Inclusion Criteria:  Healthy men and women aged 18-65 years are recruited. As part of the screening, volunteers will also be asked to indicate known medical issues or diseases. Participants are included if they have no known medical conditions such as cognitive impairments, neurological, orthopaedic, or neuromuscular problems that might affect the somatosensory system or preclude stretching exercises or range of motion testing at the knee.  Exclusion Criteria:  Individuals who regularly engage in flexibility training (e.g., stretching, tai chi, pilates or yoga) or use any medication that might affect the somatosensory system, such as pain medication, are excluded.