Have you tried stretching first thing in the morning? Within the first 30 minutes after we awake, we are at our “stretchiest”. 😉 What this highly technical technique really is almost like cheating, but there’s a catch. Do tend to be careful and not to overdo it, champ.
If that still doesn’t work for you, keep a slight bend in the knees and remember to use your core. This is basically a functional athletic position to protect your joints while giving you maximum performance. Try breathing into the stretch while thinking warm compassionate thoughts for yourself and sink in deeper.
The plank is probably not the best thing to do first thing in the morning. Wait until your body is more stable to attempt feats of strength building. And don’t forget the modified plank – kneel on knees and even elbows. You got this!