After about 3 hours of hiking, I can get really tired. What is happening

So I’m not uber fit, but I’m still fairly mobile. I sometimes like to go hiking and I will start early in the morning.

My routine is to do about one hour of hiking or walking, then drive to a new location (maybe 10-30 minutes of driving) then do another hour, then drive again, then another hour, etc. I travel at about 3mph with no backpack.

Usually by the end of the third hour, especially if on that third hour I am doing a lot of uphill hiking I am really worn out and can barely make it. If I’m not going uphill its not as bad though.

Is this due to a lack of cardio fitness, or the fact that I haven’t eaten enough? Like I said when I go I go in the morning, if I do eat breakfast it is usually under 1000 calories (online calculators say I burn about 800+ an hour hiking).

Shouldn’t my body be able to use muscle glycogen or fat stores to get me through?

Or is being able to do 8-10ish miles of hiking in 4-5 hours considered good?

If it is lack of calories (which is what I suspect, I think if traveling uphill I’m undergoing anaerobics w/o any external calories) is fast acting carbs the best thing to take with me (like sugary drinks) or do I want something like trail mix that has a lot of fat and protein in it?

My first thought is that you are bonking.

It sort of depends what you mean by “tired” but if what you mean is a leaden, wobbly feeling in your muscles, that’s glycogen depletion. A small breakfast with multiple trail snacks will probably be better for performance while remaining in the right calorie range… a mix of protein, fat (nuts) and sweets (chocolate chips or fruit) is traditional for a reason. :slight_smile:

If what you mean is that you’re winded and can’t maintan your pace because you’re out-of-breath, then your issue may be aerobic fitness.

Another factor: your driving breaks. You’re going from exertion to sitting still, muscles cool down and stiffen.

I don’t think it is due to lack of aerobic fitness, I can do uphill hikes fine it is just that I can’t do them after 3 hours and I can do more intense aerobics in the gym. Bonking sounds like the most likely culprit. Yesterday I got nausea when I was hiking uphill as well as severe muscle fatigue, but my mind was fine. So according to the website listed, that sounds like glycogen depletion and not low glucose or low aerobic fitness.

Even walking on flat land after I finished the hill had me totally fatigued. This was more of an issue where my muscles felt heavy and weak, and even basic moving was hard.

It’s simply aerobic fitness and the fact that you are substantially overweight is beating up your joints and making your body work extra hard. I don’t know what online calculator you are using but it’s unlikely you are burning 800 cals per hr walking 3 mph in the woods unless you are a tremendously large person.

I have to disagree astro he’s describing glycogen depletion which can happen to aerobically fit people, because it has to do with the body’s ability to make energy, not with the heart’s ability to oxygenate the blood.

OP, you don’t mention whether you’re hydrating, but dehydration can also be a factor over three hours of exertion no matter the weather.

I don’t really like gatorade at full strength (especially not on an upset stomach), so I buy it in powder form and mix it half-strong. I started doing that out of preference, but some authorities say it’s a better practice to drink gatorade half-strength.

When I’ve bonked, my mind was not fine. It went right along with everything else. But, everyone’s different.

I don’t think you’ll want/need anything quite like you’re suggesting for the type of activity you’re doing. Take a bottle of water with you on the hike, drink while you’re walking, and refill it when you go back to your car. Put a sandwich and/or piece of fruit or two in the car and eat between hikes. See if it works.

Hell, three hours is pretty good. An awful lot of people can’t walk for three hours.

Three hours at 3 mph is nine miles. Substantial little hike. I do a lot of short walks, for health. Nine miles is my very longest! I usually start to get weak and wobbly at seven miles.

Up and down hills just adds to it. I’ve actually found that going down a steep hill is worse than going up! I have to sort of “hover” and lower my weight to the leading foot. This means gently bending my knee, under my full weight, slowly. If I do it fast, it’s too likely my leading foot will shoot right out from under me and I’ll go down in a tangle.

(Much worse on hills with slippery slidey gravel surfaces! They don’t call it the Rolling Hills Trail for nothing!)

The usual advice: lots of water, rest often, sun hat and sunscreen, eco-friendly insect repellent, a walking stick, and, if at all possible, a walking buddy. Go till you don’t feel like going any more. Don’t push it. Build up stamina over time.

Make it fun! If you get tired and ouchie, you’ll be less likely to keep it up as a lifelong habit. Build a mental association between walking and happiness. Reward yourself. Make yourself think of it as a treat. Think like a doggie! “Oh, goodie, I am going walkies! Yay yay yay!” This can entail a kind of “self hypnosis,” where you deliberately create mental associations. But it works! If you look forward to a good walk, and are happy while walking, and are contented afterward, you’re doing your mind – and your body! – a wonderful favor.

One last weird item: a walking buddy is a great thing, because talking gives you most of the same aerobic benefits as breathing heavily…and is a lot more fun! Instead of gasp…gasp…gasp… it’s “So, I said to Allen, I said, ‘Isn’t it time you got rid of that old car?’ And Allen said…” It really makes the miles go by faster!

I don’t think its aerobic fitness. I can walk up hills fine in the first hour of a hike, but if I am waking uphill after 3 hours then I can barely make it. Even when I get to flat ground I am still exhausted.

So it sounds like mostly glycogen depletion. I think fast acting carbs is something I"ll have to take along with me next time. I can either eat it during or between hikes.

When 900 years old you get to be, see if you don’t bonk.

I never realised there was so much public bonking going on in the US


Like others have suggested, I would consider making sure you stay hydrated during your workout time. You might also some sort of healthy snack in between hike #2 and hike #3, so that your blood sugar stays up for that last hike.

Perhaps that will make a difference for you.

I do some multi-day backpacking. Yeah, three hours will bonk you if you don’t take in some food and water.

The classic trail mix with nuts, raisins and M&Ms, Clif bars (some flavors have much more sugar than others, so read the label if you’re counting calories), and Snickers candy bars are all popular with long distance hikers – all are easy to nibble a bit of while walking.

And water. Carry a bottle or get a hydration pack and take a few sips every 10 to 15 minutes.

I have to ask… Are you quite overweight? As a daily hiker myself, I would not find the activities you describe (slow hiking plus lots of rest breaks) to be particularly stressful to someone of normal fitness.

Like others here, I would recommend drinking water before the hike and during breaks. Unlike others, I really would not recommend eating anything substantial before going on a hike. Digesting a large meal takes resources from your body that will compete with your physical activity. If you need sustenance, eat only small amounts during breaks.

Weigh yourself before and after the hike. If you lose more than 2 pounds, you’re probably getting dehydrated. A pint of water = a pound is a good rule of thumb.

After a couple of hours of strenuous exercise, your blood sugar will start to drop. It will take much longer to get into a full-blown bonk (which I have done) however even some drop in blood sugar will start slowing you down. Next time bring some trail mix and start eating a little at a time right from the start. Don’t wait until you feel bad. Little GU packets are good if you are feeling bad. I’ve started feeling poorly and one of those 100 calorie gels had me feeling better about 10 minutes after consuming them.

Of course you could try sports drinks such as Gatorade to help with both dehydration and low blood sugar. I did a 68 mile bike ride on Saturday mostly fueled and lubricated by a sports drink. If the stuff bothers you, try diluting it in half.

If the goal is losing weight, the time to do is isn’t during the long exercise. Afterwards the ‘burn’ will keep on burning calories. Just watch your intake after exercise to lose weight. That is unless you plan on doing more of the same the next day. But that’s another conversation.

Agreed. I’ve made that mistake a few times, and it can lead to discomfort, and sometimes stomach cramps. It’s the basis for the old standby about not eating just before going swimming. You want the bloodstream supplying energy to your limbs, not supplying blood to the stomach!

A small baggie of trail mix is very nice for the halfway point of a five miler. (I love the Japanese variety of trail mix with dried shrimp!)

A pen-pal of mine once wrote about the worst hiking trip ever, a day hike to the top of Mount Fuji. Because it was such an important ceremonial event, all of his friends bought new shoes and new backpacks. It was a mob of very sore people who arrived at the top, and doubly sore again at the bottom.

(He said they also all bought gifts at the gift shop at the summit…and had to haul them back down again…when the same gifts were available at the bottom, and cheaper!)