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Increasing the mechanical load on skeletal muscle results in increased expression of insulin‐like growth factor I (IGF‐I), which is thought to be a critical step in the induction of muscle hypertrophy. To determine the role of the IGF‐I receptor in load‐induced skeletal muscle hypertrophy, we utilized a transgenic mouse model (MKR) that expresses a dominant negative IGF‐I receptor specifically in skeletal muscle. Skeletal muscle hypertrophy was induced in the plantaris muscle using the functional overload (FO) model, a model which has previously been shown to induce significant elevations of IGF‐I expression in skeletal muscle. Adult male wild‐type (WT) and MKR mice were subjected to 0, 7 or 35 days of FO. In control or unchallenged animals, the plantaris mass was 11% greater in WT compared to the MKR mice (P < 0.05). After 7 days of FO, plantaris mass increased significantly by 26% and 62% in WT and MKR …