Zone 2: A distance runner’s secret weapon.

A 2014 study by Saragiotto in the Journal of Sports Physical Therapy investigated the beliefs and opinions of runners about risk factors associated with running injuries. They found that 29% of the group cited excessive training as a cause for running-related injuries. This is important to me because “excess” is not universal. You can be over reaching with volume, frequency, single session intensity, time between efforts with higher intensity, single session duration, inadequate rest, etc. Two things I see missing in the subjective information of the injured athletes who walk into my office are honest self-assessment and guiding training with an awareness of your body’s physiologic response to the stress you place on your systems and structures.

It has been recently made popular that “volume is king” and athletes who can run more miles in a given week have been found to have more resilient bodies, but one important caveat is that a large majority of those miles can and should be done at a low intensity. So let’s apply this concept to your running!

“Easy running” is operationally defined as light to moderate in intensity, rate of perceived exertion (RPE) of 3/10, and within the boundaries of zone 2 on your heart rate monitor.

What happens when you work at this intensity?
- In this zone, we are working at an aerobic level (aka oxygen is readily available and able to get to work).  At this intensity, your cardiovascular system experiences increased heart rate and stroke volume, and since oxygen is readily available you have optimized oxygen delivery to the muscles. Regular Zone 2 exercise has been found to enhance mitochondrial density. The mitochondria are the powerhouse of the cell, so more mitochondria means that the muscles’ ability to produce energy aerobically increases. In zone 2 fat oxidation becomes a primary energy source, contributing to endurance. Additionally, running in Zone 2 promotes capillary density and efficient blood flow, supporting sustained performance while minimizing reliance on anaerobic pathways.

How exactly does it help me?
- Zone 2 running helps improve cardiovascular fitness, endurance, and fat utilization for energy. The safest way to build up running volume is to keep the overall intensity low and strategically build time on feet. Running your base miles (actually) easily allows your body’s systems and structures to recover between efforts, become more efficient, and it produces less metabolic stress than running at or above lactate threshold so you have a reduced risk for injury.

How much of my week should be spent in zone 2?

• As always, I have to say…it depends. One very popular recommendation is: 80% of your weekly mileage should be spent in zone 2 and 20% should be spent at or above your lactate threshold. My specific recommendation for how much of your weekly volume should be done within zone 2 depends on your running experience, the season of training you are in, and how your body tolerates each intensity.

If you want guidance on how to structure your training? I’d be happy to help! Reach out to me at Bethany@physio330.com with “run coaching” in the subject line!

Questions, concerns, comments? I’d love to hear ‘em. Send me an email or message me on IG @Physio330