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Nausea?  Causes and
     cures for Biker's Nausea.

Tossing your cookies along the side of the trail? Mountain biking is supposed to be fun, and there are few experiences less fun than spewing half-digested Egg McMuffin among the aspens. Yeah, anybody can catch a stomach virus. But if you frequently feel nausea when biking, read on.

This article will give you the lowdown on Biker's Nausea. You'll learn to diagnose why you feel sick. That's important, because the right treatment depends on what made you nauseated. And you'll learn some strategies for preventing on-trail nausea. 

Let's jump in, with the question Why do I feel sick? I'll divide the causes of Biker's Nausea into three categories: (1) physiologic-stress nausea, (2) metabolic nausea, and (3) gastric nausea. Of course, many times it's not just one thing; it's a combination of causes that makes you hurl.

1. Physiologic-stress Nausea
Scenario:  Your bike has been hanging in the garage all winter and spring. Now some friends have asked you to join them for a cruise on the Wasatch Crest. You're struggling to keep up. Within a half-mile, you're snorting and blowing like a rhino, your legs are already burning, and you feel awful all over. Long before the crest of Puke Hill, you're kneeling down on the edge of the trail, hoping the queasies will pass before you barf in front of the guys. 
The Cause:  This is nausea that's due to abusing your body. You've exceeded its capacity to deal with the work load you're putting on it. Your muscles are screaming for oxygen and your lungs hurt. Many organs and tissues are complaining simultaneously, and the brain responds by turning on the nausea circuits. Nausea is an expected response to severe physiologic stress or pain. It's why heart attack victims feel nauseated, and why you may feel sick after smacking your thumb with a hammer.
The Circumstances:  This nausea usually hits early in the ride, just as you're hitting maximum effort. You usually know you're "pushing beyond the limit" before the nausea starts. It most often happens after a layoff, but overtraining can also make this type of nausea more likely! Other villains: lack of sleep, riding during or after a cold or flu, exercise-induced asthma, and pain.
The Quick Cure:  Take a break. Restart slowly, and cruise gently until you're sweating lightly and fully warmed up. Then gradually pick up the pace. Don't attack as hard as you'd planned, because after the violent exertion, you may also be dealing with a bit of residual "Metabolic Nausea," as discussed below.
Prevention:  For each future ride, warm-up slowly and thoroughly before "going all out." Long-term, train regularly, with your heart rate in the "target zone" that's appropriate for you. Train for aerobic capacity (endurance activity), and for peak effort (intervals).

2. Metabolic Nausea
Scenario:  You had to work a couple of Saturdays and haven't been biking, so it was only natural that you forgot your water bottle. You've mooched a couple of swigs from your biking buddies. Now, 8 miles into the planned 13-mile loop around Gooseberry Mesa, your stomach is upset. Resting eases it a bit, but it won't go away. After your upteenth rest stop in under a mile, you get the dry heaves.
The Cause:  Metabolic nausea is caused by derangement of your body's chemical environment. It can be seen with dehydration, hyperthermia, metabolic acid buildup, ketone buildup, electrolyte derangement, and muscle damage. Basically, the body can't function properly because something's fouled up. Nausea is the result. This is why diabetics who've missed their insulin vomit, and it's why you feel sick at the end of a long brutal ride.
The Circumstances:  This nausea comes on after a period of fairly intense activity, but it usually isn't directly at the peak of activity like physiologic-stress nausea. It's the nausea you get at the end of a long climb, as you're standing around looking at the view. The villians: inadequate hydration, low muscle glycogen, inadequate calorie replacement on long rides, and heat. It's more likely to occur after a layoff, because your enzyme systems may not be prepared to deliver. (Your body recycles anything that's not used regularly. When not exercising, your body doesn't just toss your muscle tissue; it also degrades the enzymes that process and deliver energy to the muscles.)
The Quick Cure:  This type of nausea often responds dramatically to glucose. Down a carbo gel (no, a Powerbar won't work as well). You might think eating while ready to puke is a bad idea, but feeding your muscles and brain is the cure. The nausea will usually disappear within 2 minutes. After the "cookie-tossing-alarm" turns off, tackle the electrolyte drink and get hydrated. When you resume riding, take it easy. If you have acidosis and ketosis, it takes hours for your kidneys to eliminate these nasty chemicals. Push electrolyte fluids for the rest of the day.
Prevention:  Hydrate well before rides. If you take diuretics (water pills) or caffeine you need to pay extra attention to hydration. During the ride, drink at pre-planned intervals -- for example, 4 oz every 15 minutes -- rather than just when you feel thirsty. Avoid alcohol within 24 hours of a ride -- the ugly effects on your metabolism persist long after you're sober. Don't ride hard when dieting. Allow yourself enough calories the evening before the ride so you have adequate muscle glycogen. Fats and proteins release acids when they're metabolized. Go easy on them when riding. If you're riding more than 1 hour, replace at least half of your estimated burned calories with carbohydrates as you ride. If your ride will be longer than 3 hours, eat carbs about every 45 minutes (sports drinks alone don't supply enough calories for these long rides). And again, training makes this type of nausea less likely.

3. Gastric Nausea
Scenario:  You're facing a long grind over Flat Pass, plus the road return. Last time, you bonked bad. So, you need calories. And because Sausage McMuffins are on special today, you eat three. Plus two big coffees, the large OJ, and a Cliff Bar on the way to the trailhead. There's a bit of slosh in your stomach as you grind over the big hill, and a couple of times you taste a bit McMuffin refluxing. On the slickrock climb across the creek, suddenly your whole breakfast is splattering on the sandstone.
The Cause:  Gastric nausea is caused by irritation of the stomach, whether through excess acidity, medication, viruses, stretching of the stomach, or just from food sloshing around. (Try 100 jumping jacks after Thanksgiving Dinner, if you don't believe that sloshing food can make you hurl.) The "slosh" may also draw irritating bile acids from the intestine up into the stomach. As you exercise, blood is diverted away from the stomach to supply your muscles. Processing of food slows, and the stomach lining isn't able to buffer acid as effectively. Once the brain receives the "things aren't going well in here" message from the stomach, it prepares for reverse peristalsis.
The Circumstances:  Big meal before a hard ride -- dumb idea. Both fat and protein delay gastric emptying. Protein stimulates extra acid secretion. The more vigorous the exercise, the more blood is shunted away from the stomach. Users of  alcohol or OTC pain medication may already have irritated stomach linings, and are more prone to gastric nausea.
The Cure:  There's no quick fix for this. Crawl under a tree, take a nap, and let your meal digest. After an hour, saddle up the bike and try again. That's assuming, of course, that you haven't already blown chunks. In that case, you still need to wait a while until your cardiovascular system normalizes, then take it easy. (Nausea slows the heart and drops blood pressure. Vomiting may have messed up your acid-base balance.)
Prevention:  Move your carb-loading to "night-before," rather than "morning-of." Meals before the ride should be small, and mostly carbohydrate. Avoid fats and high-protein foods before a ride. If you're a protein-stuffer, use your protein supplements after the ride, not before. Don't "pre-treat" your biking aches with pain killers like ibuprofen, ketoprofen, or aspirin -- these drugs irritate your stomach lining. And never combine alcohol with biking.

Well, that's the story. But let's repeat the headline:  To avoid biker's nausea, train properly, warm up, hydrate, and eat right.