There are several ways to measure intensity in cycling, each with its own advantages and disadvantages. Here are three commonly used methods:

1. Power: Power is the direct measure of output and is measured in watts. It represents the actual work produced to move yourself and the bike forward. One of the main advantages of power measurement is that the feedback is instantaneous, providing real-time information on your current power output. It is also an objective measure that is not influenced by external factors like heart rate. However, power meters can be expensive.
2. Heart Rate: Heart rate is a valuable measure, especially in the absence of a power meter. It is measured in beats per minute (bpm). While heart rate provides useful information, it has some limitations. It takes time for the heart rate to stabilize, usually around three minutes. High-intensity workouts with short intervals may not reflect accurate heart rate responses. Additionally, heart rate can be affected by various external factors such as caffeine, hydration, weather, temperature, and recovery status.
3. RPE (Rate of Perceived Exertion): RPE is a subjective measure that relies on your perception of effort during exercise. It is typically measured using a 10-point scale, with 1 being very easy and 10 being maximum exertion. RPE can be useful, especially for experienced endurance athletes. It provides a holistic understanding of the effort level, considering factors like heart rate, breathing, muscle fatigue, and overall sensations. RPE can be a good alternative when power or heart rate data is not available.

Determining Training Zones and FTP (Functional Threshold Power):

Training zones are often based on the concept of FTP, which is the maximum power output you can sustain for one hour. Here’s a general overview of the training zones based on FTP:

1. Zone 1 – Active Recovery: Less than 55% of FTP or 68% of the functional threshold heart rate. This zone is used for cooldowns, rest between intervals, early parts of warm-ups, and active recovery rides.
2. Zone 2 – Aerobic Riding/Endurance: Below 75% of FTP or 83% of the functional threshold heart rate. This zone is used for long, steady, aerobic workouts to build endurance.
3. Zone 3 – Tempo: This zone is around the aerobic threshold, still below the anaerobic threshold or FTP. It typically ranges from 76-90% of FTP. It is used for longer tempo intervals and race-specific workouts.
4. Zone 4 – Threshold: This zone is defined as 90-105% of FTP. It is used for threshold intervals to increase your FTP. It can include workouts like 6-10 minute intervals or over-under intervals.
5. Zone 5 – VO2max / Maximum Aerobic Capacity: This zone ranges from 105-120% of FTP. It is used for short, high-intensity intervals to improve your maximum aerobic capacity. Workouts in this zone are typically shorter and very intense.
6. Zone 6 – Max Effort / Anaerobic Capacity: This zone is characterized by maximum effort and ranges beyond 106% of the functional threshold heart rate. It is used for short all-out efforts, such as 30-second sprints.

When planning your training, different combinations of these zones can be used based on your goals, training volume, and the number of cycling sessions per week. The selection of specific zones depends on the desired training stimulus and the adaptation you aim to achieve.

It’s important to note that these guidelines are based on general principles, and individual variations and specific training programs may deviate from them. Consulting with a coach or sports specialist can provide personalized guidance for your cycling training.