Posts tagged stretching
Stretching Not Shown To Improve Muscle Length
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Static stretching, involving holding a muscle at end of its’ length for a sustained period of time, is a common component of most individual’s exercise programs but its’ useful compared to other forms of exercise including aerobic and strength training is questionable. Research is unclear on the benefits of static stretching for most individuals, as well as, the ideal parameters for the most effective stretch. Conversely, utilization of mobility or dynamic warm up activities has been shown to improve subsequent performance and reduce an individual’s injury risk.

Our understanding behind the benefits of static stretching has evolved over the years due to research indicating flexibility gains are more likely due to changes in stretch tolerance (neural adaptations) vs. changes in length (muscular adaptations). Thus, individuals who stretch reduce their sensitivity to the tensile load and in turn are able to stretch beyond previous sensory barriers. A recent review of the literature shines further light on this area of exercise and further questions previously held beliefs.

Freitas and colleagues reviewed the available evidence on the impact of stretching on muscle and tendon tissue (Scand J Med Sci Sports. 2018). Authors reviewed 26 studies for their review of the literature. They reported stretching programs ranged from 3 to 8 weeks with an average of 20 minutes of exercise per week. Consistent with our current understanding participants demonstrated improvements in tolerance to passive stretch after training, but no changes were noted in muscle or tendon mechanical properties. This indicates the flexibility gains which followed the exercise programs were primarily due to an improvement in the ability to tolerate a stretch (desensitization). Thus, the authors concluded benefits experienced under 8 weeks are most likely to occur at the sensory level. Those without a specific mobility need (ex. post operatively or post immobilization) are advised to strength train through a complete range of motion to maintain and improve their current flexibility.

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Does Hamstring Stretching Improve Muscle Length?
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Stretching either dynamically or statically has long been shown to create both short and long term improvements in flexibility, but the mechanism of action behind this form of exercise continues to evolve. Changing human tissue takes considerable time and consistent forces. For example, consider muscle growth or bone density adaptions to exercise. Previous research on the benefits of stretching assumed a structural change in the muscle (sarcomeres in series) was responsible for improvements in muscle flexibility, but more recent research demonstrates improvements in stretch tolerance are more responsible for these positive changes. A recent article examined these mechanisms in a group of individuals with limited hamstring length.

Brusco and colleagues assessed the impact of static hamstring stretching in a group of individuals with limited hamstring flexibility (Eur J App Physiology. 2019). Participants performed a seated hamstring stretch on an isokinetic machine to their maximum tolerance. Hamstrings were stretched for 8 bouts of 60 seconds, twice a week for 6 weeks. Total duration under stretch equaled 96 minutes over the 6 weeks. Authored measured both flexibility and muscle characteristics before and after the study. Consistent with prior research each individual’s range of motion improved but no changes in muscle tendon mechanical properties were noted. This indicates improvements in flexibility were secondary to the improvements in an individual’s tolerance to stretch. Thus, trained individuals were conditioned to tolerate more stretch as they moved through the study.

Is Lack Of Mobility Or Flexibility A Factor In My Running Injury?
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Lower extremity stiffness (“leg stiffness”) describes the resistance the joints and muscles in your lower body will have to movement when your foot contacts the ground during running. Think of your leg as a spring; the more tightly coiled spring will be stiffer, the more loosely coiled will be more deformable. A stiffer leg is associated with less joint movement (less mobility) and increased loads to bones and cartilage whereas a less stiff leg is associated with increased joint motion/mobility and relies more heavily on active muscle contraction to dissipate forces when your foot hits the ground.

 Leg stiffness may be one of many variables that contribute to running related injuries. A recent study of 92 runners {Goodwin:2019bk} identified 4 variables that may allow us to more easily predict leg stiffness with clinical measures versus technical laboratory analysis. Less mobility in the ankle joint, hip and big toe joint along with increased BMI are associated with greater leg stiffness. What is the clinical significance of this for our Boulder runners? For runners suffering from knee pain or stress fractures, reducing leg stiffness by improving the mobility of hip, ankle and foot may reduce joint loading. Conversely, in runners with soft tissue injuries such as Achilles or tibialis posterior tendinopathy, increasing leg stiffness with targeted strengthening exercises to improved stability and control of the joints of the lower extremity may be an important component of rehabilitation.

Contact your physical therapy experts at Mend to learn more about how your mobility may contribute to running injury.

Eccentric Quad Strengthening Shown To Improve Strength And Flexibility Of Muscle
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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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Should I Stretch My Pectoral Muscles To Relieve My Shoulder Pain?
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Our current understanding of posture has changed dramatically over the past 20 years due to the influx of scientific literature on posture and muscle and joint pain. Previously, posture was thought to be strongly associated with muscles imbalances including tightness or weakness. For example, forward shoulders were thought to be associated with shortened pectoral muscles. Our current understanding has reduced the importance of posture on both clinical decision making and an association with a patient’s current symptoms. Patient’s with poor posture can demonstrate normal muscle function and those with great posture can demonstrate significant muscle imbalances and pain. A recent research paper highlights these concepts on patient’s with shoulder pain.

Navarro-Ledesma and colleagues examined the muscle length and available joint space in patients with shoulder pain compared to their pain free peers (PT in Sport. 2018). Each participant’s pectoral minor length and shoulder joint (subacromial) space was measured clinically with ultrasound. The authors reported pectoral muscle length was poorly associated with both shoulder joint space and the presence of shoulder pain. These findings are consistent with our currently held belief on the limited importance of pectoral muscle length or flexibility and the presence or development of shoulder pain. Patient’s are encouraged to work with a local Physical Therapist on a shoulder and shoulder blade strengthening program instead of stretching their pectoral or chest muscles.

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Reducing Your Risk Of Developing Low Back Pain
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Death and taxes are said to be the two certainties in life for adults, but Ben Franklin may have added low back pain given its’ current prevalence. Up to 90% of adults will report an episode of low back pain during their lifetimes. Fortunately, the vast majority of these episodes are not secondary to any serious pathology in the spine and respond well to low cost, conservative treatments including Physical Therapy interventions such as manual therapy and exercise interventions. In particular, strength training is one of the most effective treatment options to get you back to 100% after these acute low back pain episodes. To paraphrase again from Franklin, if you had an ounce of prevention new research reports it would be composed of exercise.

Researchers in the American Journal of Epidemiology conducted a review of the available evidence on the prevention of low back pain (Shiri et al. 2018). Authors reviewed 13 randomized controlled trials and 3 non randomized controlled trials for the analysis. They reported exercise alone reduced a person’s risk of developing low back pain by 33%. In addition, the severity and disability of the patient’s low back was also less in the active group compared to their sedentary peers. Authors recommended combining aerobic or stretching exercise with strength training, 2-3 days per week, for reducing a person’s risk of development of low back pain.