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Why Muscle Stiffness Isn’t Always Bad (and How to Tell the Difference)

No one wants to be sidelined by pain or injury, which is why you might wonder if something is up when you notice that you don’t have as much flexibility as the instructor in your yoga class, or when your muscles feel especially stiff after a workout.

However, muscle stiffness — or being unable to bend like gumby — isn’t necessarily a sign that something is wrong. It’s beneficial to understand what defines normal flexibility, why you might feel muscle stiffness, and when what you’re experiencing could be a sign of an injury for which you should seek medical advice.

Defining Normal Range of Motion

Injury, trauma, and movement dysfunction aside, range of motion and flexibility are influenced by a number of factors including:

Age and Sex
Women are generally more flexible than men and we typically lose flexibility as we get older.

The makeup of your connective tissue can predispose you to be more or less flexible.

Joint Structure
Every joint is built to accommodate a different range of motion. For example, while both are ball and socket joints, the hip joint is built to have less range of motion than your shoulder joint, so it’s able to support you when you stand on it.

Types of Activities Performed
Your body adapts to the positions that you put it in. If your training or daily activities involve moving through large ranges of motion, then you will often have more flexibility around the joints that you move. If you sit most of the day and your training involves more isolation work in a fixed position, then you will often have less range of motion available to you.

Muscle Mass
Weight training doesn’t necessarily reduce flexibility. However, as previously mentioned, your body adapts to the type of training you do. If you have a lot of dense muscle around a joint and thicker tendinous attachments, then you might not have as much range of motion there.

Normal range of motion and flexibility are different for every person and are dependent on a number of factors, both within and outside of your control.

However, just because another person has more flexibility than you do doesn’t mean that there is anything wrong with yours.

Flexibility is also joint-specific. This means that some joints are built to have more range of motion, and also that it’s possible to have too much range of motion in one joint, and not enough in another. For example, you could have too much flexibility in your lower back, not enough in your hips, and an appropriate amount in your shoulders.

How much range of motion you need is activity-dependent, which can help you determine if you need to work on your flexibility.

As a general rule, you want enough range of motion to be able to perform activities without compromising function or structure. For instance, you want to have enough hamstring length to be able to bend over to tie your shoes without compromising your lower back.

Additionally, if you strength train, you’ll want enough hamstring flexibility to allow you to hinge forward to grab the bar, without rounding your lower back, which could result in a disc injury under load. However, you do not necessarily need the hamstring flexibility that would allow you to do the splits, which might be the case for a professional dancer.

The same idea can be applied to the upper body. You need a certain amount of movement in the upper back and shoulders to get your arms overhead to grab objects from high shelves or perform overhead presses. Without that range of motion, you might end up creating some of that movement from your lower back, which over time could result in pain or injury. However, you also don’t necessarily need the upper body flexibility of a competitive gymnast performing advanced tumbling skills.

It is also important to note that a certain amount of muscle stiffness can be protective against injury. For example, If you are back squatting a heavy barbell, having some stiffness around your spine can prevent you from hyperextending your lower back. Additionally, if you play an impact-based sport like football, muscular stiffness can help protect your spine when someone tackles you on the field.

Hypermobility and Too Much Flexibility

It is possible to have too much flexibility, which is sometimes referred to as hypermobility. This occurs when the joint is able to move beyond its normal range of motion.

While having a lot of flexibility isn’t always a sign of dysfunction, it can result in pain and injury, especially when one is lacking the stability and strength to control the joint at the end of its range of motion, particularly in loaded movements.

Most injuries occur at the end of a joint’s range of motion, because it’s where we are weakest, since we don’t use our end range in daily life. For example, walking isn’t going to activate your hip muscles at their end range. This is important to note, because if you are working on your flexibility by doing a lot of passive stretching, you want to make sure that you also train your body to use and control that additional range of motion to reduce your risk of injury.

For example, after stretching your hamstrings and hip flexors, you could train your body to use and control that newfound range of motion by performing exercises like glute bridges and seated leg lifts.

Joint Instability vs. Delayed Onset Muscle Soreness

Sometimes a feeling of muscle stiffness or tightness is a sign of weakness at the joint, or joint instability. In this case, it is believed that your nervous system is sending a signal of stiffness as a warning sign that there is weakness at that joint, so you don’t injure yourself by moving into a range of motion that you can’t control.

Researchers at the University School of Physical Education in Katowice, Poland tested the effects of training the lumbo-pelvic-hip complex, or core and hip stability training, on hamstring stiffness over four weeks. They found that stability training appeared to be effective in reducing hamstring stiffness, when compared to the control group [1].

It is not uncommon to feel tightness and pain in the areas where you’re hypermobile and have too much range of motion. In this case, even though it might feel like that area could benefit from being stretched, stability and strength work may actually be a better choice for alleviating pain and discomfort.

Stiffness and pain with limited range of motion can also be a sign of instability or potential injury. However, this is different than the the  burning sensation you might feel in your muscles during exercise, which indicates effort, or discomfort or muscle stiffness you might feel during challenging workout or 24 to 72 hours after you workout, which is called delayed onset muscle soreness, or DOMS.

DOMS typically presents as muscle soreness and stiffness hours or days after new or strenuous exercise. According the the American College of Sports Medicine, it’s believed to be caused by microtrauma to the muscle fibers, which stimulates your muscles to adapt and get stronger [2].

This is also why DOMS will sometimes appear when you have tried a new activity or have switched up your workout. Your body has not yet adapted to those movements. However, the next time you repeat that activity, it is likely that you won’t be as sore.

DOMS will typically present as tenderness when touching the muscle, a temporary reduction in strength, or a minimal achy or tight feeling at rest. It will usually respond favorably to gentle stretching or movement and will dissipate within a few days, which is when it is suggested that you resume the activity that incited the soreness.

Conversely, a potential injury will typically present as a sharp ache or pain during or after exercise, around the muscle or the joint. This pain will usually present within the first 24 hours of exercise or during the activity. It will often feel worse with continued activity or movement, and will linger longer than 72 hours. It may also present with excessive stiffness, significant feelings of weakness, or a loss of range of motion.

If you experience this type of pain, it is recommended that you consult a medical professional for diagnosis and treatment.

Coaches’ Corner

If your client comes to you with a concern about muscle stiffness, how do you know if you should suggest rest and exercises to improve flexibility, or refer them out to a medical professional before working with you?

As fitness professionals, it is out of our scope of practice to diagnose or treat pain.

If your client is presenting signs of pain, instability, or potential injury, as outlined above, then it is advised that you refer them to a medical professional. However, if they are showing symptoms of DOMS and their discomfort and stiffness lessens after a day or two, then you can educate them on the difference between discomfort and pain and they can resume their workouts as appropriate.

Additionally, this provides an opportunity for you to talk to your clients about while it’s not necessarily a sign of injury, soreness also isn’t the mark of a good workout. In fact, because DOMS can temporarily decrease athletic performance and increase the risk of injury, it isn’t something that should be sought after [3].


  1. Kuszewski M, Gnat R, Saulicz E. Stability training of the lumbo-pelvic-hip complex influence stiffness of the hamstrings: a preliminary study. Scandinavian Journal of Medicine & Science in Sports. 2009: 19, 260-266.
  2. ACSM information on Delayed Onset Muscle Soreness, American College of Sports Medicine, 2011.
  3. Cheung K, Hume P, Maxwell L, Delayed onset muscle soreness : treatment strategies and performance factors, Sports Med. 2003;33(2):145-64.




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About The Author: Nikki Naab-Levy
