A recent study by Seiler and Tonnessen analyzing scores of top endurance athletes from numerous sports argues for a new distribution of workload supporting an 80:20 ratio in low to high-intensity training effort. Notwithstanding differences in methods used for quantifying training intensity, consistency in training distribution patterns used by successful athletes tends to the 80:20 ratio. In other words, the evidence in the study suggests that training roughly 80% of the time at lower-intensity sub-lactate threshold levels, coupled with 20% at or above lactate threshold levels, results in long-term improvements in endurance performance for athletes training daily.
This 80:20 ratio can be further broken down into a Three-Zone intensity scale of training. A total of 80% of an athlete’s weekly workout is completed in Zone One, which includes intensities under the first ventilatory turn point or blood lactate concentration, at approximately 50% to 70% of VO2max. The other 20% is split between Zones Two and Three: Zone Two is at or near the lactate (anaerobic) threshold (approximately 70% to 90% VO2max), while Zone Three is at 90% to 100% of VO2max, and is usually reached by interval training.
For elite athletes who are typically training around 10 to 12 times per week, this translates to 1 to 3 sessions at or above the lactate threshold. This lends further support to much recent thinking that athletes should incorporate no more than 2 or possibly 3 interval training sessions into their weekly exercise regime.
Seiler and Tonnessen conclude that the optimal training distribution ratio for endurance performance should be approximately 75% to 80% of time spent in Zone One, 5% in Zone Two, and 15% to 20% in Zone Three. However, individual athletes competing tend to distribute their training slightly differently within Zones Two and Three, depending on their practiced sport.
There are a number of reasons why training in these distinct zones can benefit an athlete’s endurance performance in his or her chosen sport. In general, low-intensity exercise is used to correct motor patterns, while smaller volumes of high-intensity exercise benefits signaling for boosting cardiac function and buffer capacity.
Ironically, Seiler and Tonnessen discovered that athletes sometimes develop training programs to incorporate more high-intensity exercises than long-duration workouts in order to reduce stress and aid a faster recovery from regular training. These patterns were found to be present in the workouts of professional cyclists during the grand tours, like the Tour de France, in a 2007 study by Foster et al. Such evidence has led researchers to the conclusion that training distribution could be affected by pacing considerations, especially when top athletes carry out months of training.
Peculiarities exist in the low-intensity end of training as well. For one, technique is known to push higher- than-normal Zone One training intensities in some cases. Many athletes often need to train at higher intensities in order to perform the correct technique, especially in sports like rowing. Outliers aside, most Zone One training in elite athletes is being performed at approximately 60% to 65% of VO2max.
The Bottom Line
The evidence supports the general conclusion that an 80:20 ratio of low to high-intensity training is an effective means of improving endurance performance in elite athletes working out daily. However, non-elite athletes should focus on improving endurance levels by increasing total training volume at low-intensity, sub-lactate threshold before incorporating high-intensity training into the mix.
Graph image courtsey of SportsScience