Understanding Cruise Intervals
Dive into the world of "cruise intervals," a training concept popularized by Jack Daniels, which involves running at a tempo pace with short recovery periods.
The fundamental advantage of this method is its ability to allow athletes to accumulate more high-quality training volume than a continuous tempo run, particularly beneficial in challenging conditions like extreme heat where frequent breaks are essential for temperature regulation. Scientifically, these intervals target the lactate shuttle system, a crucial metabolic pathway where lactate produced by actively working leg muscles is transported to more oxygenated tissues like the heart, brain, and liver for efficient energy utilization. This training, supported by elite coaches such as Renato Canova and Peter Thompson, focuses on running at a pace that elevates blood lactate levels, followed by brief recovery to train the body to clear this lactate rapidly before the next interval. This process enhances energy processing efficiency and ultimately contributes to improved running speed. Traditional cruise intervals often feature longer repetitions, ranging from 1000 meters to 3 kilometers, performed at lactate threshold pace—roughly equivalent to a 60-minute race pace—with recovery durations approximately one-fifth of the running time. For instance, a runner capable of a 40-minute 10K might execute 1000m repeats with 45-second rests, miles with 60-75 second rests, and 3K repeats with 2-2.5 minute rests.
The Rat-a-Tat Approach
The "Rat-a-Tat 400s" workout represents a significant evolution of the cruise interval concept, by dramatically shortening the duration of both the work interval and the recovery. Instead of longer repeats, this protocol centers on running 400-meter bursts with an exceptionally brief 15-second recovery period. The execution requires meticulous timing: after completing a 400m lap and crossing the finish line, the runner immediately jogs back towards the starting point, aiming to be ready for the next repetition precisely 15 seconds later. This rapid turnaround demands a keen internal clock, though slight variations in recovery time are not critical for the workout's effectiveness. The intended pace for these 400s is slightly faster than lactate threshold pace, ensuring that lactate accumulates within the short interval. However, the speed should not be maximal; a pace approximating 10K race effort is generally appropriate. The aim is to strike a balance: fast enough to stimulate lactate production but not so fast that sufficient recovery within 15 seconds becomes impossible. For runners who maintain a pace faster than approximately 6:15 per mile, 15 seconds of recovery is suitable. Those who find this too demanding may extend the recovery to 20 seconds or slightly longer, but the crucial principle is to keep recoveries brief, ideally not exceeding one-fifth of the time taken for the 400m run.
Workout Variations and Benefits
The Rat-a-Tat 400s can be integrated into training plans in a couple of effective ways. As a standalone session, a complete workout typically involves a substantial number of repetitions, usually between 16 and 20, accumulating 4 to 5 miles of total running work. This high volume of short, intense efforts is challenging. Runner Lauren Elgee found this workout particularly beneficial for focusing on consistent pace maintenance, noting that while it initially felt manageable, the cumulative effect of the short recoveries became increasingly demanding about three-quarters of the way through the session. Alternatively, these 400s serve as an excellent "finisher" to an existing longer workout. This application arose organically when a runner needed to shorten her planned session involving longer intervals but still wanted to incorporate tempo work. The 400s proved to be a highly effective substitute. Coaches like Thom Hunt, a former American 10K record holder, view cruise intervals as a valuable tool for breaking the monotony of extended runs, acknowledging that while he might personally prefer longer intervals, shorter, faster repeats offer a productive alternative or addition. Corrina Jackson, another runner, observes that performing a few Rat-a-Tat 400s at the end of a workout leaves her feeling less fatigued than immediately transitioning to a recovery jog. She speculates that the contrast between the demanding 400s and the preceding tempo effort makes the latter seem comparatively easier. Additionally, ending a workout with 4-5 such repetitions, provided the earlier training wasn't overly taxing, can provide a significant confidence boost, allowing the runner to feel invigorated by quickly turning over their legs and finishing strong without feeling depleted.
