The present study aimed to test if a long-term passive stretching training causes adaptations of the medial gastrocnemius architecture and the Achilles tendon (AT) tangent modulus.

A total of 20 males took part in the study. The stretching group (n = 12), performed stretching exercises for the plantar flexors for 10 weeks, 4–5 times a week, which comprised two static positions sustained twice each during 30 s.

For the stretching group, maximum dorsiflexion angle, peak passive torque, and muscle–tendon unit maximum length significantly increased after training. No other differences were found related to muscle architecture and AT tangent modulus.

Joint amplitude gain after a long-term stretching of the triceps surae was not accompanied by structural or mechanical changes of the medial gastrocnemius and AT tendon, and seems to reflect an increasing stretch tolerance level.