The following is an add-on to my previous post about workout frequency during the base phase. I’ve received a couple of questions about HR zones and difficulty in being able to reach the specified HR zones during the base phase. The following addresses why this happens and how it should be dealt with:
This is very common toward the end of the base phase due to frequent workouts and an improved aerobic pace. Bottom line is that fatigue of your peripheral system due to workout frequency and accumulated fatigue begin to make zone 1 type efforts feel much harder. If you recover for a few days, the perceived effort at zone 1 will be back to the normal 4 out of 10 range (e.g., for a race). The peripheral system becomes the limiter as it becomes fatigued and the cardiac system becomes more efficient and robust. So, not only are you running faster because of improved stroke volume at a given heart rate, frequent workouts and accumulated fatigue make the peripheral system feel fried. Here’s how to handle the situation if you feel this:
1) During the base phase since almost every single workout is a zone 1 effort, there is no real risk of injury. The whole purpose is to build aerobic capacity and durability. We address these two objectives by:
a. Keeping the same relative workload on the body from a cardiac standpoint, by following your HR zones as fitness improves…..this means a faster pace at the same zone.
b. By pushing to these zones even when feeling fried peripherally which will build durability. This is the exact situation you will face in the IM run. Again, since there are no key intense workouts to be ready for where the objective is to push core systems, and the intensity is relatively low, there is no real risk for injury/burnout.
2) During the build and race phases, since there are key intensity sessions, the objective is to have a very fresh peripheral system going into those workouts in order push previous bests. This is why every workout during the build phase besides the key intensity sessions and long weekend workouts are in zone R. The purpose of the base phase and associated frequent workouts is to improve recovery time and durability in preparation for this build phase. This brings us to the only time you should not force your HR higher into zone: recovery (zone R) workouts. If you feel you need it, feel free to stay below zone in order to be 100% for the key workouts. The best effort key days don’t use HR zones at all. However, if you feel you will not beat previous bests during one of these workouts, back the workout down to a zone R or zone 1 effort. All this means is that your peripheral system is too fried to push on your core system effectively, which is the purpose of the key workout. The purpose of the weekend workouts is again durability and are therefore worth pushing your HR into zone 1/2. To make the whole system work though, the athlete must recover well on recovery days by sticking to zone R or lower, and take care of nutrition/sleep.
Another thing worth noting: in my experience, the folks that stick with their HR zones (zone 1 and 2 when prescribed) no matter what the WHOLE season, make the most progress. If they let it slip for just a couple of workouts (i.e., stay under zones because it feels tough to get up to zone), it can be VERY hard to get it up to the proper range going forward in future workouts, if not impossible. Without a doubt, forcing your HR higher into zone 1/2 when required (during base phase and long weekend workouts), results in the best adaptation with the few exceptions above.