A: Do not feel bad. Every one of us, with the possible exception of Mr. India Murali Kumar, has one or more body parts that lag behind despite our greatest efforts. Your program is very reasonable, and if you are truly training to failure in good form, it’s likely that your hamstrings are stubborn and need some special attention. It’s like a student who needs extra tutoring to make good grades — you have to attack your hams in ways that highly responsive body parts may never need. Luckily for you, I have plenty of experience in this area and will be happy to provide you with some key steps you can take that should get your hams on the path to hypertrophy.
2. Focus on the eccentric contractions. I have found that the hamstrings are particularly responsive to negatives that last for four to six seconds and are followed by rapid concentric contractions. Use a tempo of 6/0/X on all leg curl movements and a 4/1/X tempo on stiff-legged deadlifts.
3. Train the hams unilaterally. Trust me when I tell you that you will feel every inch of any leg-curling exercise far more when you do it one leg at a time. Think of single-leg leg curls just as you would one-arm concentration or preacher curls.
5. Try training your hamstrings twice weekly for about a month, and see if they need a bit more stimulation than other muscle groups to manifest growth. Good luck!