Research Rundown: Sprint Training for Endurance Runners & Why You Should Add It to Your Routine (But With Caution)

As a coach, one of the most common goals runners come me with—whether training for a marathon, half marathon, or just trying to improve their general fitness—is also ways to feel BETTER when running, reduce fatigue, and run more efficiently (while also hoping to shave down those race times!) And while actually running EASY on your easy runs & doing the right types of workouts is a huge part of that, there's something else that can help: sprint interval training.

A recent study explored the benefits of sprint training on running economy (RE) and leg stiffness (LS)—two essential components of running performance—and the findings support the idea that sprinting can absolutely make a difference for endurance runners. But here’s the thing: while I’m all for incorporating sprinting into a training plan, we need to be careful. It’s easy to overdo it, and sprinting is not something we need in our routine every single week, year-round.

I’m here to share my thoughts as a coach on why sprinting is beneficial but needs to be approached cautiously, and why the obsession with “longer” workouts (more reps, longer reps, shortened rest) being more effective is misplaced.

The Study: Sprint Training and Its Impact

The study in question, titled The Effects of Intermittent Sprint Training on Running Economy and Leg Stiffness in Highly Trained Runners, explored how once-weekly sprint training affected highly trained runners. The results were interesting, and they provide insight into how even a small amount of sprint training can improve your running efficiency.

Sprint Training Protocol: How It Worked

The study had 25 highly trained runners (12 males, 13 females) participate in a 12-week sprint training program. These runners were already logging a solid 4 hours per week of running. The protocol was simple, focusing on short, intense sprint intervals to stimulate the body’s neuromuscular system and improve performance:

• Frequency: Once per week

• Duration: 12 weeks

• Sprint Distance: 6 x 30-second sprints at maximum intensity (all-out effort)

• Rest Period: 3-4 minutes of passive recovery (walking) between each sprint

• Target Intensity: The sprints were done at 100% of maximum effort, with the goal of improving explosive power and speed, which ultimately affects how efficiently they ran.

After 12 weeks of this sprint-focused training, the study observed significant improvements in leg stiffness (LS) and some improvements in running economy (RE), although the improvements in RE were not statistically significant across the group. This is a classic example of how even small changes can make a difference over time, especially in terms of leg stiffness.

What Are Running Economy and Leg Stiffness?

Before diving into how these results can benefit you, let’s first explain running economy and leg stiffness, and why they matter:

• Running Economy (RE): This refers to the energy efficiency with which you run. It’s essentially how much oxygen you need to sustain a given pace. The lower your RE, the more energy you expend, which leads to fatigue more quickly. Improving RE allows you to run faster with less effort, extending your endurance and helping you feel less fatigued.

• Leg Stiffness (LS): Think of your legs like springs. Stiffer legs allow for a more efficient transfer of energy during each stride. With better leg stiffness, you’ll be able to store and release more energy with each step, minimizing wasted energy and improving your running performance.

In the study, runners showed a significant increase in leg stiffness, which directly contributed to improved running mechanics and, potentially, more efficient use of energy during their runs.

So, Should You Sprint? Yes, But Not Too Much

As a coach, I truly believe that every endurance runner would benefit from adding sprint training to their routine—but not in the way you might think. It’s important to recognize that sprinting is high intensity, and with that comes a higher risk of overtraining or injury if we go too hard, too often.

Sprinting is intense and requires full recovery. It's easy to fall into the trap of thinking more is better, but doing too much sprint work can actually slow you down in the long run. Instead, I recommend adding sprinting carefully and strategically to your schedule, using it sparingly to improve speed, leg stiffness, and overall running efficiency.

Breaking the “Longer is Better” Myth

Here’s a mindset shift I encourage you to adopt: the effectiveness of a workout is not determined by its length. I know it’s tempting to think that longer runs or more time spent on your feet will somehow translate to better results, but that’s not how it works.

In fact, longer workouts often come with diminishing returns. Your body can only handle so much volume before fatigue sets in, leading to overuse injuries, mental burnout, and even performance plateaus. Sprint training, in contrast, can give you powerful gains in just a small amount of time.

In the study I referenced, runners were doing only one sprint session per week, yet they experienced measurable improvements in leg stiffness and efficiency. This proves that short, intense efforts can go a long way—without the need for hour-long runs every single session.

When and How to Include Sprint Interval Training in YOUR Training

Timing is everything. Sprint interval training can be incredibly effective if used at the right time, but it’s not always appropriate in every phase of your training cycle. Let’s break down how to incorporate sprint intervals most effectively, comparing when it’s feasible to include them during different training phases—specifically during base-building and race-specific training.

1. Base-Building Phase: A Great Time to Add Sprints

The base-building phase is the foundation of your training. During this phase, you’re focused on building your aerobic endurance and gradually increasing mileage. While this phase is all about volume and steady-paced runs, it’s also a great time to include sprint intervals for a few reasons:

• Building Strength and Power: Sprint intervals target fast-twitch muscle fibers and neuromuscular systems, helping you build strength and power that will benefit your endurance in the long run. These adaptations are easier to achieve in the base-building phase when you’re not yet focused on high-intensity efforts like tempo or interval workouts.

• Enhancing Leg Stiffness Early: Leg stiffness and running efficiency take time to develop. Adding sprint intervals early in your training cycle can gradually improve your ability to store and release energy, which will help you later on during race-specific training.

• Complementing Your Easy Runs: Base-building is primarily composed of easy, aerobic runs. Sprint intervals can be added to or can replace one easy run per week. It provides variety, keeps things exciting, and helps you develop speed and strength.

• Lower Risk of Injury: During the base-building phase, you’re not overloaded with high-intensity work, so you can afford to add sprints once per week with full recovery between efforts. This allows you to avoid overtraining while still reaping the benefits of power and efficiency.

Example of Sprint Inclusion in Base-Building:

• Frequency: Once a week (on it's own dayor after an easy run in lieu of strides )

• Session Example: Example: Run 45 minutes easy effort, and then do 6 x 30-second sprints with 3-4 minutes rest between each sprint.

2. Race-Specific Training: Yes, But Be Cautious with Sprint Intervals

As you move into race-specific training, the focus of your workouts changes. You begin to concentrate more on race-specific workouts, speedwork, and long runs, with the goal of building race-specific fitness. Sprint intervals, while still beneficial, become trickier to incorporate during this phase for several reasons:

• Risk of Overtraining: Race-specific training tends to include a good amount of moderate- and higher-intensity workouts, such as speedwork, race pace workouts, threshold runs, and long run workouts. If you’re also adding sprint intervals, the intensity of your training can accumulate too quickly, leading to fatigue, burnout, or injury. This is a case of "more is not always better", so be judicious in making adjustments to your training to cram some sprints in, especially as your training cycle progresses.

• More Focus on Endurance: When you’re deep into race-specific training, you need to be prioritizing endurance, pacing, and race-day preparation. Sprinting is more anaerobic and doesn’t directly mimic the race effort you’ll be using during long-distance races, so it can take a back seat in favor of workouts that better simulate race conditions.

• Recovery Needs: Sprint intervals require full recovery, which might conflict with the structure of race-specific training. For instance, your long runs or tempo efforts require a lot of recovery time, so adding high-intensity sprint training could prevent you from getting the rest you need to maximize your more important endurance sessions.

Example of Sprint Inclusion in Race-Specific Training:

Frequency: Once every 2 weeks during the initial phase of your training (i.e. the first 4-6 weeks of a race-specific build)

• Session: 6 x 20-second sprints with 4 minutes of rest after an easy run, in place of strides; OR, opt to replace a super-threshold interval workout with sprints.

Comparing How to Add Sprint Interval Training to Base-Building vs. Race-Specific Training

Factor	Base-Building Phase	Race-Specific Phase
Purpose of Training	Build aerobic base, strength, and power	Build race-specific endurance, pace, and efficiency
Sprint Training	Go for it – Sprints can be added once per week for efficiency, leg stiffness, and strength.	Be cautious – High-intensity sprints risk overtraining and fatigue, especially as race day nears.
Workout Focus	Aerobic runs + power development (sprints)	Endurance runs + specific race-pace efforts
Risk of Overtraining	Low risk if sprinting is kept to 1x/week with proper recovery	High risk if sprinting is included too frequently. Recovery is essential.
Example Workouts	6 x 30-second sprints after easy run	6 x 20-second sprints every 2 weeks (early phase)

Wait a Minute... These Sound Like Strides? How Are They Different?

Strides are short bursts of faster running, typically around 80-90% of your maximum speed. They are used to improve running form, increase leg turnover, and enhance your ability to run faster over time without the intense fatigue that comes from full sprinting.

Strides are often incorporated after easy runs or as part of a warm-up before a workout or race as a way to improve running efficiency without overexertion. They’re excellent for warming up before harder workouts, improving your running form, and building speed endurance.

Sprint training, on the other hand, involves short bursts of maximum effort running that push you to your limits, often used to improve speed, power, and neuromuscular coordination. Unlike strides, sprints are all about going full-out for a short period, followed by complete recovery.

Sprint training is intense and designed to push your muscles, cardiovascular system, and energy systems to the max. It’s typically done in intervals, with rest periods long enough for your heart rate to lower significantly between efforts.

Key Differences: Strides vs. Sprints

Now that we know what each one is, let’s highlight the key differences between strides and sprints:

Factor	Strides	Sprint Training
Intensity	80-90% of maximum effort	100% of maximum effort
Duration	15-20 seconds	20-30 seconds (or more)
Purpose	Improve running form, increase leg turnover, and build speed endurance	Increase maximum speed, power, and neuromuscular coordination
Rest/Recovery	Short recovery, usually 30-60 seconds	Longer recovery, typically 3-5 minutes for full recovery
Training Focus	Focus on maintaining form while increasing pace	Focus on explosive speed and anaerobic capacity

Similarities: How They’re Alike

Despite these differences, there are a few key ways strides and sprints overlap in your training:

1. Improved Speed and Power: Both strides and sprints help increase your ability to run faster. Strides improve your leg turnover and efficiency at a faster pace, while sprints focus on developing your top-end speed and explosive power.

2. Running Form: Both strides and sprints emphasize proper running mechanics. When you’re running faster, you have to engage your muscles more effectively, making both strides and sprints great for reinforcing good running form. This translates to better posture, stride length, and efficiency during regular runs.

3. Anaerobic Energy Systems: While sprint training is more focused on anaerobic endurance, strides also recruit anaerobic energy systems because they are faster than your normal running pace. Both help improve how your body handles lactic acid, which means you can run at faster paces without fatiguing as quickly.

4. Incorporation into Easy Runs: Both strides and sprints can be included in easy runs. Strides are often used to improve form without fatiguing the runner, and sprint intervals are a great way to add intensity to a workout without overloading the system if done infrequently.

   
   

Key Considerations for Adding Sprinting to Race Training

• Volume and Frequency: Because sprint training is taxing, it’s important to keep the volume low, especially when balancing it with marathon or half marathon training. Ideally, one sprint session per week is sufficient, especially if you're already logging higher mileage.

• Listen to Your Body: Sprinting places high demands on the body, so be sure to listen to how you feel during your training. If you start to feel overly fatigued, it might be a good idea to back off and adjust your sprint days or volume.

• Recovery: Sprint training demands good recovery strategies. Make sure you're getting plenty of rest, hydration, and nutrition to help your muscles and energy systems recover fully after sprint sessions.

Final Thoughts: The Sprint Training Advantage for Recreational Runners

Incorporating sprint interval training into your distance training can certainly help you become a faster, more efficient runner. However, timing is key. Base-building is the perfect phase to introduce sprinting, as it allows you to build strength, power, and efficiency without compromising endurance-focused training.

Once you shift into race-specific training, be more selective. Sprint intervals can be used sparingly, but they should never interfere with the primary focus of preparing your body for the race. Sprinting is a tool, not a constant fixture. Use it wisely, and you'll reap the benefits when it counts most.

So, sprint smart, not hard—add speed when it fits your training cycle, and balance your workload to avoid overtraining. You'll run stronger, faster, and more efficiently for every race and every long run.