Here's what's up with that and what you can do about it.
1. You’re Not Getting Enough Circulation
If you sit at a desk all day and keep your legs crossed most of the time, a sudden change in activity could cause feelings of heaviness in your lower legs, says Rebecca Pruthi, M.D., a podiatrist specializing in sports injuries and owner of Foot Care of Manhattan. Other circulatory issues, such as diabetes, varicose veins, or smoking could lead to a heavy feeling in your stems, too.
The fix: Start out slow, says Atlanta-based exercise physioligist, Janet Hamilton, C.S.C.S., founder of Running Strong. If you’re a new runner, she suggests you warm up with five minutes of walking and stretches that keep you moving, such as walking lunges for your quads, side stretches for your core, and calf raises for your hamstrings. Then, transition to a light jog and eventually start running. (Work some low-impact yoga into your routine at home with Women's Health's Flat Belly Yoga DVD.)
If you’re sedentary at work, try changing positions. Try taking a quick lap around the office and stretching at your desk. You can do a standing thigh stretch, pulling your heel to your butt with the arm on the same side. Another option: a sitting lower-back stretch, hugging a bent leg to your chest. If the issues persist, see a doctor to make sure there are no underlying issues.
2. You’ve Gained Weight
“If you recently gained weight from pregnancy or just life, you'll feel a lot of stress on the feet and legs,” says Pruthi. “This results in a pounding feeling when running," she says. It's important to think of weight gain as relative to the individual, says Hamilton. "Most people report feeling a difference after gaining 2 percent of their body weight," she says. Since a smaller weight gain is often caused by fluctuations in water retension, try to pinpoint why you're a little bloated. Maybe you're eating more carbs or salty food than usual, which can cause your body to hold onto excessive amounts of water, says Hamilton.
The fix: Try briskly walking or using lower impact exercises to shed some of the extra weight, before you start running. If you suspect you're holding on to more than just water weight, check out these tricks to burn more calories during any workout.
3. You’re Vitamin Deficient
If you're not getting enough magnesium, iron, or folate in your diet, it can make you feel a stronger gravitational pull, says Pruthi. Iron, for example, is what your blood requires to produce hemoglobin, a.k.a. the part of your red blood cell that carries oxygen. So if you have an iron deficiency, it could mean that having less oxygen in your blood stream is causing a general feeling of fatigue.
The fix: Incorporate these vitamins into your daily diet through whole foods that are naturally packed with them, like leafy greens, legumes, and seafood. As far as supplements go, proceed with caution. "It's a good idea to get your blood tested by a physician to identify any specific deficiencies rather than just jumping on the supplements," says Hamilton. "Too much iron can be problematic."
4. You’re Not Drinking Enough Water
As with any form of exercise, dehydration and a lack of electrolytes will make you feel sluggish. The reason you notice it more when you run is because it’s a high-impact activity, says Pruthi. High-intensity activities make you sweat more, and when you drip you lose electrolytes and water. That lack of electrolytes messes with the functionality between your muscle contractions and nerve conductions (the electrical signals that your brain uses to communicate with your nerves), making it difficult to run, says Hamilton.
When you're dehydrated, your blood volume depletes. And since blood is responsible for fueling muscles with oxygen and cooling the core, your body has to choose between these two functions. Ultimately your body will choose the most necessary function, cooling you down, so your muscles get the shaft and you're left feeling exhausted, says Hamilton.
The fix: Get your daily dose of recommended H2O—and we don't mean that age-old eight glasses a day. Hydration is not one-size fits all, says Hamilton. I always tell my clients to drink to thirst, meaning if you're thirsty, go ahead and drink. Another great way to monitor if you're getting enough water is to look at your pee. Is it dark? that means you're not getting enough water. Simple as that. If you're going on a run longer than 30 minutes in the summer heat, bring a water bottle with you, she says. And if you're somewhere extra hot, have a sports drink containing extra electrolytes before hitting the road.
5. It’s in Your Bones
If your gait (the manner in which you walk) is off, that will be exacerbated during running, says Pruthi. “If you pronate (roll your foot inward) or if you supinate (roll your foot outward), you may need to be fitted for orthotics to help you stride in a neutral position.”
The fix: Rather than focus on what part of your foot hits the ground when, put your efforts toward monitoring your cadence, says Hamilton. Your cadence is the amount of beats (i.e. steps) you take per minute while running. The best way to monitor your cadence is by running on a treadmill barefoot for one minute, taking down your cadence number, then comparing it to your cadence after a minute with shoes on. Your cadence with shoes on will likely be lower than that with shoes off. You want to get your cadence with shoes on as close as possible to that of when you have shoes off for a more efficient run. Hamilton says we have better form running barefoot because we're more likely to keep our feet under our bodies and pick them up quickly. The next time you run, try listening to a song that has the desired beats per minute you're trying to reach (Spotify has a tool for that). If that doesn't work, see a podiatrist for a gait analysis and foot exam. They may fit you for custom molded orthotics.
6. You Need New Kicks
As any runner will tell you, it all comes down to the shoe. If you’re experiencing heaviness, you may need a more supportive, cushioned shoe. This prevents excess stress on your joints, so you don't get worn out as fast. Pruthi also suggests a lower-heeled option for a smoother run. And don't forget to switch out your sneaks every 500 miles for maximum comfort, she says.
The fix: If you’re not sure what shoe to buy, hit up your local running store where the employees know their stuff. You can tell them your current activity level, goals, and sensitive areas, and they should be able to fit you properly with a shoe you’ll love. Or, just check out our running shoe guide.
7. Your Form Is Off
“When the foot strikes the ground, it should be light and quick,” says Pruthi. “Your foot should not be extended out in front of you with a locked knee.”
The fix: Keep your foot close to your body rather than over extending your stride, says Pruthi. This facilitates a smoother, lighter-feeling run. The easiest way to make this correction is by starting out running on flat, unobstructed surfaces, like a flat street in your neighborhood or a track. You can transition to non-flat surfaces when the flat paths begin to feel too easy, says Hamilton. Start slowly, incorporating hills, and keep in mind that you don't need to do a super strenuous path every day. Try hills and longer routes for days when you want a challenge and shorter flatter runs in between. That way you don't over fatigue your muscles, says Hamilton. (Looking for your next challenge? Sign up for Women's Health's RUN10FEED 10 10-K!)