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Training Zones: The 3-Zone System

Training Zones: The 3-Zone System

The 3-Zone system is the widely cited in the scientific realm and is utilized across multiple endurance sports. The system organizes intensity into three zones: low, moderate and high intensity (or Zones 1, 2 & 3 or moderate, heavy, severe). The boundaries between these zones are usually identified in a lab by either VO2 or Lactate Testing.

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This system has been around for decades but has gained renewed attention as the system utilized by Dr. Stephen Seiler when discussing "polarized training". "Polarized training" refers to the distribution of duration and intensity in the overall training plan and is one of several approaches to how one might organize training activities. Dr. Seiler and others have described the training of various elite athletes as being "polarized", that is, characterized by the vast majority of training being done in Zones 1 & 3, and very little training in Zone 2. (stay tuned for a future series of articles on this topic ). While "polarized training" can be done with any training zone system, many of the published studies of elite runners, cross country skiers, and other endurance athletes have relied on the 3-Zone System.

Ideally, you would utilize lab testing to identify the zone boundaries. In the absence of formal testing, the transitions between zones in the 3-Zone system can be roughly correlated to points in the 7-Zone System. Low Intensity encompasses Zones 1 and 2 in the 7-Zone System (although for some the upper boundary may be mid-Zone 3). Moderate Intensity corresponds to Zones 3 and 4 in the 7-Zone System. High Intensity encompasses Zones 5-7 in the 7-Zone System. However, these are rough correlations and physiological testing would identify the specific transition points for a particular individual.

Typically, we see heart rate used as the metric to direct, monitor and analyze training under this system.

Positives about this approach:

  • Relatively simple structure
  • Zones are linked to underlying metabolic phenomena
  • Extensive scientific evidence supporting and describing the underlying physiology
  • Broad zones make it easy to execute training efforts in specific zones
  • Can be done by heart rate, avoiding costly equipment, e.g., power meter

Negatives about this approach:

  • Low Intensity/Zone 1 covers a broad range of intensity, there may be reason to direct training with greater specificity, i.e., low-Zone 1 or high-Zone 1.
  • Lab testing may be required to identify the boundaries with enough individual specificity
  • Relying on heart rate for the upper zones may require some special care to account for the delay in HR response to activity
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