a guide • Stronger by Science

Compared to the quads, the hamstrings usually receive far less attention. This is true both in the research and in the gym. In the gym, most lifters do plenty of squats, leg presses, and lunges – movements that hammer the quads whether you like it or not. Hamstrings, on the other hand, rarely get that same automatic volume. Unless you’re deliberately adding in leg curls and hip hinges, they can end up as an afterthought.

In the research, the quads tend to simply be easier to study. Most people store less fat on top of their quads, and the individual heads of the quads are easier to image using ultrasound on account of consistently being closer to the skin than the hamstrings.

However, there is research on hamstring training that most people simply aren’t aware of. We mostly have to thank strength and conditioning folks for that. With how prevalent and debilitating hamstring strains are, hamstring training (Nordic curls in particular) has received increased attention as an intervention to reduce strain injury risk. In this newsletter, we’ll break down the research we do have on exercise selection for the hamstrings.

First, some quick anatomy. The hamstrings have four heads: the biceps femoris long/short heads, the semitendinosus, and the semimembranosus. All heads of the hamstrings flex the knee (like a leg curl). Minus the short head of the biceps femoris, the hamstrings also extend the hips.

As you may have intuitively guessed, good hamstring exercise selection therefore needs two types of exercises: leg curls and hip hinges. Importantly, however, exercises like squats and leg presses likely aren’t great for building the hamstrings.

This was illustrated most clearly in a couple of recent studies (​1​, ​2​). The first compared the hip thrust to the barbell squat; neither grew the hamstrings much.

The second compared a squat to 90 degrees of knee flexion to a squat to 140 degrees of knee flexion; again, neither variation grew the hamstrings much.

Why? It likely has to do with the fact the hamstrings are biarticular. In any movement that requires you to extend the knees and hips simultaneously (i.e. the squat), ​the hamstrings are a double-edged sword​. They’ll help you extend the hips, but they’ll also generate torque to flex the knees, actively resisting the quads. To circumvent this issue, your body will usually recruit muscles that don’t present this issue: the gluteus maximus and adductor magnus, specifically. As a result, compound movements that require a large degree of torque to achieve both knee extension and hip extension simultaneously likely aren’t great for hamstring growth.

Instead, if we want to make hip hinges effective for the hamstrings, we need to keep the knee joint relatively fixed, and the knee extension demands minimal. Interestingly, hypertrophy patterns may differ between leg curls and hip hinges.

For instance, ​a study​ by Kawama et al investigated the effects of different frequencies of training the eccentric-only lengthened partial stiff-legged deadlift exercise. The long head of the biceps femoris, semimembranosus, and semitendinosus grew quite well, whereas the short head of the biceps femoris didn’t grow nearly as much.

A couple of studies have also directly compared a hip hinge to a leg curl variant. First, ​a study by Bourne et al​ compared the 45-degree back extension to the Nordic hamstring curl. The long head of the biceps femoris and semimembranosus grew better using the 450-degree back extension, whereas the short head of the biceps femoris and semitendinosus grew better from the Nordic hamstring curl.

Likewise, ​a recent study by Morin et al​ compared the Nordic hamstring curl to the stiff-legged deadlift. The Nordic hamstring curl resulted in greater growth of the semitendinosus than the stiff-legged deadlift, whereas the stiff-legged deadlift resulted in greater growth of the semimembranosus. Similar growth of the biceps femoris long head was observed. Unfortunately, the authors didn’t measure short head growth.

These three studies collectively tell us that hip hinges are probably slightly better for long head and semimembranosus growth, whereas leg curls are probably slightly better for short head and semitendinosus growth. Beyond functional anatomy, this forms a compelling rationale for including both in our training.

We also have a couple of studies by Maeo et al that can help guide us when it comes to selecting the right leg curl. The ​first study​ compared the seated and lying hamstring curl. A seated leg curl flexes the hips, increasing stretch on the biarticular hamstrings compared to the lying leg curl. Conversely, the sartorius, a knee flexor that also flexes the hip, is more stretched in the lying leg curl compared to the seated leg curl. The seated leg curl led to greater growth of the biarticular hamstrings, whereas the lying leg curl grew the sartorius more.

The ​second study​ compared the seated leg curl, with a lean forward for extra stretch, to the Nordic hamstring curl. Where the seated leg curl emphasizes length for the biarticular hamstrings, the Nordic curl emphasizes resistance in the stretch – the movement gets harder as you go down. The Nordic curl led to greater short head and sartorius growth, whereas the seated leg curl led to greater long head and semimembranosus growth. Semitendinosus, gracilis, and popliteus growth were similar between groups.

Taken together, these two studies suggest that the seated leg curl is probably the best bet for overall hamstring growth. However, the lying leg curl can be useful occasionally for sartorius growth, and the Nordic curl may be particularly beneficial for the short head of the hamstrings and the sartorius. It’s also important to note that these studies simply compared different leg curl variants. In the context of also performing hip hinges, these comparisons could have played out differently.

There are a couple more studies that, while not strictly exercise-selection related, are interesting to discuss in the context of hamstring training.

First, ​a study by Maeo et al (only currently available as a conference abstract)​ compared performing half-reps in the stretched position to full range of motion reps on the multi-hip machine. Growth of both hamstrings and glutes was generally greater with the lengthened partial technique. Experimenting with this technique for hamstring training may not be a bad idea.

Second, ​a study by Cadeo et al​ compared the effects of performing lying leg curls with the ankle fully plantarflexed or dorsiflexed on biceps femoris long head growth. This was done to manipulate length of the gastrocnemius – one of the calf muscles that also flexes the knee – and shift more/less work to the hamstrings. Ankle position did not impact the growth observed. So, ankle position during leg curls is mostly a matter of personal preference.

In summary: Hamstring growth likely requires both hip hinges and leg curls. Hinges tend to bias the long head and semimembranosus, while curls better target the semitendinosus and short head. Among curl options, the seated leg curl seems most effective overall, with lying curls and Nordics offering complementary benefits. Together, these findings suggest that a balanced hamstring program should combine both movement types and thoughtfully selected variations.