If you spend enough time at the gym or on an on-line bodybuilding chat site, there will inevitably be a periodic debate about the superiority of some exercise against another exercise. Fortunately, academic and research-minded iron warriors also like to tackle those debates. In a new study1, lying leg curls and seated leg curls were put in the “which is better for muscle growth?” octagon.
The study was done in two parts. The first part used 20 untrained subjects and had them do seated leg curls with one leg and lying leg curls for the other leg for 2 sessions/week for 12 weeks to study hypertrophy. The second part of the research looked at muscle damage and involved using 19 of the 20 from the first part plus another 12 untrained subjects doing only the eccentric part of the movements.
The hamstrings are composed of the muscles: semitendinosus, semimembranosus, and biceps femoris (short and long head). The study found seated leg curls caused more hypertrophy in the semitendinosus, semimembranosus, and the long head of the biceps femoris. Both exercises caused similar hypertrophy of the short head of the biceps femoris.
The end conclusion was hamstrings muscle size can be more effectively increased by seated leg curls than lying leg curl training, suggesting that training at long muscle lengths promotes muscle hypertrophy, while both are similarly effective in reducing susceptibility to muscle damage.
A review published earlier this year looked at a half dozen studies and also concluded that, for lower body exercises, training at longer muscle lengths leads to greater muscle growth (results were mixed for upper body). But…there are not a ton of studies on range of motion, so it is an area where more research would be welcomed.
One tip: Many people do not get the maximal benefit on leg curls due to using too heavy of a load. On the lying leg curl, you often see people lifting their butt and arching their back to help move the weight. That removes the focus on the hamstrings by involving other muscles to help move the load. Proper form to effectively target the hamstrings is a neutral spine and keeping your hips and quads pushed down into the pad.
1) Maeo S, Meng H, Yuhang W, Sakurai H, Kusagawa Y, Sugiyama T, Kanehisa H, Isaka T. “Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection after Training at Long versus Short Muscle Lengths.” Medicine & Science In Sports & Exercise. 2020 Oct 1. doi: 10.1249/ MSS.0000000000002523. https://pubmed.ncbi.nlm.nih.gov/33009197/