Biceps Femoris

The biceps femoris is part of the collective hamstring muscles, along with the semitendinosus and semimembranosus, which are located at the rear of the thigh. Biceps in Latin means ‘two heads,’ and femoris- 'of the femoris'. Biceps femoris has a long head and a short head.

The Biceps femoris is recruited during flexion of the knee and also extension of the hip.

The biceps femoris will be recruited effectively by exercises that require knee extension, such as leg curls. This will place direct stress onto the hamstring muscles. The biceps femoris is also recruited during exercises such as stiff leg deadlift, that require extension of the hip.

It has become popular for some trainers to only include the stiff leg deadlift to target the hamstrings during a leg session. This could be down to the mindset that compounds rule over isolation exercises, therefore some people see the SLDL as a superior choice. Truth is that isolation work for a muscle group such as the hamstrings will often prove an integral role for overall development. Exercises such as the leg curl will stimulate the biceps femoris effectively. The SLDL will recruit the hamstrings during extension of the hip, and exercises such as the leg curl will recruit the hamstrings during flexion of the knee.

Isolation exercises that involve flexion of the knee to target the Hamstrings, such as leg curls, will also allow for direct stress to be placed on hamstrings whilst not requiring as many stabilisers and synergists to aid the lift. This could prove advantageous for people who have injuries to areas and therefore not able to perform exercises such as Good Mornings and SLDL.
Isolation work can also allow for isolateral training.

The Hamstrings have been shown to have an abundance of type ii fibres.

6-12 reps will likely provide optimal time under tension for the biceps femoris muscle, providing adequate stimulation for sarcoplasmic hypertrophy for its type ii fibre majority make up. Furthermore, acute response to anabolic hormone concentrations, compared to that of lower rep ranges.
1-5 reps may prove more advantageous if the goal is power and strength. This will ideal for recruitment of the large motor units and type iiB fibres, and neural adaptations of the nervous system.