So a close training buddy and I were chatting many years ago on one of our trips up to the North Country about this common phenomenon in endurance athletics and athletes. The phrase "cumulative fatigue" came up in conversation and I asked him to elaborate on what he meant. Basically what he meant was that this is the residual fatigue of the relentless breaking down of your bodys muscles over time in training for an endurance type event. Even though we take "rest weeks" and train with periodization, we never FULLY recover from weeks past as the season goes on. So what we are left with is a phenomenon that cannot be measured, but still lingers - cumulative fatigue.
So let's shoot an example out there to see how this would affect John Doe Athlete. John is training for an ironman and he's putting in some good hours every week. He typically abides by the traditional 4 week build structure to enable him to do 3 weeks "on" and 1 week "off" of reduced volume. Generally he tracks his progress by total # of workout hours and over the course of the year, will typically start off with 15 hours per week for his "on" weeks and then drop down about 40% when he has a rest week to about 8-9 hours on those rest weeks. John's goal is to work up to a consistent 20-25 hours per week over the course of the season, eventually peaking only a few weeks before he races to ensure that his taper will take effect.
In years past, John previously thought that 15 hours were "maxing" him out and he wasn't able to get much more done in his normal life because of his 40+ hour work week and other committments. This year, John was pretty comfortable with the 15 hour base to start and began his training program at that level with a keen eye on his "Stress Budget" and recovery among other factors. Triathlon Coach Jesse Kropelnicki wrote a solid article a while ago about the potenial "Stress budget" that an athlete has when training for a race. We all know that "life" gets in the way of training and we all have commitments and other things that would keep us occupied when we're not swimming/biking/running. Jesse goes on in the article to define the Stress Budget as "the maximum level of stress that can be added to your system, without it becoming counterproductive"
John realized that his body was able to handle the 15 hour weeks pretty well and he was able to recover properly and then also have a little extra "spare time" to get things done outside of training. John started his training in January for a late summer Ironman. As the season drew on, he was increasing his longer rides and runs inside that 15 hour week and eventually pushing it towards 20 hours and ultimately peaking out at about 25 hours. As this season drew on, John realized that he wasn't feeling peppy and his legs weren't coming back around until later and later in his rest weeks. This is a prime example of cumulative fatigue.
As John's season drew on, he was pouring on the hours and while he was able to handle a 15 hour week with relative ease, when he got to 20, he was getting cramped for time and sacrificing things like rest, down time, and stretching. This creates kind of a snowball effect and as type-A athletes that are incredibly numbers driven, we all want that massive XX hour training week in our logs. So by the time John got up to 25 hours per week, he was feeling pretty smoked and wasn't really recovering to 100% on his rest weeks because he was digging himself into a hole with other training. John might have been able to previously handle one or two 20 hour training weeks, but throw 3-4 of them in a row on top of eachother and week over week, John was feeling rather sluggish and pretty much at the end of his rope.
This is how I explain cumulative fatigue. It happens that when you are doing 3x15 hour training weeks and then you have a rest week, you could probably do that all year and recover fully to 100% after each training block and have no problems at all. But once you start increasing hourage, increasing the stress budget and life gets in the way, you might only recover to 95% after a build, then 90%, then 85%, and maybe as low as 80% of your max. I know my speeds and paces as of late have been a little low because of this. The good thing is though that a solid taper will fix this problem. Taper comes, you reduce volume for a few weeks, rest, recover and your body gets back from the cumulative fatigue that has been plaguing it for the weeks past and you're ready for race day, like a man being shot out of a cannon. A caged animal ready to attack, you're ready to roll.
It's a good feeling to taper and that's a no brainer. You've been trashing your body for a good 8-9 months prior to your race and it's time to let it heal up and get ready. Keep it sharp my friends, watch your stress budget and know that your taper will take effect and you'll be ready to roll when the time comes. Get after it. Cheers!