Amateur boxing is a variant of boxing practiced at the collegiate level, at the Olympic Games, Pan American Games and Commonwealth Games, as well as many associations. Amateur boxing bouts are short in duration, comprising three rounds of three minutes in men, and four rounds of two minutes in women, each with a one-minute interval between rounds. Men's senior bouts changed in format from four two-minute rounds to three three-minute rounds on January 1, 2009. This type of competition prizes point-scoring blows, based on number of clean punches landed, rather than physical power. Also, this short format allows tournaments to feature several bouts over several days, unlike professional boxing, where fighters rest several months between bouts.