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Calf Weakness – June Newsletter

Implications of Age-Related Calf Weakness

John Fiore, PT

The trails and roads of Missoula confirm the following fact: 30 million people ran at least 50 days annually in the United States in 2012-2013.i Running efficiently and injury-free, however, is more elusive. Nearly 79% of all runners experience a running injury annually.ii As runners age, the primary site of overuse injuries changes from the knee to the Achilles, ankle, and calf. Observation of running stride (on the roads, trails, and in our running lab) and research correlates the increase lower leg injuries with altered running biomechanics and reduced calf muscle power measure as ground reaction (the reaction to the force the body exerts on the ground) force.iii

Picture of John Fiore hiking up side of mountain.Despite our best efforts to train consistently, understanding what happens to our running stride as we grow older allows us to shift our efforts on lower leg strengthening to reduce injury risk and maximize running performance. A September 9, 2015 article in the New York Times brought to the forefront the work of Paul DeVita, a professor of kinesiology at East Carolina University in Greenville, N.C., and president of the American Society of Biomechanics. Dr. DeVita’s 2016 research looked at running gait changes in a sample of 110 runners.iv The runners were a mix of male (54%) and female (48%) who had been injury free for at least 6 months. The age range was 23-59 years old. DeVita and his colleagues found that the older runners ran with a shorter stride length, a higher turnover (cadence) rate. The net result is a slower running pace which research has shown is due to altered running mechanics, decreased calf-lower leg muscle strength, and increased stiffness in the ankle with age. Between the ages of 20 and 60, runners typically experience a 31% reduction in ankle power, total power (ground reaction force to lift you off the ground and in a forward direction), along with a 13% decrease in stride length and running speed.

The statistics referenced above should be a strong motivator to middle-aged and young runners alike to be proactive with targeted strength training. Much of the internet focus on running injury reduction focused on foot strike pattern and core strength, the importance of the calf musculature (gastrocnemius, soleus) is often overlooked. The calf muscle aids in initiating the push-off phase of the running stride, and plays a key role in absorbing impact as your foot hits the ground. The importance of the calf muscle in absorbing impact loads is phenomenal: 160-180 foot strikes per minute with 2.5 times your body weight plus the force of gravity exerted through each foot strike over “x” number of minutes running equals a HUGE demand placed through the foot and lower lower leg. Eccentric (resisting gravity) calf strengthening will increase the resilience and shock absorption properties of your calf musculature, while concentric (against gravity) and plyometric strengthening will increase the power generation of your calf muscle. Ankle stiffness predisposes one to developing further calf weakness by further shortening stride length.

To summarize, DeVita’s research confirmed running stride length, speed, and lower leg muscle function decline in a linear manner with age. Calf (gastroc-soleus muscle) and ankle strength declines with age as well. A reduction in lower leg muscle strength (both concentric and eccentric) and ankle motion (dorsiflexion) shifts the burden of self-propulsion to our knees, hips and gluts which are already physically challenged by prolonged sitting and tight hip flexor muscles. Lower leg, foot, and Achilles tendon injuries become increasingly common in runners over forty. Gradual degradation of muscle and tendon tissue integrity and nerve innervation sets the stage for an increase in running-related overuse injuries. Stretching the calf and lower leg muscles, Active Release techniques, dynamic warm-up, and rolling are great ways to improve lower leg muscle tissue mobility. Lower leg, ankle, and foot strengthening exercises must be a part of every runner’s training program, not just those in the fourth decade of life and beyond. Strengthening exercises should include single leg heel raises, heel drops, resisted ankle inversion, eversion, dorsiflexion, and intrinsic foot strengthening exercises (*see photos below*).

If you have been battling a lower leg issues, call or email the running injury and biomechanics experts at Sapphire PT. Our physical therapists will not only return to pain-free running, but also reduce future injury occurrence while improving your running efficiency and performance. Targeted strengthening and muscle-tendon tissue mobility are the keys to improving running performance at any age.
demonstration of toe raise exercise demonstration of toe raise exercise demonstration of foot balance on uneven platform
demonstration of toe flexing exercise demonstration of foot exercise with band demonstration of foot exercise demonstration of box jump exercise demonstration of box jump exercise


Muscle of the Month: Tibialis Posterior

Jesse Dupre, DPT

image of the tibialis posteriorThe tibialis posterior is a relatively long muscle that is located deep in the back of the calf. It originates at the inner edges of the tibia and fibula, as well as the interosseous membrane, and runs the length of the calf. The tendon of the tibialis posterior wraps around the medial malleolus and inserts at the navicular, cuneiforms and metatarsals on the plantar, or underside of the foot.

The role of the tibialis posterior is to plantar flex and invert the ankle, or tilt the foot and ankle down and in. The more important function of the tibialis posterior is to support and stabilize the foot and ankle when weight bearing. Weakness or poor function of the tibialis posterior can contribute to decreased ankle stability and increase injury risk at the ankle and foot.

Acting with the fibularis longus, the tibialis posterior helps support the longitudinal arch of the foot. When the tibialis posterior contracts eccentrically, it acts to control ankle pronation when standing, walking or running. Ankle pronation is necessary as part of shock absorption when landing or stepping. However, if the foot and ankle are allowed to pronate too much or too quickly, or remain pronated for too long during the stance phase of the gait cycle, it can increase the stresses on the Achilles tendon and plantar fascia, increasing injury risk. The tibialis posterior does not act alone to stabilize the foot, but when coordinated with the intrinsic muscles of the foot and muscles at the hip it will help control pronation and the foot to function optimally and ultimately help decrease risk of injury.

picture of an exercise to help strengthen the tibialis posteriorAn exercise that can be used to strengthen the tibialis posterior is open chain ankle inversion. Start with a band at the ball of the foot so the band is oriented outward. Allow the band to pull your foot slightly up and out (pronation), and then use the muscles in the ankle to move the foot down and in (supination) against the resistance of the band. Repeat.


References:
Reynolds G, Why Runners Get Slower with Age. New York Times. 2015, Sept 9.
i Running U. Running USA 2014 state of the sport – part ii: running industry report http://wwwrunningusaorg/2014-running-industry-report?returnTo=annual-reports. 2014.
ii Goss DL, Gross MT. A review of mechanics and injury trends among various running styles. US Army Med Dep J. 2012; 62–71.
iiiMcKean KA, Manson NA, Stanish WD. Musculoskeletal injury in the masters runners. Clin J Sport Med. 2006; 16 (2): 149–54.
ivDeVita P, Fellin RE, Seay JF. The relationship between age and running biomechanics. Med & Sci Sports & Exerc. 2016; 48 (1): 98-196.