Muscle-specific hypertrophy: biceps, back and lower body

In the first part, I talked about the muscle fiber composition and biomechanics of the chest, triceps and shoulders. In this article I will cover the other primary muscle groups.

Biceps & brachioradialis

The biceps, which consists of a long (outer) and short (inner) muscle head, may seem like a simple muscle with straightforward biomechanics, but in reality it is a more complex muscle that crosses the elbow, forearm and shoulder.

The short muscle head of the biceps is a shoulder flexor, albeit a weak one, which means that it is not sufficient for simultaneous flexion of the elbow and shoulder. In other words, it cannot perform these two tasks simultaneously, so any biceps machine or biceps exercise where your elbow is in front of your shoulders will only train the long head of the biceps muscle.

The same applies to a lesser extent to exercises that involve shoulder abduction. So the next time you want to do standing cable curls in front of a mirror with a double bicep pose, remember that you'll probably be training your ego more than your biceps. Take care of the biceps mass first before worrying about developing biceps peaks like Albert Beckles.

Another way to preferentially recruit one muscle head over the other is to manipulate the position of the hands relative to the elbows. A wide grip emphasizes the short muscle head, while a narrow grip emphasizes the long muscle head. A shoulder-width grip still emphasizes the long muscle head more than the short one.

As mentioned earlier, you should be quite advanced before you should even consider this. Most exercisers are best served by sticking to exercises where the elbows are closer to the side of the body.

To emphasize the brachialis more than the biceps, you should perform slow contractions with the biceps in an awkward position (flexed shoulders). The slow-contracting muscle fibers dominate the brachialis more than the biceps, which respond best to fast contractions.

Another consideration for optimal biceps recruitment is the position of the hands. The biceps are very effective when the palms are facing upwards, slightly less effective when the hands are in a neutral position and inefficient when the palms are facing downwards.

But why are some exercises easier with the hands in a neutral position? It's because the brachioradialis, another elbow flexor and one of the larger forearm muscles, is most effective in this position.

In terms of the number of repetitions, a medium to low repetition range is most effective because the fast contracting muscle fibers in the biceps dominate - even if only by 5%. The brachioradialis has a higher dominance of fast-twitch fibers, with about 60% type II fibers, which is why you should train with heavier weights for hammer curls.

The bottom line:

- For standard curls, stay with the elbows at the sides of the body before thinking about emphasizing the brachialis and biceps peak.

- Use an underhand grip and a medium repetition range for biceps training and a neutral grip and a lower repetition range for brachioradialis.

The forearms

The forearms are made up of so many small muscles with varying compositions of muscle fiber types and different biomechanics that a full description is beyond the scope of this article.

Suffice it to say that an elbow flexion and extension covers the largest forearm muscles, which is why you should perform these exercises before trying finger exercises and the like.

In line with their frequent use, most forearm muscles are dominated by slow-contracting muscle fibers, which is why you should use high repetition numbers. You should also make sure to use more wrist flexion than wrist extension in your training program.

Latissimus & teres major

The latissimus dorsi and its little helper, the teres major, function primarily as shoulder adductors (pulling the elbows to the side of the body) and shoulder extensors (the opposite movement to front raises).

Shoulder extension is primarily performed by the higher fibers of the latissimus, while shoulder adduction is primarily performed by the lower muscle fibers of the latissimus. Maximum hypertrophy of the latissimus therefore requires both of these movements.

Many exercisers skimp on shoulder adduction - probably because it is more strenuous (like wide overhand pull-ups compared to underhand pull-ups) - and thus limit the width of their back.

A little known fact about the latissimus is that just like the chest, shoulder rotation affects the biomechanical efficiency of the muscle. During shoulder adduction, the latissimus is at its strongest when the shoulders are slightly rotated outwards. During shoulder extension, the latissimus is at its strongest when the shoulders are in a neutral position.

If you place your arms out to the side as in the Iron Cross exercise (https://www.youtube.com/watch?v=f24Vd_qGkKU), rotate your shoulders inwards when your thumbs are pointing towards the floor and rotate your shoulders outwards when your thumbs are pointing towards the ceiling.

Observe the movement of your shoulders. If you are using a rope, rings or any handle that can be rotated, then you should automatically rotate your shoulders into the optimal position for most pulling exercises. If you don't do this, you need to use a handle that puts your shoulders in the optimal position. For lat pulldowns, for example, you should use a slightly V-shaped handle instead of a straight bar to maximize the recruitment of your latissimus.

As for the composition of muscle fiber types, the latissimus normally consists of an identical amount of slow and fast contracting muscle fibers, so it responds best to a medium repetition range.

The bottom line:

• Include both shoulder extensions and shoulder adductions in your program.
• Think about your grip and shoulder rotation for your exercises.
• The latissimus responds best to a medium volume.

The trapezius

The trapezius is an exemplary muscle. The upper trapezius is visible in the mirror, but the middle and lower trapezius are not, so only the upper trapezius gets attention - a perfect example of the mirror muscle effect.

Even among people who train their backs as hard as their mirror muscles, the trapezius tends to get neglected. When was the last time you did isolation training for your middle or lower trapezius?

Even though the lower and upper trapezius muscle fibers have opposite functions (pulling the shoulder blades up and down), training the trapezius is pretty basic - pull the shoulder blades down, up and together in equal amounts against resistance. (The key phrase here is "to the same extent").

And while you may think you're achieving structural balance with your program because you're pulling and pushing in a 1:1 ratio, you should be performing a higher volume of pulling movements than pushing movements.

The chest is dominated by the fast contracting muscle fibers, but the trapezius is a postural muscle and accordingly the slow contracting muscle fibers dominate, so you should use a higher volume for the trapezius than for your chest.

It's worth noting that the rhomboids, which also retract the shoulder blades, are made up of about 55% fast contracting muscle fibers, but because these muscles are not visible from the outside, this should not concern bodybuilders.

For those who train their neck muscles, it's worth noting that the sternocleidomastoid, a neck flexor and extensor, is made up of 65% fast-contracting muscle fibers.

The bottom line:

• Your trapezius is important. Train it fully and train it more than your pressing muscles.

Gluteus, leg flexors and lower back

These muscles form the middle/lower posterior muscle chain and have massive strength release potential. They often work together during a hip extension, while the erector spinae stabilizes the spine and the gluteus and leg flexors move the hip. In addition to extending the spine, the erector spinae also rotates the spine and flexes it to the side.

The gluteus maximus and the leg flexors are mainly responsible for extending the hips, but the leg flexors also bend the knees. (The short muscle head of the biceps femoris is exclusively responsible for knee flexion). This dual function of the hamstrings has very important implications for gluteus, hamstring and calf training.

When the leg flexors attempt to extend the hip and knee, they achieve passive insufficiency. When they try to flex the hip and knee, they achieve active insufficiency. Basically, the leg flexors cannot perform their functions on both joints at the same time.

This means that during hip extension exercises like deadlifts, the more you bend the knees and the more you emphasize the gluteus, the less the leg flexors come into play. If you only perform bent-knee exercises for your legs (and no leg curls), then you are not fully training your hamstrings.

On the other hand, many exercisers have weak, underactive glutes and strong, overactive leg flexors, so you should perform your hip extension exercises with bent knees.

Since the gluteus and the hamstrings both flex the hip, bodybuilders may tend to train both muscle groups at the same time. This is suboptimal. The gluteus is a few percent dominantly slow-contracting, but the hamstrings are made up of a gigantic 70% fast-contracting muscle fibers.

The erector spinae contains about 6% more slow-contracting muscle fibers. This means that you should use a low repetition range for the leg flexors, but a medium to high repetition range for the lower back and gluteus.

The bottom line:

• Bending the knees during a hip extension takes the leg flexors out of the movement.
• Use straight leg exercises (or leg curls) with low reps to work the hamstrings and medium to high reps with bent knees to work the glutes and lower back.

The calves

The long, deeper calf muscle, the soleus, keeps you upright throughout the day and is therefore made up of almost 90% slow-contracting muscle fibers, so you don't need to worry about reps below 15. The gastrocnemius is often referred to as the fast-contracting part of the calves, but this is only in comparison to the super slow-contracting soleus.

In the lateral muscle head, the fast-contracting muscle fibers are indeed dominant, but only by a few percent and in the middle muscle head, the slow-contracting muscle fibers dominate by a few percent, which is why you should use a medium volume for the gastrocnemius. You can emphasize the middle muscle head by turning the tips of the toes outwards and you can emphasize the lateral muscle head by pointing the toes inwards.

Both the soleus and gastrocnemius perform plantar (sole of the foot) flexion, but the gastrocnemius, which runs across several joints, also flexes the knee and cannot flex both joints at the same time. For this reason, you can isolate the leg flexors during a knee flexion by plantar flexion and the soleus by flexing the knee

The anterior thighs

The front of the thighs consists mainly of the quadriceps. The quadriceps themselves consist of three main muscle heads - the vastus lateralis, the rectus femoris and the vastus medialis oblique (alias VMO).

All of the quadriceps muscle heads extend the knee, but the rectus femoris also flexes the hip, so it becomes actively insufficient if you try to do both at the same time. To demonstrate this, pull your knee up as far as you can. Now try to straighten your knee. Difficult, isn't it? That's an active insufficiency of the rectus femoris (and a passive insufficiency of the leg flexors).

The vastus medialis oblique and vastus lateralis also pull the kneecap in opposite directions during knee extension, so it's important to maintain a structural balance between these two muscles. There is controversy regarding whether and how to preferentially recruit the vastus medialis oblique over the vastus lateralis, but healthy exercisers should have no problems as long as they perform bilateral and unilateral exercises through the full range of motion.

As for the muscle fiber type composition of the quadriceps, this varies significantly between muscle heads. The vastus medialis oblique has a slight predominance of slow-contracting muscle fibers, the vastus lateralis consists of about 57% fast-contracting fibers, and the rectus femoris, the center of the thighs, consists of 65% fast-contracting muscle fibers. Now you know why Olympic weightlifters tend to have large quadriceps. For maximum muscle mass, I recommend mainly lower repetition ranges but at the same time a wide variety of repetition ranges for the quadriceps.

There are a number of other smaller thigh muscles including the adductors. I won't cover them all. Simply put, the adductors are made up of about 60% slow contracting muscle fibers and the other hip flexors have a ratio of 50% slow contracting muscle fibers to 50% fast contracting muscle fibers.

The bottom line:

• When training the quadriceps, use a wide variation of repetition ranges with an emphasis on the lower repetition ranges.

The center of the body

The rectus abdominis, aka six-pack, flexes the spine. The obliques support the abdominal muscles here and rotate and bend the spine to the side. Together with the transverse abdominis, they also generate intra-abdominal pressure.

The obliques and the transverse abdominis are trained through heavy multi-joint exercises such as squats and deadlifts. However, the rectus abdominis may remain untrained without direct training, depending on your exercise selection.

Another consideration is that anecdotal reports suggest that the anterior midline muscles have limited hypertrophy potential, even though fast-twitch muscle fibers dominate these muscles by about 5%. And then there's the debate about whether flexion of the spine is healthy, or whether extra mass in the midsection is even aesthetically desirable.

With all this in mind, I think beginners should perform exercises such as planks, rollouts and reverse crunches with low repetitions to strengthen the front core, even if it is only for the purpose of establishing structural balance and learning to stabilize the trunk properly with the muscles of the core.

After this phase, heavy multi-joint exercises such as vertical pushes and pulls may be sufficient training for bodybuilders depending on exercise selection and individual preference.

Conclusion

And with this, you should be clear. You now have almost all the knowledge of biomechanics and muscle fiber composition you'll ever need to optimally recruit your muscles, manipulate exercises to emphasize specific muscles, and choose optimal training parameters for each muscle.

And now you should modify your training program and grow!

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By Menno Henselmans | 10/27/11

Source: https://www.t-nation.com/training/muscle-specific-hypertrophy-biceps-back-and-lower-body

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