I noticed that fatigue increases significantly in colder weather and this is reflected sharply in the graphs, unlike in warmer weather. This made me wonder: why is this happening?
TSS does measure load based on the cardiovascular response of the body (e.g., heart rate or power), but it doesn’t account for a number of other factors that can affect well-being and recovery.
Cardiac fatigue and TSS: TSS is focused on the load placed on the cardiovascular system, so it primarily tracks how the heart is handling the stress. This is helpful for avoiding overloading the heart, but it doesn’t always give a full picture of the body’s condition. For example, TSS might not reflect the fatigue of other systems.
Nervous system fatigue: The nervous system is also under strain, and if it becomes overburdened, it can affect recovery, even if TSS shows a “normal” reading. Nervous fatigue often manifests not in heart rate metrics but in emotional or mental fatigue. This is an important factor for recovery that TSS doesn’t account for.
Muscle fatigue: Muscle fatigue is another key factor. For example, when the external temperature drops, muscles start working less efficiently and fatigue more quickly. TSS doesn’t take this into account because it doesn’t measure how effectively your muscles are functioning in cold weather or other stressors. Your heart rate may stay the same, but your muscles will tire faster.
Post-illness recovery: When you’ve been sick and are recovering, your body hasn’t fully returned to its usual state. Recovery occurs at different levels: nervous system, immune system, tissues, etc. This doesn’t always show up immediately in heart rate data, and TSS can’t account for this recovery process either.
Thus, while TSS is a useful tool for tracking cardiovascular load, for a more complete picture, it’s important to consider other factors like nervous system recovery, muscle fatigue, emotional state, and external conditions (temperature, humidity, etc.). It’s also useful to track subjective feelings, fatigue levels, and sleep quality to make more informed decisions about your training loads.
Knowing about potential discrepancies between the calculations and reality, you’ll be able to approach your training and recovery process more effectively.
Subjective feelings should be considered mandatory!
TSS and anything related is after all only capturing a small percentage of your total life-style. Someone working out 14 hours a week, captures just 8%…
Anything in your daily life has effect on recovery, stress, fatigue…
Sleep, nutrition, work-stress, etc, all influence the ability of your body to recover and cope with the total load you’re putting on it.
BTW: I would like to correct you on some of the subjects of your post.
TSS is not a metric describing cardiovascular response, or at least, that was not the intent
TSS is a metric for ‘work done’ and saw the light when Power Meters became available. It just tells you how much work you’ve delivered relative to FTP. It’s what’s called an ‘external measure’ because it gives you an idea of the work done regardless of HR. Unlike HR, TSS from power, gives you a very consistent measure of the work you’ve done. It’s a ‘true’ measurement, not influenced by heat/hydration/fatigue/elevation…
Before Power meters became available, HR was used as a measure of intensity. HR is an ‘internal measure’ and gives you an idea of how your body reacts when subjected to a certain power load. Before the whole power thing, load was estimated from HR and was called TRIMP, Training Impulse. HR does give you an idea of cardiovascular load and by following up the trend of both HR and Power, you can follow up on fitness. Two workouts with the same HR intensity do not necessarily result in the same TSS from power because the ‘work done’ for the same internal load will depend on your fitness, fatigue, condition,…
At this moment there are a number of models/algorithms that try to derive ‘load’ (as we know it from TSS) from HR by calibrating the TRIMP to TSS. But this will always be an estimate and hide some of the information that you will get when having both Power and HR.
Because TSS tracks your effort based on load, which doesn’t as you note match the total potential impact on your body. I’ve sometimes felt fine when my fagitue should be off the charts based on load and vice versa felt sore after an intense session with low fatigue scores. The Session RPE can be much more interesting and is something intervals.icu can already provide: valuable Session-RPE Method for Training Load Monitoring: Validity, Ecological Usefulness, and Influencing Factors - PMC
Something I’ve learned about life in general is that improvement not only comes from optimizing your objective function but by doing so without it being at the expense of your constraint functions.
So your TSS should be used as a function to optimize but it’s only one function in a multivariable optimization problem to predict a “state of fitness” that matches your goals. There are many states of fitness and defining that state is the first step. A track sprint’s fitness is not the same as a multi-day stage racer.
I’ve been cycling for several years, and over this time, I’ve noticed an interesting pattern that’s been bothering me, especially during the cold season. I have a regular 50 km route that I ride consistently. In the summer, I cover it at a speed of about 30 km/h, and there’s almost no fatigue, especially if I’ve properly warmed up before. However, as soon as the cold weather hits, for instance, when the temperature drops near zero, I experience significant fatigue, even when riding at a speed of 15-17 km/h.
What’s interesting is that in the summer, when I get tired, the fatigue accumulates normally and gradually. But in winter, the feeling of fatigue often passes faster — sometimes after just one day of recovery, I feel much better.
I dress warmly, I’m not cold and don’t feel chilled, but despite this, the fatigue feels much stronger than in the summer. During the summer, I can ride longer distances, even 100 km, without experiencing the same fatigue issues that arise in winter.
Here are a few things I think might be contributing to this:
Thermoregulation: In colder weather, our bodies spend more energy to maintain body temperature. Even if I don’t feel cold, this process could put additional strain on my body.
Muscle Efficiency: In the cold, muscles work less efficiently and tire more quickly. Even though I dress warmly, muscles likely lose flexibility and don’t adapt as quickly to the load.
Oxygen in the Air: It’s possible that the oxygen content in the air changes in cold weather, which may reduce the body’s aerobic capacity.
Hydration: I’ve noticed that I don’t feel as thirsty in winter, but maintaining hydration is still critical for recovery.
I’d like to understand what might be causing this. Has anyone else experienced something similar and can share insights or tips on what else I should consider under these conditions?
Are you primarely mouth breathing or nose breathing?
You may have over sensitive airways that constrict when the cold air hits them.
Nose breathing lengthens the path and inhaled air can warm up a bit more before it gets to the lungs.
I don’t think this problem concerns only me. In fact, I haven’t seen cyclists who can maintain high speeds in such temperatures. Obviously, low temperatures affect everyone, and even the most well-trained athletes feel much more fatigue in these conditions. I believe it’s more about the overall environmental factors, such as the temperature, and not just the breathing
I would recommend looking at an app like HRV4Training and see what changes there are to your training load effects. Found this to be accurate and shows when to go back to training, how your are dealing with getting back after illness and when you are overtraining.
With regards ot the differences between fatigue and recovery. I am assuming you are in a European country and the difference is due ot the road surface as to why its harder or esier on the body. Since oyur speed difference is so drastic, this is either your are grinding the gears with little traction on the roads. On the recovery time, since you live in a colder climate you may not be heat adapted and therefore you lose more salts in the summer from sweating so you don’t replenish them as quickly like in winter. Supplementing this would tell you if that is the factor affecting you in the recovery time differences.
Thank you very much for your feedback and thoughtful suggestions! I really appreciate your attention to this issue.
However, after further consideration, I think the main factor affecting my fatigue might be the oxygen levels, rather than the road conditions or electrolytes. I’ve noticed that the recovery time seems to be much faster when I’m training in colder conditions, and I believe this is related to how oxygen is available to the body in these temperatures.
I will definitely look into HRV4Training as you suggested, and I appreciate the tip. However, for now, I’m focusing on how the body reacts to oxygen availability in different conditions. I hope to continue investigating this and find a clearer understanding soon.
Exactly, and the difference between 20° and 0° is negligible.
Altitude is much more impacting because pressure diminishes and the same volume of air at lower pressure has less molecules of everything.
