Part 2: Your Training Toolkit

Introduction: Building Your Speed Endurance Toolkit

In our last newsletter, we explored the fundamental science of speed endurance and how your body adapts to this crucial training. Now, let's dive into the practical application: the diverse toolkit of workouts designed to build your speed endurance. Understanding these different modalities will empower you to strategically enhance your speed, power, and overall running efficiency.

Training for Speed Endurance: A Toolkit for Every Runner

Developing speed endurance involves a strategic approach, utilizing various training modalities that each offer unique benefits. The primary modalities include Speed Endurance Training (SET), Tempo Runs, and Interval Runs. They push runners to operate at paces faster than their normal easy pace, thereby improving leg turnover and muscle firing efficiency.

Speed Endurance Training (SET)

Speed Endurance Training (SET) is performed at intensities higher than that eliciting maximum oxygen uptake (V̇O2-max) and is primarily dominated by anaerobic energy systems. SET is often divided into two main types:

• Production Training (SET-P): This focuses on achieving high anaerobic, primarily glycolytic, ATP turnover during repeated short intervals, typically 10-40 seconds, with relatively long recovery periods (e.g., 30-second intervals separated by 3 minutes of complete rest). A typical SET-P session might involve 6-10 repetitions of 30-second maximal efforts followed by 3-4 minutes of complete rest. The goal is to maximize the anaerobic energy contribution during the work interval.

• Maintenance Training (SET-M): While SET-P builds the capacity for anaerobic power, SET-M focuses on sustaining these adaptations and improving the body's ability to clear lactate at high intensities over slightly longer durations. SET-M typically involves longer work intervals than SET-P, often ranging from 1 to 3 minutes, with shorter, incomplete recovery periods (e.g., 1-minute efforts followed by 1-2 minutes of jogging). An example could be 4-6 repetitions of 90-second efforts at a very hard pace, with 90 seconds of recovery jog. The aim here is to push the anaerobic threshold and improve sustained power.

The benefits of SET are profound, improving performance across various event durations, including short (20-60 seconds), medium (1-10 minutes), and longer (10-60 minutes) events, as well as intermittent sports. Notably, these performance enhancements often arise despite no significant changes in V̇O2-max, instead being linked to improved exercise economy and an increased capacity to handle muscle ionic shifts.

Tempo Runs (Threshold Runs)

Tempo runs, also known as threshold runs, are continuous, moderate-to-high intensity efforts completed at a steady pace just below your lactate threshold—the point at which lactic acid begins to accumulate in the bloodstream faster than the body can remove it. This pace is often described as "comfortably hard," meaning you can speak in short sentences but not hold a full conversation. A common tempo run might be 20-30 minutes at this sustained effort. For example, a runner might aim for a 25-minute tempo run at somewhere around their perceived half-marathon race pace. The consistency of effort is key to teach your body to efficiently process lactate.

The primary objective of tempo run training is to improve the lactate threshold, which enables a runner to maintain a faster pace for longer durations without fatiguing as quickly. These runs predominantly target the aerobic energy system, teaching the body to use oxygen more efficiently for energy production. Benefits include improved endurance, enhanced mental toughness, and direct suitability for longer races such as 10K or half marathons. They are highly effective for boosting cardiovascular endurance.

Interval Runs

Interval runs feature a varied pace, with "work" intervals performed at very high intensity, often reaching 90-100% of maximum effort, followed by "rest" intervals where the pace is much slower, sometimes even a walk. A key distinguishing feature of interval runs compared to tempo runs is the presence of a complete or near-complete break between repetitions. The pace during intervals is generally faster than that of tempo runs or fartlek workouts. An example might be 6-8 repetitions of 400m at a very fast pace (e.g., mile race pace), followed by 400m of easy jogging recovery. The length of the work and rest intervals can be adjusted to target different energy systems; shorter, faster intervals with longer rest build anaerobic power, while longer intervals with shorter rest challenge aerobic capacity and lactate clearance.

The primary objective of interval runs is to improve speed, power, and running economy. They primarily focus on the anaerobic energy system. Benefits include significant speed development by activating fast-twitch muscle fibers, enhanced anaerobic capacity, increased VO₂max, and a boost in metabolism. Interval training is broadly useful for improving endurance, strength, and speed.

Fartlek Training: Play with Speed

Fartlek, Swedish for "speed play," is a less structured but highly effective form of speed endurance training. Unlike traditional intervals with fixed distances and recovery, Fartlek involves continuous running with varied bursts of speed and recovery periods determined by feel or terrain. For instance, you might run hard to the next lamppost, jog easily to a tree, then pick up the pace for a downhill stretch. This unstructured approach allows for greater flexibility and can be less mentally taxing than formal track workouts. Fartlek sessions improve your body's ability to adapt to changing paces, enhance running economy, and build both aerobic and anaerobic fitness in a dynamic way. It's an excellent method for developing a sense of pace and improving your ability to surge during a race.

Aerobic Intervals (Broken Tempos)

Aerobic intervals, often referred to as "broken tempos" or "threshold intervals" by coaches like Steve Magness, are a strategic variation of tempo training. Instead of one continuous effort, these involve breaking down a longer aerobic threshold run into multiple, slightly shorter intervals, separated by brief, incomplete recovery periods (e.g., 1-2 minutes of very easy jogging). For example, instead of a continuous 25-minute tempo, you might do 3 x 8-minute efforts at the same threshold pace with 90 seconds of recovery between each. The intensity remains aerobic (Zone 3 to low Zone 4), similar to a continuous tempo. The primary benefit is the ability to accumulate more total time at this valuable lactate threshold intensity than might be possible in a single continuous block, often with less overall fatigue. This allows for greater physiological adaptation to clear lactate efficiently and sustain a faster pace over time, without pushing into higher anaerobic zones.

Gauging Intensity: RPE, Heart Rate, and Run Power Zones

To ensure you're hitting the right intensity for each speed endurance workout, understanding and utilizing tools like Rate of Perceived Exertion (RPE), Heart Rate (HR) zones, and Run Power zones is crucial.

• Rate of Perceived Exertion (RPE): This is a subjective scale, typically from 1 (very easy) to 10 (maximal effort). For tempo runs, you might aim for an RPE of 7-8 ("comfortably hard"), while intervals could push you to 9-10 ("very hard" to "maximal"). Learning to listen to your body and accurately assess your effort level is a powerful skill for effective training.

• Heart Rate Zones: Using a heart rate monitor allows for a more objective measure of intensity. Different workouts target specific heart rate zones (e.g., Zone 3-4 for tempo runs, Zone 4-5 for intervals and SET). Knowing your maximum heart rate (MHR) or lactate threshold heart rate can help you set personalized zones, ensuring you're training within the desired physiological range for optimal adaptation. Combining RPE with heart rate data provides a robust approach to managing workout intensity.

• Run Power Zones (I highly recommend Stryd): For precise and immediate feedback, especially during high-intensity, short-duration efforts where heart rate can lag or max out, run power meters offer a superior solution. Power, measured in watts, reflects the actual work your body is doing, accounting for factors like hills, wind, and fatigue. This makes it a highly reliable metric for maintaining consistent effort regardless of external conditions. Training with power zones (which typically go up to 7 to reflect the nuances of these target zones, allowing for very specific targeting of physiological systems) allows you to hit specific intensity targets with greater accuracy than pace or heart rate, ensuring you're getting the intended physiological stimulus from your speed endurance workouts. It's particularly relevant for efforts where RPE might feel low due to the short duration, but the physiological demand is very high.

The distinction between SET, Tempo, and Intervals is not arbitrary; it reflects a targeted approach to energy system development. Tempo runs primarily build the aerobic capacity to clear lactate at a higher threshold. Intervals (especially shorter, higher intensity ones) and SET (particularly SET-P) push the anaerobic system for rapid ATP production and tolerance to severe metabolic stress. This means a well-rounded speed endurance program is not just about "doing speed work" but strategically choosing workouts that stress specific energy pathways to achieve desired adaptations for different race demands, such as a strong finish versus maintaining sustained high pace.

The strategic integration of these intense sessions throughout a training cycle further highlights the importance of periodization, where varying intensity and volume ensures optimal adaptation. The choice between tempo and intervals should be based on specific running goals. This indicates that these training types are not interchangeable but are tools to be deployed strategically within a larger training plan, aligning with specific phases (e.g., early season focus on speed development, later season on race pace maintenance).

Speed Endurance Training Modalities Comparison

This table provides you with a quick reference to understand the nuances of different speed endurance workouts. It helps demystify the terminology and allows you to make informed selections for the right workout to achieve your specific goals and current training phases. This reinforces the idea that "speed work" is not a monolithic concept, but a diverse toolkit, with each tool serving a distinct purpose in enhancing your performance.

Addressing the Injury Myth: Speed Work and Safety

It's a common concern among endurance runners: won't adding speed work just lead to injuries? This apprehension often stems from a fear of "too much, too soon" or the perception that faster running inherently carries higher risk. While it's true that any sudden increase in training load or intensity can lead to issues like stress fractures or muscle strains, the idea that speed work itself is a primary cause of injury is largely a myth, especially when approached intelligently.

In reality, properly incorporated speed work can be a powerful tool for injury prevention. Here's why:

• Improved Form and Biomechanics: Speed work, particularly strides, forces you to focus on efficient running form, including posture, stride length, arm swing, and foot placement. By training your body to move with better mechanics, you reduce unnecessary stress on joints and muscles, making you a more efficient and resilient runner overall.

• Gradual Conditioning: Strides, in particular, serve as a low-stress, highly effective introduction to faster paces. They allow your neuromuscular system to adapt incrementally without the high impact and fatigue associated with all-out efforts. This gradual conditioning strengthens your body and improves flexibility, preparing it for higher demands and reducing injury risk.

• Strengthening Muscles and Tendons: Running at faster paces, even for short bursts, activates and strengthens fast-twitch muscle fibers and connective tissues. This "micro-trauma" is a desired adaptation that builds stronger, more resilient muscles. Hill strides, for instance, offer a unique way to build strength and speed with less impact on joints compared to flat running.

• Avoiding Overtraining, Not Speed Work: Injuries often arise not from the type of training, but from how it's implemented. "Faster workouts are not better workouts; going too hard on every speed workout impairs your body's body to recover". Overtraining, inadequate recovery, or a sudden jump in volume are far more likely culprits for stress fractures and muscle strains than properly executed speed sessions.

To safely incorporate speed work and bust the injury myth in your own training:

• Start Gradually: Begin with low-volume, low-intensity speed work like strides, especially if you're new to it.

• Prioritize Form: Focus on maintaining good running mechanics during all speed efforts. "Focus on form, not speed".

• Listen to Your Body: Pay close attention to warning signs of fatigue or pain, and adjust your training as needed.

• Ensure Adequate Recovery: Recovery is paramount for adaptation and injury prevention. Don't rush into your next session if you're not fully recovered.

• Warm-up and Cool-down: Always include dynamic warm-ups before and static stretches after your runs.

• Incorporation Strength and Cross-Training: These activities build overall resilience and support your running.

By understanding that speed work, when done correctly, is a vital component of building a robust and injury-resistant runner, you can confidently add these powerful tools to your training arsenal.

References

• [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC12203883/

• [2] https://ocmarathon.com/tempo-runs-vs-interval-runs-whats-the-difference/

• [3] https://blog.runningcoach.me/en/2023/03/24/intensive-training-the-importance-of-intervals-and-tempo-runs/

• [4] https://www.polar.com/blog/tempo-run-fartlek-intervals-running-workouts/

• [5] https://simplifaster.com/articles/chase-speed-gain-endurance/