Our bodies have 3 energy systems that power everything we do, from simply keeping our heart pumping to keep us alive, to ripping it in a bike race. First, we have the ATP/pcr system (phosphocreatine) which is a relatively small amount of energy stored in the muscle and used for very hard efforts only lasting a few seconds. Next, we have the Glycolytic system, which utilizes carbohydrates for relatively short, high-intensity efforts, lasting up to about 90 seconds, and finally, there is the body's preferred energy system, the Aerobic, or "with oxygen", system that runs on fat, carbohydrate, and sometimes protein to power anything longer than about 90 seconds or so. Note that all 3 systems are always working just in different proportions based on energy demand. The extent to which each of these energy systems contributes to the overall is based on duration, intensity, and energy demand.
We use training zones to more precisely target each of these systems and to produce the desired training effect based on the demands of your race. All of the "classic" power zones are based on a percentage of your Functional Threshold Power (FTP) or the maximum power you can sustain for around 30-60 minutes, in order to individualize it to your unique physiology. We discuss each of the zones below including the percentage of FTP, how it feels, and the desired training effect.
Zone 1: Active Recovery
This is the easiest power zone, where the goal is to increase blood flow and help muscles recover from previous rides. Power output should stay below 55% of your functional threshold power (FTP), and the pace should be easy and conversational.
Zone 2: Endurance (Extensive Endurance)
This zone is focused on building endurance and increasing your body's ability to use fat as a fuel source. Power output should stay between 55-75% of your FTP, and the pace should be steady and comfortable.
Zone 3: Tempo (Intensive Indurance)
In this zone, you'll be pushing yourself to improve your endurance and increase your lactate threshold. Power output should stay between 75-90% of your FTP, and the pace should be challenging but sustainable for long periods of time.
Zone 4:Functional Threshold Power
This zone is where you'll be working to improve your lactate threshold, which is the point at which lactic acid starts to accumulate in your muscles. Power output should stay between 90-105% of your FTP, and the pace should be fast but sustainable for short periods of time.
Zone 5: VO2 Max
In this zone, you'll be working to improve your body's ability to use oxygen, which is an important factor in cycling performance. Power output should stay between 105-120% of your FTP, and the pace should be very fast and challenging.
Zone 6: Anaerobic Capacity
This zone is focused on improving your ability to perform high-intensity efforts, such as sprints or hill climbs. Power output should stay above 120% of your FTP, and the pace should be all-out and unsustainable for more than a few minutes.
Zone 7: Neuromuscular Power
This is the highest power zone, where the goal is to improve your power and explosiveness. This zone is typically only used for short, all-out efforts, such as sprints.
It is important to note that the power zones are not absolute and could vary depending on the individual's physical condition and fitness level. It is also important to note that it is always recommended to consult with a healthcare professional and a coach before attempting any training program. Additionally, it is important to note that FTP is a relative measure that can be improved over time.