Precious Blood Mo \ I'm a Full Grown Fetus

Fetal suckling.

One important misconception around Substrate utilization during exercise is that during low exercise intensities you don’t use CHO as your energy is derived from fat... When I started performing fat and CHO oxidation assessments in 2005, I was quite surprised by the amount of CHO oxidized (“burned”) even at low exercise intensities. During rest, CHO contribution to total energy expenditure is ~40% while FAT is ~60%. As exercise intensity increases, CHO contribution increases as well and by your Zone2 intensity, you are normally already burning slightly more CHO than FAT. At your Zone 3, your fat oxidation declines significantly and at your Zone 4, fat oxidation normally disappears (see picture 2- "the metabolic map"). Picture 1 is data that we presented at ACSM back in 2008. Check that at even low exercise intensities, you oxidize CHO and that at FATmax point you can oxidize ~2-2.5g/min. This is one of the reasons why if we ride at our zone 2 for 4h and don’t eat, you can eventually bonk. When I started to see these numbers in 2005, I perceived that the current guidelines those days calling for 35-55g/h of CHO were quite low and then I proposed and started to use 80-100g/h, although I was highly criticized by most back then… Picture 2 shows what I called “the metabolic map” trying to describe different metabolic “events” at different exercise intensities in relation also with muscle fiber recruitment. It is a very simplified version of exercise metabolism but I found through many talks and conferences over the years, that it is useful to many. Picture 3 is the original figure of the “Crossover Concept” by George Brooks and Mercier where Fat and CHO oxidations are expressed in % of VO2max. You can also see that even at low exercise intensities (50-60% of VO2max), CHO is significantly utilized by muscle. As an important point for this misconception, graphs haven’t helped as the visual seems that there is more FAT oxidation than CHO at low exercise intensities. At FATmax point, FAT oxidation can be generally ~0.3-0.7 (depending on fitness level). However, CHO oxidation at FATmax can be 2-2.5g/min which is still higher than FAToxidation although in the graphs it sits below… Hope this helps 😉

How will your kids remember daily "Dad Time" — the mornings, lunches, evenings, and bedtimes when you are with them? Will these be remembered as simply those brief pauses between work, in which you were distracted, anxious, busy, and in a hurry to get back to your to-do list? Or will these be remembered as the most important parts of your day — those moments when you turned your full attention, curiosity, and love to those people for whom you are working?