Q: Everyone says that squats are the best exercise for total leg development, but I'm not feeling it in my hamstrings. Are squats really all I need to build my hamstrings?
It's a claim that never seems to die. It's published in magazine and internet articles, bandied about in fitness forums and social media outlets, and perpetuated by high-profile fitness pros. "Just do compound lower-body movements, and your hamstrings want to get all the work they need to grow." Many simply take it as gospel, but this advice actually has little basis in science.
The idea that the hamstrings are maximally stimulated during a compound movement does not make sense anatomically. The hamstring muscles are biarticular, meaning that they are cross two joints ̵
What happens when you descend into a squat? Try it. The hamstrings shorten at the knee and lengthen at the hip. When you come back up-the hamstrings at the knee and shorten at the hip.
Research supports the fact that hamstring activity is low during lower-body exercises. In a study from my lab involving the leg press, the biceps femoris were significantly less active than the quadriceps muscles during the exercise-roughly 25 percent as active as the vast muscles and just as active as the rectus femoris. 
A 2009 study showed only 27 percent of maximal voluntary isometric contraction of the disease 
Maybe you do not put much stock into muscle activation and you want to argue that long-hamstrings term studies that directly measure hypertrophy are all that matters. Fair enough. A study published in the Journal of Orthopedic and Sports Physical Therapy provides direct evidence that squats do not do much for hamstring growth.  The subjects performed 4 sets of squats to approximately parallel depth using either a low, medium, or high rep range, training three days a week for seven weeks.
So, how do you get your hammies to grow? The answer is simple: Do single-joint exercises that directly target them. Good choices include exercises originating at the hip joints, like stiff-legged deadlifts and good mornings, as well as exercises originating at the knee, like leg curls.
A key point about these single-joint exercises is that when one joint is working, the other is fixed, creating a favorable length-tension relationship in which the hamstrings are stretched and shortened throughout the range of motion.
If the hamstrings are a weak point for you, prioritize them by training them first in your leg workout. Haul.
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- Schoenfeld, B.J .; Contreras, B .; Willardson, J.M .; Fontana, F .; and Tiryaki-Sonmez, G. (2014). Muscle activation during low-versus high-load resistance training in well-trained men, European Journal of Applied Physiology, 114 (12), 2491-2497.
- Ebben, W.P. (2009). Hamstring activation during lower body resistance training exercises. International Journal of Sports Physiology Performance, 4 (1), 84-96.
- Weiss, L.W .; Coney, H.D .; and Clark, F.C. (2000). Gross measures of exercise-induced muscular hypertrophy. Journal of Orthopedic and Sports Physical Therapy, 30 (3), 143-148