From 1917 to 1919 was H.F.C.President of amateur football. In 1921 he became coach of the first team. During this time he developed the concentration and mentaltraining method by which he became famous.
Karel Lotsy was also active as a driver in the NFL and he became President of the selection Committee of the Dutch national football team. Under his leadership the success of the Dutch national team remarkable began to rise.
Karel Lotsy, which also in other branches of sport than football has had great influence, was known as a very dynamic and charming figure, which could organize excellent.His idealism has very inspiring worked on others. Because of its great achievements, he was awarded numerous times.Karel Lotsy reaches the Dutch Cup of 1944 from.
In the late 1970s, well after his death, changes the picture about Lotsy. Journalists Frits Barend and Henk van Dorp Vrij Netherlandsmake for a series about sport in the Second World War, in which she comments on the role of Amateur sites. From October 1940 until autumn 1941 he was attached to the Department of education, science and cultural protection. And in the middle of the war, in 1942, he became President of the Dutch football association. Many, including his second cousin Dirk Lotsij, found that he was far too accommodating towards the Germans.
Although the treatment Commission for the sport had acquitted him of collaboration in 1945 , pulling old-referee Leo Horn and former footballer Bram Appel of leather against the ' bobo '. According to Apple was 1944 in amateur football in Berlin as a spectator at a match between Netherlands and Czech Republicteams of forced labour. Seven other players deny this story. ,, The 85-year-old Baha(the only living player in 2008) says he did not see amateur football in Berlin that he and Apple just squirt like a ' get to know ' the Hague has. ' "
The criticism holds to: André Swijtink historian writes in 1992 with a thesis on sports practice in World War II. Lotsy is referred to as ' performer of anti-Jewish politics of the occupier '. There came an action to go to Amateur named streets of name change. Baptized the Karel Lotsy Amsterdam Avenue to Gustav Mahlerlaan. The Karel Lotsypad, Karl Lotsyweg in Dordrecht and the Karel Lotsy Street remained in Gouda . 
In 2009 a biography: "the canons magician-the fall of a folk hero" (publishing house Nieuw Amsterdam), by Frank van Kolfschooten in which argued is that Karel Lotsy not ' error ' would have been.Amateur  would have been the victims of journalistic, scientific and political errors. In the biography from new sources would appear that Barend and Van Dorp, Swijtink and fish were based on unreliable witness accounts and careless source research. The author makes use of extensive source research and documents collaboration with amateur football and argues that not of or sympathy towards the German occupiers can be accused.Kolfschooten's further discovered that NOC * NSF Sports Dome for the reminder marks on the Sports Centre Papendal Lotsy (that was founded on the initiative of amateur football) had tacitly removed. Both the bust of amateur football as a plaque at the Hall named after him were gone after reports about his alleged missteps during the occupation period. Both NOC * NSF as the KNVB, Dutch amateur football President and keuzeheer of the team which had been refused, the presentation of the book on May 9, 2009 to attend, in order not to get involved in a debate about his war record       . This, however, came criticism from the side of Swijtink, which in 1992 had dedicated a thesis at amateur football: the proposed rehabilitation would be completely unjustified according to him . Also Matty Verkamman left in International Soccerknow that the rehabilitation was undeserved. "I am came into possession of a letter, which the book of victory with one stone degrades to waste paper," said Verkamman. So far, Verkamman not made clear on which letter he is referring to.
' I dare to claim that Rie Mastenbroek in the Olympic Games of Berlin no title would have conquered and Osendarp and Valentine and the others not such times would have made if there came out of the bus. Lotsy extracted the maximum out of a sports guy or sports girl, that came under his wing. The jovial, as he wanted, extremely charming guy had on sports people a preponderance that the side of hypnosis went out. '(Herman Kamath after Lotsy's death in 1959)
If Mr Lotsy speaks, grasp every word, is often like a bullet of B or Vente, ' writes a reporter from the associated press about his last speech in the Miracle tent. ' Here is the quiet, then suddenly the applause as a hurricane by the davert become quiet space.