These muscles are used for middle to lower body posture and can exert a large amount of force.
The gluteus maximus and hams are mainly responsible for extending the hips, but the hamstrings also flex the knee.
The hamstrings are biarticulate, connect at two joints, and thus again cannot perform at both the hip and the knee.
This means that during hip extension exercises, such as deadlifts, the more you flex your knees the less the hams can come into play, and the more you emphasize the glutes. If you only do bent-knee exercises for your legs (and no leg curls), you’re not completely training your hamstrings.
The glutes are marginally slow twitch dominant by a few percent.
The hamstrings are composed of a huge 70% fast twitch fibers.
This means you should use relatively low reps for the hamstrings, but medium to high reps for the glutes.
Take home messages:
• Flexing the knee during hip extension takes the hamstrings out of the movement;
• Use straight leg or knee flexion movements for relatively low reps to train the hamstrings;
• Medium to high rep exercises with bent knees to train the glutes.
The Calves
The calves consist of the soleus and the gastrocs.
The soleus, the long, deeper calf muscle keeps you upright all day and is thus close to 90% slow twitch, so requires high reps.
The gastrocnemius responds much better to training and is relatively compared to the soleus. The lateral head is indeed fast-twitch dominant, but only by a few percent, so use medium volume for the gastrocs.
Emphasize the medial head by pointing your toes out and the lateral head by pointing the toes in. Both the soleus and the gastrocs perform during calf raises.
The biarticulate (connect at two joints) gastrocs also flex the knee, therefore can’t flex at both joints at the same time.
Therefore, you can emphasize the hamstrings by flexing the knees and you can emphasize the soleus by bending your knees.
The Quadriceps
The quads are composed of three main heads – the vastus lateralis, the rectus femoris and the vastus medialis oblique.
All heads extend the knee, but the rectus femoris also flexes the hips, and so cannot perform at both joints at the same time.
The vastus medialis oblique is slightly slow-twitch dominant, the vastus lateralis is approximately 57% fast twitch, and the rectus femoris, is a 65% fast-twitch powerhouse. For maximum muscle mass, use low reps but also high variety for the quads. There’s a bunch of other small thigh muscles, including the adductors and abductors.
The adductors are around 60% slow twitch and the other hip flexors (including abductors) have equal amounts of fast and slow muscle fibers.
Take home message:
• For quad training, use a large variation of reps with an emphasis on the lower rep ranges.
