Muscular contraction is a process in which muscles shorten and produce force. SPASM, TIC, and CRAMP are all types of muscular contraction. A SPASM is an involuntary, sudden, and often painful contraction of a muscle or group of muscles. A TIC is a sudden, repetitive, nonrhythmic motor movement or vocalization involving discrete muscle groups. Lastly, a CRAMP is an involuntary and often painful contraction of a muscle or group of muscles.