Context: The architectural characteristics of a muscle determine its function.
Objective: To determine the architectural adaptations of the lateral gastrocnemius (LG) and medial gastrocnemius (MG) muscles after a functional eccentric strength training protocol consisting of heel drop exercises, followed by a subsequent detraining period.
Design: Pretest and posttest.
Setting: Training rooms and laboratory.
Participants: The participants (N = 45) who were randomly divided into an experimental group (EG, n = 25) and a control group (CG, n = 20).
Interventions: The 13-week intervention included participants (N = 45) who were randomly divided into an EG (n = 25) and a CG (n = 20). The EG performed a week of control and training, 8 weeks of eccentric training, and 4 weeks of detraining. The CG did not perform any type of muscular training. The architectural characteristics of the LG and MG muscles were evaluated at rest in both groups using 2-D ultrasound before (pretest-week 1) and after (posttest-week 9) the training, and at the end of the detraining period (retest-week 13).
Main outcome measures: One-way repeated measures analysis of variance was used to determine training-induced changes in each of the variables of the muscle architecture.
Results: After the training period, the members of the EG experienced a significant increase in the fascicle length of LG (t = -9.85, d = 2.78, P < .001) and MG (t = -8.98, d = 2.54, P < .001), muscle thickness (t = -6.71, d = 2.86, P < .001) and (t = -7.85, d = 2.22, P < .001), and the pennation angle (t = -10.21, d = 1.88, P < .05) and (t = -1.87, d = 0.53, P < .05), respectively. After the detraining period, fascicle length, muscle thickness, and pennation angle showed a significant decrease. In the CG, no significant changes were observed in any of the variables.
Conclusions: The heel drop exercise seems to generate adaptations in the architectural conditions of LG and MG, which are also reversible after a detraining period. These results may have practical implications for injury prevention and rehabilitation programs.
Keywords: fascicle; muscle adaptation; muscle morphology; muscular injuries; ultrasound.