How can I reduce knots in my shoulders (trapezius muscles)?

From a reader:

How can I reduce knots in my shoulders (trapezius muscles)? I work at a computer most of the day, and have tight knots in my shoulders; specifically, in my trapezius muscles. How can I reduce the tension in these muscles, without having someone else massage them? Are there self-massage techniques I can use? What are appropriate stretches?


My answer:

EVERYBODY gets tension (and sometimes, pain) in the neck and shoulders as well as in between the shoulder blades. This has, of course, increased in these times when we’re all looking down and hunching up at our phones and laptops. Here’s how to get rid of it. Based on the reader’s questions, I’ve broken up my answer into 3 sections below.


How do I reduce tension in these muscles?

This is the most important question. You could have the best therapist to resolve the tension for a time, but if you continue to do the actions that result in the tension and pain, they will just keep coming back and probably keep getting worse.

The most common problem that exacerbates tension and pain in the neck and shoulders is holding the neck in an unnatural position. The two most common are looking down for extended periods and craning the neck and head forward (most probably to focus on miniscule print on a device such as a smartphone or laptop). The answer is to figure out how to keep the head as upright and without rotation as possible, while you relax your shoulders and arms at your sides.

The trapezius itself is, ironically, not the most common cause of neck/shoulder pain in the curve of the shoulder (the levator scapula is). However, TrP1 (Trigger Point 1) at the curve of the neck/shoulder is one of the myofascial TrPs observed the most often [1]:

Trigger Point 1

There are about seven common trigger points located in the upper, middle and lower portions of the trapezius muscle:

Trigger points located in the trapezius muscle

Point 7 (x) produces pilomtor activity or “gooseflesh” to the upper extremity [2]

Trapezius trigger point 7

“In study of static loading, Bearns (1961) discovered that the upper fibers of trapezius, contrary to universal teaching, ‘play no active part in the support of the shoulder girdle in the relaxed upright posture.” [3]


Are there self-massage techniques I can use?


FIRST, you must have been assured by a proper diagnostician (MD/DO) that there are no problems (such as a herniated disc, bone spurs, etc.) that will constantly madden the nerves that feed the musculature of the neck and shoulder. If there is such an inflammatory component, anything I write here will be transitory because the true cause has not been addressed. My suggestions below can temporarily interrupt the pain signal, which has benefit, but ALL pieces of the problem must be addressed to have lasting comfort.

First, it is very helpful to heat the area first. This will dilate blood and lymph vessels, bringing an influx of fresh blood into the area. It will also soften the connective tissue (fascia) that surrounds and binds the muscle fibers and heads, which will make the whole area more amenable to stretching. This step also prepares the tissue for massage (flushing) of the inflammatory chemicals that are making it hurt.

You can use a couple Swedish massage techniques to soften and relax the tissue. These are friction (rubbing along the fiber) and kneading (like with bread dough). For more information, see my blog entry What is the difference between kneading, rolling, percussion, and vibration?

For trigger point deactivation, you can use point-compression with fingertip(s) or a pressure tool (such as a backnobber or theracane):

Using a backnobber

You can also use a tennis or pinky ball against a wall, but they are notoriously difficult to use on the curve of the shoulder. I’ve found the backnobber to be the most useful. It’s only $30, and the product and subsequent comfort can last the rest of your life (no affiliation, just a big, big fan of one of the coolest designs EVER!) [4]

Here’s what you do:

  1. Find the trigger point (any “x” in the above diagrams) that produces the pain pattern that you have, or alternately find a knot in a band of muscle in the curve of the neck/shoulder.

  2. Heat first!

  3. Apply pressure with a fingertip or tool, just enough to “feel it,” and HOLD for 15-60 seconds, until it feels like it is “dissolving/softening,” or until it feels “done.”

  4. Apply the same technique to adjacent and associated trigger points

  5. At this point, you MUST take the muscles released through their normal resting range of motion!


What are appropriate stretches?

This is a tricky one for the neck and shoulder, which have an astonishing array of motion capabilities.

PLEASE NOTE: The exercises below will NOT help and will probably be painful and/or harmful if the tissue is not softened first. Before doing any of the below stretches, follow steps 1 and 2 above. Take it slow and EASY, and remember to breathe. Do NOT make it hurt, just stop at the first point of stretch and relax into it.

Stretches that are most helpful for neck/shoulder pain are as follows:

Stretches helpful for neck and shoulder pain (points 4-7)

(points 4-7)

Stretches helpful for neck and shoulder pain (points 5-7)

(points 5-7)

Stretches helpful for neck and shoulder pain

If you follow the steps above, you should get immediate, long-lasting relief from neck/shoulder pain from computer use. If you do not, it’s time to see a pain-management doctor. Don’t wait. The longer these muscles go on in an inflamed, irritated, shortened state, the longer it takes to deactivate and rehabilitate them.

Ultimately, the triggers must be eliminated, the tissue must be softened/relaxed/deactivated, and then it must be strengthened within its current capability.

[1] Myofascial Pain and Dysfunction; the Trigger Point Manual, Travell and Simons, pg.184

[2] Ibid., pg.186

[3] Muscles Alive; Their Functions Revealed by Electromyography, John V. Basmajian, Carlo J. DeLuca, pg.266

[4] The Pressure Positive Company

How long does the pain last once you start walking again after foot surgery?

From a reader:

“I fractured my fifth metatarsal and, after attempting to heal naturally for a couple weeks, I ended up getting it fixed surgically, with a titanium plate. Ten weeks after the injury occurred, I finally was able to walk again, using a cam boot and cane. I have no balance issues, but the pain was pretty severe.  I’d say it ranged from 7 or 8/10 at first, and now, a week later, it’s around 5-6.

I’m wondering if you have a sense of when my foot will feel normal again? As in being able to maybe take a jog, or chase my cat?”

My answer:

How long the pain lasts can differ from case to case, but from these descriptions, several ideas come to mind. However, anything I say here is obviously trumped by your podiatrist, who has seen you and directed your care.

You say that you are now at 11 weeks post-op, and you only began mobilizing the foot/ankle last week. My guess is that the area of the heel, where the achilles tendon anchors, has become tight and somewhat adhesed. This creates inflammation in the area. Also, I would bet that the soleus muscle has an active trigger point which needs to be deactivated, and that the muscle needs to be mobilized and rehabilitated.

The reason that I say the soleus muscle, in particular, is that the referral zone for the soleus is nearly unique to that muscle. It looks like this (see TrP1 in the diagram):

Soleus muscle

Keep in mind, 10 weeks (2.5 months, roughly) is a LONG time for your foot to be immobilized. Muscle / connective tissue that has been damaged begins to heal, literally, overnight. Unfortunately, when there is bony tissue fracture or damage that requires immobilization, the soft-tissue takes a backseat to healing the bones completely, which results in the soft-tissue being pretty darned stiff and sore when you begin to re-mobilize.

Here’s what I recommend to those who present with this type of complaint:

  1. Heat the foot and calf with a hot water/epsom salt soak for 10-15 minutes to dilate the blood/lymph vessels and reduce swelling in the joints.
  2. Use a rolling pin (yes, that’s right, like for pastry) to roll across the soleus muscle and compress the trigger point (“X”, above, for TrP1). You can also use the Tiger Tail, a cool new tool I learned about:

Tiger Tail

  1. Use a tennis ball or other compression ball (not too small or hard!) to roll the foot and heel on, to massage it.
  2. Take the foot, ankle and calf through a more challenging series of motions, such as “drawing the alphabet, A-Z” with the foot.
  3. If still sore, either use an ice pack or a lidocaine cream on the heel (only, not the ankle or calf, and please clear with your podiatrist first):


The ice or 4% lidocaine will temporarily deaden the superficial sensory nerves, and hopefully lessen the soreness.

I also recommend walking on a soft surface (such as sand or with your body supported in water) very slowly and barefoot to maximize mobility and minimize impact and weight-bearing to the heel.

Good luck!

What does scapular retraction do?

Scapular retraction is movement of the scapula (shoulder blade) backwards and inwards towards the spine. It is mainly produced by the rhomboids (M/m) and medial / lower trapezius in this isolated movement:

Movements of the upper limbMovements of the Upper Limb

Keeping these muscles toned is important in order to support functionally healthy placement of the scapula in static postures and to have good shoulder girdle strength. This strength is balanced with those muscles that pull the scapula forward, which can be overly tight and weak with extended slouching.

A simple isolation exercise to strengthen these muscles of scapular retraction involves squeezing the muscles backwards against resistance. Such resistance can be accomplished by using simple arm weights, or by using an added weight or resistance device, such as free weights (or even a soup can), strengthening bands, pulleys, etc.

"Such resistance can be accomplished by using simple arm weights, or by using an added weight or resistance device, such as free weights (or even a soup can), strengthening bands, pulleys, etc."

Any of these variations of this exercise will be more effective in isolating these muscles if you bend your torso forward 90′, which prevents primary loading of supporting muscles.

Here’s a video which shows such an exercise (credit: WellCor):


If you have ANY neck problems or discomfort, support the head with a towel and relax it (do NOT lift up head or tuck the neck). Remember to breathe in a relaxed manner during the exercise: breathe IN through the nose during the contraction, then EXHALE through the mouth when you relax the contraction.

If you experience any discomfort during or following the exercise, alert your therapist or doctor immediately.  Good luck!


Are dental guards and occlusal splints really effective to treat Bruxism (teeth grinding)?

As long as the guards / splints are well designed and worn consistently, they can be effective for those people who grind so badly that they damage their teeth. Ill-fitting splints, however, can create more problems than they solve (besides which, they are rarely worn because they are uncomfortable).

In my practice, the most common problems I’ve seen with splints is that they are too big. This throws off the placement of the temporomandibular joint (TMJ) which then makes the muscles of the jaw (most notably the masseter and pterygoid muscles) painful and tight. Very often, the tension in these muscles feeds into the grinding through muscle tension and heightened activation.

In the below diagrams, the red areas indicate the primary patterns of pain associated with bruxism. In the first diagram, the muscle drawn at the back of the jaw is the masseter, which is the main chewing muscle. You can easily feel this muscle when clenching your jaw:

Masseter muscle

Bruxism also affects the medial and lateral pterygoid muscles:

The medial and lateral pterygoid muscles

which are very difficult to reach, but important to treat for TMJ pain and bruxism.

There is a good product out now for self-treatment of the muscles of the jaw, called The MyoFree Solution:

The MyoFree Solution

Very often, if you deactivate trigger points in the jaw and restore normal tone and resting length, the bruxism reduces or is eliminated entirely.

In the meantime, though, let your dentist know that the splint is uncomfortable, and ask them to reexamine the fitting. Good luck!

Why do we get knots in our back muscles, but not in other areas (e.g. arms or legs)?

Why do we get knots in our back muscles, but not in other areas (e.g. arms or legs)?

“Muscle knots,” otherwise known as trigger points, can occur in any muscle of the body when that muscle is used improperly or damaged. With repeated misuse or damage, the affected sarcomeres (contracting fibers) can “lock” into immobility and inflammation of varying levels. Online research of any skeletal muscle of the body reveals images of trigger point pain patterns for that muscle. (Various muscles associated with locations of pain throughout the body are shown here too: National Association of Myofascial Trigger Point Therapists | Symptom Checker)

Current wisdom on this subject is as follows: “The presence of CGRP (calcitonin gene-related peptide) drives the system to become chronic, potentiating the motor endplate response and potentiating, with SubstanceP, activation of muscle nociceptors. The combination of acidic myofascial pH and proinflammatory mediators at the active trigger point contributes to segmental spread of nociceptive input into the dorsal horn of the spinal cord and leads to the activation of multiple receptive fields. Neuroplastic changes in dorsal horn neurons occur in response to constant nociceptive barrage, causing further activation of neighboring and regional dorsal horn neurons that now have lowered thresholds. This results in the observed phenomena of hypersensitivity, allodynia, and referred pain that is characteristic of the active myofascial trigger point.” 1

To put it in simpler clinical terms, an active trigger point that is referring pain will activate (as a result of tissue metabolism and biochemistry altering the nociceptive threshold) associated soft tissue and neural regions through neuroplasticity.

1. An expansion of Simons’ integrated hypothesis of trigger point formation (pg. 474, 1st P.)

When you’re injured and something is swollen, why is it good to ice it?

When you’re injured and something is swollen, why is it good to ice it?

Your body’s soft tissue includes muscle, fascia (connective tissue), nerves, blood vessels, and lymph vessels, predominantly. When this soft tissue is injured (via bruise, tear, sprain, etc.), it is like a bunch of broken fluid pipes that require the “pressure” to be turned off until the pipe can heal enough to resume stable and reliable function. To reduce this pressure, short, local applications of cold are called for.

The effects this has on the injured joints, bursae, or fascia include:

  • vasoconstriction of blood and lymph vessels, which squeezes out excess plasma and lymph from the site of damage and helps control hemorrhage and hyper-edema (excessive swelling), and
  • brief analgesia, or relief from pain, which may help moderate the inflammatory response from excessive to helpful.

What we’re going for here is modulation of the inflammatory response from over-reactive to measured. This allows the tissue to begin healing in the most helpful bio-environment possible. When applied properly, cold will accelerate the healing rate via beneficial tissue metabolic activity and enhanced return to comfortable function.

1. Hydrotherapy; Theory and Technique, 3d Edition; Patrick Barron; Pine Island Publishers, 2003; pg 72

What should I do to relieve a nerve pain above my fingers?

Finger pain

My answer here is based on the following question: (paraphrased) “I work on a computer keyboard quite a lot. When doing so for a long time, I get pain in the circled area (above). If I take a rest of around 2 days, the pain goes away. However, I have to work at the keyboard, and taking breaks of that length is not an option. Are there any exercises, medicines or foods that can help me with this?”

First of all, you MUST get a physical exam from a physician to receive the best advice. Another thing to address is whether or not you might be holding your hand in slight extension/elevation above your keyboard when you type, like this:

Conventional keyboard trays can increase injury risks

This position puts undue strain on the Extensor Carpi Radialis Brevis muscle (which extends the hand at the wrist), and can produce a pain pattern as follows:

The extensor carpi radialis brevis muscle

You might examine your keyboard and hand positions during typing and bring them both back to neutral (straight).

Another thing you might try involves the following steps:

  1. Heat the forearm (particularly the muscles, around where the “x” is above),

  2. Compress the muscle knot (trigger point) around the x until it feels dissolved,

  3. Then massage and lightly stretch the muscle, like this:

Massaging the arm

(image: Page on Easyvigor)

Be sure not to stretch so hard that it produces pain; this could further irritate the muscle and tendon.

How does one transition from a narcotic-based pain-management system to one that is non-narcotic-based? How do the two compare?

How does one transition from a narcotic-based pain-management system to one that is non-narcotic-based? How do the two compare?

The most important thrust of the question is: “I’d really like to come off the narcotics but I have no idea what else would successfully cover my pain.” THIS is what is facing most people in the midst of chronic pain: they don’t want to become addicted to pain medications, but they can’t function without them.  What effective alternatives are there?

This is a really great question, and it is one of the questions dominating focus, research, debate and policy in pain management today. Narcotics work very, very well: they “turn off” the pain signal, so that you don’t perceive it through your sensory nervous system. This is a delight for the pain patient who is constantly suffering. “A relief from that pain? Heck yeah, sign me up!”

The problem that pain management clinicians and researchers are struggling with is the “activation threshold” of pain. That is, when you dampen the pain signal over time, your system adjusts to that factor, and then the pain threshold lowers, UNLESS you have the medication intervening. Which means you need higher doses of your medication to achieve the same level of relief from pain.

Initially, this means that you can essentially do more with less pain. Yay, right? Not necessarily. What if, even while you feel less pain, you do more damage to the mechanical tissues of your body because you can’t feel the painful feedback your body sends to tell you you’re hurting it? If this happens, it usually results in further injury. For example, let’s say you have a torn muscle in your leg. You numb it with narcotics so that you can run on it. While you don’t feel the pain caused by running on the leg with the torn muscle, this exercise, in this state, almost guarantees extra damage to the torn muscle.

This brings up the crucial factor with which all researchers and clinicians struggle: What is actually causing the pain, both anatomically and physiologically? How did it start? What sustains it? How does one address both anatomy and physiology without making the patient increasingly dependent on medication for relief, or hopefully, recovery?

For this, you need a case director (usually MD/DO) who is well educated and experienced with a BROAD variety of treatment options. These options need to include “alternatives” such as chiropractic, acupuncture, biofeedback and advanced manual therapy. All of these techniques (tools in the therapeutic toolbox, if you will) do have limited studies done regarding their efficacy. The best “director” for your case will be an advanced MD/DO who has been apprised of those studies, and who also has had significant clinical experience with these “tools” and their benefits.

They will know how to best reduce your current medication (possibly in favor of one with lesser side-effects) and also how best to integrate effective “alternative” techniques into your treatment plan and its goals. These goals, often including comfortable and effective resumption of activities of daily living (ADLs) are superimposed with medication dosages in order to determine their therapeutic efficacy.

A good place to start finding a knowledgeable physician to guide your case is with the American Academy of Pain Management. The AAPM is the only institution to currently accredit those in multidisciplinary pain management, and they are committed to an interdisciplinary approach.

If you are merely exploring competent practitioners in alternative methods, PLEASE study their CVs, license, certifications and experience. I would recommend distrusting anyone who says, “Oh, I can cure you; the technique I use is the only one that works.” NO technique is a panacea – NONE. If they can’t discuss the strengths and limitations (almost more important) of their technique, then they are downright dangerous to you.

You need a good guide. That’s what a great pain management doctor does. Go find yourself one! Best of luck.

What can cause muscles to be sore for weeks to the point that they're painful when used?

What can cause muscles to be sore for weeks to the point that they’re painful when used?

Unfortunately, there are quite a few diagnoses that are relevant to muscle soreness and weakness beyond a week’s span. Be sure to have a physician examine you to at least rule out some of the more basic physiological diseases.

Once those are cleared satisfactorily, ask yourself the following questions:

  1. Was there a precipitating event? That is, did it happen all of a sudden? If so, how?

  2. Where in the body did the pain originate? What was the quality of the pain (sharp/burning/dull & aching/sore/tingling/numbness)?

  3. How long did the pain last?

If the pain began with a precipitating event (e.g. “I lifted something;” “I slept funny;” “I twisted in the shower;” “I leapt to catch a ball;” etc.), it usually indicates a sprain or strain to muscle, tendon, or ligament. If you hear a “pop” or “crack” in a joint, it is most likely a connective tissue rupture. If this is the case, you will need a good interview by a sports medicine physician (MD/DO) and probably a scan of some kind (x-ray or CAT scan for bony/cartilage tissues; MRI for muscle/tendon/ligament tissues). This will help to determine what damage, if any, has been done, and if the issue warrants surgery and/or therapeutic intervention. This needs to be your first port-of-call for pain lasting longer than 1-2 weeks.

Once you have determined that there is minimal damage, and therefore, that surgery is unwarranted, you can determine that the cause is one of the following:

  1. Not normal delayed onset muscle soreness (lasting 24-72 hours): See my answer to What causes delayed onset muscle soreness?

  2. A sprain or strain: See Sprains, Strains and Other Soft-Tissue Injuries

  3. If there are multiple areas around the initial location of pain and injury, you may have developed myofascial pain syndrome: “Myofascial pain syndrome typically occurs after a muscle has been contracted repetitively. This can be caused by repetitive motions used in jobs or hobbies or by stress-related muscle tension. While nearly everyone has experienced muscle tension pain, the discomfort associated with myofascial pain syndrome persists or worsens.”

Myofascial pain syndrome (Mayo Clinic)

As a bit of an aside, sub-acute (1-6 months) and chronic (more than 6 months) of myofascial pain are treated thus:

“A successful treatment protocol relies on identifying trigger points, resolving them and, if all trigger points have been deactivated, elongating the structures affected along their natural range of motion and length. In the case of muscles, which is where most treatment occurs, this involves stretching the muscle using combinations of passive, active, active isolated (AIS), muscle energy techniques (MET), and proprioceptive neuromuscular facilitation (PNF) stretching to be effective. Fascia surrounding muscles should also be treated, possibly with myofascial release, to elongate and resolve strain patterns, otherwise muscles will simply be returned to positions where trigger points are likely to re-develop.

The results of manual therapy are related to the skill level of the therapist. If trigger points are pressed too short a time, they may activate or remain active; if pressed too long or hard, they may be irritated or the muscle may be bruised, resulting in pain in the area treated. This bruising may last for a 1–3 days after treatment, and may feel like, but is not similar to, delayed onset muscle soreness (DOMS), the pain felt days after overexerting muscles. Pain is also common after a massage if the practitioner uses pressure on unnoticed latent or active trigger points, or is not skilled in myofascial trigger point therapy.” (Wiki: Trigger point)

(PS – I’m really proud of the Wiki on this. They nailed it, spot on.)

In a standard clinical interview, you have to go over all the aforementioned patient history, physicians’ reports, scans and anything else you can tell or show the practitioner about what may be the cause of the pain. Your practitioner can then figure out what muscles do the motion that produced the injury & other perpetuating factors, which allows the practitioner to decide what to treat first. This is the general clinical starting point for therapeutic focus.

What causes delayed onset muscle soreness?

This is a hot topic in physiotherapy, so I’m adding some research and detail to this. If you’re looking for a quick answer, see the first three points, because I agree with them. For those who want more data, I provide further detail to the symptom/diagnosis below.

The generally accepted characteristics of Delayed Onset Muscle Soreness (DOMS) are: [1] [2] [3] [5]

  1. generally due to unusual or unaccustomed muscular activity (What did you do that was new or different?)

  2. most often associated with eccentric (lengthening) contraction versus concentric (shortening) loading. For example, when your torso returns slowly to the floor after a sit-up (eccentric for rectus abdominus) versus the sit-up itself (concentric for rectus abdominus). Another example is lifting and lowering a barbell using your biceps:

Isometric contraction

  1. general period of onset is 24 hours or so after exercise-incident, peaks around 24-72 hours after exercise-incident, and then mostly subsides (versus a muscle/tendon STRAIN or ligament SPRAIN, which continues beyond this timeline).

The two major associated theories for DOMS:

  1. “The view taken here (see also Morgan & Allen, 1999) is that the damage process begins with overstretch of sarcomeres. [1]

The damage process begins with overstretch of sarcomeres

“Postulated series of events leading to muscle damage from eccentric exercise:

  1. During an active lengthening, longer, weaker sarcomeres are stretched onto the descending limb of their length-tension relation where they lengthen rapidly, uncontrollably, until they are beyond myofilament overlap and tension in passive structures has halted further lengthening. Repeated overextension of sarcomeres leads to their disruption.
  2. Muscle fibres with disrupted sarcomeres in series with still-functioning sarcomeres show a shift in optimum length for tension in the direction of longer muscle lengths. When the region of disruption is large enough it leads to membrane damage. This could be envisaged as a two-stage process, beginning with tearing of t-tubules. Any fall in tension at this point would be reversible with caffeine (see text).
  3. It would be followed by damage to the sarcoplasmic reticulum, uncontrolled Ca2+ release from its stores and triggering of a local injury contracture. That, in turn, would raise muscle passive tension. If the damage was extensive enough, parts of the fibre, or the whole fibre, would die. This fall in tension would not be recoverable with caffeine.
  4. Breakdown products of dead and dying cells would lead to a local inflammatory response associated with tissue oedema and soreness.”

(Source: The Journal of Physiology, Volume 537, Issue 2, pages 333–345, December 2001)

  1. “The alternative view is that the starting point is damage to components of the excitation-contraction (E-C) coupling process. In a recent review, Warren et al. (2001) summarised their position by declaring that 75% or more of the decline in tension after eccentric exercise was attributable to a failure of the E-C coupling process. The remaining damage seen during the first few days after the exercise was attributed by the authors to physical disruption of the tension-bearing elements within the muscle. So the suggestion is that most of the primary damage arises in the E-C coupling system and only a small component occurs at the level of the sarcomeres. Supporting evidence comes from the observation that in mouse muscle the post-exercise deficit in tension can be recovered with caffeine (Warren et al. 1993; Balnave & Allen, 1995). In the first of these studies, tension was recovered with 50 mm caffeine, which releases Ca2+ from the sarcoplasmic reticulum and leads to development of a contracture in the muscle. In the second, 10 mm caffeine was used to potentiate tension in single fibres in response to direct electrical stimulation. It was concluded that in mouse fibres changes in E-C coupling may be a major contributor to the observed fall in tension after eccentric contractions (Allen, 2001). [2] [4]

Neither of these theories will be resolved without:

  1. a way to measure pain objectively, and

  2. a way to measure the biochemical millieu of the area from “start to finish” in a controlled setting. This is a key area for fMRI studies.

What does it all mean??

Isometric contractions may not build hypertonicity (excessive tension) as quickly, but they will also produce less widespread micro-damage, with its resultant pain and inflammation lasting up to 4 days. This may allow you to resume continuing strengthening faster than if you concentrate mainly on eccentric strengthening. This does not make it less valuable, simply more dangerous to the user of new methods/exercises It also makes them more needful of longer recovery periods in order to avoid repeated and deeper strain/sprain.

[1] Delayed onset muscle soreness (Wiki)

[2] Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications

[3] Eccentric exercise-induced injuries to contractile and cytoskeletal muscle fibre components

[4] Mechanisms of Exercise-Induced Muscle Fibre Injury

[5] Sprains, Strains and Other Soft-Tissue Injuries