Is Zone 2 Training Overrated? What the Latest Research Actually Says

A 2025 narrative review, Much Ado About Zone 2, questions whether Zone 2 is the optimal intensity for improving mitochondrial and fat-oxidation capacity in the general population. The authors favour higher intensities for maximizing these benefits, particularly at lower training volumes.

That is a narrower conclusion than saying easy exercise produces no adaptations or that every runner should replace easy sessions with intervals. The useful question for a Garmin user is how the evidence relates to their own plan and the zones shown on their watch.

What the Review Actually Found

The review considers low-intensity exercise below the lactate threshold and challenges recommendations drawn from observations of elite endurance athletes. It concludes that current evidence does not establish Zone 2 as the optimal intensity for the two capacities it examines.

It is a narrative review, not a trial comparing complete training plans for individual runners. Its conclusions should not be presented as a measurement of your injury risk or a prescription for your weekly schedule. Read the authors' abstract.

What That Means for Easy and Hard Sessions

Our practical reading is to avoid choosing every session around a claim that one zone is uniquely effective. Decide what the session is for, then check whether its intensity fits the plan you are following.

A recovery run, a long run and intervals have different purposes. A single zone label does not tell you whether a session fits your current circumstances. Include the duration, your recent training and how you feel when discussing changes with a coach.

Neither a watch score nor an online article can tell you exactly what intensity your body can safely handle. If pain, illness or unusual symptoms are affecting exercise, seek appropriate medical advice rather than trying to solve them by adjusting a heart-rate zone.

The Garmin Zone Problem: Check What the Number Means

A useful first check is the method behind the label. The Forerunner 965 manual allows zones based on BPM, percentage of maximum heart rate, heart-rate reserve or lactate-threshold heart rate. It also supports separate settings for different sports. Available settings vary by device.

Before comparing your watch with a training plan, check:

• Which zone method does the plan use?
• Which method is selected on your watch?
• Are you looking at the general profile or a sport-specific profile?
• What maximum, resting or threshold heart rate values are those settings using?

Changing methods can change the displayed boundaries. It does not prove that the new boundaries match a physiological threshold. A slow pace or needing to walk also does not, by itself, prove the settings are wrong. Avoid moving the boundaries simply to make a preferred pace display as Zone 2.

There is a separate distinction about Garmin's calculations: Garmin states that personal zone settings do not determine advanced metrics such as Training Load, Training Effect or Training Status. An inaccurate maximum heart rate can affect their reliability. Changing displayed zones and correcting maximum heart rate are different operations.

Our Garmin heart-rate zones guide provides more setup context; use your device's official manual for its supported settings.

A Practical Framework for Reviewing Your Week

Use this as a record for reviewing your plan, not a replacement training schedule:

1. Write down the planned purpose. Was the session intended to be easy, long, hard or recovery-focused?
2. Record what happened. Note duration, perceived effort and any relevant heart-rate readings. Keep the same zone method when comparing sessions.
3. Add context. Include sleep, symptoms and recent changes in training. HRV Status and Training Readiness can be discussion inputs, not automatic diagnoses.
4. Review patterns. Bring repeated mismatches between intended and actual effort to your coach. Avoid rewriting a whole week because of one reading.

We do not assign a universal number of hard sessions from running frequency alone. We also do not use a fixed Training Effect cutoff to declare every easy run successful or too hard.

Training With a Chest Strap and Phone

If you train without a watch, the same setup questions still apply: which zone method is in use, and what inputs define its boundaries?

The chest strap heart-rate monitor app guide explains the phone-based setup. The Strap Zone page lists the app's features and compatibility. Heart-rate tracking supplies information for a training decision; it does not validate a zone model or guarantee the result of a workout.

FAQ

Is Zone 2 training a waste of time?

That conclusion does not follow from the review. Questioning the optimal intensity for particular adaptations is different from demonstrating that easy exercise has no benefit.

Should I stop doing Zone 2 runs after this review?

Do not treat a research headline as an individual prescription. Review the purpose of those sessions within your current plan before changing their intensity.

Is Zone 2 training worth it for beginners?

The label alone cannot answer that. A beginner's appropriate plan depends on their starting point, goals and health. There is no rule here that beginners must run faster or that walking proves their zones are incorrect.

How do I know if my Garmin Zone 2 is accurate?

Start with the zone method, the sport profile and the values used to calculate it. Compare those with the method your plan expects. Matching a preferred pace to a displayed zone is not an accuracy test.

Does the 80/20 rule still apply after this review?

The review does not establish a universal weekly split for you. If you follow a plan using 80/20, check how that plan defines intensity and counts training before comparing it with Garmin's zone totals.

Review Your Data With Should I Train

Bring the planned session, actual effort and recovery context together when reviewing your week. Should I Train can support that conversation with your Garmin data. Its output remains guidance to assess against your circumstances, not a guarantee of a safe or optimal intensity.