Calf Injuries and Masters Runners

Calf injuries don’t distinguish between victims. Consider David Habas. Habas, 56, has chronicled an impressive resume’ of endurance events during his athletic career.

A franchise operator from Lafayette, Cal., he has completed an Ironman triathlon, three marathons and ten half-marathons. But, despite his success in endurance sports, there is one thing that stands in his way of continued competition: injuries.

“It’s been frustrating, I’ve had to cut my running back a lot because of fears of re-injuring my calf,” Habas says. “If I keep my runs to below an hour, aggravation of the problem seems to be less likely.”

For many runners like Habas, the masters years are notable for an increase in the risk of injury. In a study of injury rates among runners, roughly half of master runners reported a running-related injury in the previous year, compared with only 45 percent of younger runners. Masters runners (30 percent) were also more likely to sustain multiple injuries compared to their younger counterparts (24 percent).

Strong Knees, Iffy Calves

While many automatically associate age and running with arthritis, those fears seem largely unfounded. In addition to research that shows the cumulative joint stress of running to be roughly equal to that of walking, a recent study found that the rate of arthritis among marathoners (9-percent) to be half that of the general population (18-percent).

“The thing that is important for Master runners, is that running seems to be protective for the cartilage, reducing the risk of knee arthritis and improving knee health,” says Rich Willy, a researcher and assistant professor at the University of Montana. But, while cartilage injuries are less of a concern, many older runners are plagued by recurrent muscle strains, especially to the calf muscles.

Muscle and tendon injuries can be a greater problem for older runners. Calf injuries in particular seem to be a male problem: a study of Masters runners reported that 70-percent of calf muscle injuries were to male runners, likely because men seem to experience more changes to muscles and tendons stiffness with aging than women.

Twitching Fast and Slow

The calf complex, sometimes referred to the as the triceps surae, is composed of two key muscles: the gastrocnemius, primarily fast twitch muscle fibers, and the soleus, a key muscle for running as it is composed of mostly slow twitch muscle fibers. Both attach to the heel bone via the common Achilles tendon.

The anatomy and fiber type of each of the two calf muscles contribute significantly to the manner in which the muscles are most commonly injured. The more powerful gastrocnemius muscle is most often injured during more quick or explosive movements — hence the sports medicine nickname “tennis leg” — with the knee straight and ankle flexed. An endurance muscle, soleus strains are more the result of overuse and repetitive stress and typically occur as a result of fatigue, uphill running or at the end of long runs.

“The calf strains occurred in both calf muscles at different times,” says Habas, “I first began experiencing calf strains in my mid 30’s and as my mileage increased, anything over 7 to 10 miles at a time, they became more frequent. After 40-years old the muscle strains became even more chronic.”

Losing Stiffness and Power

The reason behind the increase in calf injuries in older runners, says Willy, lies in age-associated changes to the muscles and tendons. “One big factor is that when we age, we lose collagen in our tendon structure, and that leads to a decrease in tendon stiffness,” says Willy.  “We like to have stiff tendons because, like a spring, a stiffer tendon stores and releases energy better. So, when we have an Achilles tendon that goes through more elongation, that leads to more strain on the tendon and calf muscle, making someone more prone to Achilles tendinopathy and calf strains.”

Along with other important performance characteristics like aerobic capacity, muscle function — strength, mass, cross-sectional area, force production—is gradually lost with aging. Notably, the power of the calf muscles during running can get cut in half between the ages of 20 and 80. This loss of calf power is not balanced by any increase in power from the quads, glutes or hamstring.

“Aging leads to a muscle being less capable of creating force,” says Willy, “and the muscle can’t resist big stretches without causing injury.”

A weak calf muscle coupled with a floppy Achilles tendon then changes the springiness of the leg when running. From a performance standpoint, often overshadowed by the hip, quads and glutes, the calf muscles are arguably the most important leg muscles for runners. That importance makes the calf muscles all the more vulnerable to age-associated changes in function.

“I had numerous physical therapy sessions and also ART over the years,” relates Habas. “But it appeared that most of the cause was a lack of strength in both calf muscles. When I fell off on the strengthening is when the strains would reoccur.”

“You can get away with a loss in hip and quad strength,” emphasizes Willy, “Because you’re not putting those muscles under as big a demand when running. Aging doesn’t cause them to bump up to edge of muscle capacity as easily. However, with the large contribution of the calf to running, you bump up to edge of their capacity with the age-related loss of calf function. That’s why injuries manifest in the calf of masters runners.”

In addition to these physiological changes, one other factor, a decrease in stride length, plays a role in the altered biomechanics seen in Masters runners. In fact, research highlights a 13 percent reduction in step length between 20 and 60 years of age, with a 20 percent reduction in step length by 80 years old. Consequently, older runners, even when running at the same speed as a younger athlete, exhibit a 4 to 6-percent increase in stride frequency.

Resisting the Decline

In general, reversing or slowing down these changes, says Willy, is the key to reducing the risk of calf muscle injury or re-injury. Strong evidence indicates that heavy resistance training can increase both tendon stiffness and muscle strength. Lifting lower loads can also increase strength but have little effect on tendon stiffness.

How much is heavy? Use a weight that is 70-percent of the maximum you can lift one time, or a weight that can’t be lifted more than 10 repetitions. The load should be sufficient enough to cause fatigue by 6 to 10 repetitions.

Add weight to calf raises: Do both straight-leg calf raises (for the gastrocnemius) and bent-knee calf raises to target the soleus. Do three or four sets to fatigue (6–10 reps) of each exercise 2 to 3 days per week.

Plyometric training can also have a beneficial effect on tendon stiffness but might pose a greater risk of injury to the Masters runner. “It would be best to try 6 months of heavy strength training before trying to incorporate any plyometrics,” says Willy.

Because they lead to changes in leg stiffness, running on soft surfaces, like sand or trails, or wearing soft, cushioned shoes, often pushes muscles closer to the injury threshold. Harder running surfaces and a stiff shoe are the best bet for injury-prone calf muscles. Calf-shy masters also may not benefit from a lower drop, or flat, shoe as it shifts load to the calf and Achilles tendon. For those looking to prevent a calf injury, Willy recommends a higher drop shoe or heel lift until you have built the necessary strength and mobility.

Calf strains can be incredibly frustrating and limiting. The good news, however, is that they can be addressed with straightforward interventions and don’t require surgery or more extreme medical measures.