Cardio for Longevity: The Science of Zone 2 and 5 Training

Optimal cardiovascular fitness combines Zone 2 training (60-70% HRmax) with strategic Zone 5 sprints (>90% HRmax), creating a powerful synergy for longevity. Research confirms cardiorespiratory fitness strongly predicts mortality, with higher CRF linked to reduced disease risk. For maximum benefits, experts recommend maintaining 7,000-10,000 daily steps while dedicating 80% of cardio to Zone 2 and 20% to high-intensity intervals.

Cardiovascular Fitness and Mortality

Cardiorespiratory fitness (CRF) refers to the ability of the cardiovascular and respiratory systems to work in sync to supply oxygen to the working muscles. Higher CRF fitness is associated with better physical health and reflects how well the lungs, heart, and circulatory system work together. It dictates endurance, stamina, metabolism, and reduces the risk of chronic diseases.

Poor cardiovascular function is primarily a result of sedentary lifestyle. The data shows CRF to be a strong predictive factor for mortality. Low CRF is one of the strongest long-term indicators of both CVD and non-CVD related mortality. (1) (2) (3) Higher CRF means greater performance, linked to lower risk of mortality and chronic diseases. (4) Men and women who met WHO guidelines for physical activity had 7% and 11% lower risk for CVD, respectively, than those who didn’t. (5)

Doing intense cardio exercise, whether aerobic or anaerobic, stimulates positive adaptations in the way the circulatory system works. It increases stroke volume, (6) reduces blood pressure, (7) and improves circulation. (8) This profoundly impacts exercise performance, increasing endurance, speed, and stamina.

Since the ability to endure higher intensity dictates one of the strongest predictors of mortality – CRF, it’s worth giving cardio a shot for a longer and higher quality life.

The Science of Zone 2 Training

Zone 2 cardio is aerobic training at 60/65–70% of maximal heart rate (HRmax), focusing on fat oxidation, mitochondrial function, and lactate clearance. It involves cyclical activities like cycling, swimming, or running, sustained just below the aerobic threshold.

Compared to LISS, Zone 2 training requires precise monitoring to maintain intensity in the specific range. It’s the highest exertion level that’s purely aerobic, creating energy via oxidative phosphorylation, stimulating mitochondria function. Beyond its use in endurance sports, it’s relevant for longevity due to its effects on heart health, energy levels, and fat loss.

The body becomes more efficient at transporting oxygen and creating energy, the aerobic way. This facilitates recovery, improves aerobic function, and supports heart health. (9) (10)

Zone 2 training provides specific benefits, including

• Heart Health → adaptations in cardiovascular function such as increased stroke volume, reduced resting heart rate, improved lipid profile, and increased blood flow. (11) (8) (7)
• Metabolic Health → improved metabolic function by stimulating fat metabolism, decreasing reliance on carbs. (12) Additionally, zone 2 cardio can improve glucose stability, insulin sensitivity, and HbA1c levels. (13) (14) (15)
• Weight Loss → zone 2 training can contribute to net energy loss and is effective in reducing fat % (16) (14) as low-intensity (at 60-70%) is precisely the range in which the body burns fats.

Zone 2 intensity corresponds to daily function. It’s the range in which we move, training the systems to become more efficient at it, supporting our function. Walking up the stairs, carrying groceries, cycling to work – are all close to zone 2.

The Science of Zone 5 Training

Zone 5 cardio is high-intensity training performed at 90–100% HRmax, (17) (18) aimed at boosting VO₂ max, heart capacity, and anaerobic performance. It’s the (near) maximal sprinting one does when running from a lion, running upstairs to catch a flight, or skiing on the Alps.

The body is challenged to a significant degree, resulting in various metabolic and cardiac adaptations which make zone 5 the central interest of longevity experts. Training at Zone 5 involves working at 95–120% of VO₂ max, with energy demands relying heavily on anaerobic metabolism, leading to elevated lactate levels.

Due to its high intensity, it can only be sustained for 30 seconds to 4 minutes at 9–10/10 effort. Zone 5 training is therefore best incorporated into interval sessions, alternating with active recovery at a low intensity. This combination allows effective recovery and higher work volume in Z5.

The advantages of Zone 5 encompass

Longevity experts continuously support zone 5 training, due to its time-efficiency and metabolic effect. While it’s not the fundamental piece to cardio, neglecting it isn’t the smartest idea. Preparing the body at high intensities occasionally stimulates profound changes that improve glucose utilization, energy creation, and heart capacity. Sprint. You may need it.

The Synergy of Zone 2 and Zone 5

The reason combining both zone 2 and zone 5 training is optimal for longevity is because that’s where most of life happens.

While there are some benefits of training in the in-between zones of Z3 and Z4, these are mostly geared towards athletes training for a specific outcome. The normal person wouldn’t get as much by training lactate tolerance, if they’d never use it.

Zone 2 cardio is the basic, fundamental step to building endurance. It’s where most of daily activities happen. Hiking up, playing with your kids, walking the dog in the park is all zone 2. By improving aerobic endurance, we create the base that gives us the energy to keep moving in life.

That being said, neglecting zone 5 training is not a smart idea. Just as one needs the fundamental aspects of endurance, one needs the occasional sprints to stimulate anaerobic adaptations. Training both the aerobic (Z2) and the anaerobic (Z5) system makes one multi-functional.

Zone 5 cardio trains the body to be able to handle intense bursts of effort, translating into practical advantages in moments that require strength, speed, or explosiveness. Think about sprinting to catch a bus, dashing after your dog when they slip, or powering through a volleyball game on the beach. Z5 pushes your limits up, building physical toughness and mental grit, while elevating your VO2max.

Optimal Cardio Protocol for Longevity

There are four parts of movement one needs to take care of for optimal health and longevity

• 7,000 – 10,000 steps daily: represents an active, non-sedentary lifestyle
• NEAT activity: moving around to efficiently burn extra calories with zero recovery cost; part of the active lifestyle
• Zone 2 Cardio: the base of endurance, heart function, mitochondria, and aerobic energy creation.
• Zone 5 Cardio: training the body to push through high, anaerobic intensity when demands occur.

Once both high-step count (7,000-10,000 steps) and NEAT activity are taken care of, the fundamental base of activity is good. Next step is focusing on training the body to become more capable at maintaining real cardio, which comes with unique advantages.

The proper ratio for zone 2 to zone 5 cardio is debatable. Ideally, many experts recommend it should be close to 4:1. This means 80% of cardio work volume is spent in zone 2, leaving ~20% for HIIT or Zone 5 training.

Volume: about 90-200 minutes spent in zone 2, and about 10-45 minutes spent in HIIT (in-and-out of zone 5).

Frequency: 1-2 longer zone 2 sessions (60-120 minutes) at 60-70% HRmax, and 1-2 shorter HIIT sessions (9-25 minutes) alternating between intense work (>90% HRmax) and active recovery (<60% HRmax).

Weekly example of close-to-optimal cardio training for longevity

There are multiple variations of cardio one can engage in, including running, cycling, swimming, rowing, ski-erg, or jumping rope. Zone 2 is relatively fixed, being a repetitive activity determined by duration and intensity. Zone 5 can include short sprints, short intervals, or longer intervals. *learn more.

This is just a simple example. There are various cardio training modalities, options, and structures to choose from. Treat it as an average guideline, comprising what the research and most experts suggest is close-to-optimal cardio for health, performance, and longevity.