Glossary Of Terms: from VO2 Max Book

The foundation of your cardiovascular fitness: how well your heart, lungs, and muscles deliver and use oxygen during long, steady efforts. A bigger base means you can walk, hike, or ride farther at a lower heart rate and recover faster afterward. It is built mostly through high-volume, easy Zone 2 training over weeks and months.

See Lactate Threshold.

The effort level where your body starts producing lactate faster than it can clear it, and breathing and fatigue climb quickly. People often call this the “lactate threshold” and use the two terms interchangeably, but strictly there are two thresholds (see Lactate Threshold, LT1 and LT2). Most references to AT mean LT2.

A gradual rise in heart rate during a long, steady effort even though your pace or power hasn’t changed. Heat, dehydration, and accumulating fatigue are the usual causes. On a long Zone 2 session, you may need to slow down slightly to stay in zone, and a lot of drift can mean you need more fluids, cooler conditions, or more base training.

A running-specific measure of the highest power (in watts) you can sustain for a long, hard effort, roughly 30 to 60 minutes depending on the device or platform. It is measured with a wearable power sensor (such as a foot pod or chest strap) and is used to set running training zones by power instead of heart rate. It is the running counterpart of FTP in cycling.

Power is the rate at which you do work, measured in watts. Unlike heart rate, which reflects how your body responds to effort, power measures the effort itself, so it is immediate and not affected by heat, caffeine, or fatigue. Power meters are common in cycling and increasingly in running, but they need extra hardware and are beyond the scope of this book.

The highest average power, in watts, a cyclist can sustain for about one hour. It is usually estimated from a shorter test, such as a 20-minute maximal effort multiplied by 0.95. Cyclists use FTP to set their training zones.

The number of years you live in good health, free from chronic disease and disability, as opposed to lifespan, which is simply how long you live. The goal of longevity training is to keep your healthspan as close to your lifespan as possible so you stay active, independent, and capable into your 70s, 80s, and beyond. Aerobic fitness, strength, and muscle mass are among the strongest modifiable influences on healthspan.

Ranges of heart rate, usually expressed as a percentage of your maximum, that correspond to different training intensities. This book uses a five-zone model:

Other systems use three or seven zones, so check which model a coach, app, or watch is using before comparing numbers.

The highest heart rate you can reach during all-out effort. The common formula, 220 minus your age, is only a rough estimate and can be off by 10 or more beats per minute for an individual. A measured HRmax from a supervised test or a truly maximal effort is far more reliable. Certain medications (especially beta blockers) and heart rhythm conditions can change heart rate response, so check with your doctor before relying on heart rate zones.

Lactate is a normal by-product of energy production that your body constantly makes and clears. As effort rises, two turning points appear:

• LT1 (first threshold): The point where lactate first rises above resting levels. It marks the upper edge of Zone 2. Below it, you can hold a conversation and sustain the effort for hours.
• LT2 (second threshold): The point where lactate climbs rapidly and can no longer be cleared. It sits near the top of Zone 4. Above it, you can hold the effort for only a short time.

A heart rate formula developed by Dr. Phil Maffetone to find your aerobic training ceiling: 180 minus your age, then adjusted for your health and training history (for example, subtract 5 if you’re recovering from illness or injury, or add 5 if you’ve trained consistently for years without problems). It tends to land close to the Zone 2 range for many people, and it offers a simple starting point if you have no lab testing.

A state of persistent physical and mental exhaustion that happens when training stress outpaces your ability to recover. Warning signs include unusual fatigue, declining performance, poor sleep, a raised resting heart rate, low mood, and frequent illness or injury. Short-term overreaching (a hard week followed by rest) is normal and productive. Overtraining is what happens when the rest never comes, and it can take weeks or months to resolve. Older athletes generally need more recovery time, so build rest days into every week.

A subjective rating of how hard you feel you are working, usually on a 0 to 10 scale, where 0 is sitting still and 10 is an all-out maximum. It is a free, useful cross-check on heart rate. Zone 2 usually feels like a 3 to 4: comfortable and sustainable, with you able to speak in full sentences.

The time your muscles, cardiovascular system, and nervous system need to repair and adapt after training. Fitness improves during recovery, not during the workout itself. You are fully recovered when you can complete your next hard session at your normal quality. Recovery needs rise with age, intensity, and life stress, so plan for it as seriously as you plan workouts.

Walking with a weighted backpack. The added load raises your heart rate and muscular demand, which can lift a walk into Zone 2 when walking alone isn’t enough. It also builds leg, hip, and back strength and bone-loading stimulus. Start light and increase gradually to protect your joints and spine.

Online platforms where you can record, analyze, and share workouts. They typically show your route, pace, heart rate, elevation, and training trends over time. See the apps section of this book for recommendations and setup.

Specific intensity ranges that guide how hard you work, defined by heart rate, power, or pace. Training by zone keeps easy days easy and hard days hard, which is the foundation of this book’s approach. See Heart Rate Zones for the five-zone breakdown.

The maximum rate, in milliliters of oxygen per kilogram of body weight per minute (mL/kg/min), at which your body can take in and use oxygen during hard exercise. It is one of the strongest predictors of healthy aging and longevity. VO2 max naturally declines with age, but consistent training can slow that decline substantially. It can be measured in a lab with a gas-analysis mask or estimated using field tests and many wearable devices.

Devices such as smartwatches, chest-strap heart rate monitors, and bike computers that track heart rate, pace, power, sleep, and more. Chest straps are generally more accurate than wrist sensors during exercise. Treat all wearable data as useful trends, not exact measurements.

Training at an easy to moderate effort, below your first lactate threshold (LT1). It improves the number and efficiency of your mitochondria, your fat-burning capacity, and your aerobic base while keeping fatigue low. A practical check is the “talk test”: you can speak in complete sentences, but singing would be difficult.