Fitness Fatigue vs. Extraordinary Fatigue Part 1

Before I get into the story of my long run and lessons I learned from it, I want to make sure you don’t get distracted by the distances I am running, as if this is too long (or too short) to apply to your situation. I am telling the story in order to describe two levels of fatigue and their costs, and these apply to you no matter how far or how fast you move because the boundary between those two are set by your current fitness level. 

 

A Long Tiring Run

I’ve had a good 3+ month stretch of run training. It took a couple months of patient base-building before I felt my body naturally rise to a new level of strength and become eager to increase weekly mileage and intensity. I started adding speed work without any alarms of strain and I started doing longer runs once every 2 weeks, gradually increasing distance each time if my body was responding well, which it has. Two weeks ago I did a 16 mile run in the mountains, with over 3000 feet of elevation gain. This time I was aiming for 18 miles on the road with maybe 2000 feet of elevation gain. I have also been doing time-restricted eating for several months – currently I eat within an 8-hour window, only between 11 am and 7pm each day, which has felt wonderful. I run in the mornings  which means all runs are done in a fasted state. When I do these long runs I bring along something to nibble on after an hour if I feel like it, but I can usually go 2 hours before I do. When I am going to run for more than 2 hours, I will start nibbling about an hour into it, so that some new calories are available an hour later when I need them.

On this run yesterday, starting at home I ran to the hills west of town where I spent most of the time climbing or descending. I made it to the 10 mile mark farthest from home and my route home would have been just over 8 miles from there. But there on the highest point I decided to go down and back up another steep side road to rack up some more elevation gain, which also added 3 more to my estimated total mileage. I figured that, on the way home if I felt like I had enough, I could just stop running after 18 miles and walk the rest of the way home. But if the body was doing OK I could go farther and just see what happens as an experiment. 

And that is what happened. By 16 miles my body was more tired than I felt at this point 2 weeks ago. That run was almost entirely on dirt trails. This run was almost entirely on paved road (I try to run on the gravel shoulders where ever possible) so I expected the cumulative impact on my body to be greater though the elevation gain would be less. Yet my form remained very good and I had no sore spots or warning signs that any particular area was at risk of injury or giving up on me. 

As I approached 18 miles I debated whether I should stop and stick to my plan or go farther to see what happens. The fatigue was fairly strong – and I could feel the siren song in my psyche to just stop and walk – why not? I made my 18 mile goal after all. But there were no specific hurting spots, my form remained very good, the discomfort was high but holding steady, and I was maintaining an equanimous emotional state. So I kept going over 2 miles more, making it nearly all the way home. 

However, in those final 2 miles, as I kept paying attention to what my body was doing and saying, I sensed that the urge to stop was connected to another warning system, the one that monitors the internal resources for action. My body was obeying my will to keep going but I imagined it was dipping more deeply into energy reserves to do so, and that the deeper it dipped in the higher the price I would have to pay in recovery. The discomfort was not increasing in overall intensity, but I noticed the quality of it was changing. When the effort crosses some sort of line and the body dips into that reserve, I know that the recovery process afterward will become more difficult and take longer. The more convincing clue that I had crossed a line was that I started to feel slightly faint in my head, like I was very slowly drifting toward a black out – a sign that though my muscles might continue to burn fat from the body, the brain needed glucose and I had depleted that completely, despite the nibbling I had done during the run. I just didn’t feel like eating much, especially while running up and down hills.

A Deeper Debt

I walked the half mile home and then began hydrating and eating. But my lower body now was crying out to stop all moving, to stop standing even, and this was more than it usually demands after a tough run. I ended up laying down for a couple hours to rest my tired brain and my tired body – the brain was glad to shut off for an hour or so but the lower body was so fatigued and uncomfortable that it wouldn’t allow me to drift off to real sleep. My body was having more difficulty than usual to repair and replenish the systems. 

A day later, there are still no tight, sore or strained body parts, but the depth of fatigue in my body is still greater than normal. My emotional response is positive and eager to run again, so that let’s me know there was no mental injury from the effort. But this was a useful experiment to confirm and reinforce my approach to training. My objective has been to train in a way to gradually expand my fitness range so that I can run (or swim) long distances in challenging terrain and do so without being injured or completely wiped out by it. I want to be fit enough that I don’t have to go into long-term debt to enjoy extended exploration of less traveled trails and roads. 

For this run, I voluntarily went a little ways into that kind of extraordinary fatigue, into that deeper debt that I don’t think is a good idea for us to go into normally, despite the fact that it seems popular in endurance athletics to do so.

In the second part I offer the analysis and lessons learned which will apply to any of you, though you may go for much shorter distances.

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