Calf muscle injuries represent one of the highest soft tissue injury incidences (3.0 per club per season) and recurrences (16%) in Australian Rules football (1).
There are two main calf muscles, the Gastrocnemius and the Soleus. Gastrocnemius crosses the knee and ankle and is largely made up of Type 2 (Fast twitch) fibres. Its fibre type, in addition to the fact that it crosses both the knee and the ankle, means it is more commonly injured during high force or high velocity movements involving knee extension (straightening) while the heel lowers towards the ground. The Gastrocnemius can produce loads of 3 x bodyweight during running tasks, with this peaking at approximately 7m/s (25km/hr) (2)
Soleus only crosses the ankle joint but has a large surface area and is made up of mainly Type 1 (Slow twitch) fibres. Soleus is more commonly injured during positions of high loading when the knee is bent. Due to its slow twitch fibre dominance, it is also common to have delayed onset Soleus injuries, that present as a gradual “tightening” instead of a clear acute event. The Soleus often takes up to 8 x bodyweight loads during running tasks, also peaking at 7m/s. Research has shown that Soleus strains make up 84% of calf injuries (3)
These anatomical differences have a profound effect on how we should be rehabilitating these injuries. A proper assessment to specifically diagnose th
e location of a calf muscle strain injury is imperative to a safe and effective return to play.
Key components of Calf rehabilitation
Return to Running considerations
· It is very important to consider the location and severity of a calf muscle injury before planning returning to run. While gastrocnemius loads peak at approximately 7m/s (25km/hr), the differences in loads are only between 1 and 3 x bodyweight as we progress from 3.5m/s to 7m/s. This means that we can generally perform lower velocity running early and safely. Soleus, which also peaks at 7m/s, has much higher loads at slower speeds, often up to 7 x bodyweight at 3.5m/s (12km/hr) (2). This means that jogging or “junk running” is ill advised when initiating a running program for Soleus injuries.
· We generally advise a period of running drills and progressions of these as a priority before formal running is initiated. Due to the high loads put through the calf complex at even low running speeds, we need to prioritise calf capacity and function before returning to running.
· While the soleus is largely a slow twitch muscle type, it has been shown to produce the largest loads of any lower limb muscle during accelerative tasks (4). Highlighting the importance of a gradual re introduction to acceleration and change of direction loads.
Locomotor loading
· Early in rehab it is important to focus on loading through our gait cycle. Exercises including loaded carries, marches and sled walks are useful to mimic the bodyweight loads that go through our calf complex during locomotor tasks.
Endurance Capacity
· High rep, low load exercises for max reps, both straight knee and bent knee
High Load Strength – through range
· Heavy, low-moderate repetition exercises including standing and seated calf raise strengthening for sets of 6-8 reps to fatigue.
High Load Isometric Strength (Long duration)
· Due to the calf complex (particularly Soleus) behaving near isometrically during higher running velocities and wanting to target Musculotendinous unit strength, incorporating heavy, prolonged holds for 20-30s will help expose the calf complex to appropriate isometric loads
Reactive, High load short duration isometrics
· By performing an isometric hold for 2-3s and quickly “switching” limbs, this targets our calf complex ability to “react” to heavy loads without a deformation in muscle length.
Early Rate of Force Development Plyometrics
· Plyometric tasks that are focused on short contact times will help the function of our calf complex / Achilles te
ndon unit tolerate high forces which will mimic that of high speed running. Drop jumps are a good example of this
Late Rate of Force Development Plyometrics
· Exercises focusing on power development at slightly slower speeds, which will mimic calf loads during acceleration. Counter-Movement jumps are an example.
In summary, there are many factors that make up a comprehensive calf rehabilitation program. These will depend on your goals, chosen sport or activity, injury history and athletic profile. Make sure you get a proper and thorough assessment before beginning any formal rehabilitation for a calf muscle strain.
References
1) Orchard J, Seward H, Orchard J. AFL injury report. Australian Football League (AFL) 2014;2014:1–20
2) Dorn T, Schache A, Pandy M. Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance. J Exp Biol (2012) 215 (11): 1944–1956.
3) Green B, Lin M, Schache, A, McClelland J, Semciw A, Rothstein A, Cook J, Pizzara T. Calf muscle strain injuries in elite Australian Football players: A descriptive epidemiological evaluation. Scand J Med Sci Sports. 2020 Jan;30(1):174-184.
4) Hammer S, Delp S. Muscle contributions to fore-aft and vertical body mass center accelerations over a range of running speeds