Endurance Athlete where to start and min hours per week

I'm. 45 yr old very competitive cyclist (race twice monthly) I have decent flexibility and decent core. I've practiced yoga on and of for 15 years. Training for bike racing takes up 6-8 hrs per week. I'm looking for a way to take core strength way up, improve overall flexibility and hopefully reduce back fatigue and hip discomfort. Knowing my background where should I start (foundation, fundamentals)?  How many times per week and for how long (30,45,60 min) would I need to commit to progress in a meaningful way. Time is in short supply with work, family and existing training so need guidance. 

Matt

I would recommend Foundations to you. Start with 3 Times a week. It will take about 30-45 minutes per session depending where in the course you are. I would also recommend getting the stretch course Thoracic Bridge. This will be a blessing to your spine as you spend a lot of time on a bike where your back is bent the other way.

@Mats Trane nailed it with Foundations and the Thoracic stretch series.  I trained GST through an IronMan a couple years ago and the Front Split and Middle Split series really helped my tight hip flexors and low back pain.