Monday, 1 September 2014

Overactive Versus Underactive Muscles: What Does It All Mean?

Overactive Versus Underactive Muscles: What Does It All Mean?
Posted on August 28, 2014 by nasm
By Kyle Stull, MS, LMT, NASM-CPT, CES, PES, NASM Master Instructor
“Do you suffer from muscle imbalances?” “Is your back pain due to a muscle imbalance?” “Prevent ACL injuries by reducing your muscle imbalances!” What does all this mean? Are muscle imbalances just a marketing craze extending beyond the fitness industry and completely overhyped by social media? Do muscle imbalances even exist, and if so, what are they? This article will help to explain the relationship between muscle imbalances along with understanding more about the implications behind overactive and underactive muscles. What is muscle balance? Efficient human movement and function requires a balance of muscle length and muscle strength around a joint. If muscles are not balanced, then the associated joint is directly affected. For example, a muscle imbalance at the shoulder involving a “tight” pectoralis minor will pull or shift the shoulder forward into a rounding position. Muscle imbalances can be due to poor posture, stress, repetitive movement, or injury. Once this occurs, the body will continue to endure movement, only now the movement occurs along the path of least resistance, otherwise known as relative flexibility (Clark, Lucett, & Sutton, 2012). This pattern can lead to altered reciprocal inhibition, synergistic dominance, and eventual injury (these terms will be further described later). As these patterns of dysfunction continue, the muscle imbalance will lead to muscles on one side of the joint becoming chronically shortened and muscles on the opposing side of the joint becoming chronically lengthened. This is where the terms “overactive” and “underactive” come from. It is generally assumed that an overactive muscle is short, tight, and strong, as opposed to an underactive muscle, which is assumed to be long and weak. While these assumptions are sometimes correct, they may also be misleading for two primary reasons:
1. The sensation of muscle tightness does not always mean that a muscle is short.
2. Just because a muscle is short does not mean that it is overactive and strong, and conversely, just because a muscle is long does not mean it is underactive and weak.
Reason #1 Two important sensory receptors are the muscle spindles and the Golgi tendon organ (GTO). Muscle spindles are receptors within the belly of a muscle that primarily detect changes in the length of the muscle and rate of length change (Magill, 2007). The GTO senses changes in muscle tension and the rate of tension change (Magill, 2007). Located near the origin and insertion of the muscle, when a muscle generates force the GTO becomes distorted and will fire nerve impulses to the central nervous system (CNS) regulating the force and tension developed. When a muscle is rapidly lengthened, the muscle spindles are excited and send a message to the CNS, resulting in the contraction of the lengthened muscle fibers (Clark et al., 2012). Consequently, this results in the sensation of tightness. An example of this is the person with an anterior pelvic tight (excessive arch in the low back). As the pelvis tilts forward, the hamstrings are lengthened. Overtime, these muscles begin to feel “tight.” In most cases, the individual will feel the need to stretch the hamstrings. As the hamstrings are stretched, the GTO will inhibit the muscle spindles (autogenic inhibition) and the hamstrings will begin to feel as though they have relaxed. Yet this altered position of the pelvis causes a lengthened resting position of the muscle, and as soon as the GTO is no longer excited the muscle spindle will begin to signal for the CNS to contract, leading to reoccurring tightness.
Anterior Pelvic Tilt
Reason #2 Sahrmann (2002) stated that the force generation capabilities of a muscle are dependent on the muscles resting length. This is known as length-tension relationship. To state it more simply, a shortened muscle has too much overlap of actin and myosin filaments, and a lengthened muscle doesn’t have enough overlap. This means that both examples could possibly be underactive and test weak compared to a muscle at ideal resting length (Sahrmann, 2002). Therefore, a lengthened muscle could actually become overactive and dominant over another muscle. Let’s further discuss hamstring length and how this affects pelvic orientation. The gluteus maximus is the prime mover during hip extension and the hamstrings provide assistance when needed. In an anterior pelvic tilt position, the hip flexors (iliopsoas, rectus femoris, and tensor fascia latae) may become shortened. According to Sherrington’s law of reciprocal inhibition, if one muscle is contracting then the muscle on the opposing side of the joint must be relaxing (Magill, 2007). If this inverse relationship is altered, as in the case of an anterior pelvic tilt, the hip flexors will be contracted during a functional movement (such as walking) while the primary hip extensors are relaxed. As mentioned previously, the body will find a way to get from point A to point B with the least amount of resistance. In this scenario, the next best muscle to perform hip extension would be the hamstrings. This is known as synergistic dominance, where a mechanically lengthened muscle is overactive and performs the work of the prime mover (Sahrmann, 2002). Conversely, in the case of shoulder dysfunction, someone who is protracted forward with a shortened pectoralis minor also has an overactive pectoralis minor. Therefore, it may be more appropriate to refer to overactive muscles as hypertonic and underactive muscles as hypotonic. A hypertonic muscle is defined as a muscle which exhibits excessive tone or tension (Medical Dictionary, Medline Plus). A hypotonic muscle would be a muscle that lacks tone. Due to the complex nature of overactive and underactive muscles, the fitness professional must begin with a comprehensive assessment. How do I know if my client has overactive or underactive muscles? An assessment should begin with a static postural analysis. Static posture can be thought of as a snap shot of the client’s daily habits. The fitness professional should always consider the five kinetic chain checkpoints: feet, knees, hips, shoulders, and head. If any of these are out of alignment there is a good chance overactive and underactive muscles will be found. A movement assessment should be performed following the static assessment. The overhead squat assessment (OHSA) is one that incorporates active range of motion of the ankles, knees, hips, and shoulders, and requires optimal stabilization from the trunk in order to be performed correctly (Bell et al., 2012). During the OHSA, the same five kinetic chain checkpoints should be viewed as the client squats down with an end goal of having the hips parallel with the ground. A client with overactive and underactive muscles will usually demonstrate predictable patterns of dysfunction (Page, Frank, & Lardner, 2010). In addition to movement assessments, more specific assessments, such as passive range of motion and manual muscle testing, can be performed by a licensed professional. More information on these and other assessments can be found in the NASM Essentials of Corrective Exercise Training textbook.
Overhead Squat Assessment
What are the next steps? After the assessments have been performed, a corrective exercise program can be developed. Corrective exercise is defined as “the systematic process of identifying a neuromusculoskeletal dysfunction, developing a plan of action, and implementing an integrated corrective strategy” (Clark & Lucett, 2011, p. 4). NASM’s Corrective Exercise Continuum consists of first inhibiting the overactive muscles with self-myofascial release (SMR), lengthening the muscles which were identified as being shortened, then activating the underactive muscles with strengthening exercises, and finally, integrating back into a total body movement pattern. As an example, let’s continue with the client that has the anterior pelvic tilt. Based on the assessment, it is known that the hip flexors are overactive and shortened. Therefore, these muscles would need to be foam rolled and statically stretched. As we mentioned earlier, in most cases the hamstrings are also overactive but they are not shortened. This means that we could foam roll the hamstrings but do NOT stretch them. Then, the client would need to activate the gluteus maximus and core stabilizers with floor bridges and planks. Finally, finish up with a squat to row on a cable machine for integration.
Inhibit (SMR)
Lengthen (Stretch)
Conclusion Overactive and underactive muscles are usually reflections of muscle imbalances and posture. Overactive muscles are not necessarily strong or tight, but are hypertonic or have chronic increased tone. Whereas underactive muscles may not always be weak and lengthened, but are hypotonic or have chronic decreased tone. The CNS regulates the length of muscles and basis much of its information from the input of different types of receptors. When developing an exercise program, a health and fitness professional must not let the sensation of tightness be the only guiding force, but to also utilize the information provided by a comprehensive movement assessment. Muscle imbalances do not cause all dysfunction in human movement, but in the presence of muscle imbalances many of the supportive tendons and ligaments may be at higher risk for overuse injuries.
Bell, D.R., Vesci, B.J., DiStefano, L.J., Guskiewicz, K.M., Hirth, C.J., & Padua, D.A., (2012). Muscle activity and flexibility in individuals with medial knee displacement during the overhead squat. Athletic Training & Sports Health Care, 4(3), 117-125. Clark, M.A., & Lucett, S.C., (2011). NASM Essentials of Corrective Exercise Training. Lippincott Williams & Wilkins, Baltimore, MD. Clark, M.A., Lucett, S.C., & Sutton, B. (2012). NASM Essentials of Personal Fitness Training (4th ed.), Lippincott Williams & Wilkins, Baltimore, MD. Hamilton, N., Weimar, W., & Luttgens, K., (2008). Kinesiology: Scientific Basis of Human Motion (11th ed.). McGraw Hill, New York, NY. Magill, R. (2007). Motor learning and control: Concepts and applications (9th ed.), McGraw-Hill, New York, NY. Medical Dictionary: Medline Plus. (n.d). August 19, 2014. Page, P., Frank, C.C., & Lardner, R. (2010). Assessment and Treatment of Muscle Imbalance: The Janda Approach. Human Kinetics, Champaign, IL. Sahrmann, S. (2002). Diagnosis and Treatment of Movement Impairment Syndromes. Mosby, St. Louis, MO.
This entry was posted in CEx, Newsletter by nasm. Bookmark the permalink.


Not published


Q & A

Saturday, 22 March 2014

To Ice or not?? Great article.

In a recent study, athletes were told to exercise so intensely that they developed severe muscle damage that caused extensive muscle soreness. Although cooling delayed swelling, it did not hasten recovery from this muscle damage (The American Journal of Sports Medicine, June 2013). A summary of 22 scientific articles found almost no evidence that ice and compression hastened healing over the use of compression alone, although ice plus exercise may marginally help to heal ankle sprains (The American Journal of Sports Medicine, January, 2004;32(1):251-261).
Healing Requires Inflammation
When you damage tissue through trauma or develop muscle soreness by exercising very intensely, you heal by using your immunity, the same biological mechanisms that you use to kill germs. This is called inflammation. When germs get into your body, your immunity sends cells and proteins into the infected area to kill the germs. When muscles and other tissues are damaged, your immunity sends the same inflammatory cells to the damaged tissue to promote healing. The response to both infection and tissue damage is the same. Inflammatory cells rush to injured tissue to start the healing process (Journal of American Academy of Orthopedic Surgeons, Vol 7, No 5, 1999). The inflammatory cells called macrophages release a hormone called Insulin-like growth Factor (IGF-1) into the damaged tissues, which helps muscles and other injured parts to heal. However, applying ice to reduce swelling actually delays healing by preventing the body from releasing IGF-1.
The authors of one study used two groups of mice, with one group genetically altered so they could not form the normally expected inflammatory response to injury. The other group was able to respond normally. The scientists then injected barium chloride into muscles to damage them. The muscles of the mice that could not form the expected immune response to injury did not heal, while mice with normal immunities healed quickly. The mice that healed had very large amounts of IGF-1 in their damaged muscles, while the mice that could not heal had almost no IGF-1. (Federation of American Societies for Experimental Biology, November 2010).
Ice Keeps Healing Cells from Entering Injured Tissue
Applying ice to injured tissue causes blood vessels near the injury to constrict and shut off the blood flow that brings in the healing cells of inflammation (Knee Surg Sports Traumatol Arthrosc, published online Feb 23, 2014). The blood vessels do not open again for many hours after the ice was applied. This decreased blood flow can cause the tissue to die from decreased blood flow and can even cause permanent nerve damage.
Anything That Reduces Inflammation Also Delays Healing
Anything that reduces your immune response will also delay muscle healing. Thus, healing is delayed by:
* cortisone-type drugs,
* almost all pain-relieving medicines, such as non-steroidal anti-inflammatory drugs like ibuprofen (Pharmaceuticals, 2010;3(5)),
* immune suppressants that are often used to treat arthritis, cancer or psoriasis,
* applying cold packs or ice, and
* anything else that blocks the immune response to injury.
Ice Also Reduces Strength, Speed, Endurance and Coordination
Ice is often used as short-term treatment to help injured athletes get back into a game. The cooling may help to decrease pain, but it interferes with the athlete’s strength, speed, endurance and coordination (Sports Med, Nov 28, 2011). In this review, a search of the medical literature found 35 studies on the effects of cooling . Most of the studies used cooling for more than 20 minutes, and most reported that immediately after cooling, there was a decrease in strength, speed, power and agility-based running. A short re-warming period returned the strength, speed and coordination. The authors recommend that if cooling is done at all to limit swelling, it should be done for less than five minutes, followed by progressive warming prior to returning to play.
Our Recommendations
If you are injured, stop exercising immediately. If the pain is severe, if you are unable to move or if you are confused or lose even momentary consciousness, you should be checked to see if you require emergency medical attention. Open wounds should be cleaned and checked. If possible, elevate the injured part to use gravity to help minimize swelling. A person experienced in treating sports injuries should determine that no bones are broken and that movement will not increase damage. If the injury is limited to muscles or other soft tissue, a doctor, trainer or coach may apply a compression bandage. Since applying ice to an injury has been shown to reduce pain, it is acceptable to cool an injured part for short periods soon after the injury occurs. You could apply the ice for up to 10 minutes, remove it for 20 minutes, and repeat the 10 minute application once or twice. There is no reason to apply ice more than six hours after you have injured yourself.
If the injury is severe, follow your doctor’s advice on rehabilitation. With minor injuries, you can usually begin rehabilitation the next day. You can move and use the injured part as long as the movement does not increase the pain and discomfort. Get back to your sport as soon as you can do so without pain.

For more information, please email us at or to book an appointment, visit us online or call 01453 762369.

Sunday, 19 January 2014

Running Pain, an overview from NaSM.

Running tops the charts as one of the most popular fitness activities. According to Running USA, women are out-participating men in road races at every distance except the full marathon. Even for teens it is one of the most participated in sport. But as runners increase their mileage, the chance for injury increases, especially if they have underlying kinetic chain dysfunctions. Here we’ll explore the more common overuse injuries fitness professionals should be on the lookout for and what can be done to help their running clients prevent them from happening. For committed runners, rest is a four-letter word, and the last thing they want to do is stay off their feet.
Some of the more common running related overuse injuries include patellofemoral pain syndrome (PFPS), IT-band syndrome (ITBS), shin splints, and plantar fasciitis. We’ll take a look at what they are and what can be done to help prevent these mileage stoppers. As you’ll see, performing an overhead squat assessment or single-leg squat assessment will help identify the clients that could be at risk for these injuries along with corrective strategies to apply (1). Key identifying compensations will be knees that move inward and feet that flatten, but each client may have additional kinetic chain dysfunctions that will still need to be addressed to run straight.
Patellofemoral Pain Syndrome (PFPS)
PFPS occurs due to a variety causes, ranging from overuse to direct trauma. Clients with PFPS typically complain of pain when going down stairs or squatting, even driving or sitting for long periods of time may illicit pain (1,2). A larger Q-angle (the pull of the quadriceps and the axis of the patellar tendon, from the hip to the tibia) is typically associated with the anterior knee pain of PFPS (1,2). This larger Q-angle and increased knee valgus leads to abnormal lateral tracking of the patella in the femoral trochlea and increased loading on the medial side of the knee (1,2).
Other issues to address with PFPS include hamstring tightness, weak hip musculature (abductors, external rotators, and quadriceps), and altered muscle activation (1,2). This was shown in a meta-analysis highlighting the contribution of muscle recruitment timing between the vastus medialis obliquus (VMO) and vastus lateralis (VL) as a factor to anterior knee pain (3). The conclusion being that there was a trend of delayed VMO relative to VL in those with anterior knee pain (3).
Since most muscles that act on the knee also act on other joints of the lower body, dysfunction can come from either above or below the joint, or both. Consider knee valgus which is influenced by weak hip abductors and external rotators (gluteus medius/maximus) accompanied by overactive hip adductors biceps femoris short head, tensor fascia latae (TFL), VL, and the lateral gastrocnemius (1,4).
IT-band Syndrome (ITBS)
The iliotibial band (IT-band) is the ligament on the outside of the thigh that runs from the hip to the tibia. It can become inflamed and irritated as it rubs against the lateral femoral condyle causing ITBS. This pain on the lateral side of the knee, also referred to as Runner’s Knee, is an overuse injury most commonly experienced by long distance runners, cyclists, and triathletes. Typically it is associated with an increase in training volume and/or abnormal running mechanics (1,2,5).
Research has indicated weakness of the hip abductors, tightness of the TFL, increased internal knee rotation, and low hamstring strength compared to the quadriceps in ITBS (1,6,7). During assessments such as the overhead or single leg squat, clients at risk of ITBS may display an inward knee compensation. Tightness of the IT-band is also associated with PFPS (8).
Shin Splints
Shin splits (or more clinically, medial tibial stress syndrome) is an overuse injury typically experienced by beginning runners, but also by more seasoned runners as they increase their mileage, training, or even change running surfaces. It is an irritation of the periosteum in the tibia, causing pain and tenderness along the medial tibia, typically the distal third, during or after activity. Caused by too much running too soon, overpronation has been linked as a risk factor, as has increased passive inversion and eversion range of motion at the ankle joint and internal and external rotation at the hip (1,5).
Plantar Fasciitis
The plantar fascia runs along the bottom of the foot, from the calcaneous to the metatarsal heads, supporting the medial longitudinal arch. Plantar fasciitis occurs when this tissue becomes inflamed and irritated. It is a common cause of heel pain- especially in the morning when first stepping out of bed. Pronated feet and a lack of ankle dorsiflexion have been associated with plantar fasciitis, as has a high BMI. Corrective stretching strategies for plantar fasciitis focus on the gastrocnemius and soleus, and recent research indicates hamstring stretching as well (1,2,9).
Though most of these common running issues can be addressed with rest, reducing mileage, and or cross training, preventing them is a better approach. By taking your client through a series of postural and movement assessments, you’ll be able to identify potential risks for running injuries and utilize corrective strategies to keep them on their feet!
1. Clark M.A., Lucett S.C. (2011). NASM Essentials of Corrective Exercise Training. Baltimore, MD: Lippincott Williams & Wilkins.
2. Bahr R. (2012).The IOC Manual of Sports Injuries. Oxford, UK: Wiley-Blackwell.
3. Chester, R., Smith, T., Sweeting, D., (2008). The relative timing of VMO and VL in the aetiology of anterior knee pain: a systematic review and meta-analysis. BMC Musculoskeletal Disorders 9:64.
4. Neumann, D.A. (2010). Kinesiology of the Musculoskeletal System, Foundations for Rehabilitation 2nd ed. St. Louis, MO: Mosby Elsevier.
5. Gotlin, R.S. (2008). Sports Injuries Guidebook. Champaign, IL: Human Kinetics.
6. Messier S.P., Edwards D.G., Martin D.F., Lowery R.B., Cannon D.W., James M.K., et al. (1995). Etiology of iliotibial band friction syndrome in distance runners. Medicine and Science in Sports and Exercise. 27:951–960. doi: 10.1249/00005768-199507000-00002.
7. Noehren B., Davis I., Hamill J. (2007). Prospective study of the biomechanical factors associated with iliotibial band syndrome. Clinical Biomechanics 22:951–956. doi: 10.1016/j.clinbiomech.2007.07.001.
8. Hudson Z., Darthuy E. (2008). Iliotibial band tightness and patellofemoral pain syndrome: a case–control study. Manual Therapy 2:147–151.
9. Bolivar Y., Munuera P., Padillo J. (2013). Relationship betweentightness of the posterior muscles of the lower limb and plantar fasciitis. Foot & Ankle International 34(1):42-48.