What is a Calf Muscle Strain Injury (CMSI)?
The lower leg is a critical biomechanical component during movements requiring both explosive power and prolonged endurance. The calf complex is essential during any weight bearing or locomotive activity to absorb and produce large amounts of force.1
Calf muscle strain injuries (CSMI) are common across sports involving high-speed running or high volumes of running load, acceleration, deceleration and upon fatiguing conditions. Muscle strain injuries involve a partial tear to the muscle and commonly occur in bi-articular muscles such as the hamstrings, rectus femoris and gastrocnemius.1,2
During sporting activities such as sprinting, these long, bi-articular muscles have to cope with high internal forces and rapid changes in muscle length and mode of contraction leading to a higher risk of strain. Muscle strains have also been reported to occur during slow-lengthening muscle actions.1,2
WHAT STRUCTURES ARE INVOLVED?
The calf, otherwise known as the triceps surae, consists of the gastrocnemius, soleus and plantaris. The aponeurosis and tendons of these three muscles converge to form the Achilles tendon.3
The gastrocnemius is the most superficial muscle of the triceps surae, containing a higher proportion of type II fast twitch fibres than soleus. The gastrocnemius is ~50% fast twitch and ~50% slow twitch muscle fibres.3 Its high proportion of fast twitch fibres is reflective of its function in tasks that require rapid contractions such as jumping, sprinting and acceleration.3,4
The soleus is a broad and flat multipennate muscle that sits deep to the gastrocnemius. The soleus accounts for ~71% of the muscle bulk of triceps surae, and contributes up to two-thirds force production.5 The soleus is comprised of 80-100% slow twitch muscle fibres, hence contributes primarily to tasks such as postural control and walking.6
The plantaris muscle is located in the posterosuperficial compartment of the calf complex. It works alongside the gastrocnemius as both a flexor of the knee and a plantarflexor of the ankle.1
WHAT ARE THE RISK FACTORS FOR CMSI? 7
Increased chronological age
Previous ankle, knee or calf injury
Previous hamstring, quadriceps or adductor strains
Increase in training loads
Large running demands in sport
Overweight
Figure 1: Intrinsic and extrinsic risk factors for CMSI 7
WHAT ARE THE SIGNS AND SYMPTOMS?
Gastrocnemius Strain:
The gastrocnemius is at high risk of strains because it crosses both the knee and the ankle as well as due to it having a large number of fast-twitch muscle fibres. A tear of the medial head of the gastrocnemius commonly occurs when the muscle attempts to contract in an already lengthened position.2,3,5 This is due to an eccentric force being applied to the muscle when the knee is extended and the ankle is dorsiflexed. The characteristics of a gastrocnemius strain include:
Sudden sharp pain or tearing sensation
Tenderness to touch at point of injury
Swelling
Bruising may appear
Stretching of the muscle will reproduce pain
Pain on resisted plantarflexion (calf raise)
Soleus Strain:
The soleus muscle is considered more of a long risk of injury is injured while the knee is in flexion. Unlike the gastrocnemius, the soleus only crosses the ankle and largely comprised of slow-twitch fibres. Soleus strains are commonly more subacute and frequently occur in the middle-aged, poorly conditioned and/or physically active patient.4
The presentation will likely be similar to gastrocnemius strain as mentioned above, however, the pain may be slightly more distal and feel deeper subjectively. Pain is reproduced when stretching the calf, walking on tip-toe and when compression is applied to the Achilles tendon.4
Plantaris Strain:
The plantaris muscle is similar to the gastrocnemius as it crosses the knee and the ankle joint as well. Depending on the extent of the injury, the individual may be able to continue exercising although they will have some discomfort and/or tightness during or after activity. When more severe, the exact mechanism of injury is easier to recall and/or the individual may be unable to walk due to severe pain. Injury to the plantaris muscle can present with similar clinical features as those of the gastrocnemius and soleus muscle.1
HOW LONG WILL IT TAKE TO GO AWAY?
Depending on the grade of muscle strain, the time period for returning to play will vary. Muscle strains are graded from one to three with three being the most severe. The treatment and rehabilitation will depend on the severity of the muscle strain as shown below in Figure 2.8
Figure 2: Grading and returning to sport for CMSI 7
REHABILITATION
There are a variety of factors that play a role in the time taken to achieve recovery milestones during rehabilitation of CMSI. The factors that appear to be most important and associated with longer recoveries are increased age, presence of aponeurotic disfunction, soleus injury, previous calf or ankle injury and if it was from a running related mechanism.9
When rehabilitating an athlete from a calf injury, the therapist must consider the demands of the sport and ensure these are incorporated into the rehabilitation. Rehabilitation for an athlete must include strength and power progressions through vertical, horizontal and off-axis planes of movement. The patient must also be exposed to accelerations and decelerations, agility challenges, sport specific training drills and advanced plyometrics that prepare the athlete for the jumping and running demands of the sport.2,7
To assist in facilitating the exercise prescription manual therapy such as soft tissue therapy, dry needling and passive talocrural joint mobilisations to regain full knee to wall range of movement. With regards to exercise selection, it is important to consider both the tensile force exposed to the calf and the loading rate. Figure 3 shows the significant differences in loading rate between standing calf raises and running, thus it is important that other exercises at high velocity are used in rehabilitation prior to returning that athlete to running.10
Figure 3: Tensile force and loading rate comparing calf raises to running at various speeds10
The initial phases of rehabilitation focused on regaining strength and power through vertical and horizontal force vectors. This phase of the rehabilitation was prior to the athlete returning to running, and was comprised of standing and seated calf raises, and commencement of a plyometric continuum to prepare the patient for the demands that running places on the calf. Figure 4 presents a graphical representation of the exercise progressions that were used to restore strength and power to build the athlete up to running. As the soleus muscle has poor sensory innervation, pain was not used as a guide to determine when exercises were ready to be progressed.10 Instead, the athlete needed to be able to perform the task without any awareness from the soleus
Figure 4: Exercise progressions used to gradually prepare the athlete for the demands of running.9
Regaining strength with calf raises is an important component for regaining the ability to run, alongside exercises at higher velocity such as plyometrics and running drills. Importantly, long and slow runs are to be avoided initially due to their high demands on the calf complex.9 The calf has high forces at all speeds and does not experience an exponential increase in force as speed increases like other muscles such as the hamstrings. Importantly during running progressions, there was the addition of decelerations and a focus on acceleration running mechanics.
During running, there is minimal lengthening of the muscle fascicles.11 The tendon lengthens at initial foot strike, and then shortens at toe-off. The muscle works quasi-isometrically, while the tendon facilitates stretch-shortening.11 In the rehabilitation, adequate plyometric loading to ensure appropriate tendon adaptation is essential. When this athlete was able to demonstrate a safe return to slow steady state running, plyometrics were progressed to include exercises such as single leg drop jumps, continuous hurdle hops and squat jumps. These exercises facilitate the significant demands on the Achilles tendon during running and jumping tasks required for athletes.
References:
Green B, Pizzari T. Calf muscle strain injuries in sport: a systematic review of risk factors for injury. British Journal of Sports Medicine. 2017 Mar 4;51(16): 1189–94. DOI: 10.1136/bjsports-2016-097177
Green B, McClelland JA, Semciw AI, Schache AG, McCall A, Pizzari T. The Assessment, Management and Prevention of Calf Muscle Strain Injuries: A Qualitative Study of the Practices and Perspectives of 20 Expert Sports Clinicians. Sports Medicine - Open. 2022 Jan 15; 8(1). DOI: https://doi.org/10.1186/s40798-021-00364-0
Prakash, A., Entwisle, T., Schneider, M., Brukner, P., & Connell, D. Connective tissue injury in calf muscle tears and return to play: MRI correlation. British Journal of Sports Medicine. 2018 Jul; 52(14), 929-933. DOI: 10.1136/bjsports-2017-098362
Balius, R., Alomar, X., Rodas, G., Miguel-Pérez, M., Pedret, C., Dobado, M. C., . . . Koulouris, G. The soleus muscle: MRI, anatomic and histologic findings in cadavers with clinical correlation of strain injury distribution. Skeletal radiology. 2013 Apr; 42(4), 521-530. DOI: 10.1007/s00256-012-1513-3
Green, B., Lin, M., Schache, A. G., McClelland, J. A., Semciw, A. I., Rotstein, A., . . . Pizzari, T. Calf muscle strain injuries in elite Australian Football players: A descriptive epidemiological evaluation. Scandinavian journal of medicine & science in sports. 2020 Jan; 30(1), 174-184. DOI: 10.1111/sms.13552
Koulouris, G., Ting, A. Y., Jhamb, A., Connell, D., & Kavanagh, E. C. Magnetic resonance imaging findings of injuries to the calf muscle complex. Skeletal radiology. 2007 Oct; 36(10), 921-927. DOI: 10.1007/s00256-007-0306-6
Pizzari, T. The risks, epidemiology and return to play of calf muscle strain injuries - by Tania Pizzari. 2021 Mar 16.
Brukner P, Khan K, Clarsen B, Cook J, Cools A, Crossley K, et al. Brukner & Khan’s clinical sports medicine. 5th ed. Vol. 1. North Ryde, New South Wales: Mcgraw-Hill Education; 2017.
Glascow, P. The calf complex: From rehabilitation to return to performance by Phil Glascow. 2021 Mar 23.
Purdam, C. Calf muscle strain injuries - zooming in at the tissue level- by Prof Craig Purdam. In. 2021 Apr 5.
Lai, A., Schache, A. G., Brown, N. A., & Pandy, M. G. Human ankle plantar flexor muscle–tendon mechanics and energetics during maximum acceleration sprinting. Journal of the Royal Society Interface. 2016 Aug; 13(121), 20160391.
