Build Your Aerobic Engine: The Clear Path to Building Your Fitness
In the first article of this series on “Move More”, I detailed how movement is the master switch for how you age, activating AMPK to support longevity and mTOR to preserve muscle, strength, and healthspan. Now it is time to zoom in on the single most underused tool for building that foundation: Zone 1 and Zone 2 cardio.
What Are the 5 Cardio Zones?
As I outlined in my book Superbodies, there are five primary training zones, ranging from easy to all-out.
Zone 1 – Aerobic base (50-65% of VO2 Max or 50–65% max HR): Easy, steady movement where you can talk in full sentences; this quietly builds cardiac efficiency and endurance.
Zone 2 – Aerobic threshold (66-80% of VO2 Max or ≈65–80% max HR): A strong but sustainable effort where breathing is heavier but controlled; this is where you start to approach lactate buildup without tipping over the edge.
Zone 3 – Aerobic power (81-87% of VO2 Max or >80% max HR): Hard work that pushes heart, lungs, and mitochondria toward their ceiling with shorter intervals of 45-seconds to a few minutes.
Zone 4 – Anaerobic tolerance (88-93% of VO2 Max or >88% of Max Heart Rate): Very hard bouts that create serious burn and train you to tolerate and clear lactate. A common structure is short, maximal bursts with about a 1:3 work to rest ratio.
Zone 5 – Anaerobic power (94-100% of VO2 Max or >93% of Max Heart Rate): Max-intensity sprints with long recoveries, used sparingly to sharpen top-end speed and power. Uses long recoveries of roughly 1:6 work to rest, with total high-intensity time capped to about 6–8 minutes.
Zones 3–5 are absolutely important (especially for athletes), but if you want to improve healthspan, mitochondrial health, and sustainable fitness, Zone 1 and especially Zone 2 are your bread and butter.
Zone 2 Cardio: Why This Heart Rate Zone Is the Key to Longevity
Zone 2 has exploded in popularity because it hits the sweet spot between enough intensity to trigger adaptation and low enough stress to repeat often. Training here:
Builds a deep aerobic base so everything else in your life feels easier – stairs, sports, and even hard workouts.
Enhances metabolic flexibility, teaching your body to switch smoothly between burning fat and carbohydrates.
Zone 1 sits just below this and is even more sustainable and accessible. It’s perfect for beginners, for active recovery, and for people with joint issues or long sedentary histories. Large, pooled analyses show that as little as 150–300 minutes per week of moderate-intensity activity (roughly Zones 1–2) lowers all-cause mortality by 31%, with even greater benefits as you move toward 300–600 minutes per week [1].
The Science: What Zone 2 Does to Your Body
When you cruise in Zone 2, you are creating the ideal internal environment for long-term metabolic health. Consistent Zone 2 work:
Increases mitochondrial density and function (mitochondrial biogenesis), improving your cells’ ability to generate clean energy [2].
Boosts fat oxidation – you literally become better at burning fat as fuel at rest and during exercise [3].
Activates AMPK and PGC‑1α signaling, which support longevity pathways, glucose regulation, and mitochondrial health [4].
Sends powerful myokine signals from contracting skeletal muscle to organs throughout the body, helping regulate metabolism, inflammation, and even brain health.
Zone 2 is not just “easy cardio.” It is cellular training for your metabolic engine.
How to Calculate Your Zone 2 Heart Rate and Start Training
To determine your target heart rate for each zone, start with roughly estimating your max HR using this formula: 220 - your age. This means a 50‑year‑old would have a max HR of 170 bpm with a Zone 1 target of ~85–110 bpm, and a Zone 2 target of ~110–136 bpm.
Examples of Zone 1–2 movement (activities can be done in either zone by adjusting speed, resistance or terrain):
Brisk walking or easy hiking.
Comfortable cycling, steady rowing, or relaxed swimming.
Easy jogging for fitter athletes; gentle run–walk for beginners.
Paddling, casual golf (especially if you carry your clubs or walk the course), and even purposeful housework or yard work when it keeps your heart rate in the right range.
In Zone 1 you should hear your breathing yet still be able to carry on a conversation using normal sentences. In Zone 2, your breathing will be laboured, but you should not be gasping. You should be able to talk, but sentences will be shorter (you would probably not want to deliver a long speech).
How much Zone 1–2 should you do?
If you are a beginner, start with five 15-minute sessions in Zone 1 each week. Build up to at least 150 minutes per week of moderate effort (mix of Zone 1/2) to hit basic health guidelines. This translates to five 30-minute sessions each week.
For optimal cardiometabolic benefits and deeper aerobic development, build toward 240–300 minutes per week (4–5 hours) spread across most days, with a mix of Zone 1 and Zone 2.
As your fitness improves, keep ~80% of your total training time in Zones 1–2, with only 20% in the hard stuff (Zones 3–5). This “polarized” model is how many endurance athletes stay fit and healthy for decades.
Maximizing Zone 1–2 Fat-Burning and Metabolic Benefits
Fueling strategy matters if your goal is fat burning and metabolic health rather than peak performance on a given day.
Doing Zone 2 cardio a fasted state (like an easy morning walk before breakfast) or after a higher‑protein, lower‑carb meal can enhance fat oxidation, nudging your body to rely more on stored fat [3], [5], [6].
Eating carbohydrates right before low‑intensity exercise raises insulin, suppresses lipolysis (fat breakdown), and reduces fat oxidation during the session [7].
For higher‑intensity work (Zones 3–5), carbohydrates become crucial because your body needs readily available glucose and glycogen to hit those efforts safely and effectively. So:
Low‑intensity, fat‑burning work → stick to protein-rich meals beforehand.
High‑intensity, performance work → strategic carbs beforehand and afterward.
Think of Zone 1–2 as the time to train your fat‑burning machinery, and the higher zones as the time to use your carbohydrate rocket fuel.
Your Aerobic Engine Is Your Foundation
By now you can see why Zones 1 and 2 are the quiet heroes of healthspan. Exercising in these zones builds the aerobic engine that powers every other aspect of your life, from climbing stairs to crushing workouts and protecting long‑term metabolic and brain health. In the next article, the focus will shift to how strength training complements this engine by preserving muscle, bone, and power as you age, and why this is particularly important for women entering menopause.
1% TIP: FIND YOUR BEST TIME OF DAY TO EXERCISE
Experiment over the next two weeks: do Zone 1–2 on different days in the morning, midday, and evening, and rate your energy, mood, and sleep after each session. Most people discover a “sweet spot” (often morning or late afternoon) when movement feels easier and gives the biggest boost to focus and well‑being. Once you find your personal best time, protect it in your calendar like any other critical meeting; tiny consistency here compounds into a massive upgrade in your healthspan.
References
[1] H. Arem et al., “Leisure time physical activity and mortality: a detailed pooled analysis of the dose-response relationship.,” JAMA Intern. Med., vol. 175, no. 6, pp. 959–967, Jun. 2015, doi: 10.1001/jamainternmed.2015.0533.
[2] J. N. Cobley, P. R. Moult, J. G. Burniston, J. P. Morton, and G. L. Close, “Exercise improves mitochondrial and redox-regulated stress responses in the elderly: better late than never!,” Biogerontology, vol. 16, no. 2, pp. 249–264, Apr. 2015, doi: 10.1007/s10522-014-9546-8.
[3] C. Laurens, I. de Glisezinski, D. Larrouy, I. Harant, and C. Moro, “Influence of Acute and Chronic Exercise on Abdominal Fat Lipolysis: An Update,” Front. Physiol., vol. Volume 11-2020, 2020, [Online]. Available: https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.575363
[4] K. Vargas-Ortiz, V. Pérez-Vázquez, and M. H. Macías-Cervantes, “Exercise and Sirtuins: A Way to Mitochondrial Health in Skeletal Muscle.,” Int. J. Mol. Sci., vol. 20, no. 11, Jun. 2019, doi: 10.3390/ijms20112717.
[5] E. Liepinsh et al., “Low-intensity exercise stimulates bioenergetics and increases fat oxidation in mitochondria of blood mononuclear cells from sedentary adults.,” Physiol. Rep., vol. 8, no. 12, p. e14489, Jun. 2020, doi: 10.14814/phy2.14489.
[6] S. G. Impey et al., “Leucine-enriched protein feeding does not impair exercise-induced free fatty acid availability and lipid oxidation: beneficial implications for training in carbohydrate-restricted states,” Amino Acids, vol. 47, no. 2, pp. 407–416, 2015, doi: 10.1007/s00726-014-1876-y.
[7] K. De Bock et al., “Effect of training in the fasted state on metabolic responses during exercise with carbohydrate intake,” J. Appl. Physiol., vol. 104, no. 4, pp. 1045–1055, Apr. 2008, doi: 10.1152/japplphysiol.01195.2007.
