The aim of this study was to investigate the effect of repeated contractions on the geometry of human skeletal muscle. Six men performed two sets (sets A and B) of 10 repeated isometric plantarflexion contractions at 80% of the moment generated during plantarflexion maximal voluntary contraction (MVC), with a rest interval of 15 min between sets. Using ultrasound, the geometry of the medial gastrocnemius (MG) muscle was measured in the contractions of set A and the displacement of the MG tendon origin in the myotendinous junction was measured in the contractions of set B. In the transition from the 1^st to the 10^th contractions, the fascicular length at 80% of MVC decreased from 34±4 (means±SD) to 30±3 mm (P<0.001), the pennation angle increased from 35±3 to 42±3 deg (P<0.001), the myotendinous junction displacement increased from 5±3 to 10±3 mm (P<0.001), and the average fascicular curvature remained constant (P>0.05) at ~4.3 m^-1. No changes (P>0.05) were found in fascicular length, pennation angle and myotendinous junction displacement after the 5^th contraction. Electrogoniometry showed that the ankle rotated by ~6.5 deg during contraction, but no differences (P>0.05) were obtained between contractions. The present results show that repeated contractions induce tendon creep, which affects substantially the geometry of the in-series contracting muscles, thus altering their potential for force and joint moment generation.