Hitting the wall is something all marathon runners fear. You know the feeling, flying along at 10K. Strong at halfway. But somewhere after 30km, your legs get heavy and your pace drops.
You hit the wall.
The problem is once you hit it, it is hard to recover from.
The key is to start fuelling earlier than you think.
Why this is needed
Most marathon runners wait until they feel tired to take on carbs.
But by then, it’s too late.
-
Your liver glycogen is nearly gone.
-
Blood glucose drops.
-
Your brain and muscles start rationing effort.
-
Digestion slows under fatigue and dehydration.
Even a small dip in blood glucose can reduce your pace and mental clarity.
Think of fuelling like a drip-feed, not a top-up. You need to stay ahead of depletion, not play catch-up.
Here is a suggested protocol based on how many carbs you are aiming for.
|
60g carbs per hour |
|
|
Time |
Type |
|
20 minutes |
30g gel |
|
50 minutes |
30g carb drink |
|
1 hour 20 |
30g gel |
|
1 hour 50 |
30g carb drink |
|
2 hours 20 |
30g gel |
|
2 hours 50 |
30g gel |
|
3 hours 20 |
30g gel / chew |
|
3 hours 50 |
30g gel |
|
4 hours 20 |
30g gel |
You can use gels such as the MARCHON Endurance Fuel 30 alongside chews and carb drinks.
|
90g carbs per hour |
|
|
Time |
Type |
|
20 minutes |
30g gel |
|
40 minutes |
30g carb drink |
|
60 minutes |
30g gel |
|
1 hour 20 |
30g carb drink |
|
1 hour 40 |
30g gel |
|
2 hours |
30g gel |
|
2 hours 20 |
30g gel / chew |
|
2 hours 40 |
30g gel |
|
3 hours |
30g gel |
|
3 hours 20 |
30g gel / chew |
|
3 hours 50 |
30g gel |
Put carb drink in your soft flask or hydration vest. Gels in the later stages may be taken from aid station
I know you probably thinking “I don’t feel like I need to eat something 20 minutes in”.
But glycogen levels can be depleted quickly and you can’t store that much.
|
Muscle and liver glycogen concentrations |
||
|
Tissue |
Average (g) |
Normal range (g) |
|
Muscle |
500 |
300–700 |
|
Liver |
80 |
0–160 |
Why glycogen levels are crucial
From the literature the critical level of muscle glycogen is approximately 250-300 mmol∙kg-1dry weight. (Reference)
Below this level a drop in performance and increased fatigue is often seen. This can be acheived EASILY during a marathon.
This may only be around a 50-60% drop in your glycogen stores.
I believe we need to shift our focus from simply trying to avoid bonking to actively maintaining high glycogen levels throughout endurance activities.
Final thoughts
You don’t wait until you’re dehydrated to drink. So don’t wait until you’re running low on glycogen to fuel. Start early. Stick to your plan to avoid running head first into the wall.
Check out the MARCHON Endurance Fuel 30 gels here and other endurance blogs below.
