Glen’s father, Paul, was diagnosed with bulbar motor neurone disease in September 2025.
Sinfield is aiming to complete seven ultramarathons in seven days, inspired by his late friend Rob Burrow, who died in 2024 after living with MND for four years.
He is running between Hull and Manchester, visiting all 12 Super League clubs before arriving at the Grand Final on Saturday.
On Sunday, Glen and Paul both ran four laps of Hull’s Costello Stadium alongside him and other members of the MND community as part of the Extra Mile event, before the official challenge got under way.
He said: “It was brilliant.
“Dad got to see a few of his friends that he has met from the MND community support group that we go to once a month. It was a really lovely atmosphere.”
Sinfield had also selected people to “bang the drum” at each pit stop along the route, which ended in Shiptonthorpe.
Paul, Glen’s father, was asked to be the representative in Market Weighton. He was also given Sinfield’s 7 in 7 changing robe at the end of the first leg.
Glen said another highlight of the day was being able to meet former England football manager Sir Gareth Southgate, who joined part of the challenge.
“I got emotional just seeing him, which shows how much of an England fan I am, and I knew it was going to mean so much to Dad.
“He was so lovely. I keep looking back at the pictures, and I just can’t believe it all happened the way it did.”