Speaker: Seth O’Neill, PhD, School of healthcare, College of Health Sciences, University of Leicester, UK
Congress: Sport & Exercise Medicine Switzerland and Swiss Sport Physiotherapy Association joint conference: “Structure & Function”, Lausanne, October 30th and 31st 2025
Scan to access presentation on Sportfisio YouTube channel
Introduction
Calf muscle injuries represent a significant burden in elite sports, with soleus injuries constituting the majority of posterior lower leg pathology. This article synthesizes current evidence on soleus injury epidemiology, biomechanical function, and evidence-based rehabilitation approaches, drawing from research presented by Seth O’Neill from the University of Leicester.
Epidemiology and injury patterns
Incidence in Elite Sports
Calf injuries demonstrate substantial prevalence across elite sporting populations. In English Premier League football, typical incidence is 2.5 injuries per squad per season, though considerable inter-squad variability exists. Notable outliers have been documented, with one squad experiencing 11 calf injuries before December, raising concerns about training load management and athlete preparedness.
Rugby union data consistently places calf injuries within the top two most common muscular injuries. UEFA epidemiological data reveals a unique age-association pattern for calf injuries that distinguishes them from other lower extremity pathologies—hamstring, quadriceps, and groin injuries show no age correlation, whereas calf injury incidence increases significantly with age. This is particularly concerning as affected players are typically squad captains and senior players critical to team performance.
Temporal and Mechanical Differentiation
Injury timing provides mechanistic insights into soleus versus gastrocnemius pathology:
• Soleus injuries: Predominantly occur during the second half of the first period or late in matches, suggesting fatigue-related etiology.
• Gastrocnemius injuries: More frequently occur at match onset or immediately following halftime, implicating neuromuscular miscoordination rather than fatigue, similar to ACL injury patterns.
Australian Football League (AFL) research by Brady Green identified distinct injury mechanisms correlated with muscle involvement. Gastrocnemius injuries demonstrate higher association with high-intensity running, while soleus injuries show more varied mechanisms including stepping back movements.
Prevalence: Soleus Dominance
English Football Association data analysis of calf injuries revealed that 75% (251 cases) involved the soleus muscle, establishing it as the predominant site of calf pathology. This distribution underscores the critical importance of understanding soleus-specific biomechanics and function for effective rehabilitation programming.
Soleus biomechanics and force production
Anatomical Complexity
The soleus is a structurally complex muscle containing three intramuscular tendons. While traditionally characterized in education as a “postural muscle” maintaining upright stance, this designation understates its primary functional role in locomotion and force generation.
Force Generation Capacity
The soleus demonstrates extraordinary force production capacity:
– Running forces: Generates approximately 8 times body weight across running velocities from 3 m/s to maximal sprint speeds (9 m/s). This constant high-force demand across speeds has critical rehabilitation implications—even slow jogging represents substantial soleus loading, challenging the traditional “easy jog” early rehabilitation approach.
– Vertical force contribution: The soleus produces 50-70% of total vertical ground reaction force during running, exceeding all other lower limb muscles. This dominance in propulsive force generation explains its injury susceptibility under accumulated load.
– Sprint acceleration: During block start acceleration, soleus forces reach 10 times body weight per step. For an 80 kg athlete completing a typical training run, cumulative soleus loading approaches 2.6 million kilograms of force, explaining both acute fatigue responses and recovery requirements.
The “Other 21 Hours” Paradigm
A critical yet frequently overlooked consideration is non-training locomotor demand. Athletes accumulate 10,000-20,000 additional steps daily through activities of daily living—walking dogs, playing with children or recreational golf. This unaccounted loading substantially impacts recovery capacity and may explain seemingly paradoxical training-related injuries where programming appeared appropriate. Total daily mechanical load must be considered when designing training progressions.
Strength assessment considerations
Force-Velocity Relationships
Successful return-to-play requires achieving twice body weight on isometric testing, corresponding to internal muscle forces of 7-12 times body weight. Importantly, strength directly correlates with sprint performance across 10 m and 30 m distances.
Position-Specific Assessment
Isokinetic testing reveals peak force production occurs in dorsiflexed positions—a finding with profound rehabilitation implications. Traditional rehabilitation emphasizing plantar grade (neutral) to plantar flexion positions is biomechanically irrelevant to functional demands.
Neuromuscular Coordination Deficits
Bilateral coordination deficits are frequently observed in calf and Achilles pathology, manifesting as a characteristic “trough” in force production between neutral and 20° dorsiflexion. This represents dysfunctional motor patterning precisely in the range where step-back movements—a common injury mechanism—occur. Slow-motion injury footage consistently demonstrates this mechanism.
Evidence-based rehabilitation framework
Load Parameter Targeting
Comprehensive rehabilitation must address three load dimensions:
1. Peak load: Maximum tissue stress magnitude
2. Cumulative load: Total volume over defined distances
3. Load rate: Stress application velocity (tissue strain rate)
Position-Specific Training
A fundamental rehabilitation error involves performing idealized, controlled gym exercises that fail to replicate sport-specific loading positions. Rehabilitation must incorporate “dirty positions”—the sport-specific, often disadvantageous positions where tissue stress concentrates and symptoms manifest.
Critical Rehabilitation Principles
– Maximal voluntary contraction: Insufficient activation represents a common limitation requiring targeted intervention.
– Dorsiflexion emphasis: Training must emphasize force production in dorsiflexed positions (0-20°) where functional demands and coordination deficits converge.
– Extreme range exposure: Athletes must train through extreme ranges encountered during competition to ensure tissue adaptation and neuromuscular control.
– Eccentric deceleration: Given the injury mechanism, eccentric loading capacity is paramount. Despite occasional negative perceptions, eccentric training is fundamental to human performance and must be properly rehabilitated considering individual athlete characteristics and recovery status.
Conclusion
Soleus injuries represent the predominant calf pathology in elite sports, distinguished by age association, fatigue-related mechanisms, and extraordinary force demands. Successful management requires understanding the muscle’s 8× body weight force production across running speeds, accounting for total daily mechanical load beyond structured training, and implementing position-specific rehabilitation emphasizing dorsiflexed ranges and eccentric function. The “other 21 hours” paradigm highlights the necessity of comprehensive load monitoring extending beyond training sessions to optimize recovery and prevent injury recurrence in this critical propulsive muscle.
References
- Green B, Lin M, Schache AG, McClelland JA et al. Calf muscle strain injuries in elite Australian Football players: a descriptive epidemiological evaluation. Scand J Med Sci Sports. 2020 Jan;30(1):174–184. doi:10.1111/sms.13552.
- Malliaras P, Gravare Silbernagel K et al. Diagnostic domains, differential diagnosis and conditions requiring further medical attention that are considered important in the assessment for Achilles tendinopathy: a Delphi consensus study. Br J Sports Med. 2025 Jul 1;59(13):891–901. doi:10.1136/bjsports-2024-109185.
- O’Neill S, Barry S, Watson P. Plantarflexor strength and endurance deficits associated with mid-portion Achilles tendinopathy: the role of soleus. Phys Ther Sport. 2019 May;37:69–76. doi:10.1016/j.ptsp.2019.03.002.
- Lee M, Lancaster M, Tulloch L, O’Leary B, Power E, Howes D, Sourbuts B, Berry A, Maher F, O’Neill S. Normative isometric plantarflexion strength values for professional level, male rugby union athletes. Phys Ther Sport. 2023 May;61:114–121. doi:10.1016/j.ptsp.2023.03.007.
- Hébert-Losier K, Ngawhika TM, Balsalobre-Fernández C, O’Neill S. Calf muscle abilities are related to sprint performance in male Rugby Union players. Phys Ther Sport. 2023 Nov;64:117–122. doi:10.1016/j.ptsp.2023.09.001.
- Hébert-Losier K, Fernandez MR, Athens J, Kubo M, O’Neill S.
A randomised crossover trial on the effects of foot starting position on calf raise test outcomes: Position does matter. Foot (Edinb). 2024;60:102112. doi:10.1016/j.foot.2024.102112.
