Myles played rugby for City of Derry and Ireland. In October 1899, together with Thomas Harvey, he was a member of the Ireland team that went on a tour of Canada. This was their first ever overseas tour. While playing, he broke his leg and he had to remain in Canada until December while the rest of the touring party returned home in November.
Myles served as an independent Teachta Dála (TD) in Dáil Éireann for twenty years. He was elected on his first attempt at the 1923 general election and was subsequently re-elected six times. He initially represented Donegal but then switched to Donegal East when the 8-seat constituency was divided in 1937. He lost his seat in 1943, and was defeated again in 1944.
- "Canada 1899". Irish Rugby 1874–1999. Retrieved 9 May 2012.
- The Ireland Rugby Miscellany (2007). Ciaran Cronin.
- "Medal card of Myles, James Sproule". www.nationalarchives.gov.uk. Retrieved 9 May 2012.
- "Major James Myles". Oireachtas Members Database. Retrieved 9 May 2012.
- "James Myles". ElectionsIreland.org. Retrieved 9 May 2012.
- "Gravestone Inscriptions, St. Anne's Church of Ireland, Ballyshannon, No. 182". www.ulsterancestry.com. Retrieved 9 May 2012.