Why do my lower calves seize up so much when I run now

tight hip flexors / forward pelvic tilt, insufficient warm up + cool down, electrolyte deficiency are probably top 3 possibilities

this is a good routine (video is crazy long but can skip through to check out the movements)

this is a good routine (video is crazy long but can skip through to check out the movements) https://www.youtube.com/watch?v=nLdjvFzjl2w

Fwiw, skate coaches have their students rub the hell out of their hip flexors with lacrosse balls to loosen

Sound response here from Charli. As a DPT I’d recommend also considering running movement quality and ensuring good range of motion and strength throughout the entire lower body.