Posts tagged eccentric exercise
Eccentric Quad Strengthening Shown To Improve Strength And Flexibility Of Muscle

Mobility exercises designed to improve range of motion within an affected joint or tissue are a valuable part of any rehabilitation program. Previously clinicians prescribed various bouts (3 x 30 seconds) of static stretching in an attempt to lengthen short muscles. Current research has shown these prescriptions are ineffective at changing muscle length and instead alter the stretch tolerance of the muscle. Thus individuals who stretch more frequently, have an increased tolerance to stretch, and therefore greater range of motion. Conversely, eccentric exercise has been shown to not only develop muscle strength and size, but also change the structure of the muscle improving its’ true length. Further, in randomized, controlled trials eccentric exercise produces greater gains in hamstring flexibility than static stretching alone. A recent study suggests this may also be true for the quadriceps.

Alonso-Fernandez and colleagues studied the effects of 8 weeks of eccentric quadricep training on muscle strength, cross sectional area, and flexibility (J Sports Med Phys Fitness. 2011). Authors placed 26 participants underwent pre and post training testing, as well as, a 4 week detraining period to determine the lasting effects of this exercise program. As expected, eccentric quadriceps training led to gains in quadriceps strength and muscle size. Consistent with prior research on the hamstrings, this eccentric training also improved muscle length and flexibility measurements. Reinforcing a commonly held belief “strengthen to lengthen”. in addition, all measures of muscle performance decreased following the 4 week detraining period. This study further supports our understanding of muscle architecture and the forces required to make a significant change in muscle tissue.

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Updates on the Successful Management of Tendon Pain
Photo Credit: Scott, A. CMAJ. 2011. Mead, M. Transl Sports Med. 2018.

Photo Credit: Scott, A. CMAJ. 2011. Mead, M. Transl Sports Med. 2018.

Tendon injuries have previously been diagnosed as tendonitis and were believed to be marked by an inflammatory process in the tissue.  Our current knowledge on these injuries has been improved by a better understanding of the disease process behind tendon pain.  Current research indicates tendon pain (tendinopathies) is caused by an ingrowth of nerve and blood vessels to the injured area of the tendon leading to increased sensitivity with loading.  Further, as our body begins to heal the injured area of the tissue, tendon cells become more disorganized in nature.  Conversely, healthy tendons display high degrees of organization with tendon fibers aligned in parallel along the lines of healthy stress.  Gradual loading of the tendon through exercise promotes remodeling of the injured tissue.  In short, both under and over loading tendons lengthens the recovery process.  

A summary article on the available evidence behind tendon treatments was published in a sports medicine journal recently (Mead, M et al. Transl Sports Med. 2018).  The authors reported on a general trend against the use of injections for tendon pain.  This includes corticosteroid injections which may provide short term relief, but at the risk of further tendon injury or rupture.  Further, the research does not support the use of injections including prolotherapy or PRP at this time.  Conversely, the authors reported Physical Therapy including the use of loaded exercises, including eccentric exercise, should be considered a first line treatment for tendon pain and injury.  

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IF I Lift Weights Slower Will I Improve My Muscle Size?

It seems there is not much eccentric exercises cannot do between healing injured tissue, improving mobility and strength, and now possibly contributing to muscle size.  We have long known muscles gain the majority of their strength after training because of the eccentric or lowering portion of any lift.  Athletes who skip or speed through this portion of the lift do not benefit as much from the same exercise as those who focus equally on the lift and lowering of the exercise.  New research compared the long term effects of strengthening either with a short or long duration eccentric or lowering phase.

A group of researchers put a group of participants, familiar with resistance training, through 2 workouts a week for 12 weeks (Pereira et al. Int J Applied Exercise Phys. 2016).  The participants were placed in either a slow group, who performed a 4 second lowering phase, or a fast group, who performed a one second lowering phase of an upper body exercise.  The exercise was performed for 3 sets of 8 repetitions to failure using either the slow or fast lowering phase, but every participant took 1 second to raise the weight.  The researchers then measured strength, muscle size, and body composition (fat and fat free mass) at the end of the 12 weeks.  As expected the slow group developed more strength than the fast group, but they also showed twice as much hypertrophy. This is the first study to report a relationship between eccentric loading and muscle growth.   


Eccentric Strength Training for Muscle Strength and Hypertrophy

Eccentric training involves a focused, slow muscle contraction in which the muscle lengthens.  For example, as you lower a weight from a bicep curl towards the floor the muscle simultaneously contracts and lengthens.  Eccentric contractions have been discussed in this blog for their ability to heal injured tendons, restore flexibility, and strengthen weakened muscles.  New research is looking at the comparison of this training with conventional strength training.

Authors studied untrained men and randomized to either strength training on workout machines or working with a flywheel focused on eccentric contractions.  Each group worked out 2 to 3 times per week for 5 weeks targeting the quadriceps muscle group.  The eccentric fly wheel training produced greater gains in muscle size and strength throughout the 4 quadricep muscles compared with the conventional machine despite similar workout frequency, sets, and repetitions.  This study highlights the importance of eccentric exercise for strength gains and muscle growth. 

Eccentric Exercise and Tissue Changes

Eccentric exericise, where our muscles contract and lengthen, is an essential part of any exercise program.  Its benefits of strength, flexibility, and injury prevention are well known in the literature and have been discussed on our prior blog posts.  Eccentric exercise as pictured above has a unique stimulus on the structure of the muscle and the nervous system's ability to communicate with the muscles not found in other exercise types.  Individuals are often too focused on the lift or shortening of the muscle and move too quickly through the eccentric portion of the lift.  This lowering is also associated with unique structural changes in the muscle likely responsible for the benefits listed above.

An article in the journal Medicine and Science in Sport and Exercise examined the impact of hamstring concentric and eccentric exercise on the muscle at both the tissue and functional level (Timmins et al. 2015).  The authors studied 28 individuals and randomized them to either concentric (shortening) or eccentric (lengthening) knee flexion (hamstring) strengthening.  The authors then examined the hamstring functionally and with an ultrasound during the 6 week training program and after 28 days of detraining.  The results showed improved hamstring length in the eccentric group, but no change in the concentric group.  As expected, the hamstring flexibility was lost after 28 days of detraining.

boulder physical therapy, flexibility, hamstring, eccentric exercise

Athletes should consider utilizing eccentric movements to restore strength, flexibility, and reduce injury risk.

Why is eccentric exercise helpful for achilles tendinopathy?

One of things I enjoy about the profession of Physical Therapy is its’ constantly changing nature of the medical evidence behind what we do.  Often I come across a new article or research report, which challenges my previous line of thought about an injury or treatment and requires me to change.  Achilles Tendinopathy is commonly and effectively treated with eccentric (lengthening) exercise in our practice.  My previous explanation on the benefits of this exercise was the positive structural effects noted in the tendon following this exercise prescription (see hyperlink above).  It now appears the structural change explanation does not completely explain the beneficial effects of this intervention.

eccentric exercise, achilles injury, physical therapy

Previously it was thought that the higher loads experienced during eccentric contractions in the Achilles tendon promoted structural adaptations, which remodeled (healed) the tendinopathy (Stanish et al. Clin Orthop. 1986).   These adaptations take time, often years, to complete yet our patients demonstrated decreased pain and improved function in less than 12 weeks.  The discrepancy between time to remodel and clinical improvement requires us to consider a different mechanism of action.

Recently, O’Neill and colleagues wrote an excellent clinical commentary in the International Journal of Sports Physical Therapy exploring other mechanisms behind the positive effects of eccentric exercise on this condition.  The authors described literature suggesting the neuromuscular output of the gastrocnemius and soleus muscles may explain more of the benefits behind exercise.  It is very common to find a loss of dorsiflexion (bending) of the ankle during the Physical Therapy examination in patients with Achilles tendinopathy.  Mueller et al. initially suggested patients with weakened plantar flexors of the ankle (heel raise or push off) use a smaller range of ankle dorsiflexion (bending) to optimize push off during walking (Phys Ther. 1995).  Thus treatments to restore ankle dorsiflexion will be more effective if we can restore the motor properties of the ankle plantarflexors.

Achilles Tendinopathy is a very painful condition and the tendon itself often has a lower threshold for producing a pain response through walking, stretch, or touch.  Authors note this may be due to an increase in nerve and blood vessel (neurovascular) growth into the tendon during the tendinopathy (Ohberg et al. Knee Surg Sports Traumatol Arthrosc. 2004).   Eccentric exercise may promote beneficial structural changes within these nerves and vessels through loading, but the contribution of neurovascular changes on a patient’s pain or prognosis is not known.

Authors previously reported a loss of plantarflexion strength and power is an independent risk factor for Achilles tendinopathy (Mahieu et al. Am J Sp Med. 2006).  It is likely that the calf muscle is able to shield the tendon to avoid excessive loading during walking or sports.  Improved strength and coordination through eccentric exercise also appears to coordinate and smooth muscle contractions in the calf thereby decreased asymmetrical loading patterns on the tendon.

physical therapy eccentric exercise, achilles tendinopathy, strengthening

In short, eccentric exercise remains a staple in the conservative Physical Therapy management of Achilles tendinopathy but the reasons on its’ effectiveness continue to develop.  Our current understanding makes passive interventions such as modalities, orthotics, etc. less likely to create the positive effects seen with exercise.  It appears the improvement in neuromuscular strength, balance, and coordination help shield the tendon from excessive loads.  In addition, these mechanismTo learn about the beneficial effects of eccentric exercise on tendon injuries contact the experts at Mend.