BLUF
Over a 4-week period, MTI athletes subscribed to our daily streams completed either 1.5 or 3 hours per week of Zone 2 running. Despite the low training volume and minimal intervention time, most athletes who completed the protocol demonstrated improvements in aerobic base, assessed by total distance covered during a fixed-time Zone 2 effort. These results suggest that aerobic capacity can be developed in a short cycle with limited Zone 2 exposure.
Background
Zone 2 training develops aerobic capacity—the body’s ability to efficiently use oxygen to produce energy at submaximal intensities. This type of training supports cardiovascular efficiency, increased mitochondrial density, fat oxidation, and muscle endurance—particularly when applied consistently. It serves as the physiological foundation for endurance performance and is frequently prescribed in endurance training models for both recreational and elite athletes.
To improve aerobic running base, traditional endurance research indicates that 3 to 6 hours of Zone 2 running per week is effective for most recreational athletes, while competitive and elite athletes benefit from 6 to 10+ hours per week. This volume is typically distributed across 3 to 6 training days, with individual sessions lasting 45 to 90 minutes.
Scientific evidence supporting this volume-based approach includes:
- Seiler & Tønnessen (2009): Elite endurance athletes trained ~9–11 hours/week, with ~80% at low intensity. This distribution supported VO₂max and long-term aerobic adaptations.
- Esteve-Lanao et al. (2007): Recreational runners saw greater race improvements from a 5–6 hour/week polarized model emphasizing Zone 2 over threshold work.
- Stöggl & Sperlich (2014): Trained athletes on a polarized model (Zone 2 + high-intensity) saw superior VO₂max and peak speed improvements compared to threshold or high-volume-only groups.
In contrast, Ciccone et al. (2018) note that even 3 hours/week of consistent aerobic training can yield meaningful improvements—providing a lower-volume benchmark that may be more applicable to general fitness populations with limited time or lower training age.
Study Design
Participants were drawn from MTI’s daily programming streams. Each group followed the same progression for 4 weeks:
- Week 1: Initial Zone 2 run assessment (either 60 or 45 minutes depending on the group).
- Week 1 Continued:
- Daily General Fitness, Operator, and LE SWAT/SRT followed with two 60-minute Zone 2 runs.
- Daily LE Patrol followed with one 45-minute Zone 2 run.
- Weeks 2–3:
- Daily General Fitness, Operator, and LE SWAT/SRT completed three 60-minute Zone 2 sessions/week.
- Daily LE Patrol completed two 45-minute sessions/week.
- Week 4: Final assessment (same duration as Week 1).
Zone 2 pacing guidance:
- For athletes without access to a heart rate monitor, we prescribed the following pacing guideline: maintain an “easy pace” where you can speak in full sentences.
- Athletes with a heart rate monitor were told to target Zone 2 heart rate using the formula:
Zone 2 Heart Rate = 180 – Age
All sessions were self-reported and executed independently.
Groups and Training Volume
| Group | Weekly Sessions | Session Length | Total Weekly Volume |
|---|---|---|---|
| Daily General Fitness | 3 | 60 min | 180 min |
| Daily Operator | 3 | 60 min | 180 min |
| Daily LE SWAT/SRT | 3 | 60 min | 180 min |
| Daily LE Patrol | 2 | 45 min | 90 min |
Results
Daily General Fitness Subscribers
| Athlete | Run 1 (mi) | Run 2 (mi) | % Change |
|---|---|---|---|
| 1 | 5.45 | 5.85 | +7.34% |
| Group Average: +7.34% |
Daily Operator Subscribers
| Athlete | Run 1 (mi) | Run 2 (mi) | % Change |
|---|---|---|---|
| 1 | 6.5 | 6.7 | +3.08% |
| 2 | 6.0 | 6.5 | +8.33% |
| 3 | 6.3 | 6.65 | +5.56% |
| 4 | 7.0 | 7.5 | +7.14% |
| 5 | 6.0 | 6.0 | 0.00% |
| 6 | 4.0 | 5.6 | +40.00% |
| Group Average: +10.68% |
Daily LE SWAT/SRT Subscribers
| Athlete | Run 1 (mi) | Run 2 (mi) | % Change |
|---|---|---|---|
| 1 | 5.0 | 5.0 | 0.00% |
| Group Average: 0.00% |
Daily LE Patrol Subscribers
| Athlete | Run 1 (mi) | Run 2 (mi) | % Change |
|---|---|---|---|
| 1 | 4.45 | 4.75 | +6.74% |
| 2 | 4.2 | 3.6 | -14.29% |
| Group Average: -3.77% |
Study Limitations
- Self-reported execution: MTI coaches were not present to verify session completion.
- No heart rate validation: Some athletes ran without monitors, relying on pacing cues.
- Athlete training age unknown: Participants may have varied significantly in baseline aerobic fitness.
- Sample size: Low completion rate limited group-level statistical confidence.
Conclusion
Despite the low total training time (either 1.5 or 3 hours/week), aerobic base improved in most athletes who completed the protocol. This challenges the prevailing consensus in exercise physiology, which recommends a minimum of 3 to 6 hours/week for general fitness and 6 to 10+ hours/week for competitive endurance athletes to improve aerobic capacity.
Scientific studies by Seiler, Esteve-Lanao, and Stöggl emphasize the role of high-volume Zone 2 training in enhancing VO₂max and endurance. However, our findings suggest that meaningful gains may also be possible with far less volume—at least over a short 4-week cycle. These outcomes align with lower-volume protocols such as Ciccone et al., who observed aerobic improvements from ~3 hours/week of structured effort.
The Daily LE Patrol group, which completed just 90 minutes per week, saw mixed but notable results: one athlete regressed slightly, while the other improved by 6.74%. This suggests that even low-end protocols like 2 x 45-minute sessions/week may hold value—especially in constrained training environments.
Next Steps
- Test the protocol with a larger sample of athletes who can be monitored directly to ensure consistency, improve data quality, and validate the effectiveness of low-volume Zone 2 training.
- Compare the effects of three 60-minute sessions per week (3 hours total) versus two 45-minute sessions per week (1.5 hours total). This head-to-head structure will help identify whether the lower volume is a reliable minimum effective dose or if higher weekly exposure is needed to consistently improve aerobic base.
- Include athletes with different aerobic training backgrounds to see how training history affects results. Athletes with a more developed aerobic base may respond differently to low-volume protocols than those who are new to endurance work. Tracking this will help determine whether previous aerobic experience influences how much training is needed to see improvement—as research shows that the more aerobically trained an athlete is, the harder it is to improve, and the more training time is typically required.
Bibliography
- Seiler, S., & Tønnessen, E. (2009). Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training. Scandinavian Journal of Medicine & Science in Sports, 19(1), 10–15.
- Esteve-Lanao, J., et al. (2007). How Do Endurance Runners Actually Train? Relationship With Competition Performance. Medicine & Science in Sports & Exercise, 39(5), 920–927.
- Stöggl, T., & Sperlich, B. (2014). Polarized Training Has Greater Impact on Key Endurance Variables Than Threshold, High Intensity, or High Volume Training. Frontiers in Physiology, 5, 33. https://www.frontiersin.org/articles/10.3389/fphys.2014.00033/full
- Ciccone, A., Weir, L., & Weir, J. (2018). Aerobic Exercise Prescription. In Conditioning for Strength and Human Performance (2nd ed.). Taylor & Francis.
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