Yoga pose for calf/legs


I have been suffering lower back pain from last 18 years and after suggestion from physiotherapy i.e. core is waek. I started gym with trainer and found it's very exhausting. I started yoga and mainly focusing on my legs and calf. I started chair pose, squts but looking more poses for legs and calf. I am already doing plank, side plank and boat pose. Please suggest some pose for my legs and calf.