetition training sessions, the energy supply gradually shifts toward the aerobic system. If your specific goal is to develop the glycolytic system, managing your rest intervals carefully becomes critical.

Repetition pace also heavily recruits fast-twitch muscle fibers, which can improve their metabolic function over time.

Mitochondrial respiratory function (the energy-producing capacity per mitochondrion) is more strongly linked to relative exercise intensity than to training volume.※2 Slow-paced running doesn’t provide sufficient stimulus for this adaptation — high-intensity efforts like repetition training are needed to drive it.

Running at repetition pace stimulates mitochondrial function in a way that easier training simply cannot replicate.

Muscle Buffering Capacity (Speed)

The “speed” quality mentioned by Daniels can be described as the ability to produce — and tolerate — high amounts of lactate. Lactic acid itself doesn’t impair performance, but the hydrogen ions produced alongside it cause acidosis, which inhibits muscle contractions and slows the legs.

High-intensity training improves the body’s buffering capacity, helping neutralize this acidosis and keeping muscles functioning at speed.

A 5-week study comparing high-intensity training (above lactate threshold) with moderate-intensity training (below threshold) found that muscle buffering capacity improved only in the high-intensity group — with no statistically significant change in the moderate group.※3

With improved buffering capacity, muscles can sustain high speed for longer even as hydrogen ion concentration rises. In short, repetition training builds the ability to hold near-maximum speed for a meaningful duration.

Running Economy

Running economy — the oxygen cost of running at a given speed — is one of the three key determinants of long-distance performance, and it becomes increasingly important the longer the race distance.

Running speed depends not just on strength and endurance, but significantly on running form.

In repetition training, the goal is to run each rep as efficiently as possible at the target pace, which naturally drives running form improvements.

When you develop a more efficient, faster form, that efficiency carries over into slower pace runs and interval training, making those efforts feel easier too.

Initially, simply focusing on running each rep comfortably at the target time will naturally optimize your form to a reasonable degree.

To make further improvements, however, you need to evaluate your form objectively and correct it deliberately.

Use video analysis or a coach’s feedback to identify and fix inefficiencies. Today, plenty of resources are available online to support this process.

How to Do Repetition Training

Repetition training is straightforward in structure. Here’s how it works:

Set your target pace using the VDOT Calculator. Adjust the number of reps to control total volume, keeping total rep distance to about 5% of your weekly mileage. The examples above are designed for a runner logging roughly 50 miles (80 km) per week.

The most important principle: take full recovery between reps and maintain good running form throughout.

One critical point on rest: if you shorten recovery or jog too fast between reps, the aerobic system takes over — defeating the purpose of developing the glycolytic system. Keep recovery slow: a light jog or walk pace.

During repetition training, keep your rest at an easy jog or walk pace.

Start with Strides

Strides are one of the easiest ways to start incorporating repetition-pace running into your training.

Daniels’ Running Formula describes strides as “20-second light dashes,” but the target intensity should be repetition pace.

Many runners add strides during or after an easy run. Even just a few strides per session add up — done consistently, they build a meaningful training stimulus over time.

For example, 3 strides twice a week adds up to 24 reps per month — that’s a legitimate repetition training volume, even if it doesn’t feel like a formal workout.

For more on strides and how to use them effectively, see the article below:

Hill Sprints: Double the Benefits

Hill sprints can be thought of as a variation of repetition training. They reduce knee stress while targeting the hamstrings and glutes — and because driving uphill requires more muscular force from a lower position, they likely provide greater fast-twitch fiber recruitment than flat repetitions.

Running uphill naturally lowers your top speed. The result: higher muscular demand with less joint impact — making hill sprints an excellent injury-prevention tool as well.

Your actual running speed on a hill is slower than on flat ground, yet the muscle load remains high. This combination — more muscle stimulus, less joint stress — makes hill sprints one of the smartest options in a runner’s toolkit.

For the physiological research behind hill sprints and how to structure them effectively:

Drawbacks of Repetition Training

Repetition training comes with a few drawbacks to keep in mind:

Runners who have rarely run at fast paces may find that repetition training leaves them with significant residual fatigue. Injury risk is also elevated when the body isn’t accustomed to high-speed running. A gradual approach — starting with strides and hill sprints — is recommended to adapt the body before committing to full repetition sessions.

Repetition training may also reduce aerobic capacity over time.

Because repetition pace exceeds 100% of VO2 max, it activates anaerobic enzyme systems — but simultaneously suppresses the aerobic enzymes that support mitochondrial oxidative metabolism.

Hypoxia-inducible factor 1-alpha (HIF-1α), activated in skeletal muscle during high-intensity exercise, has been shown to upregulate glycolytic enzyme expression while suppressing enzymes involved in mitochondrial oxidative metabolism.※4

For runners focused primarily on the full marathon, keeping repetition training frequency and volume low — just enough to maintain the adaptation — is likely the wisest approach. Balance is everything in training.

Try it out with your own body and observe how it responds.

Because repetition pace feels intimidating, many runners never include it in their programs. But once you realize that strides count as repetition training, the purpose of every fast stride becomes clearer — and that mindset shift alone makes a difference.

References

※1 MacDougall JD, Hicks AL, MacDonald JR, McKelvie RS, Green HJ, Smith KM (1998) “Muscle performance and enzymatic adaptations to sprint interval training.” Journal of Applied Physiology 84(6):2138-2142.

※2 Granata C, Jamnick NA, Bishop DJ (2018) “Training-Induced Changes in Mitochondrial Content and Respiratory Function in Human Skeletal Muscle.” Sports Medicine 48(8):1809-1828.

※3 Edge J, Bishop D, Goodman C (2006) “The effects of training intensity on muscle buffer capacity in females.” European Journal of Applied Physiology 96(1):97-105.

※4 Lindholm ME, Rundqvist H (2016) “Skeletal muscle hypoxia-inducible factor-1 and exercise.” Experimental Physiology 101(1):28-32.