Crocker became involved in the Amateur Athletic Union of Canada (AAU of C) via his YMCA work, and was the Canadian representative on the International Basketball Rules Commission from 1905 to 1947.

During his AAU of C tenure, he stood for amateur ideals, sought for youth to be educated to play sport for fun, and for athletes to represent Canada without financial gain.

[12] Crocker won the 1896 and 1897 Canadian championship in the pentathlon, competing in the 100 metres sprint, mile run, high jump, pole vault, and hammer throw.

[18] He played halfback on the Dalhousie Tigers men's soccer team, worked as a server at a local pub, and served as a physical education instructor at the YMCA in Halifax, Nova Scotia.

He arranged for annual indoor athletics competitions between local YMCA branches, and oversaw recreational programs for baseball, basketball, fencing, gymnastics, lacrosse, rugby football, swimming and lifesaving, track and field, and wrestling.

[57] He conducted services at Sydenham Street Church in absence of its pastor,[58] and when the Reverend Maxwell was absent due to illness, Crocker filled in at the pulpit with an address on "The Vision of Jesus Christ".

[69] He instead collaborated with Elwood Brown and from missionaries in China, Japan and the Philippines, to establish the Far Eastern Championship Games in 1913, becoming the secretary for the biannual international sporting event operating on a smaller scale than the Olympics.

[71] Canadian missionary Reverend Gordon R. Jones, credited Crocker as the driving force behind establishment of the Far Eastern Games, due to visits to Japan, Hong Kong and the Philippines to organize the event.

[38][76] Crocker co-operated with the government's effort to organize student athletics at universities and colleges,[23] and felt that Yuan Shikai was "friendly to foreigners and courteous to the YMCA", while financially supporting the association's work.

[80] He took a leave of absence from his work to spend the summer in Canada, to study and accumulate resources for further of training physical education directors, and attend YMCA conferences in Chicago and Cleveland.

[89] He oversaw fundraising to support the war effort and Canadian troops, and received an endorsement for his work from Lieutenant General Richard Ernest William Turner.

[94] Frequently travelling Western Canada to interact with physical education directors, Crocker implemented YMCA programs despite austerity measures during World War I.

[97] As secretary of the YMCA's Red Triangle Fund to benefit education for boys, Crocker oversaw fundraising for missions around the world, including China and India.

[1][27] In advance of the 1924 Summer Olympics in Paris, Crocker was appointed chairman of the track and field sub-committee to select athletes, and named committee members to represent each province.

[151] When Crocker declined to be Chef de Mission for Canada at the 1924 Summer Olympics due to his commitments to YMCA, Patrick J. Mulqueen replaced him as manager of the Canadian delegation.

[153] At the 1924 AAU of C annual meeting in Winnipeg, president W. E. Findlay paid tribute to Crocker, Patrick J. Mulqueen, and treasurer Fred Marples, for their efforts in establishing the COC as a permanent body.

In addressing the Canadian Club of Toronto in 1926, Crocker stated that participation at the Olympic Games improved Canada's world status and "brotherly spirit" among nations.

[165] While planning for the 1928 Summer Olympics, Crocker spoke with journalist Melville Marks Robinson of The Hamilton Spectator, about hosting an international sporting event in Canada.

[169] The AAU of C subsequently established a permanent committee to select athletes for the British Empire Games, naming Edward Wentworth Beatty as chairman, and Melville Marks Robinson as secretary.

[135][170] When hosting duties of the 1931 Canadian track and field championships were awarded to Vancouver, Crocker stated that it was contingent upon construction of a stadium at Hastings Park, and a $2,000-guarantee for the AAU of C. When no progress was made on a stadium, Crocker expected the event to be held instead in Hamilton, Ontario[171] As of the 1931 general meeting, the AAU of C reserved the right to choose the location for the Canadian track and field finals.

[120] The 1932 AAU of C general meeting was hosted in Ottawa at the Château Laurier in December 1932,[178] where Crocker was elected president to succeed James I. Morkin of Winnipeg.

He sought to resolve this with a proposal to eliminate a clause in the constitution which gave executives the power to approve exhibition games between amateur and professional teams for charitable purposes.

[201] The COC planned to send 120 athletes to the 1936 Winter Olympics in Germany, but Crocker noted a lack of funds to pay travel expenses, except for the Canada men's national ice hockey team financed by the CAHA.

[203] When the second-place finish was heavily scrutinized by media in Canada, Crocker felt that any dissatisfaction should be directed towards the CAHA, which "had asked to be allowed to run its own show", instead of the AAU of C being in charge.

[209] As president and secretary of the British Empire Games Association of Canada, Crocker was also the manager and treasurer of the national delegation to the event, and travelled with the Canadian contingent aboard MV Aorangi from Vancouver to Sydney, Australia.

[217] During Crocker's tenure, the Western Mustangs men's ice hockey team won its first Canadian Interuniversity Athletics Union (CIAU) championship in the 1932–33 season.

[229] Crocker sought to establish a Bachelor of Arts degree in physical education, as a means to produce teachers at secondary schools and instructors at recreational institutes.

[237] On a summer fishing trip in 1930, he visited Rainbow Country in Northern Ontario, where he purchased an island cottage near Whitefish Falls which he named "Sous Bois".

In 1916, the International YMCA College granted him an honorary Master of Physical Education degree, for a thesis and his lectures on work done in China, and for establishing the Far Eastern Championship Games.

[253][254] At the 1925 AAU of C general meeting, Joseph Thompson, the speaker of the Legislative Assembly of Ontario, presented Crocker with a silver tea service in recognition of his work on the COC in preparation for the 1924 Summer Olympic Games, including his thorough records and reporting.