Trail Intake for Longer Trails
Why worry about eating on the trails? Can’t you just have a big meal afterwards? As you hike, you use your body’s fat, muscle tissue and stored carbohydrate (called “glycogen”) as fuel. A body can keep exercising on fat and muscle tissue alone but once the stored carbohydrate runs out
• the pace you can maintain drops dramatically
• coordination decreases
• you get light headed or dizzy and possibly grumpy.
• Among American athletes, this collection of symptoms is known as ‘bonking’.
Bonking on the trail makes you dangerous to yourself and your travel companions.
Glycogen is stored in your muscles and liver. The amount you can store depends on how fit you are. While you have enough fat and muscle to keep you going, slowly, for days, even the best-trained individuals can store enough glycogen to support only about an hour of exercise at lactate threshold (right on the edge of heavy breathing), or perhaps six hours of easy trailing. High altitude or low temperatures increase the use of carbohydrate and speed the depletion of glycogen.
The Gut Sets the Upper Limit
Food must be digested in your stomach and intestine before it can be absorbed into the blood and delivered to the muscles. The harder you trail, and the higher the altitude the less blood goes to the gut and the more digestion slows down. That’s one reason people get nauseated if they eat while exercising vigorously.
Fit individuals develop the ability to continue digestion and absorption of food at higher exercise intensities compared to sedentary people, but even in the fittest people the rate of possible absorption is lower than the rate of carbohydrate use during hard exercising, or during moderate exercise at altitude.
• For a large, fit athlete, the upper limit of absorption is ~350 Calories per hour, versus a possible fuel utilization rate of ~1000 Calories per hour.
• For small but athletic adults, the upper limit could be as low as 175 Calories per hour, versus a maximum steady expenditure of ~500 Calories per hour. During high intensity exercise, the rate of carbohydrate utilization will always be higher than the maximum possible rate of absorption so stored carbohydrate will eventually run out.
If you are trailing hard, no matter the sport, enough to need a mountaineers step for instance, glycogen depletion limits endurance no matter how much you eat. Eating a dense source of carbohydrates while exercising can delay fatigue for some time. At lower trailing intensities, you can absorb enough carbohydrate to keep exercising indefinitely, or until something else slows you down.
Taking/ during breaks on the trail to eat allows your gut time to absorb food while your muscles aren’t using it and you can replenish glycogen stores and extend you range for the day.
Carbohydrate Amounts?
Your body has enough stored fat and protein to fuel any one-day hike. Eating them while trailing won’t help keep you strong. On multiday hikes in extreme conditions, you’ll need fat and protein for recovery and to maintain your body weight as you burn fat and muscle as fuel day after day. Of the three macronutrients (protein, fat and carbohydrate) only consumed carbohydrate keeps you strong on today’s hike.
Your ability to absorb the food you eat sets an upper limit on how much you should consume, but how much do you need? For hard runs up to an hour and easy hikes up to two hours, a snack before the trip and a meal after works just fine. As the trail gets longer or your speed goes up though, carry food and eat to keep your energy up. The amount of food needed varies from person to person so here are some tips to help you dial in your own eating:
1. More is better so long as your belly is comfortable.
2. If you feel better after eating, you were already getting depleted and should have eaten sooner.
3. If you bonk or you are very hungry after the trail, you should have eaten more on the hike. If the refrigerator seems to be magnetic and you can’t stop eating when you get home, you are hungry.
4. If you feel full, bloated or sloshy in the gut, you should eat less next time, eat smaller, more frequent bites, take more water with your food or try more easily digestible foods. Many beginner athletes who can’t tolerate solid foods while exercising hard do okay with carbohydrate gels.
With these rules in mind, experiment with different foods and amounts. Keep track of what works and what doesn’t. Soon you’ll settle on some go-to favorites and be sharing them with your trailing companions. You’ll stay stronger and feel better during and after long hikes. Keep Trailing and Trail with Wisdom.
Trail On!
Your Trailulive Trainer,
Scott Saifer
