Road Bike, Cycling Forums banner
1 - 14 of 14 Posts

·
Yo no fui.
Joined
·
8,486 Posts
Discussion Starter · #1 ·
I boked on a long ride yesterday and, after I got some food in me, was curious what was happening in there. Thanks.
 

·
Shirtcocker
Joined
·
60,886 Posts
Pablo said:
I boked on a long ride yesterday and, after I got some food in me, was curious what was happening in there. Thanks.
In a nutshell--you run out of glycogen (your muscle's preferred fuel) and have to start burning fat and muscle tissue for fuel. Not as efficient to use for fuel as glycogen so you slow down and hurt bad.

http://en.wikipedia.org/wiki/Bonk_(condition)

The average human body stores enough glycogen to generate 1500 to 2000 kcal of energy. Intense cycling or running can easily consume 600-800 or more kcal per hour. Unless glycogen stores are replenished during exercise, glycogen stores will be depleted after 2 hours of continuous cycling or 15 to 20 miles (24 to 32 km) of running.
 

·
Yo no fui.
Joined
·
8,486 Posts
Discussion Starter · #3 ·
That would explain it. I rode from my house up the Big Thompson canyon up to the top of the switchbacks abaov Glen Haven. Did I eat extra food before hand? Did I bring food? No and no. I bonked on the decent. Misery.
 

·
Registered
Joined
·
11,561 Posts
Pablo said:
I boked on a long ride yesterday and, after I got some food in me, was curious what was happening in there. Thanks.
When you exercise you rely to a great extent on carbohydrates for fuel (the greater the intensity the greater the reliance). This is stored in your muscles and liver as glycogen. Certain tissues in your body can not derive energy from fats/proteins nor do they store carbohydrates in the form of glycogen to any significant extent either. The relevant one here is your brain. So circulating glucose is the primary energy source.

When your muscles are working they start taking up glucose that is circulating for energy. So to maintain blood glucose you either eat/drink carbohydrates and your body releases glucose into the blood from the stored liver glycogen. However, most people at most work rates considered exercise you're working hard enough that your replacement can't keep up with your use of carbohydrates. So your blood glucose levels eventually drop, as liver glycogen is depleted.

At that point your brain can't work very well because it isn't getting the fuel it needs since blood glucose levels have dropped below normal. So you get the confusion, dizziness, elevated sense of effort for the work rate, etc.
 

·
Registered
Joined
·
21,832 Posts
Running on empty

Pablo said:
I boked on a long ride yesterday and, after I got some food in me, was curious what was happening in there. Thanks.
Your body can metabolize about 200 calories per hour from fat stores. Once you run out of glycogen in the muscles and liver, and your digestive system is empty, that 200 calories per hour is all you have left. That's enough energy to ride at about 10-12 mph. Sound familiar?
 

·
Cannot bench own weight
Joined
·
4,298 Posts
Kerry Irons said:
Your body can metabolize about 200 calories per hour from fat stores. Once you run out of glycogen in the muscles and liver, and your digestive system is empty, that 200 calories per hour is all you have left. That's enough energy to ride at about 10-12 mph. Sound familiar?
Explains my ride from last weekend. I had suspected a case of the bonk. I'm riding to lose weight though, so I try not to eat during any ride. Problem is I was out for 4.5 hours Saturday.
 

·
Shirtcocker
Joined
·
60,886 Posts
Einstruzende said:
Explains my ride from last weekend. I had suspected a case of the bonk. I'm riding to lose weight though, so I try not to eat during any ride. Problem is I was out for 4.5 hours Saturday.
you are not doing your body a service by not eating for that long of a ride. What happens is you start catabolizing your muscle along with fat--not something you want to do if you want to get stronger or lose weight (the more lean muscle you have the higher your metabolism)--if you eat the right amount of food you'll lose weight just as fast and keep more muscle.
 

·
aka Zoo
Joined
·
763 Posts
I've always been interested in this as well, if this is really just a lack of blood sugar then why does it take so long to recover from it? I had a REALLY bad bonk last year, like I thought I was going to literally fall off my bike, and it took me several days to recover. The thing too is that there was no warning, I was riding strong and then bang, I was dead. Are you already beyond quick recovery if you reach that point? I would think that just slamming down a Gatorade or something would be enough to get you going again after a few minutes. no?
 

·
Registered
Joined
·
5,270 Posts
b24fsb said:
so whats good amount of food to intake on a long ride (60+ miles) while still trying to cut some weight off?
IMO a 60 mile ride is not the time to worry about caloric restriction. In a hard ride, you can't take in more than you put out without serious stomach issues, anyway. Fitness comes from intelligent training (and eating) on the bike, weight loss comes from intelligent caloric restriction off the bike.

http://www.hammernutrition.com/za/H...NGTIPS&OMI=&AMI=&RETURN_TEXT=Performance Tips

Based on what science has shown us, plus two decades of working with athletes, we have determined the following ranges as ideal for most athletes the majority of the time for maintaining optimum exercise performance:

Fluids: 20-25 ounces hourly
Sodium chloride (salt): 300-600 mg hourly (3-6 Endurolytes)
Calories: 240-280 calories hourly


http://www2.trainingbible.com/joesblog/2008/06/weight-loss.html

A triathlete recently wrote to ask how he could lose weight before an important race he has coming up in a few weeks. He'd like to shed 5 pounds (2.3kg) before his A-priority race. There is indeed a cost to be paid when carrying excess fat around. One extra pound (0.45kg) costs about 2 seconds per mile running and takes roughly 3 watts to get it up a hill on a bike. So that 5 pounds represents about 10 seconds per mile running and 15 watts on a climb. That's significant and so dropping a bit of excess baggage has the potential to make him faster on race day. The problem is timing. Trying to lose weight while also training at a high level is not conducive to high performance. Losing weight is additional stress for a body already dealing with the stress of quality training. Recovery will be compromised. Such a path is likely to lead to illness, injury and possibly overtraining.

[...]

I try to get the athletes I coach to drop weight in the Base period. Once into Build we accept the current weight.
 

·
Registered
Joined
·
11,561 Posts
DRLski said:
I would think that just slamming down a Gatorade or something would be enough to get you going again after a few minutes. no?
There are many physiological parameters your body defends well because the consequences of have them stray beyond the normal range can have significant, even devastating, consequences. These include blood pressure, body temperature and blood glucose levels. Ask any diabetic about the consequences of abnormal blood glucose levels. So I don't think it is so surprising that bonking can take some time for recovery.
 

·
waterproof*
Joined
·
41,745 Posts
b24fsb said:
so whats good amount of food to intake on a long ride (60+ miles) while still trying to cut some weight off?
200-250 cals/hour seems to be the consensus wisdom. If you're going "at your limit" the whole time, you'll need to experiment with what you can eat / drink that doesn't cause problems. If you're "just riding along" you can eat / drink almost anything within reason.

Don't worry; you do long rides, you'll burn weight off. The net effect even after what you eat on the bike is a lot of calories burned.
 
1 - 14 of 14 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top