I met him when I went running for the first time, about a year ago. It was winter, but the sky was clear and bright as I ran along the sea wall. There were plenty of other runners. Some were in pairs or even groups, but the only sound was the traffic and the gulls and the rhythmic waves.

I had just arrived, and I was unsure of what to do, so I lingered with my hands on the wall watching the sun go down. To the left, a young man sat on a peeling green bench, slowly lacing up his sneakers – procrastinating like me, it seemed. Then he stood up and began to run. That was when I stopped watching him subtly out of the corner of my eye and turned to face his receding form, staring.

His movement was so awkward that it was painful to watch. He lurched forward like a startled colt (but without any of the natural elegance) and carried on cantering, with stiff legs. Other runners turned to look too, their mouths slightly agape. An old couple walking their dog stopped talking to watch, eyes wide. I even noticed the people's heads in cars turn in his direction.

The young man didn't slow, but staggered on in his sideways gait. I turned away and began running in the opposite direction, a fierce blush burning my cheeks. I felt humiliated for him.

I saw him every night, always at sunset, and I did my best not to stare, as others did. As my running became stronger, his seemed to weaken and become even more pained. Several times I caught him bent over his shoelaces with tears in his eyes. Whether they were from embarrassment or pain, I couldn't tell.

Everything changed that spring. Though it was May, the sea was churning and the rain was swept sideways by the wind, freezing my fingers and cheeks. I had just finished my circuit and sat proudly with my legs dangling over the sea wall, breathing deeply. The young man collapsed onto a bench nearby, grimacing, with his legs stretched out in front of him. As is the way with wet tracksuits, his had ridden up so I could see his socks. Sock, I corrected myself. He was only wearing one. He didn't need one on the other foot; metal isn't affected by the cold.

I couldn't stop my tears from forming, and my fists clenched in helpless shock. He caught me looking and I smiled encouragingly, hoping the rain would disguise my sadness.

“Hi,” I said, before I realized what I was doing.

“Hi,” he replied. Noticing my shivering, he said, “We should run in the morning.” He turned his face skyward and let the rain fall on it. “Maybe it wouldn't be so cold.”

“We should,” I agreed. He looked back at me as he slowly got up. Then he squared his shoulders and began running again.

The next day, I ran as the sun was rising, instead of setting. I'm not sure why I did this, but I just did. I think about this decision a lot because it makes me question fate, which until then I'd never given a second thought to. But this is not about me, it's about him.

I didn't expect him to be there, but he was, and I caught up with him halfway through my route. We fell into step and he smiled, pleasantly surprised. We didn't say anything. In fact, we rarely say anything, even though we run together almost every day now.

People still stare at him, unabashed by their rudeness – which infuriates me – but he never says a word. He just puts his head down and keeps on going. He is getting better, though he has good days and bad days. Sometimes he can't manage more than a few hundred yards. Those are the days when tears of shame come into his eyes and there is nothing I can do to help. But sometimes he runs for miles and miles with me.

His name is David.