Review of Knuiman et al. 2015

Knuiman, P., M.T.E. Hopman, and M. Mensink. 2015. Glycogen availability and skeletal muscle adaptations with endurance and resistance exercise. Nutrition and Metabolism 12:59.

There isn't anything special about this article by Pim Knuiman and collaborators, but at some point I printed out a copy and read it because I thought it would be useful. It's a review article. It starts with background on what effect starting exercise with low amounts of stored glycogen (while fasting, weight loss diets, or just many hours since a meal) had on muscle adaptations following the exercise. In endurance exercise, studies have shown that mitochondrial biogenesis increases to a greater degree in this condition, but only when glycogen is only mildly depleated.

Also in the background material I found some interesting facts about the distribution of glycogen within muscle. There is glycogen stored within the sarcomeres (5-15%), within the myofibrils (5-15%), and between the myofibrils (75%). Each location uses the glycogen to fuel different molecular processes.

I learned that in general, moderate intensity endurance exercise (30-65% VO2 peak) is predominantly fueled by fat, whereas exercise exceeding that degree of intensity is fueled more by carbohydrate. I had heard that before, but somehow in my mind I reversed it until reading it again here. An interesting note is that this is just a general rule, and that well-trained individuals will have different abilities to use fat and carbs at different levels; they have "greater metabolic flexibility."

The article later addressed resistance exercise and confirmed the general rule that exercise + protein ingestion = muscle hypertrophy. This is not as true for endurance exercise, only because the protein gain (which is real) is simply replacing the protein lost during the exercise (known as the "interference effect"). In any case, protein consumption with a small amount of carbohydrate is important following exercise of all kinds, either to increase or simply maintain muscle mass, strength, and efficiency.

There is a general understanding that when one does both endurance and resistance exercises in one day, the endurance exercise should be conducted in the morning at a somewhat depleted glycogen state, and the resistance exercise should take place in the afternoon (since depletion wasn't shown to be important), followed by a high-protein meal.

Yearly totals for 2018

2018 fitness totals: 103 miles of swimming (2% higher than my yearly average), 503 miles of running (52% higher than my yearly average), and 1,740 miles of biking (44% higher than my yearly average). You know, Ironman training does that. My plans for 2019 include my Masters Swim meets, a half-marathon in May, a 150-mile bike ride in June, a sprint triathlon in August, and a full marathon in September.

 

 

 

March 2018 update

One week from now my competitive swim season will be over. I'm excited. But I'll still swim each week for triathlon season! Here are my March totals: Swimming 12 miles + Cycling 97 miles + Running 38 miles = 148 miles. This total is about 20% less than last month, but that's ok. My bike's been in the shop and my foot's been sore. Gotta take care of those things to make way for a big spring.

Pull-ups

I don't do a lot of pull-ups, for three reasons. First, it's hard to do them at home because I can't find a doorway tall enough to get my feet off the floor. Second, I don't want to do them anywhere else because it's embarrassing that I can't do that many at a time. Third, I end up hurting myself. It turns out I was trying somewhat hard to improve during the year 2010. Here is a graph showing my (lack of) progress.