ME & Z3 Training Impact on Aerobic Capacity

Keith, There are some differences between whether we are talking about unladen zone 3 intensity or ME type work where the HR happens to be in Z3 but I’ll limit the answer here to the conflict between aerobic capacity and ME which is what I think you’re asking. In this case the answer is both. Aerobic capacity can suffer a bit once you start doing hard ME work as you are likely to be doing less total volume of sub AeT work both because you’re replacing a workout and because you may need to do less volume in the day(s) following the ME to allow for adequate recovery. This can be mitigated a bit by doing the ME at a frequency and a load that doesn’t leave you totally debilitated, by cycling on and off of it (not running it all year round), and by still doing a solid volume of AeT work but making some of it more Z1 than Z2 to allow proper recovery. The second part of the answer is yes there is also a conflict between the recovery/compensation pathways between hard ME and aerobic capacity work in a physiological way. This is not perfectly understood but there has been a lot of studies about raised cortisol levels and the conflict between mTOR and AMPK pathways. This is getting pretty deep down the rabbit hole but I think in general they are a little overdramatized. For a well aerobically trained athlete the benefits of a solid block of this ME type work greatly outweighs any very slight erosion of aerobic capacity for mountaineering. The two real pitfalls in my mind are 1) doing way to much high intensity work and then getting way less sub AeT volume in which of course will cause you to lose aerobic fitness and 2) training in a way that is greater than your overall recovery ability can handle leading to over training. A hard ME session about 1X per week in the right phase is really helpful to most athletes but it isn’t a more is better kind of thing which is where folks can get into trouble.