Pez: The cycling popular press and coaching programs have most cyclists thinking about five zones of training intensities as being gospel, with Zone 1 being dead easy recovery, 2 = aerobic or endurance, 3 = sub-threshold, 4 = lactate threshold, and 5 = anaerobic. Yet you told us that you prefer simplifying physiological terms and reducing the number of intensity zones to three. Can you elaborate?
A.L.: There is still great scientific debate about how to define “anaerobic” or “lactate threshold,” making it very imprecise and vague when you try to define it for athletes. Here are generally the terms I prefer using and what intensities they correspond to:
Zone 1: ‘low intensity’, i.e., below 70%VO2max (or about 70%HRmax)
Zone 2: ‘moderate intensity, i.e., between 70 and 90%VO2max (or 70-90%HRmax)
Zone 3: ‘high intensity’, i.e., above 90%HRmax/VO2max
Compared to the 5 zones, I think the good thing of this model, is that it simplifies things for use by athletes actually exercising in the field, although it obviously has scientific limitations. I have many troubles myself understanding the meaning of the nomenclature used in the 5-zone model (i.e., ‘aerobic’, ‘anaerobic’, etc). What does this mean? Not much, physiologically (in my opinion). I think just low, moderate and hard is easier for everybody. Besides, with things like cardiac drift (especially at high temperatures and/or with dehydration) happening over the course of exercise, it is not so difficult to have one’s HR jump from zone 3 to 4 or from zone 4 to 5 without really a concomitant change in metabolic pathways. The 3-zone model is more conservative and simple.
The limits between Zone 1 and 2 and Zone 2 and 3 are the ventilatory and the respiratory compensation threshold, respectively (or the lactate threshold and the OBLA). The latter variables are controversial from a physiological point of view, but they can be easily determined during a ramp cycle-ergometer test. This makes it quite easy to define the limits of these different zones. In contrast, I don’t really see the physiological basis behind the four limits of the 5-zone model (i.e., there is no ‘magic point’ after which we switch to anaerobic metabolism, etc).
The “Heart” of the Matter
Talking with Dr. Lucia, I get the sense that most of us have swung from one extreme of riding by “feel” to the other extreme of becoming robotic slaves to our heart rate or power monitors and ignoring our inner sensations. Remember that, while they certainly have their advantages, their biggest role are as tools to help you understand your body and get in tune with how it feels and responds to different efforts. Every so often, be brave enough to ditch your high-tech geek toys and do your workout by how your body feels. Or as Obi-Wan once told Luke, “Close your eyes and use the Force!”
Stephen Cheung is an Associate Professor of Kinesiology at Dalhousie University in Halifax, Nova Scotia, Canada, with a research specialty in the effects of thermal stress on human physiology and performance. He has been an avid roadie since beginning university in the mid-eighties, and still has non-indexed downtube shifters on his winter bike and wool jerseys hanging in his closet. He can be reached for advice or comments at firstname.lastname@example.org