Do your legs feel heavy when you run? We’ve all been there.
You wake up nice and early, put on your running shoes, and try to convince yourself that you are strong enough to get through an ‘easy’ 5k… only to realize you can barely walk.
Your first thoughts might be that it’s simply because you’re tired, but after several days of tired or sore legs, it feels more like a brutal leg day hangover than anything else.
If this sounds familiar, there are common causes, and most have easy fixes. Let’s find out what these are so you can finally regain your running mojo.
So… Why Do My Legs Feel Heavy When I Run?
Here are some of the most common reasons your leg muscles are probably killing you during a run.
1. Poor Blood Circulation
When there is insufficient blood flow to your muscles, there is insufficient oxygen to convert into energy. This will cause tired or heavy legs when running.
Poor blood circulation normally occurs when you run longer distances or overexert yourself before your body is ready to cope with the demand.
Although the tingling sensation often goes away after a few short strides, it may put you at risk of blood pooling if the blood cannot pump back up to your heart properly.
And when this happens, the blood collects in your feet, ankles, or legs.
Warming up at least three to five minutes before your run, followed by a gradual intensity increase, can prevent blood pooling. 
Source: Getty Images/Canva
You’re not the only runner who loves to work hard and push your limits. Watching your body transform and seeing yourself achieve new goals can be exciting and, quite honestly, even addictive.
However, overtraining is detrimental in the long term. You may soon find yourself with heavy and tired legs when running, although you’re not out of breath. Or your body will tell you that you can still run further, only for your legs to hurt too much.
This happens because your bones and joints strengthen at a slower rate compared to how your cardio fitness improves. Sure, your bones and muscles are capable of completing the 10k run, cardio-wise. However, if their legs don’t have enough time to strengthen, they shouldn’t run that distance regularly.
Overtraining is also a common culprit of heavy legs among beginner runners. If you feel any leg fractures, sprains, or strains, allow your leg or legs to heal – take a rest.
3. Lack of Sleep
One in three people don’t get enough sleep.  And that lack of sleep is one of the most important reasons runners feel they have heavy or tired legs when running.
Lack of sleep also increases your risk of injury and makes your run feel harder. Over-tiredness decreases your reaction time, affects the speed you can run, leads to poor running form, and affects your concentration levels.
The amount of sleep a person needs varies. While most need at least seven to nine hours of good quality sleep daily, others will function well on as little as 6 hours of sleep daily.
4. Poor Nutrition
You might have heard of the saying – you are what you eat.
The right kind of food not only helps you perform at your best but keeps your bodily systems in good health and working in harmony, helping you recover more effectively and faster.
In contrast, poor nutrition, especially before a distance event or a long run, won’t provide your body with enough fuel to sustain the energy levels needed during the event. This leads to fatigue, tiredness, and the familiar heavy legs feeling.
To prevent this, consume complex carbohydrates such as whole-grain bread and pasta, oatmeal, and rice.
They are a runner’s best friend. Anti-inflammatory foods such as berries, nuts, leafy greens, and oatmeal are also ideal for reducing muscle soreness.
Dehydration can cause general fatigue during a run that people may perceive as heavy legs.
Your blood volume may become thicker when you lose fluids through sweat and don’t offset it by drinking enough. As a result, your body works harder to pump blood, your run feels harder, or your legs are more tired than usual.
How dehydration worsens delayed onset muscle soreness (DOMS)
The National Athletic Training Association showed that dehydration worsens DOMS or muscle soreness you experience a day or two after a workout or run. Further, the intensity of DOMS increases over time if you don’t normalize your water intake levels. 
You need to make up for the lost sweat by drinking water regularly.
6. Poor Running Form
Good running form reduces the chance of injury, helps you run faster, and improves your running efficiency.
On the other hand, poor running form makes you slower and tires you out fast. This means that your legs are more likely to feel tired and heavy. As such, it is important to maintain a good running form to prevent fatiguing your body too quickly.
A few indicators of poor running form include swinging your arms too much, over-striding, and reaching out too far. Another indicator includes starting the push with your quads (except if it’s a steep hill) or you are running from the hips.
7. Iron Deficiency
Iron is an essential mineral that aids in transporting oxygen to the rest of the body. Sufficient oxygen is needed to enable the muscles to execute their work.
If you’re iron deficient, your body has more difficulty supplying oxygen to the muscle groups that need it most, like your hamstrings, thighs, and calve muscles.
Taking iron supplements is an option, although such should be one of many sources of iron.
8. Excessive Weight Training
Too much weight training can lead to sore and stiff legs that may feel like you’re running with bricks in your legs.
So, to avoid overdoing your lower body strength training, here’s what we need you to know:
- It’s common to feel sore two days after your leg workout. Expect your running performance to be impeded immediately after leg day.
- You can do your heavy leg workouts (i.e., lunges, weighted squats) the same day as an intense speed session. Just ensure you do the speed session first before the leg workout.
- If you combine weight training and a speed session (fartleks or hill sprints), then consider taking a rest the following day.
- You can make light recovery runs one or two days after your leg workout to shake off DOMS.
9. Taking Too Little Rest in Between Runs
Another common cause of heavy legs after running is when you don’t allocate enough time for rest or recovery between runs.
If you ignore active recovery between interval runs, skip post-run cool down, or don’t take rest days seriously, it can be a reason your legs feel so heavy.
Here’s how to fix this problem and prevent heavy legs when running:
Use Carnosine To Prevent Heavy Legs When Running
One of the best recommendations for preventing the feeling of heavy legs in the first place is to use a sports gel that has a high concentration of carnosine as a main ingredient, which will act as a buffer between your leg muscles and the build up of lactic acid which is sure to make your legs feel heavy.
Carnosine is a dipeptide comprising two amino acids: beta-alanine and histidine. This dipeptide has been extensively studied for its health benefits, such as improving athletic performance. 
Created in cooperation with Tartu Pharmacology Institute, CarnoSport contains carnosine as its main ingredient. CarnoSport is a gel that can help specifically for sore legs, as it creates a buffer between your muscles and the build-up of lactic acid, meaning that you won’t suffer from sore muscles for nearly as long after a run or leg day workout as you would without it.
Microscopic tears in the muscle fibers heal more quickly
When the doping-free gel is applied to your leg or other affected area, your body responds by improving tendon, joint, and ligament health. As a result, the microscopic tears in muscle fibers heal more quickly than without using the gel.
Other interesting things about this product include being dermatologically tested, considered a clean sport, and made in alliance with science.
There are so many different reasons why an athlete might have the feeling of heavy or tired legs when out for a run.
And not all reasons are serious; sometimes you’re simply tired and need proper rest.
The more effective your recovery is, the faster it’ll be to get back into your training, and that’s what you should be after.
Taking a proactive approach and doing whatever you can to prevent that feeling of heaviness makes much more sense than trying to treat the painful muscles after a run.
Carnosine is that sports gel that has an all-around positive effect on all athletes, especially those who engage in long-distance running.
If you’re serious about maximizing the speed of your leg day recovery, try CarnoSport and see for yourself how it yields a greater recovery effect than an individual action.