Wednesday, April 14, 2010

Thursday WOD - Glucose vs Fructose


(AMRAP in 2 minutes) X 5 of:
10 Pushups
10 Situps
10 Squats

2:00 Rest in between efforts

Focus on speed, going all out during efforts. (WOD=Workout Of the Day; AMRAP=As Many Rounds/reps As Possible)
Post times to comments.

Hey guys! We've been invited to come train at my buddy's CrossFit gym, Stoneway CrossFit! We'll have to take a bus down there and back (unless you want to run, haha), and we'll try to do it at around 4:30 like normal. We'll all meet at Terry-Lander, the bus stop in front has a route right by Stoneway CF. I'd like all of you to get ahold of me either on facebook or my email ( and tell me all days you're available to do it.

Glucose vs Fructose

Different types of carbohydrate you consume will have different effects on your body hormonally, and it is important to know what these differences are, so you can make informed decisions in your nutrition and training. In short, sweet potatoes, yams, and other root vegetables/tubers(potatoes are not a root veggie, they are a nightshade) are a better choice for carbohydrate than fruit. This is because glucose better fills muscle glycogen, and retains insulin sensitivity than does fructose. Keep in mind that we should be eating a large amount of non-starchy vegetables as the majority source of carbs.

All carbohydrate is digested, absorbed, and then either used as energy, stored as glycogen, or stored as fat. Storage of fat typically happens only once the body's glycogen stores are topped off. Glycogen has two main storage sites, the liver, and the skeletal muscles.

Glucose and fructose are two sugars found very commonly in the diet. Fructose is commonly found in high amounts in fruit, and also makes up half of the mass in table sugar, the other half is glucose. Glucose is found in varying amounts in many carbohydrate sources, including fruit, vegetables(small amounts). The most concentrated form of glucose however, is in starch, which composes the majority of the carbohydrate content in potatoes, grains, and root vegetables like yams and sweet potatoes(that's right, potatoes are not a root vegetable, they're a 'nightshade'. Sweet potatoes aren't in the same family as potatoes, despite the name). Starch is made up of long strings of glucose molecules.

Glucose is the form which our body uses(also called blood sugar), and there is a certain level of glucose constantly circulating in our bodies. Our bodies keep this level within a very tight range because bad stuff happens when our blood sugar gets out of control, including damage to the blood vessels, and in extreme cases, medical emergencies. Insulin and glucagon play the two key roles in blood sugar regulation. Glucose itself, or from the breakdown of starch molecules, can be transported directly into the bloodstream to be used by the cells of the body.

Fructose must be first converted to glucose in the liver, before it can be used by the body. This is why it has a low glycemic index, which would usually be good, but in this case, is deceiving. Because fructose is broken down in the liver, it replenishes liver glycogen preferentially, rather than muscle glycogen.

The majority of our insulin sensitivity is based upon our liver glycogen levels. The problem with fructose is that by replenishing liver glycogen preferentially, much of our insulin sensitivity is lost. So less fuel is stored in the muscles and we become less insulin sensitive, two bad things for an athlete.

Liver glycogen can be both created and broken down to maintain blood sugar levels. Muscle glycogen, however can only be created, then used locally in the muscle. So, by eating foods like root veggies and tubers, that are still nutritionally dense(better than just a glucose drink), and have starch as their main energy component, we can optimally refuel our muscles, while preserving insulin sensitivity.

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