"It took some time, but I'm flying now. I trust my knee, because I trust in the medical team that I have here and the people around me.
"Now I'm just putting it against the boys to see how it goes."
Tuivasa-Sheck admits he still has bad days, but has learned to cope with those minor setbacks, as he prepares for the new season.
"About two weeks ago, I thought I was flying, and I woke up one morning and I was puffing again," he says. "That's probably the toughest part - when I think I'm right and then it just doesn't work with me.
"It's a normal thing, they keep telling me, so don't get too hard on myself. It's been nine months since I ran, so it's going to flare up.
"They know about it - it's not something random, so just keep going, ice up, recover well and be healthy, because there will come a time when my knee will be normal again."
Part of the recovery process for Tuivasa-Sheck has been a greater awareness of running mechanics. The thing that once came naturally now come as a conscious effort.
"I was probably doing it anyway, but now I'm just more aware of it."