Posts in the category Nutrition

Physiology and Nutrition: Dealing with the Heat

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Summer’s hot. And as you get hot, your performance drops. Here’s the how and why, and how to keep your cool.

Human temperature regulation processes maintain a core body temperature over a very narrow functional range despite elevated metabolic rates and exposure to very hot environments. During submaximal exercise, we can limit the effects of the increased heat production through sweating and evaporative cooling. But as intensity climbs, our ability to offload heat becomes limited; in conjunction with a hot/humid environment; we are most likely going to experience hyperthermia. Technically, heat stress and hyperthermia are the overarching umbrella terms for heat illness (heat exhaustion, heat stroke), and are identified as an elevated body temperature due to failed thermoregulation that occurs when the body produces or absorbs more heat than it can dissipate.

During exercise in the heat, the most significant physiological burden is supporting blood flow to the skin: high skin blood flow is needed for heat dissipation. (The average blood volume of an adult male is ~5 liters, and the average female ~4.4 liters, not much to go around!). We often think of a high core temperature as being the limiting factor for performance; eg the “critical core temperature”, but it is more the temperature of the skin that affects aerobic performance. Skin temperature is highly influenced by the ambient temperature and humidity, whereas the core temperature is influenced by the intensity of the exercise (which is partially why a power decline is seen with elevated internal temperatures). Warmer skin induces a greater amount of skin blood flow, decreasing blood volume available for circulation. For example, with a sustained elevated core temperature, an increase in skin temperature will have a concomitant increase in heart rate but the reverse is also true- cooling the skin even with a sustained elevated core temperature will reduce heart rate due to more blood shunting back into circulation(1).

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GU Brew Sports Drink Gets Nekkid & Fruity

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Last summer, GU reformulated their Brew sports drink to have a bit lighter carbohydrate load and improved electrolyte profile. Now, for summer 2014, they’re adding four new flavors, including the unflavor Tastefully Nude. It’s joined by Lemon Tea, Watermelon and Blueberry Pomegranate.

The new formulation has 70 calories and 19 grams of carbohydrates per serving, with 250mg of sodium and 30mg of potassium in all but the Blueberry Pomegranate, which bumps up to 500mg of sodium. Carbs come from maltodextrin and fructose in a 50-50 balance.

The entire line uses a lighter flavor profile since everything tastes sweeter and stronger during hard exercise, and the new options help prevent “flavor fatigue”. Brew comes in 24-serving canisters ($20) and single-serve packets ($1.50).

Must Watch: Forget Gels, Corn Dogs For the Win

Bikerumor reader Peter Koch found inspiration in the video above, which lovingly shows Team Sky’s rice cake fuel in the warm, fuzzy glow that only Rapha pulls off. His parody, embedded after the break, was shot with SF Composite High School mountain bike team riders and is pure awesome.

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Trailside Review – Bearded Brothers Raw, Natural Real Food Energy Bars

Bearded Brothers raw vegan real food nutritional energy bars review

While the brand name may not conjure up images of delicious food, Bearded Brothers’ raw, 100% natural and vegan friendly bars are, in fact, quite delicious.

They’re made from real, whole foods like dates, almonds and other nuts, dried peaches, coconut, cocoa, chia seeds, cinnamon and more, most being organic. The texture’s lightly moist, and satisfyingly hefty such that you need to give it a few noshes before swallowing, but not so thick or dry it needs immediate chasing with water. You can let the flavor linger a bit and enjoy.

Four flavors -Blueberry Vanilla, Ginger Peach, Maca Chocolate and Coconut Mango- are made in small batches in Austin, TX, using raw, vegan, 100% natural ingredients that are free of gluten and soy. Each 20z bar packs roughly 240 calories. Check below for ingredients lists and mini review…

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Physiology and Nutrition: Why Not Gels, Part 2

biol-3-1-3It seems I hit a nerve with my last post on “Why No Gels”.  There is a nuance to be highlighted with regards to performance nutrition: the separation of fatigue due to a drop in blood volume and fatigue due to a lack of carbohydrate.  This Part 2 will focus on the basic physiology to give insight on Part 1 (as well as some solutions!)

Open any exercise physiology textbook and the first factor of fatigue is a drop in blood volume, with the second factor of fatigue decreased carbohydrate availability. Why? Simplistically, you can rectify low circulating carbohydrate pretty effectively by eating something and feeling the effects within minutes. A drop in blood volume is more complex, and it takes hours to rectify (as it involves the kidney regulatory hormones aldosterone and arginine vasopressin).

Blood volume is the red cells and plasma in circulation. When discussing exercise and fluid shifts, the term “plasma volume” is often used, as this refers to the watery component of blood. With the onset of exercise, there is a shift of blood flow to supply the working muscles and to the skin, to divert the increased heat produced (from muscular contraction). With the increased demand for blood to the muscles and skin, there is hypoperfusion of other organs, including hypoperfusion of the GI system.

As exercise continues and plasma volume is lost through sweating, breathing, and gastrointestinal water usage, available circulating blood diminishes (there is less overall water in the blood, thus it is “thicker”).  An endurance athlete will feel the drop in blood volume as “muscle fatigue”. As the viscosity of blood increases, the competition between the skin and muscles becomes fiercer; with the skin winning over muscle perfusion.  Heat is a large threat to the body, the actual window of survival core temperature perturbation is quite narrow: 37-39.5°C (98.6-103.1ºF – Athletes often push themselves to a core temperature of 40°C before true adverse effects of heat stress are seen.). As heat storage of the body increases and more blood is shunted to the skin, there is less blood for muscle metabolism- nature’s purpose: shut down the threat. By this, I mean, less blood for muscle metabolism means fewer contractions, thus less heat produced (the temperate of the muscle itself contributes to fatigue as well by denaturing the contractile proteins). This is muscle fatigue – a drop in power. In a traditional mentality, this is when an athlete will typically reach for a gel or other quick hit of carbohydrate, thinking they are low in carbohydrate; but it is water deficit of the blood that forces the fatigue.

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New Honey Stinger Gels and Waffle Add Delicious Options, Caffeine

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If you’re a believer in gels for your athletic performance, Honey Stinger has some new options for you – especially if it’s caffeine you crave. Starting with their organic tapioca syrup and organic honey base, the new Strawberry Kiwi and reformulated Chocolate gels offer the same electrolytes and natural flavors of their other gels, just with a little boost. Harnessing the natural power of green tea extract, each gel pack manages to carry 32mg of caffeine which should be plenty to keep you going.

Honey Stinger received a small shipment of the new gels, but they’re expected to go fast, with 24 gels retailing for $33.36 on their web store. However, more gels are on the way along with a brand new waffle flavor…

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Rebuttal: Why Athletes Should Use Gels

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Editor’s Note: Last month’s Physiology & Nutrition post, OSMO co-founder Stacy Sims’ regular column, discussed why she thinks gels are a poor choice for fueling endurance athletes. It’s a good read and generated a lot of comments and questions. It also piqued the interest of several brands known for their gels, one of which sent a rebuttal. As did one of the Peaks Coaching coaches, which serves as their column for this month. Both responses are posted below unedited, as was Sims’ post. 

As an introduction and a little background, we’ve interviewed Sims when OSMO launched. We’ve also interviewed Allen Lim when he launched Skratch and asked similar questions. Then, in preparation for last year’s TSEpic, I interviewed Sims again about food choices. That post has a primer about why solids work when gels may not, which was one of the common questions in the comments. And Sims has already prepared Part 2 of “Why No Gels” which expands on that. Look for it this Friday. In the meantime, here are a few counterpoints to the original.

Dear Bikerumor,

My name is Magda Boulet. I have been a pro athlete since 1997, training and competing with GU product for 17 years now. As the VP of Innovation and R&D at GU Energy Labs, I work closely with athletes of all walks of life who train and compete with gels every day at the highest competitive level. Understanding fueling strategies is essential to my long lasting success as an Olympic distance runner.

As an athlete, a scientist, and a consumer, I am passionate about formulating products and delivering research that are supported by experts in the scientific community and validated by athletes in the field. Having said this, I was disappointed to read the recently published article on “Why Not Gels?” in which the author misrepresented scientific facts and concluded that gels are “the most detrimental fuel sources for performance.”

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GU Energy Launches New Chocolate Peanut Butter Gel and Black Cherry Chomps

Chocolate Peanut Butter GU GivesHot on the heels of last years popular Salted Caramel Gel, the new Chocolate Peanut Butter Gel flavor packs the soul of Reese’s Peanut Butter candy in a performance boosting package – complete with 125 mg of sodium, 60 mg of Potassium, and electrolytes.

In addition to giving you a boost, a part of each sale goes towards funding important charities like the Challenged Athletes Foundation.

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Nutrition Roundup: New Treats from CarboRocket, Skout, PowerCrunch, Movit, Powerbar & Sly Fox

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CarboRocket’s Rehab brings a rapid fire recovery formula in two versions, one with Whey and the other a vegan-friendly Pea Protein.

The Chocolate Coconut (whey), shown, is absolutely delicious and a welcome blend of flavors compared to standard chocolate. The coconut flavor comes from dried coconut water and is subtle but refreshing. The recovery part comes from 15g protein (14g for the Pea Protein’s Cappuccino flavor) and 40g of glucose per serving, plus 5g glutamine and 4g BCAA’s. By using straight glucose, the formula moves through your tummy quickly and causes the insulin response you want to drive the nutrients into your muscles. They’re all natural, gluten free and mixes very easily. And the chocolate coconut flavor is really, really tasty…one of my new favorites. Retail is $44 for a 16-serving canister.

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