The Queen reportedly stopped horse riding two months ago during her summer break in Scotland.
A Balmoral source told The Sun that the 95-year-old monarch had suffered "discomfort" during her rides and was reportedly told to stop her favourite pursuit in September.
According to the newspaper, Her Majesty is keen to return to horse riding after rest and recuperation.
Buckingham Palace declined to comment.
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It comes after the Queen stayed overnight at King Edward VII Hospital last week for some "preliminary investigations".
She also cancelled a two-day visit to Northern Ireland and has "regretfully" decided not to travel to Glasgow for the COP26 Summit on Monday.
© Photo: Getty ImagesThe Queen, pictured in 1947, learned to ride from a young age
In a statement, Buckingham Palace said on Tuesday: "Following advice to rest, The Queen has been undertaking light duties at Windsor Castle. Her Majesty has regretfully decided that she will no longer travel to Glasgow to attend the Evening Reception of COP26 on Monday, 1st November.
"Her Majesty is disappointed not to attend the reception but will deliver an address to the assembled delegates via a recorded video message."
Earlier in the day, she carried out her first royal engagements since her hospital stay, as she held virtual audiences with the ambassador from the Republic of Korea, Gunn Kim and the ambassador from the Swiss Confederation, Markus Leitner, from Windsor Castle.
The Queen then had a phone call with the Chancellor, Rishi Sunak, ahead of the Budget 2021.
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© Photo: AlamyThe Queen during her virtual audiences at Windsor Castle on Tuesday
On Wednesday, Her Majesty also held her first telephone meeting with Prime Minister Boris Johnson for the first time in three weeks.
There are no details in the Court Circular of Mr Johnson having an audience with the Queen last week when she was advised to rest and cancelled a two-day trip to Northern Ireland.
The Prime Minister was on holiday the preceding week, and the last official note of a telephone meeting between the pair was on 6 October.
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