For Racers, Tempo vs. Interval Training

Wed, 12 June 2013 - 1:20 a.m. MT
Credit: ARA Staff - American Running Association

Much of what we discuss in Running & FitNews® addresses the moderate exerciser trying to maximize the health benefits of slow distance running or other endurance activity, as the protections from diabetes, metabolic syndrome, hypertension, high LDL blood-cholesterol—and overall enhancements to both cardiovascular and bone health—are well known and legion.

Yet for serious competitors, the very useful “distance covered” metric discussed in Is a Mile a Mile? in this issue is not the whole story. Competitors must train at a higher stress level than the brisk walker or easy jogger because the focus is on finish times, not life fitness. And the body’s progressively improved ability to tolerate a certain stress at a certain pace for a certain amount of time is what achieves PRs on the middle- or long-distance race course. 

 There are several types of workouts that improve various aspects of your running performance—we’ll look at two up close here. Tempo runs are designed to increase your lactate threshold. Interval training is about increasing your maximal oxygen consumption (VO2max). 

Regarding Threshold Running. To briefly review, a high lactate, or anaerobic, threshold allows you to compete without lactic acid build up, which often occurs when you sprint or when you hit mile 22 in a marathon because your elevated pace leads to an elevated need for CO2 removal from the blood, a process which then can no longer keep down your blood acidity (pH) within reasonable limits. Muscle cramping and fatigue result. Below your anaerobic (lactate) threshold, aerobic metabolism can handle all the work; in between this threshold and VO2max, the transition to anaerobic metabolism begins. At VO2max, the volume of CO2 exhaled exceeds the volume of oxygen inhaled, and blood acidity increases dramatically. Therefore, having the abilities to both 1.) run fast beneath your anaerobic threshold, and 2.) acquire and use lots of oxygen for energy are necessary to compete well. 

How They Differ. FitNews editorial board member Jack Daniels, who has been named “The World’s Best Coach” by Runner’s World, says that the goal of interval training is simply to spend as much time as possible running at VO2max. To achieve this, you always run at a consistent pace, regardless of distance, but alter the length of recovery periods to keep your heart rate up accordingly. VO2max training, then, occurs best at near 100% VO2max, which amounts to about 98% MHR and is a pace akin to that which you could sustain for 10 to 15 minutes of racing—so quite fast. Recoveries are slow jogs about as long (in time, not distance) as the interval. Daniels’ inalterable rule is that no interval should exceed five minutes; beyond that, the demands of interval running lead to too much blood lactate, which by instigating fatigue compromises time spent at maximal oxygen consumption. And remember, always run 400s at the same pace as miles: uncomfortably hard but not all out.

Tempo runs help you improve your lactate threshold. The goal is to run comfortably hard, or at near-anaerobic threshold, which amounts to around 90% MHR (85 to 90% VO2max). This pace, according to Daniels, is roughly that which you could sustain for one hour of racing—considerably slower than interval training. (Competitors, depending on your fitness level, this is roughly 30 seconds per mile slower than 5K pace.) 

Threshold workouts come in two tempo-run forms: 20-minute (or so) tempo runs at this comfortably hard pace, or shorter cruise intervals, which are anywhere from 3 to 10 minutes, with a 1-minute recovery in between. A good example of this latter type of threshold training is five repeats of a mile. 

If you prefer to gauge your pace by effort, Honolulu Marathon Advanced Runner Training Program coach Brian Clarke says in his book 5K and 10K Training that during threshold runs, breathing has advanced beyond quiet huffing to audibly loud, and conversation is not possible. By contrast, his description of “ragged edge” effort, which is just one level below “maximum” in the book’s section on exertion, sounds a lot like Daniels’ interval pace. 

How Important is Lactate Threshold? Some studies have suggested that lactate-threshold speed is the best predictor of endurance performance. Swedish physiologist Bertil Sjodin, for example, found that a weekly 20-minute workout at lactate-threshold speed, when carried out over a 14-week period, improved lactate-threshold velocity significantly. However, Anderson points out that Bertil's subjects were not compared with runners who worked at paces faster than their thresholds, and in fact there was not even a control group in Bertil's inquiry.

Do tempo sessions have a larger effect on your fitness than intervals? The answer is that lactate threshold is a key predictor of performance, but speed, running economy, and aerobic capacity may have even more of an influence than lactate threshold. If you must choose, choose interval training.

Olympic-gold-medalist-turned exercise physiologist Peter Snell examined the values of these two training types at the University of Texas Southwestern Human Performance Center by asking vertan runners to focus on one or the other for 10 weeks.

Two 30-minute tempo runs a week at roughly 80% VO2max did not fair as well in racing as two 3-mile bouts of interval training in the form of 200-meter intervals in an average of 35.5 seconds  and 400s in 77.5 seconds; intensity averaged 90 to 100% VO2max.

The interval runners improved 800-meter time by an average of 11.2 seconds and bettered previous 10K times by 2.1 minutes. Tempo subjects shaved 6.6 seconds from their 800-meter times and decreased 10K finish times by only 1.1 minute. This roughly half improvement is thought to be the result of VO2max increasing by 12% for the interval runners but only 4% for the tempo runners. However, the tempo runs here do not follow the VO2max prescription outlined in Daniels’ Running Formula. It is unclear whether proper intensity tempo training would have helped the tempo runners match the gains enjoyed by the interval subjects.

It is noteworthy that these results were observed even though the tempo-trained runners engaged in a far greater amount of such speedwork over the 10-week period. Tempo runners completed 58 minutes per week of tempo training, while those running intervals spent just 31 minutes per week doing so. Of course, training volume alone has never been claimed to be as effective in improving finish times as quality, run-ready workouts at a high intensity.

Both forms of training have their place. Once you have your LTV, you can sculpt workouts that favor threshold running or VO2 training to your liking. Fr each of the workouts described below, always warm up for at least 15 minutes and cool down for 5.

Interval Workouts.

  1.  For runners who prefer to use distance as their primary measure, Jack Daniels suggests 8 x 400s with 200 meters recovery jogging in between.

The idea is to run at a certain pace and grant rest that isn’t sufficient to bring you out of a VO2maxed state. So try this Daniels-inspired workout, with a disregard for distance covered:

  1.  6 x 2-minute runs with 1 minute of recovery following each, then 8 x 1-minute runs with 30 seconds’ recovery, then 8 x 30-second runs with 15 seconds recovery in between. You’ll spend 36 minutes total, 24 of which will be at interval pace.

Tempo Workouts.

In addition to straight-out, 20-minute tempo-paced running, Brian Clarke offers a few ideas for cruise intervals that go beyond the above-mentioned 5 x 1-mile repeats with 1 minute of recovery in between:

  1.  Run 30 seconds slower than your 5K race pace, or roughly 80% MHR (up to 90% VO2max) for 5 minutes. Slow jog for 75 seconds in between, completing six to eight bouts. 

Anderson favors even shorter cruise-interval training to combat boredom and give tempo workouts “more lift.” Unlike Daniels, he also allows small fluctuations in speed during such training, as is evident in the below workouts:

  1.  Run 4 x 2000 meters with equal time recovery jogs—aim for :02 faster per 400 meters than LTV pace.
  2.  Run 5 x 1200 meters, with equal time recovery jogs, at :04 faster per 400 meters.
  3.  Run 8 x 800 meters, with equal time recovery jogs, at :08 faster per 400 meters.
  4. Run 10 x 400 meters, with equal time recovery jogs, at :12 faster per 400 meters.

 Finally, Anderson says, “The study which produced the greatest increase in lactate threshold in runners was the research by Leena Paavolainen and Heikki Rusko in which experienced runners reduced their mileage from 70 to 45 miles per week, substituting a progressive series of jumps, bounds, hops, and very fast running.” The three-times-weekly workouts yielded an almost 7% increase in lactate threshold over the course of nine weeks.

For more on measuring LTV, please see How to Determine Your Lactate Threshold Velocity in this issue.

 

The Complete Guide to Running by Earl Fee, 2005, Meyer & Meyer Sport, New York, NY, pp. 23-25

Daniels’ Running Formula by Jack Daniels, PhD, 1998, Human Kinetics, Champaign, IL, pp. 52-53, 94-112

5K and 10K Training by Brian Clarke, 2006, Human Kinetics, Champaign, IL, pp.3, 101

 

Running Research News, Dec. 2011, Vol. 21, No. 12, “Best Lactate-Threshold Workouts,” by Owen Anderson, PhD, ed., http://runningresearchnews.com/News_And_Events.php?cid=1&iid=89

 

Running Research News, 2007, “The Merits of Tempo vs. Interval Running,” by Owen Anderson, PhD, ed., http://www.pacificstriders.org/data/RRN022707.html

 

 

(RUNNING & FITNEWS® January / February 2012 • Volume 30, Number 1)




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