Running-Related Injuries and Neuromuscular Adaptation in Barefoot Running: An Epidemiological Survey and Intervention Study of Grass-Based Running

Interest in barefoot running has grown, driven by suggestions of injury reduction and strength improvements. This PhD project investigated the epidemiology of running-related injuries and neuromuscular adaptations to extended periods of barefoot running on grass. A rapid review of the literature (Chapter 2) revealed limited evidence of strength improvements, though some studies suggested increased cross-sectional area and volume of foot intrinsic and anterior leg muscles with prolonged barefoot running. However, no studies had specifically examined muscular adaptation to grass-based barefoot running. A retrospective injury survey (Chapter 3) captured self-reported data on injury location and prevalence among barefoot and shod runners. Injury prevalence did not significantly differ between groups (p = 0.112), though a near-significant increase in Achilles and shin injuries was found in barefoot runners (p = 0.06). Barefoot running did not significantly alter the odds of injury (OR = 0.886, 95% CI [0.749–1.048]). A pilot study (Chapter 4) evaluated muscle contractile properties using tensiomyography following a six-week treadmill running intervention. No consistent changes were detected across participants, regardless of footwear, indicating that tensiomyography was unsuitable for assessing neuromuscular adaptation. Electromyography was selected for the grass-based study to allow real-time measurement of muscle activity during running. A grass-based study (Chapter 5) examined differences in muscle activity using electromyography between barefoot and shod runners following a six-week grass running intervention and also explored participant experiences via semi-structured interviews. A two-way mixed ANOVA showed no significant interaction effects on rectus femoris (p = 0.125), biceps femoris (p = 0.980), or gastrocnemius medialis (p = 0.619). The relatively low training volume, combined with participants’ ongoing running routines, may have reduced the likelihood of observing meaningful neuromuscular adaptations. However, individual variability in muscle activation, particularly in rectus femoris and biceps femoris, highlights the importance of examining personalised responses to surface-based interventions. Interviews revealed that participants enjoyed the novelty of barefoot running on grass but noted barriers such as environmental conditions, surface safety, and temperature challenges. In conclusion, while the study aimed to explore neuromuscular adaptations to barefoot running on grass, changes in muscle activity were observed in some individuals across both barefoot and shod groups, suggesting that surface compliance may influence adaptation alongside footwear. These highly individual responses may have been shaped by prior experience, biomechanical variations and transition duration. The absence of clear group-level trends may reflect limited training volume or study power, underscoring the need for larger trials. A key takeaway from this research is the importance of recognising and interpreting individual responses, rather than relying solely on group averages.