Inevitably, every runner will ask “why do my legs hurt when I run?” Sore legs are a universal part of the running experience. Sometimes, it progresses past soreness and running is painful. A majority of runners will experience a running injury at some point. Even if you are never injured, you may experience aches and pains that are more than soreness but aren’t injury (sometimes called “niggles”).
Why Do My Legs Hurt When I Run?
Why do legs hurt during running? Running places a high stress on your muscles, tendons, ligaments, and bones. The longer or faster you run, the more stress and breakdown occurs. Sometimes, this breakdown results in soreness.
Novice runners may experience soreness or mild pain more than experienced runners. During your first 6-12 months of running, your musculoskeletal system has to adapt to the high-impact nature of running.
A hard or intense effort, such as a race, will lead to more soreness than a regular training run. Likewise, a long run or interval workout may cause more soreness than an easy run. The more you adapt to training, the less soreness you will experience.
Other times, too much breakdown results in overuse injuries such as stress fractures or muscle strains. You may have an injury if you experience if running is painful for several runs in a row. Running-related injuries happen for many reasons: overuse, poor nutrition, muscular imbalances, and sometimes sheer bad luck.
Other causes of pain while running can be related to your running shoes. Old, worn-out shoes provide less cushion, which means less protection from the impact of running – and less protection causes aches in your legs and feet. The wrong running shoes for you will also feel uncomfortable when you run. (Here’s how to find the right running shoes for you.)
Soreness vs. Injury
If you have ever walked down a flight of stairs following a long race, you know that soreness can be quite intense. Likewise, if you have had a running injury, you know that it can start out as a whisper of pain. So, how do you know the difference between soreness and injury?
Soreness typically manifests as:
- Diffuse ache
- A sensation of tightness or stiffness
- No to minimal gait alteration, especially after warming up
- Bilateral (i.e. both quads are sore)
- An ache that subsides during a run
- Less than 3/10 on the pain scale
Meanwhile, an injury will present differently than soreness. Common signs of an injury include:
- Pain lasting longer than 5 days
- Localized pain, often unilateral (i.e. one spot on one quad hurts)
- Sharp pain, more than 3/10 on the pain scale
- Your running gait is altered
- Worsens during a run or after a run
If ever in doubt about soreness vs an injury, treat it like an injury. Take a day or two off of running and see if it improves. Soreness will resolve in a few days; if it has not resolved with rest, it is more than likely an injury.
If My Legs are Sore, Should I Still Run?
Generally speaking, you can still run if your legs are sore. It’s important that you accurately assess your pain using the steps below. If it is true soreness – diffuse, mild ache with no alteration to your gait – then you can run on sore legs. This article helps you understand what causes muscle soreness and how to treat it.
Tips to Assess Your Running Pain
How do you know if you can run or should rest when you have running pain? If running is painful, you can ask yourself some simple questions to assess running pain. These questions are based on clinical opinions, such as this 2017 piece in Current Sport Medicine Reports.
Disclaimer: All the advice provided is generalized. Your exact pain may be different. If in doubt, consult a physical therapist, sports medicine doctor, or your primary care physician.
Does It Worsen or Subside When You Run?
As noted above, a significant difference between soreness and injury is how it feels when you run. Running increases blood flow to working muscles, which will decrease soreness as you run. However, an injury will typically either remain at the same level of pain or worsen as you run.
The same guideline applies after a run. If you were sore when you started a run, you will feel the same amount or less soreness after. If a run causes soreness, you may not notice it for several hours. However, an injury often feels worse after a run – and may continue to hurt more throughout the rest of the day.
Can You Hop on The Affected Leg Without Pain?
The hop test is not a sensitive diagnostic test. In this test, you hop on the injured leg for approximately 10 seconds and observe how the pain changes. Traditionally, the hop test is used to determine if an injury is potentially soft tissue or bone. If you can hop without intense pain, the test suggests that your injury is likely not a bone stress injury. However, some soft tissue injuries will trigger pain in the hop test (such as plantar fasciitis), so it’s not always 100% reliable.
The hop test can assess if you should still run when you have pain. If you are able to hop on the affected side without the pain intensifying, you can try a run. If the hop test causes pain to intensify, it is advised not to run.
Using the Pain Scale
The severity of the pain often indicates the severity of the injury. A torn plantar fascia will cause more pain than plantar fasciitis, which causes more pain than sore feet.
A pain scale typically uses a range of 0 to 10. 0 is the absence of pain. 1-3 are mild pain; 4-6 are moderate; 7-10 are severe. If pain is mild (<3/10), you can keep running on it. If the pain is greater than a 3/10, then you should rest or cross-train instead. Importantly, you should rank the both the average and the peak pain during your run.
Does It Alter Your Gait?
Soreness will typically not alter your gait when you run. If running is painful, you may change how your foot lands or your hip moves to avoid worsening the pain. An injury can alter your gait and if it does, you do not want to run on it.
There are two reasons why you should not run if pain is bad enough to alter your gait. Firstly, if you have to alter your gait, then an injury is present and requires care to heal. Secondly, gait alteration can overload other muscles, and you risk a secondary compensation injury.
How Does the Pain Last?
Soreness tends to subside within a couple of days of its onset. Muscle pain that lasts more than 3 days is likely injury, not soreness. Likewise, joint pain lasting longer than 24 hours after a run indicates potential overuse or injury.
How to Prevent Legs from Being Sore From Working Out
Soreness is part of running – but you can take steps to reduce soreness. If your legs are sore from working out often, but you are not injured, try these steps to prevent muscle soreness.
Wear Cushioned Running Shoes
Cushioned running shoes are not what they were a decade ago. Now, cushioned shoes feature lightweight, responsive foams that let you train efficiently without beating up your legs so much. A 2022 study published in Medicine and Science in Sports and Exercise found that cushioned shoes encourage better running performance when there is muscle damage – while also reducing strain and soreness while running. The researchers theorized that this effect means that cushioned shoes will let runners train more and harder without feeling sore or broken down.
Eat Enough Protein
Research indicates that runners need more protein than was previously thought. High-volume training, long runs, and hard workouts break down the muscles. Dietary protein is used to repair muscle damage. Without enough dietary protein, the muscles will not fully repair – and therefore you will be more sore. Most runners need a minimum of 20-30 grams of protein per meal, plus protein at snacks – and some runners may need more.
Maintain a Consistent Training Load
The vicious cycle can trap many runners: you train, experience soreness, take a break, try to train again, get sore, and take a break. A new stimulus will often trigger more soreness. While you should rest if you are injured, a consistent training load can reduce sore legs from running since your body has time to adapt.
Take One Complete Rest Day Per Week
Run streaks, team no days off, whatever you want to call it – the avoidance of rest can be the culprit if running is painful or you are often sore. Rest means rest – not cross-training, weight lifting, or a recovery run. Rest days encourage a hormonal response for muscles to repair. One day or rest per week will remove the load just enough for healing to occur so that you are not always sore.
How to Avoid Pain When Running
Running can cause soreness. However, if running is painful, you want to rest from running and seek medical advice. Soreness vs injury can be tricky to discern, but you can assess the difference and know if you should rest or run.
Want more evidence-based information on running? Listen to the Tread Lightly Podcast; Amanda of Run to the Finish and I provide answers to all your running questions.