How to ride in the heat, you must prepare

From: Kelso, Dr. T.S.
Sent: Wednesday, 2006 June 14 13:49
Subject: RE: ACS Bike-A-Thon

As you prepare for this year's ride, the one thing you certainly don't want to forget about is your nutrition. What you eat and drink before, during, and after the ride (and your training rides) can make a tremendous difference in how enjoyable the ride is and how sore you are afterwards. As I've been preparing for my major cycling events this year (two centuries already and 12 days/880 miles/56,000' starting next week), I've spent a good deal of time researching nutrition as a major part of my preparation. The good news is that current research clearly shows what you need to do--the bad news is that most people simply follow conventional wisdom marketing hype and that is usually far from the mark. During my 2,100+ miles of training already this year, I have noticed a tremendous difference following these guidelines, so if you're interested, read on.

Rule 1: Carbohydrates are your friend

While preparing for and during a ride, carbohydrates provide the fuel you need. Your body needs ATP to drive muscle contraction. ATP is produced through aerobic and anaerobic pathways, but the latter is only effective for very short bursts (8-12 seconds). Carbohydrates are the most efficient way to produce ATP (in fact, fat is only converted for low-intensity exercise and converting muscle protein results in muscle damage and soreness). Your body, however, can only store at *most* about 2 hours of carbohydrates (as glycogen and glucose) at moderate exercise levels. You must replenish your carbohydrate levels during the ride or you will bonk (you'll know it if it happens, as you will have greatly diminished energy levels and mental confusion). The best way to maintain your carbohydrate levels during a ride is through carbohydrate drinks and gels. You should plan to replace at least 25% of your carbohydrates during the ride. If you burn 400 kcal/hr, that's 100 kcal/hr (1 gel) through drinks and gels. I recommend one gel every 45-60 minutes (or about one every 10 miles) to maintain your carbohydrate levels.

Rule 2: Drink before you are thirsty

Don't wait until you're thirsty to drink. By that point, you're already becoming dehydrated. Even small reductions in your body water levels will affect your performance. A drop as small as half a percent (12 oz for a 150-pound person), will put an increased strain on your heart and by the time you get to 4%, you'll suffer reduced muscle strength, reduced fine motor skills, and heat cramps. Physical exhaustion, heat stroke, and coma can happen at 6%. For each 1% loss in body fluid, your heart beats 5-8 bpm faster and pumps less blood. If you think 12 oz is a lot of fluid to lose, consider that a typical person loses 37 oz/hr at moderate exercise intensity in 90-degree weather (typical July day in NJ). You should plan on replacing any lost fluids during the ride. Since everyone is different, you can estimate your own sweat rate (a geeky thing to do) by weighing yourself before and after a ride and keeping track of how much you drink. If you drink 16 oz during an hour ride and you lose one pound, you sweated 32 oz/hr (and should be drinking more). Remember, rates will vary with temperature and humidity, so don't skimp. I recommend establishing a regular drinking rate (I take 3-4 sips every 10 minutes).

Rule 3: Don't forget nutrition once the ride is done

Your body does its rebuilding *after* you stop and it needs the right fuel to do it. Current research shows that timing is critical, too. Failure to fuel between 15 and 30 minutes after the ride (the metabolic window) greatly diminishes your body's ability to fuel its anabolic (muscle-building) processes. By 60 minutes, it's down 40% and after 2 hours it's down by 85%. The result is a build up of the catabolic hormone cortisol which breaks down muscle (which makes you sore) and suppresses the immune system. My experience is that following this rule has almost eliminated post-ride soreness (I was amazed). Details of what you need follow.

Specifics

To get the most out of your fueling, here's what you need: drinks should have a 6-8% solution with 4:1 carbohydrate/protein (actually, branched chain amino acids or BCAAs), along with electrolytes, to speed absorption and retention. Post-ride, your best bet is a 12-15% solution drink with 4:1 carbohydrate/protein (since most people can't eat much right afterwards). You should use your ride drink to get 14-20 oz 30 minutes prior to starting your ride to kick things off. Your pre-ride meal (breakfast for the ACS ride) should be 2-3 hours before starting and avoid fats and protein (yeah, skip the bacon and eggs), as well as fiber.