Rest Periods Between Intervals Does Not Affect Performance Adaptations
First day back running after last Saturday nights mysterious left knee strain while running hill laps on Sleeper. I could still feel the knee a bit, which prevented me from opening up my stride. However, it was only a minor ache (and also mysteriously, it has switched from the outside middle of the left knee to the lower inside of the knee), so I was able to enjoy the fantastic temps. Did 9 miles and 1,500' of gain in 1:21. Seems like the knee will be fine after another day or so, which is exciting as February is when I start "ramping" things up and "getting after it."
A new article has just been published, which is fairly interesting. I've never really thought much of the "rest period" between intervals in terms of time. I know there are many coaches and philosophies surrounding intervals, the length (both distance and time) the interval should be, and also the period of time between interval efforts. However, despite this, I've always focused on the interval itself, and just sort of doubled the interval time/length and used that as the rest period. Well, I guess the rest period time is highly contentious, with some arguing that it must be a specific time/distance based on the interval workout, while others argue it matters little. Thankfully, we now have some science to help answer this question and settle any debates. It turns out, at least based on this (one) study, that the rest period time matters little when looking at the performance adaptations one receives from interval training. Published in Experimental Physiology, the authors found that the rest period between interval efforts among 12 highly trained women did not affect the performance adaptations that resulted from the interval training, namely improvements in muscle Na+,K+-ATPase content, PCr resynthesis and VO2max. Na+,K+-ATPase is highly complex, but basically it is a sodium-potassium pump that is found in all cells and is essential for properly working cells (you can find out more here) and thus any athletic endeavor. PCr resynthesis (again, highly complex) basically acts as a high energy reserve and is crucial in any speed type of effort. Finally, VO2max is fairly well known and understood. So, it seems that all of these things benefit from interval training, but the period of rest between the intervals matters little (up to 3 minutes of rest between interval efforts; the study did not address longer rest periods). For me, the take home message is that interval or speed training is essential, but whether I need only 1 minute between efforts (feeling good that day) or 3 minutes between efforts (feeling tired that day) will not affect the overall benefits of the training session. This is good news, as it is the effort put forth during the interval, and not how you feel during the rest period, that matters. Put 100% into the interval. If you need to take a bit longer to be able to put in another 100% effort, take it. It won't negatively affect the performance adaptations, and may even positively affect them as it will allow you to give a real 100% each interval.