One of These Things Is Not Like the Others: Disentangling the Concepts of Range of Motion Versus Flexibility, and Flexibility Training Versus Stretching.

In this Current Opinion, we revisit key terminological distinctions in sports sciences, emphasizing the implications of conflating related but distinct concepts, particularly range of motion (ROM) versus flexibility and flexibility training versus stretching. While often used interchangeably, these terms represent nuanced constructs with distinct physiological and practical implications. ROM encompasses both modifiable (e.g., soft tissue extensibility, neural control) and non-modifiable factors (e.g., bone structure), whereas flexibility is only one of several trainable components of ROM, largely referring to the extensibility of periarticular soft tissues. Misunderstanding these distinctions risks erroneous assessments and inappropriate exercise prescriptions. We also challenge the common practice of equating flexibility training with stretching. While stretching is effective to enhance flexibility, other methods, such as strength training at long muscle lengths and foam rolling, produce comparable chronic ROM gains. Furthermore, stretching has a diverse array of effects that extend beyond flexibility, including strength development and neural modulation. Mischaracterizing flexibility training as synonymous with stretching perpetuates myths and constrains innovation in training practices. By differentiating these terms, we advocate for clearer language in research and practice to avoid miscommunication and ensure effective training interventions. In summary, we propose that flexibility is only one component of ROM, and that flexibility training and stretching should not be equated. We hope this Current Opinion paper generates a healthy discussion within the sports science and medicine communities.