Calf Muscle Strain injuries in Runners (2025 update)
Epidemiology pop
Calf muscle strain injuries (CMSI) are a common running related injury. In athletics they are the third most common injury ranking behind hamstring strain injuries and achilles tendinopathy (Kelly et al, 2022). Kelly et al (2022) reported a soleus muscle strain injury incidence of 0.1 per athlete year, and a mean time loss of 25.1 days. This is in comparison to the 18.8days mean time loss Kelly et al (2022) reported for hamstring strain injuries. There can be high recurrence rates for calf muscle strain injuries, with Green (2020) outlining that there is heightened risk for the first eight weeks post index injury and that approximately ninety percent of all repeat CMSI will occur at the soleus. Green determined that a running related mechanism of injury would often be consistent with soleus based injury, and that this MOI was associated with the longest return to play times.
Known risk factors for CMSI include the ageing athlete, a prior history of CMSI. The ageing athlete will lose approximately 30% of plantar flexor force production (1% per year) from 30 years of age onwards. The below image from Dr Rich Willy presented at the 2018 La Trobe University Running Symposium depicts this reduction in force generation and achilles tendon stiffness. Regression models based on runners across adulthood predict a 13% reduction in step length between 20 and 60 years of age, with a 20% reduction in step length by the age of 80 (Willy & Paquette, 2019). Concentric ankle power during running can decrease up to 47.9% between ages 20 to 80 (Willy & Paquette, 2019). Greater eccentric elongation of the plantarflexor musculature can occur in the masters runner due to a more compliant achilles tendon. Therefore it is not surprising that CMSI are common in master runners.
Image Source: Rich Willy, 2018 La Trobe Running Symposium
Functional Anatomy
Notably the plantarflexor musculature are the largest muscular contributors to propulsion and vertical support during running with circa fifty percent of propulsion for running being derived from ‘below the knee’.
A calf muscle strain can occur to either of the two primary ‘calf muscles’; the soleus or gastrocnemius. Anatomically within the soleus muscle there are three intramuscular tendinous structures: medial and lateral aponeuroses, and a distal central tendon, shown below.
Soleus intramuscular tendons: (1) medial and lateral aponeuroses, (2) central tendon. (Source:Dalmau-Pastor et al 2014)
The purpose of these three soleus tendinous structures is to act like rigid fibrous ‘struts’ to assist the upper part of the soleus to gain more origin. The gastrocnemius and plantaris are biarticular muscles responsible for both knee flexion and ankle plantar flexion. The soleus is a uniarticular muscle responsible for ankle plantar flexion. The plantaris is generally considered a vestigial muscle and provides a weak contribution to knee and ankle flexion when it is functional (Dalmau-Pastor et al 2014).
Although the gastrocnemius has a mix of fibers, more are fast twitch (type 2) muscle fibers allowing for explosive/powerful contractions. The soleus is primarily composed of slow twitch (type 1 muscle fibers) and is the key muscle for endurance running. The anatomical elements of gastrocnemius and soleus inform their function. Soleous is often referred to as the ‘powerhouse’ of the running kinetic chain, generating up to eight times body weight in force production with running irrespective of running velocity (Dorn et al 2012). The soleus plays a key postural role, resists triple flexion of the foot-ankle- knee, and draws the tibia posteriorly, and is proportionately comprised of Type 1 slow twitch muscle fibres reflective of its ‘endurance’ role. In contrast the gastrocnemius has a phasic recruitment pattern whereby higher force production occurs with higher velocity running, up to three to four times body weight (Dorn et al 2012), being predominantly composed of fast twitch fibres.
Imaging
Imaging to determine the integrity of possible aponeurotic or tendon involvement with CMSI can be very helpful. While imaging is not required to make a diagnosis of CMSI, practitioners that do not image soft tissue calf injuries do run a risk of ‘getting caught out’ if -don’t get caught out in the rehab (ie not progressing, or not breaking down) -be proactive even for mild- moderate, def for severe. Prakash et al 2020 reported that mean time to RTP with grade 0 injuries was 8 days, grade 1 tears was 17days, grade 2 tears 25days and grade 3 tears was 48days. They concluded that the integrity of the connective tissue can be used to estimate and guide RTP.
Rehabilitation of CMSI
Despite CMSI being highly prevalent across running sports there is a dearth of research to guide clinicians in their rehabilitation and prevention efforts.
Conceptually the key rehabilitation principles for successful CMSI rehabilitation are ensuring an accurate diagnosis has been made, the treating practitioner has a clear understanding of the demands associated with the return to sport (RTS) aspirations of the athlete, and a rehabilitation program that addresses impairments identified through physical examination and history taking. Inherent in such an approach is addressing identified risk factors which will vary between athletes.
Green et al 2022 published a seminal rehabilitation guide which was informed by their qualitative research whereby they interviewed twenty expert clinicians on their approach to the rehabilitation of CMSI. Key findings from this paper included the experts concurred that CMSI characteristics were unique in comparison to other sift tissue injury strains. The experts stressed the need for close ongoing monitoring of calf capacity and symptoms through rehabilitation, and that a universal injury prevention program for CMSI rehabilitation did not exist. Rather the experts agreed that individualised strategies should reflect athlete intrinsic characteristics and sports demands.
The experts concurred that while best management is highly context driven and individualised , exercise therapy and load were progressed sequentially along six management phases. These six management phases were: acute injury, early rehabilitation, intermediate rehabilitation, return to full training, return to play, and post return to play. The authors outlined that as rehabilitation progressed clinical reasoning would progress from a ‘medical mindset’ to a ‘performance mindset’.
A clinical construct I find helpful in educating patients and athlete stakeholders around is the ‘calf capacity’ stool (see below image). Each leg of the calf capacity stool represents a different characteristic of requisite calf function for return to sport. These functional components are: peak force (Fmax) development, repeated force (endurance), and reactive strength (plyometric properties). These calf muscle properties need to be assessed and ideally quantified through the assessment, with any impairments being addressed through progressive exercise therapy.
The experts agreed that successful CMSI management was perceived to be determined by three outcomes: return to play as safe as possible, restoration of the athlete’s performance to the required level, and no adverse effects such as injury recurrence.
Return to Run Considerations
There are several key considerations for treating practitioners when returning an athlete to running following a CMSI. The athlete’s prior history, current physical capacity, level of sport returning to, and other variables will collectively influence the decision making regarding the athlete’s return to running and sports.
With a high risk and rate of recurrence following CMSI, it is important that the practitioner doesn’t feel rushed trying to return the athlete to running too soon. It may be clinically more wise to hold someone back a bit longer in the early phases of rehabilitation. However it is a fine line between holding a runner back to reduce the risk of further injury, and holding a runner back for too long and potentially deconditioning the runner.
Green (2021) outlined several clinical criteria that can be used for clearing an athlete to commence running. These clinical criteria can include: pain free walking, pain free single leg hoping & single leg calf raising, nil pain on stretch or palpation.
Return to run programming for soleus CMSI should ideally avoid too much early volume, and in particular slow loading that occurs with steady state running. This approach can assist with reducing some of the accrued fatigue that elevates soleus strain risk.
A few clinical tips with return to run programming post CMSI:
- Begin with small intervals, for example may start with 10x 50m and progress to 10x 100m> 1min> 2min> 3mins> 4mins, when satisfied add in strides eg 4×60-80m, 6×60-80m, 8×60-80m twice per week.
- Can use standing and no walking between run bouts (to reduce re-injury risk)
- Schedule runs on alternate days
- Always allow adequate recovery between each bout of running
- When introducing back: back days be careful if training has been extensive/long duration. One strategy can be to schedule/allow for maximum time between runs on consecutive days
- Be mindful of how a runner recovers after their weekly long run. This can be a time where the risk for recurrence may be elevated. A strategy here may be to allow for example 48 hours post long run before a workout is scheduled.
- Be careful when adding intensity and hills concurrently.
- Stiff surfaces are generally better than compliant (soft) surfaces such as grass for a runner returning from a CMSI. The less stiff surfaces will increase muscle demands and may serve to elevate the risk of recurrence.
Brad Beer
APA Titled Sports & Exercise Physiotherapist (APAM), POGO Founder
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References
- Kelly S, Pollock N, Polglass G, Clarsen B. Injury and Illness in Elite Athletics: A Prospective Cohort Study Over Three Seasons. Int J Sports Phys Ther. 2022 Apr 1;17(3):420-433. doi: 10.26603/001c.32589. PMID: 35391874; PMCID: PMC8975568.
- Green B, Lin M, Schache AG, et al. Calf muscle strain injuries in elite Australian Football players: A descriptive epidemiological evaluation. Scand J Med Sci Sports. 2020; 30: 174–184. https://doi.org/10.1111/sms.13552.
- Willy RW, Paquette MR. The Physiology and Biomechanics of the Master Runner. Sports Med Arthrosc Rev. 2019 Mar;27(1):15-21. doi: 10.1097/JSA.0000000000000212. PMID: 30601395.
- Counsel P, Comin J, Davenport M, et al. Pattern of fascicular involvement in midportion Achilles tendinopathy at ultrasound. Sports Health. 2015; 7:424–8.
- Dalmau-Pastor M, Fargues-Polo B Jr, Casanova-Martínez D Jr, Vega J, Golanó P. Anatomy of the triceps surae: a pictorial essay. Foot Ankle Clin. 2014 Dec;19(4):603-35. doi: 10.1016/j.fcl.2014.08.002. Epub 2014 Sep 30. PMID: 25456712.
- Dorn TW, Schache AG, Pandy MG. Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance. J Exp Biol. 2012 Jun 1;215(Pt 11):1944-56. doi: 10.1242/jeb.064527. Erratum in: J Exp Biol. 2012 Jul 1;215(Pt 13):2347. PMID: 22573774.
- Prakash A, Entwisle T, Schneider M, et alConnective tissue injury in calf muscle tears and return to play: MRI correlationBritish Journal of Sports Medicine 2018;52:929-933.
- Green, B., McClelland, J.A., Semciw, A.I. et al. The Assessment, Management and Prevention of Calf Muscle Strain Injuries: A Qualitative Study of the Practices and Perspectives of 20 Expert Sports Clinicians. Sports Med – Open 8, 10 (2022). https://doi.org/10.1186/s40798-021-00364-0.
- Green B, Pizzari T. (2021) Episode 27 The Physical Performance Show, Episode 276. https://physicalperformanceshow.com/episode/tania-pizzari-phd-brady-green/
