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The Germans missed three spot-kicks - more in one shootout than in their history - before Jonas Hector converted for a 6-5 win.
Hummels, who scored his penalty, told BBC World Service: "We didn't shoot like a German team.
"I saw Gary Lineker posted about it already and of course he's right."
Thomas Muller, Mesut Ozil and Bastian Schweinsteiger failed to score from the spot, with Muller's miss Germany's first in a shootout since 1982.
They have been involved in six penalty contests, losing only once in the final of the 1976 European Championship against Czechoslovakia.
Saturday's failures, albeit in victory, prompted Match of the Day presenter Lineker - who was part of the England team beaten on penalties by West Germany in the 1990 World Cup semi-finals - to jokingly tweet: "Germany are useless at penalties these days."
Hummels, who has just moved from Borussia Dortmund to German champions Bayern Munich, added: "You won't believe it, but yes we [practised penalties] in training a few times.
"I was very happy that I did because I worked out which shot would work well for me today - because it worked well yesterday.
"It's hard to simulate the real situation."
Italy missed four penalties during the shootout, including one from Leonardo Bonucci who had scored from the spot in normal time to earn his side a 1-1 draw and extra time.
Germany defender Mats Hummels says Gary Lineker was correct to describe their penalty taking in the Euro 2016 last-eight win over Italy as "useless".