From Running Research News: The best type of training to increase your fitness:
THE MERITS OF TEMPO VS. INTERVAL RUNNING
Which will have a bigger impact on your performances?
As you plan your workouts, you probably wonder from time to time about whether tempo sessions or interval workouts have a larger effect on your overall fitness. Tempo sessions have been a mainstay of running training for over 40 years, and they are thought to have a positive influence on lactate-threshold running speed, a key predictor of performance. Interval training has been around for even longer, and many experts link interval work with upgrades in speed, running economy, and aerobic capacity, which are all decent indicators of performance potential.
To examine the relative value of interval and tempo training, New Zealand Olympic great Peter Snell and his colleagues at the University of Texas Southwestern Human Performance Center asked some well-conditioned runners to focus on either tempo running or interval training for a period of 10 weeks (1). If the name Peter Snell rings a bell, the researcher from Texas Southwestern is the same Peter Snell who won a total of three gold medals at the 1960 and 1964 Olympics and also captured two gold medallions at the Commonwealth Games in 1962. Snell's world-record performance of 1.44.3 for 800 meters, accomplished in February, 1962, remains the New-Zealand national record to this day. After his running career ended, Snell earned a Ph. D. in exercise physiology and has been a researcher at Texas Southwestern since 1981.
In Peter's research, one group of runners carried out tempo runs twice a week (the rest of their running was moderate-paced effort). These tempo workouts involved running for 29 minutes at a running speed which roughly corresponded with lactate-threshold velocity - the pace above which blood-lactate levels begin to increase dramatically. The average intensity during these sessions was about 70 to 80 percent of maximal aerobic capacity (VO2max).
Runners in a second group carried out no tempo running at all but instead conducted two interval sessions per week. During these interval workouts, the runners cavorted through 200-meter intervals in 33 to 38 seconds and performed 400-meter intervals in 75 to 80 seconds, completing a total of about three miles of interval running per workout. Exercise intensity during this interval running averaged 90 to 100 percent of VO2max.
After 10 weeks, the runners from both groups ran 800-meter and 10-K races. In these competitions, the interval-trained runners fared far better than the tempo-tutored harriers. For example, the interval-based runners improved 800-meter time by an average of 11.2 seconds and bettered previous 10-K times by 2.1 minutes.
Meanwhile, the tempo-training devotees shaved just 6.6 seconds from their 800-meter times and upgraded 10-K running by only 1.1 minute, roughly half the improvement achieved by the interval-trained competitors. VO2max soared by 12 percent for the interval runners but nudged upward by only 4 percent for the tempo-trained runners.
These results were observed even though the tempo-trained individuals engaged in a far-greater amount of quality work over the 10-week period. Specifically, the tempo runners completed 58 minutes per week of tempo training, while the interval individuals spent just 31 minutes per week conducting fast interval effort. This led to a 270-minute edge in quality training for the tempo group over the 10-week period.
Despite this apparent disadvantage, the interval-trained runners gained considerably more physiological and competitive fitness. A key lesson to be learned here is that intensity is always the most-potent producer of fitness; it is a much-stronger stimulus for improvement than training volume and workout frequency. When you conduct your intervals at 90 to 100 percent of VO2max (and at higher intensities, too), the amount of fitness gained per minute will always be greater, compared with the running capacity accrued at lower intensities. As you can see from Snell's research, each minute of high-quality work can sometimes produce twice as much gain in fitness as double the amount of lower-quality exertion.
Incidentally, recent research has discredited tempo training as a powerful booster of lactate-threshold speed, the adaptation with which it has been traditionally linked. The problem is that tempo training, carried out at close to lactate-threshold velocity, by definition produces very little increase in blood-lactate concentrations and thus does a poor job of stimulating muscle cells to get better at clearing lactate from the blood. Blood-lactate removal by the muscles is a key component of improving lactate-threshold speed.
Note, too, that interval training is superior to tempo running when it comes to matching training paces with goal race speeds (unless you are planning to run only 15Ks and half-marathons). This is obviously a good thing from the standpoints of enhancing goal-speed running economy and mental confidence. As Snell pointed out in a telephone interview with Running Research News, "Perhaps the best way to train is to spend the maximum-possible amount of time running at a pace which is closely related to the demands (or pace) of the race you're shooting for, without getting overtrained."
So what kinds of intervals would work well for you? 1600s at 5-K pace, 800s at four seconds per 400 meters faster than 5-K pace, and 400s at eight seconds per 400 meters faster than 5-K speed would all be very productive. During such interval sessions, each jog recovery can last about as long as the duration of the preceding work interval. Especially for the 1600-meter intervals, it is smart to pare down the time-lengths of these recoveries over time, as you get fitter.
Courtesy of Owen Anderson. Owen Anderson's new site:http://www.educatedrunner.com