UT2 vs UT1 vs Threshold Rowing: Understanding Training Intensities for the Erg

April 17, 20266 min read

Every erg session should have a purpose, and that purpose is defined by intensity. The most important intensities for rowers — UT2, UT1, and anaerobic threshold (AT) — each target different physiological systems. Understanding the difference between them is the key to training smarter, not just harder.

The 6-zone system at a glance

Rowing training uses a 6-zone model. The three zones that matter most for day-to-day training are UT2, UT1, and AT:

| Zone | Name | 2K pace offset | Heart rate range | Rate | Primary adaptation | |---|---|---|---|---|---| | UT2 | Utilisation 2 | +20–26 sec | 130–155 bpm | 18–22 | Aerobic base, fat oxidation | | UT1 | Utilisation 1 | +14–18 sec | 155–170 bpm | 22–26 | Aerobic power, lactate tolerance | | AT | Anaerobic Threshold | +8–12 sec | 170–180 bpm | 26–30 | Threshold pace, lactate clearance | | TR | Transport | +4–6 sec | 180–190 bpm | 28–32 | VO₂max development | | AN | Anaerobic | +0–3 sec | 190+ bpm | 32+ | Anaerobic power | | Max | Maximum | Faster than 2K | Max | Max | Sprint power |

For a full summary of all six zones, see Rowing Pace Zones Explained. This post focuses on the three zones that make up 90%+ of your training.

UT2: the aerobic foundation

What it is: The lowest training intensity. Easy enough to sustain for 60–90 minutes. Conversational.

What it trains: Mitochondrial density, capillarisation, cardiac stroke volume, fat oxidation, stroke efficiency. These are the slow-building adaptations that form your aerobic engine.

How to calculate: 2K split + 20–26 seconds per 500m. Or 60-minute test split + 12–18 seconds.

Typical sessions: 60 min continuous, 3×20 min, 2×30 min — all at rate 18–22.

How it should feel: Easy. Boring, even. If you finish a UT2 session feeling like you worked hard, you went too hard. The effort should be sustainable — you could do another session tomorrow without issue.

How much: 70–80% of weekly training volume. For most rowers, that's 3–5 sessions per week.

For a deep dive, see Steady-State Rowing.

UT1: aerobic power

What it is: Moderate intensity. Hard enough to feel like training, easy enough to sustain for 20–40 minutes per interval.

What it trains: The upper end of your aerobic system. UT1 teaches your body to clear lactate at a faster pace, raises your anaerobic threshold over time, and develops race-specific efficiency.

How to calculate: 2K split + 14–18 seconds per 500m. Or 60-minute test split + 5–8 seconds.

Typical sessions: 4×10 min with 3 min rest, 3×15 min with 3 min rest, 2×20 min with 4 min rest — all at rate 22–26.

How it should feel: Controlled but challenging. You can say a few words but not hold a conversation. Heart rate will be elevated but not anaerobic. You should finish feeling worked but not destroyed.

How much: 10–15% of weekly training volume. Typically 1–2 sessions per week, introduced after a base-building phase.

AT: the threshold

What it is: The pace where lactate production roughly equals lactate clearance — your anaerobic threshold. Sustainable for approximately 30–40 minutes in a trained rower.

What it trains: Lactate clearance, muscular endurance at high output, mental tolerance of sustained discomfort. AT work directly raises the ceiling on your sustainable pace.

How to calculate: 2K split + 8–12 seconds per 500m. Your 6K test pace is approximately your AT.

Typical sessions: 6×5 min with 3 min rest, 4×8 min with 4 min rest, 3×10 min with 5 min rest — all at rate 26–30.

How it should feel: Genuinely hard. You can't speak beyond single words. Heart rate will be near threshold (170–180 bpm for most). Each interval should feel like the maximum pace you could hold for 30 minutes.

How much: 5–10% of weekly training volume. Typically 1 session per week, introduced in the build or peak phase. More than this creates excessive fatigue without proportional benefit.

How they fit together

The relationship between these zones follows the polarised training model: most training is easy (UT2), a small amount is moderate (UT1), and a smaller amount is hard (AT or above).

| Phase | UT2 % | UT1 % | AT/higher % | |---|---|---|---| | Base phase (weeks 1–6) | 85% | 10% | 5% | | Build phase (weeks 7–12) | 75% | 15% | 10% | | Peak phase (weeks 13–16) | 65% | 15% | 20% | | Taper (final 1–2 weeks) | 70% | 10% | 20% (reduced volume) |

This distribution is not arbitrary — it mirrors the training patterns of elite rowers documented in rowing research.

The key differences, summarised

| Aspect | UT2 | UT1 | AT | |---|---|---|---| | Pace (from 2K) | +20–26s | +14–18s | +8–12s | | Heart rate | 130–155 | 155–170 | 170–180 | | Stroke rate | 18–22 | 22–26 | 26–30 | | Session duration | 40–90 min | 20–40 min/interval | 5–10 min/interval | | Recovery need | Low (daily) | Moderate (24–48h) | High (48h+) | | When to use | Always | Build phase | Peak phase | | Feels like | Easy | Controlled effort | Hard |

Common mistakes

Gray zone training

The biggest error in erg training is spending too much time between UT2 and UT1 — too hard to be steady-state, too easy to stimulate threshold adaptations. This "gray zone" produces fatigue without optimal adaptation. The fix: make easy sessions truly easy and hard sessions genuinely hard.

Too much threshold, not enough base

Threshold work feels productive because it's hard. But doing AT intervals 3–4 times per week doesn't build a bigger engine — it just fatigues a small one. Trust the process: most of your metres should be easy.

Treating UT1 like UT2

UT1 requires recovery. If you're doing UT1 sessions 4 times a week and feeling flat, you're probably accumulating fatigue that undermines your training quality. Drop some sessions back to genuine UT2.

Ignoring heart rate

Heart rate is the best indicator of what zone you're actually in — splits can be misleading if you're fatigued, dehydrated, or having a bad day. If your split says UT2 but your heart rate says UT1, believe the heart rate.

Using the pace calculator

If you know your 2K split, you can calculate all three zones in seconds. The pace calculator converts a single benchmark into UT2, UT1, and AT targets. You can also use the watts calculator to compare power output across zones.

How ErgBuddy distributes intensity

When you set a goal in ErgBuddy, the generated programme follows the polarised model automatically. Your pace zones determine the split targets for each session type, and the programme distributes intensity across phases based on your goal date and current benchmarks.

For more on how phases work, see Periodized Rowing Training.