By Bret Contreras Flex
If you want to maximize the development of any muscle, it’s imperative that you fully stimulate all the fibers within the muscle. In the case of hamstrings, achieving this task isn’t as straightforward as it may seem. This column will consider the three primary mechanisms of muscle hypertrophy—mechanical tension, metabolic stress, and muscle damage—as it pertains to hamstring training.
Electromyography (EMG) doesn’t measure muscle tension; it measures muscle activation. Regardless, it’s a decent way to estimate the active tension on a muscle. Heavier weight will generate higher levels of mechanical tension, at least up to a certain point, so be sure to include some heavier hamstrings work in the lower rep ranges. When seeking to target the outer hamstrings, externally rotate the feet to increase muscle activation in the lateral hamstrings, and internally rotate the feet to increase muscle activation in the medial hamstrings.
Many believe that plantar flexing the feet during leg curls will increase hamstring activity. Although you can’t use as much weight when plantar flexing due to decreased gastrocnemius activity, hamstring activity is unchanged, therefore you don’t need to concern yourself with ankle position during leg curls. When performing hip-extension movements, bending the knee will decrease hamstring activity, so if attempting to target the hamstrings, you’ll want to avoid going into deep knee flexion. In support of this contention, research overwhelmingly supports the notion that the squat, leg press, split squat, step up, and lunge exercises are not effective for achieving high levels of hamstring activation.
Perhaps surprisingly, hamstring EMG doesn’t differ much between a conventional and stiff-leg deadlift or between a conventional and sumo deadlift. The lying leg curl activates the lower hamstrings to a greater degree than the stif-leg deadlift, but their upper-hamstring activity is similar. As to which exercises elicit the highest levels of hamstring activation, the Nordic ham curl, stiff-leg deadlift, leg curl, seated leg curl, and weighted back extension appear to top the charts. Leg curl variations and weighted back extensions will preferentially target the lateral hamstrings, whereas kettle bell swings will preferentially target the medial hamstrings.
With regard to metabolic stress and hamstring training, common sense tells us that medium to high reps with shorter rest periods will be ideal for creating high levels of metabolic stress. Common sense also tells us that knee flexion movements (leg curl exercise variations) will be better suited for maximizing metabolic stress in comparison with hip extension movements. Keeping constant tension on the hamstrings by eliminating rest in between reps will increase metabolic stress. Finally, drop sets or “running the rack” can be highly effective in generating large levels of metabolic stress. There are six different studies that examine the fiber type proportion of the hamstrings, and when considering the entire body of evidence, it appears that the hamstrings have a fairly even blend of type I and type II fibers. Therefore, be sure to incorporate some higher-rep hamstring training.
As far as muscle damage and hamstring training go, exercises that exhibit peak tensions at long muscle lengths will be superior for creating high levels of muscle damage. Therefore, stiff-leg deadlifts, Romanian deadlifts, good mornings, and seated leg curls all make for good, muscle-damaging hamstring exercises. Lunges create damage in the upper lateral hamstrings to a greater degree than leg curls. A focus on the eccentric phase of the movement will lead to greater levels of muscle damage, as will performing unfamiliar hamstrings movements or protocols. Pelvic tilt can impact hamstring muscle length, which can therefore influence strain. Maintaining anterior pelvic tilt likely leads to higher levels of hamstring muscle damage when compared with posterior pelvic tilt during exercise, so make sure you keep an arch when performing deadlifts, good mornings, and back extensions.
If you want to maximize hamstring hypertrophy, then you’ll need to utilize suffcient variety in your training. For maximizing tension on the hamstrings, go heavy and perform leg curls, Nordic ham curls, and weighted back extensions. Turn the feet out to activate more lateral hamstrings and turn the feet in to activate more medial hamstrings. For producing high levels of metabolic stress, go a bit lighter and perform higher reps with shorter rest periods. Use leg curl variations and keep constant tension on the hamstrings. For creating hamstring muscle damage, perform eccentrics, incorporate good mornings, stiff-leg deadlifts, seated leg curls, and Nordic ham curls, and switch up your hamstrings training regularly.