Introduction
Base building is essential for every cyclist, but it’s not a one-size-fits-all process. The key lies in understanding your unique recovery capacity and using metrics like VO2Max, TSS, CTL, ATL, and TSB to guide your training. By focusing on steady progress and balancing training with recovery, you can build a base that supports long-term performance and enjoyment on the bike. Building your aerobic base is a cornerstone of cycling success, laying the foundation for endurance, efficiency, and sustained power. However, the journey to a strong base comes with a critical challenge: balancing training with recovery. Overtraining is a real risk that can derail progress and lead to fatigue, injury, or burnout.
This article explores how to build your base effectively, focusing on individualized training loads tailored to your recovery capacity and current fitness. We’ll also introduce metrics like Functional Threshold Power (FTP), Training Stress Score (TSS), and VO2max to help guide your progress. For a deeper dive, check out my blog posts on Aerobic Base Building and Overtraining.
What Is Base Training and Why Is It Important?
Aerobic Base Defined: The aerobic base is your body’s ability to generate energy efficiently for extended periods. It forms the foundation for long rides, sustained efforts, your ability to recover from anaerobic efforts and, in general, your ability to recover, period. The stronger your aerobic system, the better your base.
Why It Matters: A strong aerobic base improves glycogen sparing (save glucose for more anaerobic efforts), reduces fatigue, and enhances recovery. It also supports high-intensity efforts during races or events as it is when you are riding below your FTP when anaerobic capacity is being restored. It is your aerobic system that is clearing lactate and removing CO2.
Common Pitfalls: Without proper planning, base training can lead to overtraining, where recovery lags behind your training load. This is a crucial understanding. Do not fall into the 'more is better' trap. Instead, try to absorb the lessons of this article and realize the best approach is seeking the 'Minimal Effective Dose.'(MED) Exercise is the dose. This MED is one that will produce the desired adaptation- improved fitness - while also reducing the risk of overtraining.
Understanding Training Load
Training Stress Score (TSS): Quantifies effort based on percentage of Functional Threshold Power (FTP) and duration. Higher TSS indicates a more challenging workout. A simplified version of TSS was created by Dr. Bannister many years ago. Users of heart rate only training may benefit from quantifying their TRIMPS (training impulses) using this system. 1 point for each minute in HR zone 1, 2 points for each minute in HR Z2 and so on up to HR Z5. The total TRIMP for any single workout is the total. CHRONIC TRIMPS and ACUTE TRIMPS and TRIMP STRESS BALANCE can be quantified using the definition below, which are used for TSS and convert them to be used with TRIMPS.
Chronic Training Load (CTL): A 42-day rolling average of daily TSS, representing your long-term training adaptations. Some people consider this their 'fitness' but this is an oversimplification of a more complex training variable. I like athletes to consider that their CTL indicates what they are used to doing over the last 6 weeks. An example of why this may be important is time off. Let's say you usually have your CTL at 70 and you have maintained this CTL level for 6 months. Then you are forced to take some time off or at least back down for a month due to personal or professional obligations. Your CTL drops to 38. Some of the guidelines I am about to discuss would tell you to not do a long ride more than 3.5 times your CTL. In this case 38 x 3.5 = 133 TSS. The issue is that just a month ago 133 TSS was less than 2 times CTL. In some ways you are still that ride. So, I am pointing this out to highlight there are nuances to consider in all scenarios. I will provide some guidelines but there are nuances.
Acute Training Load (ATL): A 7-day rolling average of daily TSS, indicating short-term training stress. When applying progressive overload, as when doing a training block, ATL will be higher than CTL. This is training load being applied in a progressive manner. It should NOT be applied too aggressively. You should avoid increasing CTL with high ATL by more than 7 points per week. I would highly recommend avoiding an increase and 7 points in two successive weeks. This usually ends poorly.
Training Stress Balance (TSB): The mathematical difference between CTL and ATL, showing readiness. Positive TSB suggests you’re fresh; negative TSB indicates fatigue. So, in the case above, where you are in a training block and ATL is higher than CTL your TSB will decrease. The opposite is true during recovery periods. You will see ATL drop below CTL and therefore TSB will increase and you will freshen.
Why Recovery Matters
Individual Recovery Capacity: Recovery varies by cyclist and depends on factors like your current CTL, your level of development, your fitness level (how high is your VO2max), sleep, nutrition, and stress.
VO2max and METmax: Benchmarks of aerobic capacity. Cyclists with higher VO2max typically recover faster and can handle greater training loads. Note: to convert VO2max numbers to METmax numbers divide your VO2max by 3.5. So, a VO2max of 35 ml/kg/min is 10 METmax.
Balancing ATL and CTL: Sustainable progress requires a delicate balance. Too much TSS and increasing ATL too much or too quickly without recovery leads to overtraining, while too little fails to stimulate growth. Below you can see a chart showing that those with higher fitness (METmax in this case) are more resilient to Training Stress UNITS in this case. You need to take this into account when planning your training ‘what is progressive overload to me' if you are to avoid a load that promotes overtraining and all its ramifications. Progressive overloads are optimal for adaptation but all doses must be balanced with appropriate recovery if the dose is to be effective. Too little dose and fitness is lost, too much and you risk the serious ramifications of overtraining including burnout, immune system flare ups, overuse injuries and worse.
Metrics to Monitor for Optimal Loading
VO2max/METmax: These metrics gauge your aerobic engine and provide context for your training load capacity. See my website for information on the difference between METmax and VO2max. It is subtle but may be useful. To define Weekly Training Loads for my patients I use MET-hours/week.
TSS, CTL, ATL, and TSB: Use platforms like TrainingPeaks to monitor these metrics. Aim for steady increases in CTL while keeping TSB in a manageable range. At the end of recovery weeks, which I plan for my athletes every third or fourth week, I try to see their TSB become positive (+3 to -2) and during the training blocks it is negative, representing the loading, in the range of -2 to as low as -25. I do NOT like to go beyond this unless we are challenging them for short periods such as at a training camp. NOTE: At training camp my athletes do accumulate deep TSB holes but they are also not handling the normal stressors of life. They are not working; they do not have to deal with other life responsibilities and so on. This helps to increase the possibilities for recovery. After camp a significant recovery period is usually planned. I often see TSBs in the negative 50 range after a camp.
Signs of Overtraining: Fatigue, poor sleep, mood changes, and declining performance. Performance fails to improve despite recovery. Adjust training if these appear. I have other recommendations on this subject. Read more about recognizing and avoiding overtraining in my blog post here.
Practical Tips for Cyclists
Weekly Base-Building Plan: Include steady-state rides and recovery days. Example:
1 long endurance ride. These are easier in intensity, 60-70% of FTP, HR zones 1-2 (TSS can be up to 3 and for very fit individuals up to 4 times current CTL)
2 tempo rides. These are rides of shorter duration but slightly higher intensity than endurance rides. 80-90% of FTP. HR Zones 2-3 and some Z4 can be seen. (TSS is for these rides are more in line with current CTL and slightly above up to 1.5 times current CTL)
2 Aerobic challenge rides. These rides challenge the upper end of your aerobic threshold (not to be confused with VO2max). This is the threshold of aerobic steady state metabolism. Many refer to this as HR Z2 training. This is accomplished in HR Z2 if you have your HR zones correct. You should be able to pass the talk test when doing HR Z2. 70-80% of FTP is the range. (TSS for these rides should be 1.5 times current CTL).
1 active recovery ride. These are short and very light intensity rides. HR Z1 and less than 60% of FTP. (TSS should be no more than half of current CTL level)
I would recommend one day of complete rest for those with lower VO2max or new to the sport. For those with higher VO2max, many years within the sport and higher race categories adding a 3rd aerobic challenge workout is how I would increase the overall load.
Not mentioned but alternative is resistance training.
Recovery Strategies: Prioritize sleep, nutrition, and hydration including electrolytes. Use tools like foam rollers or massage for muscle recovery.
Heart Rate and Power Data: Cross-check perceived exertion with heart rate and power output to ensure you stay in the aerobic zone. There are many nuances regarding the use of these metrics, including PE to tell you about your training status. Unfortunately, these are beyond the scope of this article.
Case Studies or Example
Case Study: A recreational cyclist aiming for a century ride builds their base over 12 weeks. Starting with a CTL of 30, they progressively increase their CTL to 60 (3 TSS/week for 12 weeks) while maintaining a TSB of -15 to +5. By monitoring TSS the document a VO2max improvement, they avoid overtraining and achieve their goal efficiently.
Case Study #2: A recreational cyclist planned to do well in the Base-Building Challenge his club has created. Previously, he has been basically off his bike for a few weeks due to colder and the inclement weather, but he plans to increase his fitness over the next 12 weeks of the challenge. Starting with a CTL of 30, they progressively increase their training load to do well in the challenge and improve their fitness. Over the first 8 weeks they increase their CTL to 75 (5.6 TSS/week for 8 weeks). During this time, they did not take a recovery week. Their TSB quickly became negative and stayed negative for the entire 8 weeks reaching a low of -60 TSB when he suddenly developed an upper respiratory infection. His doctor prescribed antibiotics. He began the antibiotics and began to feel better. After 5 days he tried to get back on the bike. This made his symptoms return and lengthened their recovery. By the time they were able to get back to training consistently their CTL had dropped back down to 45 CTL. Their VO2max was only slightly above where it was at baseline. This athlete did not read my article on base building, overtraining or my article about Training with Illness.
Conclusion
For further reading, explore my blog posts on Aerobic Base Building and Overtraining for actionable insights.