While this is a really nice way to spend an hour it will do nothing for your vitamin D levels. What were you wearing? I guess at most your face and hands were exposed to sunlight, perhaps forearms if you stripped to a T-shirt.
Anyone living north of a line through Birmingham cannot manufacture vitamin D through the winter months. The sun is too low, it doesn't appear for days on end and we cover our skin in clothing. You said you go outside for five hours a week in winter, basically zero exposure to sunlight. For many people even the summer months are useless.
The only worthwhile solution is to take a supplement year round.
Yes, I thought that after posting!
The vit K2 supplement that I already take also has vit D3 in it. I have now checked the amount and it is actually 250% of the NHS recommended minimum daily dose. It is about 25% of the recommended
maximum daily dose so I
could take more, but vit D deficiency probably
isn't the issue after all.
My sister and niece took several months to get over one of their winter bugs so maybe I have just been unlucky like them.
I feel okay as long as I don’t exert myself but my elevated heart rate soon limits me when I do make an effort. On tonight's turbo session I had to drop my power from 120 watts to 100-110 watts to stop the rise to 135+ bpm. I can normally do 160+ watts at that heart rate. Some of it will be due to detraining but the sore throat is a reminder that I haven't recovered properly from the cold (or Covid, or whatever else it is).
It is a bit frustrating but at least the gentle turbo sessions are keeping me ticking over until I feel healthy again.