February 2021

Normative Parameters of Gastrocnemius Muscle Stiffness and Associations with Patient Characteristics and Function

Authors: Larisa R Hoffman, PT, PhD 1 , Shane L Koppenhaver, PT, PhD 2, Cameron W MacDonald, PT 1, Johnny M Herrera, SPT 1, Joshua Streuli, SPT 1, Zachary L Visco, SPT 1, Nicole Wildermuth, SPT 1, Stephanie R Albin, PT, PhD 1

Author information:

  1. Regis University, 3333 Regis Blvd, Denver, CO, US
  2. Baylor University, Waco, Texas 76798, US

Journal: International Journal of Sports Physical Therapy - February 2021, Volume 16, Issue 1 (DOI: 10.26603/001c.18803)

Background: Quantifying muscle stiffness may aid in the diagnosis and management of individuals with muscle pathology. Therefore, the primary purpose of this study was to establish normative parameters and variance estimates of muscle stiffness in the gastrocnemius muscle in a resting and contracted state. A secondary aim was to identify demographic, anthropometric, medical history factors, and biomechanical factors related to muscle stiffness.

Methods: Stiffness of the gastrocnemius muscle was measured in both a resting and contracted state in 102 asymptomatic individuals in this cross-sectional study. Differences based on muscle state (resting vs contracted) and sex (female vs male) were assessed using a 2 X 2 analysis of variance (ANOVA). Associations between muscle stiffness and sex, age, BMI, race, exercise frequency, exercise duration, force production, and step length were assessed using correlation analysis.

Results: Gastrocnemius muscle stiffness significantly increased from a resting to a contracted state [mean difference: 217.5 (95% CI: 191.3, 243.8), p < 0.001]. In addition, muscles stiffness was 35% greater for males than females in a resting state and 76% greater in a contracted state. Greater muscle stiffness in a relaxed and contracted state was associated with larger plantarflexion force production (r = .26, p < 0.01 and r = .23, p < 0.01 respectively).

Level of Evidence: 2b Individual Cohort Study

Clinical Relevance: Muscle stiffness has been shown to be related to individuals with pathology such as Achilles tendinopathy; however, research is sparse regarding normative values of muscle stiffness. Measuring muscle stiffness may also be a way to potentially predict individuals prone to injury or to monitor the effectiveness of management strategies.

This study established defined estimates of muscle stiffness of the gastrocnemius in both a relaxed and contracted state in healthy individuals. Myotonometry measures of muscle stiffness demonstrated an increase in stiffness during contraction that varies by sex. Greater gastrocnemius muscle stiffness was associated with increased plantarflexion force production.

Establishing estimates of muscle stiffness in healthy individuals may aid in identifying individuals with aberrant muscle stiffness who may be prone to injury, variations in normal muscular function and inform goal setting in rehabilitation.