Sometimes I’ll feel some tightness in the above mentioned thigh muscles when I train. I dont believe it has much to do with growing though.
Maybe only in so far as improving vascular circulation would aid the growth process. I believe core strengthening improves this circulation and facilitates general health more than isolated weight lifting. Try this also:
Stand up straight, put hands on hips, get down on both knees. Push your hips forward as far as you can while keeping your head and shoulders in original position. Imagine pulling a bow string-The hips being the pulled part the ends stay in position like your head and knees on the floor. Feel tightness in hips? Hip flexors may need to be loosened up. Anyway, this tightness of core and hip muscles in conjunction with other smaller pelvic muscles may link up to contribute to excessive turtling. To find out for sure, get on an intensive program of Yoga and stretching exercises for the hips and hamstrings. See how it is in 6-8 weeks.