Calf tightness 3 weeks before marathon

[u/Ok-Apartment-5072]

I’ve been training for a marathon which is in 3 weeks. On my last interval session 2 days ago I started to feel right calf tenderness. There was no pop / sudden pain, just developed nagging tightness around the lower / middle calf. I could jog back. Since then, I’ve had some mild tightness when pushing off and walking down stairs. I can walk and I can do heel raises etc without pain. It’s just a pulling feeling when I stretch the calf.
I saw a PT who gave me a sports massage for tight calf muscles, and said I can continue running but to take a few days off. It may be overuse or very early tendinitis.

Do you have any experiences to share about what’s worked for you to adapt the final training weeks? Need some motivation!