Athletes and coaches must balance training volume and intensity to achieve the ultimate goal: improving performance. Training load is commonly managed by dividing intensity into zones separated by physiological thresholds, such as the anaerobic threshold or a given percentage of VO2max, or by intensities relative to a target pace, such as a percentage of marathon pace. One of the most common approaches uses three zones:
- Zone 1: below the aerobic threshold, low intensity.
- Zone 2: between thresholds, moderate intensity.
- Zone 3: above the anaerobic threshold, high intensity.
These “training zones” can be combined into different planning models, and there is considerable debate about which model is optimal. Some leading marathon runners, particularly Kenyans, and most recreational athletes accumulate most of their training in zone 2, or “at threshold.” They focus training near race pace in the belief that more specific work will provide greater benefits. By contrast, high-intensity training, also known as HIIT or high-intensity interval training, is gaining support because it can produce substantial benefits while greatly reducing training time.
To determine which method produced the greatest benefits, a study published in Frontiers in Physiology (Stoggl, 2014) analyzed 48 highly trained athletes who were randomly assigned to four experimental groups:
- High volume and low intensity: training performed in zone 1.
- Threshold training: intensity close to the anaerobic threshold.
- High-intensity interval training (HIIT): close to 95% of maximum heart rate.
- Polarized training: alternating high- and low-intensity sessions while avoiding intensities close to the anaerobic threshold.
Polarized training produced the greatest improvements in fitness, including VO2max and time to exhaustion. Moreover, speed at the anaerobic threshold improved only in the polarized-training and HIIT groups. Although the traditional tendency is to perform most training at an intensity near the anaerobic threshold, this strategy may therefore be neither the most effective nor the most efficient.
Supporting these findings, a recent review (Kenneally, 2017) including 16 studies and 215 endurance athletes examined which periodization model most effectively improves performance. The authors found substantial evidence for pyramidal periodization, in which the greatest volume is accumulated in zone 1, less in zone 2 and still less in zone 3. However, growing evidence also supports polarized training, which alternates high and low intensities while avoiding work near the anaerobic threshold or race pace. Both pyramidal and polarized periodization proved more effective than traditional “threshold training.”
In conclusion, although threshold training is the model most widely used by recreational athletes and some leading marathon runners, scientific evidence suggests that other periodization models—pyramidal and especially polarized training—may be more effective. Nevertheless, race-pace-specific training may be useful in the weeks before an event.
References
- Stöggl, T. & Sperlich, B. Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. Front. Physiol. 5, 1–9 (2014).
Kenneally, M.; Casado, A. & Santos-Concejero, J. The Effect of Periodisation and Training Intensity Distribution on Middle- and Long-Distance Running Performance: A Systematic Review. Int J Sports Physiol Perform. 28, 1-26 (2017).
AUTHOR
Pedro Valenzuela
Researcher in the Physiology Unit at the University of Alcalá and the Performance Monitoring Unit at the Sports Medicine Center (AEPSAD, Madrid High Performance Center).
Website: www.fissac.com
