Increase cardio

Why cardiovascular fitness predicts how long you live

VO2max, the maximum rate at which your body uses oxygen during intense exercise, is the single strongest predictor of all-cause mortality. It outperforms smoking, hypertension, and diabetes as a risk factor ^[1]. An overview of 26 meta-analyses covering over 20.9 million observations found that each 1-MET increase in cardiorespiratory fitness was associated with an 11-17% reduction in all-cause mortality ^[2]. Moving from the bottom 25th percentile to above-average fitness cuts mortality risk by roughly 50%, regardless of age, sex, or ethnicity ^[3]. Each unit increase in VO2max has been linked to a 45-day increase in life expectancy. This isn't about running marathons. It's about building the aerobic engine that powers every system in your body, from brain function to immune defense.

Zone 2 training: the aerobic base that matters most

Zone 2 exercise, performed at an intensity where conversation is possible but requires effort, targets the mitochondrial machinery of slow-twitch muscle fibers. Fat oxidation peaks here, and mitochondrial biogenesis is stimulated through upregulation of PGC-1alpha. A 2025 narrative review confirmed that zone 2 training activates signaling pathways for mitochondrial adaptation, though higher intensities may be needed to maximize cardiometabolic gains ^[4]. Zone 2 also lowers resting heart rate, improves parasympathetic tone, and reduces blood pressure over time.

For most people, zone 2 corresponds to 60-70% of maximum heart rate or a blood lactate level around 2 mmol/L. Aim for 150-180 minutes per week across 3-4 sessions. Cycling, jogging, rowing, or brisk walking all work. The point is consistency, not heroic effort. These sessions should feel sustainable.

High-intensity interval training (HIIT) for VO2max

While zone 2 builds the foundation, HIIT develops the upper ceiling of cardiovascular capacity. Intervals of 3-8 minutes at 85-95% of max heart rate, alternated with equal recovery periods, challenge the heart's stroke volume and the muscles' oxygen extraction ability. Norwegian 4x4 intervals (4 minutes hard, 3 minutes easy, repeated 4 times) are among the most studied protocols for VO2max improvement. Endurance training produces eccentric left ventricular hypertrophy with LV mass increases of 15-25%, while HIIT can boost VO2max by 20-30% ^[9].

One to two HIIT sessions per week is enough for most people. More than that without an adequate zone 2 base raises injury risk and cortisol load without proportional returns.

Cardio, aging, and cellular protection

Cardiovascular exercise does more than strengthen the heart. A 2025 meta-analysis found that individuals with VO2max values at or above the 70th percentile had significantly longer telomeres, the protective chromosome caps that shorten with age ^[5]. Moderate training volumes were sufficient; extreme endurance wasn't needed. A separate 30-year prospective study of over 116,000 adults showed that those meeting physical activity guidelines (150-300 min/week moderate or 75-150 min/week vigorous) had 19-31% lower cardiovascular mortality ^[6]. Even 15 minutes of daily exercise reduced all-cause mortality by 14%, with each additional 15 minutes cutting risk by a further 4% ^[7].

Why fitness matters more than body weight

A 2025 systematic review and meta-analysis in the British Journal of Sports Medicine found that fit individuals had no increased mortality regardless of BMI, while unfit individuals faced 2-3x higher mortality risk across all weight categories ^[8]. This finding is worth repeating: being fit and overweight carries less risk than being thin and sedentary. Cardiorespiratory fitness independently attenuates the health risks of excess body weight.

Combining cardio with strength training

Cardio alone isn't the full picture. Research consistently shows that combining aerobic training with 2 or more weekly strength sessions produces the best longevity outcomes. A study in the British Journal of Sports Medicine found that engaging in both moderate-to-vigorous aerobic exercise and resistance training reduced mortality risk by 24-34%. For adults over 50, pairing 150 minutes of zone 2 cardio with two full-body strength sessions improved both VO2max and insulin sensitivity within 8 weeks ^[10]. The optimal weekly structure for longevity: 3-4 zone 2 sessions (45-60 minutes each), 1 HIIT session, and 2-3 strength training sessions.

Heart rate training zones explained

• Zone 1 (50-60% max HR): Active recovery and warm-up. Enhances blood flow without significant stress.
• Zone 2 (60-70% max HR): Aerobic base building. Fat oxidation, mitochondrial development.
• Zone 3 (70-80% max HR): Tempo or threshold. Improves lactate clearance.
• Zone 4 (80-90% max HR): VO2max intervals. Maximum cardiac output development.
• Zone 5 (90-100% max HR): Anaerobic sprints. Neuromuscular power, used sparingly.

Building a cardio program for longevity

A practical weekly plan: three zone 2 sessions of 45-60 minutes, one HIIT session of 20-30 minutes, and at least two strength training days. Track resting heart rate over weeks as a simple marker of cardiovascular adaptation. A declining trend means improved cardiac efficiency. Annual or biannual VO2max testing gives the most accurate picture of progress. Most people can improve their VO2max by 15-20% within 2-3 months of structured training. Cardiovascular fitness supports everything else: better sleep, sharper cognition, improved fat metabolism, and greater stress resilience.