Researcher(s)
- Mei Tobin, Exercise Science, University of Delaware
Faculty Mentor(s)
- Karin Grävare Silbernagel, Department of Physical Therapy, University of Delaware
Abstract
Background: While the cause of adolescent heel pain is unknown, it is hypothesized that overload of the Achilles tendon during adolescent growth causes structural pathology that results in heel pain with physical activity. Understanding the relationship between calf muscle-tendon structure and functional loading is vital for injury prevention and rehabilitation.
Purpose: The purpose of this study was to determine the relationship between calf muscle-tendon structure and loading in adolescents with and without heel pain.
Methods: Six adolescents with heel pain and 12 adolescents without heel pain were included in this study. Participants performed lower limb functional movements which included a single-leg countermovement jump (CMJ), a single-leg drop CMJ, and single-leg hopping. During these movements, plantar (i.e., in shoe ground reaction) forces were measured and Achilles tendon load was estimated using force sensing insoles (loadsol®, Novel Electronics). Three key measures of Achilles tendon load (peak load, loading impulse, and loading rate) were averaged over 3 trials and normalized by body weight (kg). Muscle-tendon structure was measured with B-mode ultrasound imaging and included: Achilles tendon thickness, Achilles tendon cross-sectional area (CSA), and CSA of the medial and lateral gastrocnemius (i.e., calf) muscles. Multiple regression determined the relationship between Achilles tendon loading and structural measures in the most symptomatic/dominant limb (self-reported).
Results/Discussion: Larger calf muscle-tendon size is associated with greater Achilles tendon loading during functional jumping and hopping activities (p<0.05). Achilles tendon loading variables accounted for 16-51% of the variance (i.e., difference) in Achilles tendon size and 38-61% of the variance in calf muscle size.
Significance: These findings highlight the strength of the relationship between calf muscle-tendon structure and lower limb function in an understudied pediatric population. Understanding this relationship is crucial for being able to design injury prevention and rehabilitation programs for adolescent heel pain.