Structural and Functional Implications Associated with Subcutaneous Fat Depth of the Medial Gastrocnemius

• Lindsay Kalish, Exercise Science, University of Minnesota Twin Cities

• Karin Silbernagel, Physical Therapy, University of Delaware

Structural and Functional Implications Associated with Subcutaneous Fat Depth of the Medial Gastrocnemius

Lindsay Kalish 1,2, Andy K. Smith PT, DPT, MS 2, Karin Grävare Silbernagel PT, ATC, PhD 2

1 University of Minnesota Twin Cities, Minneapolis, MN

2  University of Delaware, Newark, DE

Introduction: Midportion Achilles tendinopathy (MAT) is a condition that affects the functionality and structure of the Achilles tendon. MAT often causes pain, swelling, and limited function of the lower limb as a result. Metabolic conditions are reported to influence onset, recovery, and tendon pathology in those with MAT. Subcutaneous fat depth is linked to metabolic conditions, therefore the purpose of this analysis was to determine if relationships exist between structural and functional variables and the subcutaneous fat depth of the medial gastrocnemius muscle (MG-SUBQ).

Methods: 29 participants (18M, 46±12yo, 27.4±5.1 kg/m2) with MAT were included. All measures were taken from the participant’s most symptomatic side as determined by self-report. MG-SUBQ, cross-sectional area (CSA) of the medial (MG) and lateral (LG) gastrocnemius, soleus thickness, Achilles tendon thickness, Achilles tendon CSA, and degree of Achilles tendon thickening were assessed with Ultrasound imaging. Functional testing included counter movement jump (CMJ) and drop CMJ height, and heel rise work. Pearson Correlations were used to assess relationships between variables, α=0.05.

Results: MG-SUBQ was significantly correlated with BMI (r= 0.728, p<0.001) and weight (r=0.437, p=0.018). Soleus thickness was significantly correlated to the MG-SUBQ (r=0.381, p=0.42), while all other structural measures of the calf muscles (MG CSA , LG CSA) and Achilles tendon (thickest portion, degree of thickening, and CSA) were not. Functional performances (CMJ height (r= -0.456, p = 0.011), and drop CMJ height (r= -0.547, p = 0.004)) were significantly correlated with MG-SUBQ. 

Discussion: MG-SUBQ was related to body metrics but the only triceps surae structure significantly correlated was the soleus thickness. In addition, MG-SUBQ was strongly correlated to functional performance. These findings suggest that deficits in function may relate to body composition rather than triceps surae structural and pathological changes in individuals with midportion Achilles tendinopathy.

References

Smitheman, H. P., Seymore, K. D., Potter, M. N., Smith, A. K., Aufwerber, S., Silbernagel, K. G. Measurement of Healthy and Injured Triceps Surae Morphology. J. Vis. Exp. (200), e65798, doi:10.3791/65798 (2023).