Novel tetrahydroisoquinoline derivative compounds are disclosed herein that may be used as an active ingredient for a pharmaceutical composition, and in particular, for a pharmaceutical composition useful for preventing or treating a disease or condition responsive to modulation of the contractility of the skeletal sarcomere. This may be accomplished, for example, by modulation of the troponin complex of the fast skeletal muscle sarcomere through one or more of fast skeletal myosin, actin, tropomyosin, troponin C, troponin I, and troponin T, and fragments and isoforms thereof. The tetrahydroisoquinoline derivative compounds can thus be used as an agent for preventing or treating 1) neuromuscular disorders, 2) disorders of voluntary muscle, 3) CNS disorders in which muscle weakness, atrophy, and fatigue are prominent symptoms, 4) muscle symptoms stemming from systemic disorders, and 5) dysfunctions of pelvic floor and urethral/anal sphincter muscle.