Thanks for the input on slow-release carbs.
I found a very good web site that describes contractile muscle energetics. It particular, it describes short-term (a few minutes) and long-term (still less than a hour) utilization of energy sources via a combination of aerobic and anaerobic reactions.
http://www.physiol.arizona.edu/PSIO201/fal...notes/lec26.pdfCourse notes, Intro Physiology, SH Wright.
I also found web site that provides a chart showing a direct comparison of a few categories of muscle exertion and the energetics (and time scale) involved.
http://faculty.washington.edu/kepeter/118/.../ms-perform.htmAgain, class notes, very nicely prepared, for a Human Phys course (Karen Petersen, Dept of Biology Univ WA).
You're right Loki - for a normal person, weight lifting exertion energetics is mainly driven by
creatine phosphokinase activity and anaerobic glycolysis, with a lesser amount of energy coming from fatty acid.
Why I brought up this topic...
If you're insulin resistant (I am, that's one of the reasons that I started a strength training program),
glucose transport and uptake is impaired.
Creatine utilization may also be impaired. That means that a higher than typical supply of muscle energy for sustained effort has to come from fatty acid oxidation in mitrochondia. Recent research in IR has hinted that fatty acid transport and utilization from lipid pools may be impaired in IR patients.
Citation: Insulin can enhance GLUT4 gene expression in 3T3-F442A cells and this effect is mimicked by vanadate but counteracted by cAMP and high glucose--potential implications for insulin resistance. Yu ZW, Buren J, Enerback S, Nilsson E, Samuelsson L, Eriksson JW. Biochim Biophys Acta. 2001 Feb 14;1535(2):174-85
The second citation below also suggests that central hyperinsulinemia predominates during the first hour of exercise, followed by peripheral tissue insulin insensitivity caused by exercise-induced release of
fatty acids.
Citations: Effects of Free
Fatty Acids (FFA) on Glucose Metabolism: Significance for Insulin Resistance and Type 2 Diabetes. Boden G.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgiSuppression of endogenous glucose production by mild hyperinsulinemia during exercise is determined predominantly by portal venous insulin. Camacho RC, Pencek RR, Lacy DB, James FD, Wasserman DH. Diabetes. 2004 Feb;53(2):285-93.
Simple starches (high glycemic carbs) are known to induce higher serum insulin and glucose concentrations and to keep them elevated longer in both normal and insulin insensitive individuals when compared to similar carb loads of complex (slow hydrolyzing or slow release) starches.
Citation: Postprandial carbohydrate metabolism in healthy subjects and those with type 2 diabetes fed starches with slow and rapid hydrolysis rates determined in vitro.
Seal CJ, Daly ME, Thomas LC, Bal W, Birkett AM, Jeffcoat R, Mathers JC. Br J Nutr. 2003 Nov;90(5):853-64.
This IR leads to a real problem during training: I can't do regular carbs as a primary source of energy during exercise, am mildly tolerant of slow release carbs (mostly veggies, flaxseed), and probably don't have a very good secondary source of energy from fatty acid oxidation.
Along with a reduced carb diet (slow-release carbs only), I have been using alpha-lipoic acid and
taurine to try to normalize muscle energetics (assuming that I am producing adequate amounts of insulin. I also use vanadyl sulfate and Cr GTF to restore insulin sensitivity.
It't like walking a very narrow fence - too much carb reduction coupled with increased insulin sensitivity can lead to hypoglycemia, and converse insulin insensitivity from some carbs also leads to impaired glucose utilization.
How best to supplement carbs while trying to manage insulin and fatty acid pools?