Bonking or just unfit.....which ?

[groskilly]

The past several months I'm having a problem with bonking.....at least I think its bonking. Occasionally I run out of energy and can not continue riding.
Its a feeling of weakness, feeling like I could loose conscientiousness. My legs feel heavy, a lethargic state.
I am following all the recomended things to prevent a bonk, hydrating, eating carbs and energy drinks at the appropriate intervals.
The most recent episode was the 2009 Solvang Century when I bonked at mile 63.
I am 60 years old.
Could it just be a lack of conditioning or fitness ?

Any thoughts ?

 

[daveryanwyoming]

...Could it just be a lack of conditioning or fitness ?...Any thoughts ?

Well it could definitely be lack of fitness or simply poor pacing. You burn through glycogen faster and fatigue more rapidly as you ride closer to your threshold power. Back off a bit and you'll burn a higher percentage of fat, preserve more glycogen and stave off fatigue and bonking.

FWIW nutrition during your event is important and necessary in longer events but what you eat day to day off the bike is more important. Most folks can only ingest roughly 280 Calories per hour while riding. Try to take on more and you'll almost certainly experience GI distress and feel lousy. But a cyclist putting out a steady 150 watts, which is typical for a moderately fit cyclist during a century ride, burns roughly 550 Calories per hour. And a racer holding 250 watts average power burns roughly 900 Calories per hour but can't ingest more calories than anyone else.

The point is that endurance cycling relies heavily on both stored glycogen and pacing during the event. Most adults can store somewhere between 1200 and 1800 Calories of muscle and liver glycogen depending on muscle mass and training history. Topping up those important reserves require daily attention to refueling, especially refueling with healthy carbs and definitely refueling immediately after workouts in the critical half hour when glycogen resythesis rates peak. Make sure you're eating a healthy diet including carbohydrates daily and don't skip the post ride refueling. If you start a long ride with your glycogen stores depleted you're handicapping yourself before the ride even begins.

The other big point is pacing. A racing cyclist with a threshold power (FTP) of 300 watts can ride all day at 175 watts as they'll be burning a relatively high percentage of fat and conserving their glycogen stores. A club cyclist with an FTP of 200 watts will be riding much closer to their limits at that same 175 watt power and they'll burn through their glycogen stores much more quickly. Possibly too quickly for the 250-280 Calories per hour they ingest to keep them afloat in which case they'll bonk when the glycogen runs out.

IOW, get fit and raise your FTP so that you can ride a long event at a lower percentage of your threshold power. That will preserve glycogen and extend your endurance. It will also give you more on demand power for that really steep climb or headwind section.

So, in a nutshell eat well every day and train more or with more focus.

Good luck,
-Dave

 

[doctorSpoc]

The past several months I'm having a problem with bonking.....at least I think its bonking. Occasionally I run out of energy and can not continue riding.
Its a feeling of weakness, feeling like I could loose conscientiousness. My legs feel heavy, a lethargic state.
I am following all the recomended things to prevent a bonk, hydrating, eating carbs and energy drinks at the appropriate intervals.
The most recent episode was the 2009 Solvang Century when I bonked at mile 63.
I am 60 years old.
Could it just be a lack of conditioning or fitness ?

Any thoughts ?

i'm not sure you are bonking.. if you are eating a lot while riding... sounds more like you might just have a great deal of fatigue because you haven't yet built of the fitness to complete the workouts you are attempting.

when you bonk you go into a frantic state with uncontrollable hunger. you run your glycogen stores so low that your body has to choose between running your brain or your muscles... since your brain only runs on glycogen... you know who's going to win that battle?

when i have bonked it comes on very suddenly and my legs feel weak... you can turn the pedals over no problem but cannot, no matter how hard you try, put any real torque on the pedals.. i've ridden 20km in a bonked state... if you don't have any food you start thinking crazy things like stealing some really immature corn out of a corn field or climbing crab apple trees to get some crab apples etc.. if you don't have access to food you really feel like you are going insane and will do anything for food... when you do get food.. you just gorge yourself.. eating everything and anything in your path.. when your start to recover.. you start to realize that eating a whole bag of chocolate chip cookies and a hole jar of pickles was not such a good idea as it seemed when you were bonked... then your throw up... lol. i usually that another whole day to start to feel normal again... can ride the next day, just don't feel right though.

 

[matagi]

You may be eating all the right things, but are you eating them in the correct amounts? When you exercise, blood flow gets diverted away from the gut so absorption is reduced, which means you're better off eating small amounts really, really frequently rather than larger amounts at set intervals. But there's nothing scientific about it, it's a bit of trial and error to figure out what amounts and how often work best.

Also, given your age, you should go and see your doctor and get checked out - you may have an underlying health problem which the increased exercise has unmasked.