END-017Z2EnduranceEnduranceRunning

DFA Alpha1 Aerobic Threshold Run

45-60 minutes of continuous running maintaining the DFA alpha1 index at 0.75 (±0.05) via an HRV-compatible chest strap. Enables precise polarized training at aerobic threshold (LT1) without a lactate meter, scientifically validated against lactate and ventilatory thresholds.

Duration: 1h05
Level: Intermediate
Target: Aerobic Base

Flat preferred

Session structure

1h05 · 3 phases

0 min · start1h05 · end

Intensity scaleZ1RecoveryZ2Endurance

Warm-up

10min

Z1RecoveryVery slow jog to stabilize HRV signal

10min

Main Set

50min

Z2Endurance45-60min continuous run maintaining DFA alpha1 = 0.75 (±0.05). Slow down if alpha1 < 0.70. Speed up slightly if alpha1 > 0.80. Record average pace at alpha1 = 0.75 as LT1 pace

50min

Cool-down

5min

Z1RecoveryProgressive cool-down

5min

Zone Distribution

Z1Recovery15min

Z2Endurance50min

Total 1h05

Tips

Requires an HRV-compatible chest strap (Polar H10, Garmin HRM-Pro) and a DFA alpha1 app (HRV Logger, RUNALYZE)
DFA alpha1 = 0.75 corresponds to the aerobic threshold (LT1), the boundary between Z1-Z2 and Z3
This session is ideal for calibrating your Z2 pace without a lab test
Perform regularly (every 4-6 weeks) to track your aerobic threshold progression

Common Mistakes

Using an optical wrist sensor instead of a chest strap (insufficient HRV signal)
Ignoring alpha1 variations and running at a fixed pace without adjustment
Running on a course that is too hilly, disrupting signal stability

Nutrition & Recovery

Nutrition

Eat your last meal at least 3 hours before the session for optimal digestion.

Hydration

Drink 400 to 500 ml of water in the 2 hours before the session.
Top up with 200 ml in the 15 to 30 minutes before heading out.
Avoid diuretic beverages (excessive coffee, alcohol) in the hours before.

Why it works

Why this format

Foundational endurance training stimulates mitochondrial biogenesis and capillary network development around type I muscle fibers. By maintaining a low intensity (below the first ventilatory threshold), the body optimizes fatty acid oxidation as an energy substrate, sparing muscle and hepatic glycogen for higher-intensity efforts.

Zones solicited

Recovery

Z1 promotes active recovery and increases blood flow to muscles without generating significant fatigue, allowing for high training volume.

Endurance

Z2 is the optimal intensity to maximize fat oxidation and stimulate mitochondrial proliferation. It is the core of polarized training, representing 75-80% of total volume.

Expected adaptations

Increased mitochondrial density in type I fibers (+40-60% after 6-8 weeks)
Development of peri-muscular capillary network (angiogenesis)
Improved oxidative enzyme activity (citrate synthase, succinate dehydrogenase)
Increased fatty acid oxidation capacity (intramuscular lipolysis)
Enhanced resting and exercise stroke volume

2 studies

Seiler S (2010) View study →What is best practice for training intensity and duration distribution in endurance athletes?
San-Millán I, Brooks GA (2018) View study →Assessment of metabolic flexibility by means of measuring blood lactate, fat, and carbohydrate oxidation responses to exercise in professional endurance athletes and less-fit individuals