Feeling sore after a workout is known as delayed onset muscle soreness (DOMS). Sore muscles after exercise are a result of muscle breakdown during a workout, particularly on the eccentric portion or muscle-lengthening phase of movements.
DOMS can generally indicate that you’ve trained hard, as it’s your body showing you that it’s repairing and building muscle. If you experience DOMS in one arm but not the other, it’s worth examining your muscle balance and training approach.
Why You’re Sorer in One Arm After a Workout
1. You Have a Muscle Imbalance
If you have arm soreness in one limb but not the other, it could be due to a muscle imbalance. Your weaker side may become sore from trying to keep up with your stronger side, as it has to work harder to complete the same amount of work. That leads to more muscle breakdown.
This imbalance could develop due to poor day-to-day posture, physical stress, repetitive movements, or injuries.
2. You Have a Muscle Strain or Other Injury
If you feel pain — not just soreness — in one arm, you may have injured it. Muscle strains, sprains, and tendonitis are all common workout injuries that could be the culprit of pain in one arm.
Muscle Strain
A strain happens when one of your muscles stretches so far that it tears, either partially or completely. The symptoms of a strain are:
Pain
Weakness
Muscle spasms
Bruising
Swelling
Treatment includes resting, icing, compressing, and elevating your strained muscle for a few days. You can also use over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), like aspirin or ibuprofen (Advil), as a pain reliever for sore muscles.
Prevent muscle strains by properly warming up your muscles before exercise and avoiding excessive repetitive motions. Also, take proper rest days to prevent muscle overuse. They need time to recover and rebuild.
Muscle Sprain
A muscle sprain is when one of your ligaments — tissues that connect two bones together in your joints — tears or stretches, according to Mayo Clinic. The symptoms of a sprain are:
Hearing or feeling a pop
A reduced ability to move the joint near the sprain
Pain
Swelling
Bruising
The treatment for a sprain is the same as a strain (see above). See your doctor if you can’t move your joint, you have pain over the bones of your joint, or your joint feels numb.
Prevent muscle sprains by regularly stretching, strengthening, and conditioning your muscles.
Tendinitis
Tendinitis happens when a tendon — the connective tissue between your muscles and bones — develops inflammation. The symptoms of tendinitis are:
Pain that may feel like a dull ache during movements
Tenderness
Mild swelling
Tendinitis may take a few months to fully heal, and physical therapy may be beneficial during this time.
You can help prevent tendonitis by warming up your muscles before each workout. Also, avoid doing repetitive movements, suddenly increasing the amount or intensity of your training, or placing too much stress on your tendons.
In severe cases, heart attack
Most arm pain does not relate to a heart attack. However, one of the symptoms of a heart attack is pain that spreads from your chest to your arms. Usually, this occurs in the left arm, but it can happen in both arms.
Other symptoms can include:
Chest pain
Shortness of breath
Nausea or vomiting
Lightheadedness or dizziness
Sweating
Coughing or wheezing
Overwhelming anxiety (like a panic attack)
If you have any of these symptoms, get medical care right away.
How to Prevent Single-Arm Muscle Soreness
1. Delve Into Dumbbells
Ditching your barbell and machines in favor of dumbbells is an effective way to fix any muscle imbalances and ensure that both sides are worked evenly. This is because you can isolate a particular arm with dumbbells, whereas both arms would have to carry the load with a barbell.
If you’re used to doing an upper-body workout consisting of bench presses, machine shoulder presses, barbell rows, chin-ups, and barbell curls, for instance, try switching to dumbbell chest presses, dumbbell shoulder presses, dumbbell rows, single-arm pull-downs, and dumbbell curls.
2. Focus Extra Exercise on Your Weak Side
The best way to correct a muscle imbalance is to strengthen the weaker muscles with targeted exercises. After finishing your normal arm workout, target your weaker side for additional stretching and strengthening. Over time, doing this will slowly even out these muscle imbalances.
3. Fix Your Form
You might use poor form when training your weaker side, which leads to the stronger side feeling sore after the workout.
On a biceps curl, for example, you may do the reps on your strong side with perfect form, which activates the biceps and produces muscle breakdown and soreness.
But on the weaker side, your biceps may not be strong enough to do the movement independently. That could lead to you relying more on body momentum, which you should avoid during a curl.
To prevent this, keep an eye on your form in a mirror when you practice at home or use a mirrored wall at the gym. Or, consider seeing a personal trainer or exercise instructor for guidance on technique.
The Takeaway
Uneven soreness in your arms after a workout may be due to muscle imbalances, emphasizing the need to target weaker muscles with specific exercises to gradually balance your strength.
After sustaining a strain or sprain, use rest, ice, compression, and elevation or over-the-counter pain relief medications to ease the pain.
Besides warming up properly to help prevent future injuries, use dumbbells instead of barbells for an even and individualized focus. Always use proper form to help avoid imbalances or injuries.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
Muscle Soreness After a Workout: Can It Be Prevented? Houston Methodist. September 8, 2021.
Jameson TSO et al. Muscle Damaging Eccentric Exercise Attenuates Disuse-Induced Declines in Daily Myofibrillar Protein Synthesis and Transiently Prevents Muscle Atrophy in Healthy Men. American Journal of Physiology: Endocrinology and Metabolism. November 8, 2021.
Scott Haak, PT, DPT, has been a member of the Mayo Clinic staff since 2000. Dr. Haak serves as faculty for the Sports Medicine Fellowship program at Mayo Clinic Florida. He is certified by the NSCA (National Strength and Conditioning Association) as a CSCS (Certified Strength and Conditioning Specialist), is a Certified USA Weightlifting Coach and Certified USA Football Coach, and possesses a MTC (Manual Therapy Certification) from the University of St. Augustine for Health Sciences.
Haak is an exercise enthusiast and enjoys running, weightlifting, and sports performance training. He is the president and director of coaching of a youth tackle football organization, JDL Providence Football, and currently coaches high school football and weight lifting.
Adam is a freelance writer and editor based in Sussex, England. He loves creating content that helps people and animals feel better. His credits include Medical News Today, Greatist, ZOE, MyLifeforce, and Rover, and he also spent a stint as senior updates editor for Screen Rant.
As a hearing aid user and hearing loss advocate, Adam greatly values content that illuminates invisible disabilities. (He's also a music producer and loves the opportunity to explore the junction at which hearing loss and music collide head-on.)
In his spare time, Adam enjoys running along Worthing seafront, hanging out with his rescue dog, Maggie, and performing loop artistry for disgruntled-looking rooms of 10 people or less.
