Interval Training: The Holy Grail for Performance Improvement

Interval training basics every runner needs to know
Interval Training: The Holy Grail for Performance Improvement

Here is the method behind the madness of achieving better running pace and improving performance. As we start to train consistently and accumulate miles, we tend to get better. Initially, these gains come quickly and slow down as we progress. Soon enough we reach the performance plateau. So what can be done differently to improve performance?

Incorporating speed runs into training is the best way to improve running performance. However running fast all the time is not very smart either; it can get hard on our body and is guaranteed to cause injuries, this is where interval training comes in handy. Interval training enables runners to maximize aerobic capacity.

What is interval training?

At the basic level, interval training involves short and high intensity running with rest intervals for recovery. High intensity running can vary from short distances of 200 or 400m to longer distances of a mile and beyond. The following graphic depicts an example interval training workout, with x-axis showing distance and y-axis showing pace. Workout starts with 2kms of warm-up, followed by 4 repeats of 400 meters of high intensity (faster pace) running with 400 meters recovery (jog pace), ends with a km of cool-down.

Structure of Interval Training

Interval training variations

There are several variations of interval training and can be designed in a variety of ways based on the performance objective. The design varies:

  • Depending on the distance you are targeting to run or the specific attribute of performance that you would want to improve
  • Instead of distance, the intervals can also be based on time (such as 3 minutes of high-intensity run, and with 3-minute recovery).
  • Distances and time can vary for intensity, and so can the recovery period.

The following are the common variations that runners of all distances can benefit from.

Interval Type Description
Sprints and Strides Very short distance interval runs (up to 200m) with close to maximum effort for a very short time. Sprints are meant to improve the efficiency of our body’s running mechanics. Whereas, strides focus is on maximizing the power to get big strides.
Hill repeats Short Interval runs are on incline terrain that involves a very short distance on uphill, and recovery jog back down the hill. These runs improve running form. Since these runs are against gravity, it helps to recruit more muscles thereby improving strength.
Speed intervals Speed intervals have the primary focus of building speed. These are slightly longer than sprints (up to 800m) but with an effort much lower.
VO2max intervals VO2max intervals are called so, because they work on maximizing the oxygen consumption, which is key to run faster, efficiently, and longer. In other words, they work to maximize aerobic capacity. These are run at 3k-5k race pace typically distance up to 1 km.
Threshold intervals (aka Tempo intervals) These are run at slightly slower than 10k pace and improve the lactate threshold(LT). Lactate Threshold is the point after which lactic acid production increases and muscles fatigue a lot quicker.

The following graphic summarizes the interval training variations and how they stack up in terms of distance/time and the intensity.

Interval training variations

Executing Interval training

For beginners, interval training can be overwhelming. Here is some guidance to help execute intervals effectively.

Each interval type has a specific objective and training schedule should include a combination of these types. The following table summarizes the interval types and how these work on each of the performance objectives. Based on the performance goals, runners can prioritize one over the other and include in their training.

Choose interval types based on performance objective

Threshold (Lactate Threshold) Intervals

Heart Rate: Focus on keeping your Heart Rate (HR) between 80% to 90% of maximal heart rate (MHR) during the interval run. Pace: LT pace is generally 5 to 10 seconds per km slower than 10K race pace Execution: LT (Lactate Threshold) pace is the best predictor of race pace for distances of 10K through the half marathon. These are comfortably hard efforts that increase your LT pace, allow you to race faster for a longer time. Sample workouts:

  • Distance 16km - Warm-up of 3km; 5 repeats of 10 min (@ LT pace) with recovery jog for 2 minutes; Cool down of 2km.
  • Distance 14km - Warm-up of 3km; 4 repeats of 1 mile (@ LT pace) with recovery jog for 3 minutes; Cool down of 2km.

VO2 Max Intervals

Heart Rate: These intervals are executed at about 94 to 98 percent of maximal heart rate (MHR). Pace: The most effective intensity range for these efforts is between your 3K and 5K race pace. Staying in the proper pace range is important for getting the full benefits of VO 2 max workouts. Execution: If the pace is too fast, anaerobic system will be used and won’t be able to complete the necessary number of intervals. Too slow a pace won’t tax the aerobic system enough to optimally stimulate improvements in VO2 max level. Sample workouts:

  • Distance 10km - Warm-up of 3km + 5 repeats of 1km (@ VO2Max Pace) with recovery jog of 2 minutes + Cool down of 2km
  • Distance 14km - Warm-up of 3km + 2 sets of ( 2x 1km + 2x 800m / recovery jog of 2 minutes) and 4 mins of recovery between sets + Cool down of 2km

Speed Intervals

Heart Rate: Heart rate is not a focus for speed intervals, but it will be typically close to MHR. Pace: These are structured similarly to VO2 max workouts but run at 800-meter to mile race pace. Execution: Emphasize good form when doing speed work and stay as relaxed as possible even though you are running hard. Tight muscles, clenched jaws, and excessive movement all inhibit the body’s ability to run fast. Sample workouts:

  • Distance 10km - Warm-up of 3km + 6 repeats of 400m with recovery jog of 400m + Cool down of 2km
  • Distance 12km - Warm-up of 3km + 2 sets of ( 4x 200m + 2x 400m / recovery jog of 200m) with recovery of 4 minutes between sets + Cool down of 2km

Sprints and Strides

Heart Rate: Heart rate is not a focus for sprints and strides Pace: The pace is not the focus for sprints and strides, but that will be close to the maximum effort. Sprints are run at maximum effort (anaerobic) with high cadence and good leg swing. On the other hand key to running effective strides to get the full knee drive and hip extension. Execution: One needs to accelerate to full speed by halfway, holding it for the remainder of the distance, and then gradually slow down. One way to do strides is to run several laps on the track, accelerating on the straightaways and jogging the turns. Sample workouts:

  • Distance 9km - Warm-up of 5km + 6 repeats of 100m sprints with enough recovery + Cool down of 3km
  • Distance 10km - Warm-up of 3km + 4km at marathon pace + 8 strides of 20s with enough recovery + Cool down of 2km

Uphill repeats

Heart Rate: Heart rate is not a focus for uphill repeats, run at close to all-out effort to maximize the speed and power gains. Pace: Run uphill for 2 to 6 minutes at VO2 max pace Execution: After the hill part of the interval, gently jog back down to the start for your recovery period. Hill repeats allow running at a high intensity with minimal impact stress, allowing for faster recovery. Running up a steep hill is an excellent way to improve your strength and power while promoting a good running form. Sample workouts:

  • Distance 7km - Warm-up of 3km + 8 repeats of 50s uphill (at 4-5% grade) with recovery jog back downhill + Cool down of 2km
  • Distance 8km - Warm-up of 3km + 6 repeats of 200m uphill with recovery jog for 200m + Cool down of 2km

Frequency of interval training

Interval training is high intensity training and definitely taxes your body. It is advised that limit interval training as a percent of weekly training mileage to be kept under 10%. It can however be adjusted based on the race distance. Incorporating interval training once a week is a good start, and can be increased to twice a week based on the mileage and race goals.

Find paces for intervals

For those who want to train with specific paces (rather than just by effort), there are several methods to determine the training paces for intervals. These calculators work by inputting current race completion time or the time goal for the target race.

  • McMillan Running Calculator - This is the go-to online resource for determining the training paces for intervals and beyond. McMillan Running calculator serves a similar function but is much easier to use.
  • Jack Daniels’ VDOT Method - This method works by determining VDOT number (similar to VO2Max) based on current performance. Based on the VDOT number, Jack Daniels’ pace tables (published in his book Jack Daniels’ Running Formula) recommends the paces for different types of running workout.

Recovery during intervals

How much time or distance to recover when training intervals is a common question. The thumb rule is to recover enough to run the next interval well. Recovery can be active (jog) or passive (walk or stop). Typically for shorter and high intensity interval training, recovery distance can be the same as the run distance. For example, for 200m intervals, 200m intense run followed by 200m active (jog or run) recovery. For the longer intervals such as 1600m, a time based recovery (jog or walk) such as 2-3 minutes is used.

Tracking interval workouts

It is ideal to run interval workouts on a track where the distance is easy to track, as well as the terrain is flat. However, for most runners track is not accessible, a running specific GPS watch serves well to execute and track interval workouts. GPS watches such as those from Garmin & TomTom allow programming intervals with desired repeats, distance/time, and recovery ahead of time, and show alerts while running. Smartphone Apps like Strava, Endomondo, RunKeeper, Runtastic also support interval training.

If you haven’t been doing interval training, today is the best day to start. If you have any questions or insights on interval training, please do post in the comments section.

Race day performance is a sum total of all your intervals, tempo and endurance running, and everything you did in between them. You are the magic.

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