How should we train the latissimus dorsi?

How can we design a strength training program that will maximize the growth of the latissimus dorsi? What factors do we need to take into account, and how do each of these factors affect the variables in the program?

What information do we need?

We can use the research literature to enhance our training programs if we search for information about the gross anatomy, regional anatomy, and internal moment arm lengths of a muscle, in addition to its working sarcomere lengths, and susceptibility to muscle damage. Each of these factors provides information that is useful for different reasons (read more).

• Gross anatomy describes the locations of the attachments of the muscle to the skeleton. Learning the basic anatomy of a muscle helps us figure out suitable exercises, and also helps us see how we might alter them to target different muscles within a group.
• Regional anatomy describes the way in which a muscle divides into several internal regions, and this tells us whether we are going to need multiple exercises to train the muscle.
• The internal moment arm lengths of a muscle determine its leverage on the joint, and therefore its contribution to a joint moment, relative to other agonist muscles. This allows us to see where peak force in an exercise joint range of motion needs to be, to target one muscle within a group (or one region of a muscle). We can alter the point where peak force occurs by our exercise selection and by our choice of external resistance type.
• The working sarcomere lengths describe the lengths of the sarcomeres inside a muscle over its joint angle range of motion. It allows us to see if the muscle can experience (1) active insufficiency (and so will be trained poorly by exercises involving peak forces at very short muscle lengths), and (2) stretch-mediated hypertrophy (and so will be trained more effectively by exercises involving peak forces at very long muscle lengths).
• The susceptibility of a muscle to damage is how easily a muscle is damaged by a workout. It is affected by: (1) muscle fiber type proportion, (2) its level of voluntary activation, and (3) the working sarcomere lengths of its muscle fibers. The amount of muscle damage that a muscle experiences after a workout is the main determinant of the frequency (and volume) we can use for training it, and it also influences our choice of exercises (single-joint vs. multi-joint, single-limb vs. multi-limb, and full vs. partial range of motion).

ANATOMY

The latissimus dorsi originates on (1) the superior, posterior aspect of the ilium of the pelvis, (2) the posterior sacrum, (3) the spinous processes of the lumbar and lower six thoracic vertebrae, and (4) posterior surfaces of the lowest three ribs. It inserts on the upper, medial humerus. Since the latissimus dorsi has a wide range of origins but single, small insertion, the muscle forms a fan shape that sits inferior (not deep) to the scapula, being quite narrow as it approaches the arm but very broad as it approaches the spine. These features make the latissimus dorsi into a pair of fan-shaped muscles that cover the middle and lower part of the back.

The latissimus dorsi is naturally lengthened whenever the arm is elevated. Arm elevation occurs whenever the shoulder is abducted (the arm is lifted laterally out to the side) or flexed (the arm is lifted up in front of the body). The latissimus dorsi is also lengthened, albeit to a lesser degree, when the shoulder is horizontally flexed (the arm is brought in front of the face from the sides of the body). Finally, owing to the location of the insertion on the medial side of the humerus, the latissimus dorsi is lengthened when the shoulder is externally rotated.

When the latissimus dorsi shortens, it causes (1) shoulder adduction (the opposite of shoulder abduction), (2) shoulder extension (the opposite of shoulder flexion), (3) shoulder internal rotation (the opposite of shoulder external rotation), and (4) shoulder horizontal extension (the opposite of shoulder horizontal flexion).

Since the latissimus dorsi originates on the pelvis and sacrum, a proportion of its fascicles have the potential to extend the lower back. Moreover, since the muscle is in two parts (one on each side of the body), those same fascicles can function as a lateral flexor of the lower back, on either side. Even so, it seems likely that the turning forces exerted by the muscle in these actions are small both in comparison with that produced by other muscles and also compared with the turning force produced by the latissimus dorsi at the shoulder.

Like the latissimus dorsi, the teres major muscle also inserts on the medial aspect of the humerus. However, it originates on the inferior, posterior aspect of the scapula, instead of on the spine and pelvis. Even so, it performs the same shoulder actions as the latissimus dorsi when it shortens, bringing about (1) shoulder adduction, (2) shoulder extension, (3) shoulder horizontal extension, and (4) shoulder internal rotation. Also, some studies have found muscular connections between the latissimus dorsi and the teres major, indicating their close functional relationship.

Practical implications

In practice, the latissimus dorsi is a large muscle that performs a wide range of movements for the shoulder and spine. Training it will therefore have a clear impact on the size of the back musculature. A range of exercises can be used to train the muscle, but shoulder (adduction or extension) exercises are likely to be much more effective than spine (lateral flexion or extension) exercises.

REGIONAL ANATOMY

Anatomical studies of the latissimus dorsi have divided it into (1) thoracic, and (2) lumbopelvic regions. The thoracic region of the latissimus dorsi includes the fascicles that originate only on the lower six thoracic vertebrae; the lumbopelvic region includes fascicles that originate on the lower three ribs, the lumbar and sacral vertebrae, and the pelvis. These investigations have found that the lumbopelvic region has nearly twice the physiological cross-sectional area of the thoracic region (3.6 vs. 2.0cm³) and that muscle fascicle lengths are longer in the lumbopelvic region than in the thoracic region. Therefore, it seems logical to infer that the lumbopelvic region is larger in volume than the thoracic region. However, since studies of internal moment arm lengths have subdivided the lumbopelvic region into lumbar and pelvic regions on the basis of muscle function, this larger region is actually comprised of two, smaller regions.

Studies assessing the internal moment arm lengths of the latissimus dorsi have divided it into (1) thoracic, (2) lumbar, and (3) pelvic regions, which are often referred to as superior, middle, and inferior regions based on their relative anatomical locations. Each of these regions differs slightly in terms of its contributions to shoulder adduction and extension. In general, the superior (thoracic) region contributes less to shoulder adduction than the middle (lumbar) and inferior (pelvic) regions, but more to shoulder extension.

Some electromyographical studies of the latissimus dorsi have divided the muscle into (1) thoracic, and (2) lumbopelvic regions. In agreement with the findings of studies that have explored internal moment arm lengths, this research shows the pelvic region is used preferentially for shoulder adduction, although this result is only apparent when testing in shoulder abduction. Other electromyographical studies have divided the latissimus dorsi into (1) medial, and (2) lateral regions. In this respect, it seems that the medial region may be more strongly activated than the lateral region by the main shoulder actions of extension, adduction, and internal rotation.

Practical implications

In practice, the latissimus dorsi can be readily divided it into (1) superior (thoracic), (2) middle (lumbar), and (3) inferior (pelvic) regions on the basis of anatomy and internal moment arm lengths, and into superior (thoracic) and inferior (lumbopelvic) regions on the basis of muscle activation patterns. This suggests that multiple exercises may be necessary to bring about maximum hypertrophy of this muscle group, with shoulder extension targeting the superior (thoracic) region, and shoulder adduction targeting the middle (lumbar) and inferior (pelvic) regions.

INTERNAL MOMENT ARM LENGTHS

INTRODUCTION

The latissimus dorsi causes (1) shoulder adduction (bringing the arms down to the sides of the body), (2) shoulder extension (bringing the arms down to the front of the body), (3) shoulder horizontal extension (moving the arms out to the sides, away from the front of the body), and (4) shoulder internal rotation. It is also involved in spine lateral flexion and spine extension.

Yet, the latissimus dorsi is a prime mover only in shoulder adduction and extension. It is not a prime mover in shoulder horizontal extension or in shoulder internal rotation, as the rotator cuff muscles are more important. Similarly, its contributions to spine lateral flexion and spine extension are likely quite small. Thus, only its internal moment arm lengths during shoulder extension and adduction are covered below.

(1) SHOULDER EXTENSION

Effects of joint angle on the whole latissimus dorsi

Taking all three regions together, the shoulder extensor moment arm of the latissimus dorsi changes with shoulder elevation angle, although its curve is quite flat. At low degrees of shoulder elevation (the arms by the sides), the shoulder extensor moment arm length is quite short. A broad peak is reached at 45 degrees of shoulder elevation, and then as the shoulder is elevated beyond 60 degrees, the shoulder extensor moment arm decreases linearly. Surprisingly, the latissimus dorsi has no leverage at all for shoulder extension once the arm is elevated beyond 120 degrees.

Effects of joint angle on latissimus dorsi regions

Looking at each region of the latissimus dorsi separately provides a different picture. Firstly, it is clear that the superior (thoracic) region contributes to shoulder extension to a far greater extent than the middle (lumbar) and inferior (pelvic) regions, at least until the arms are elevated beyond 90 degrees (arms at shoulder height). Secondly, the regions peak at different joint angles. The middle (lumbar) region peaks at 30 degrees, the superior (thoracic) region peaks at 45 degrees, and the inferior (pelvic) region peaks at 60 degrees of shoulder elevation. Thirdly, the middle (lumbar) region ceases to have any moment arm at 90 degrees of shoulder elevation, and the superior (thoracic) region ceases to have any moment arm at 120 degrees of shoulder elevation. However, the inferior (pelvic) region maintains a small moment arm that extends to more flexed joint angles.

Effects of joint angle on other muscles

When moving the shoulder in the sagittal plane, many muscles are involved. The anterior and middle deltoids, pectoralis major (clavicular region), and supraspinatus are primary shoulder flexors. The posterior deltoid, latissimus dorsi, teres minor, and teres major are primary shoulder extensors. The moment arms of all of the shoulder extensors alter with joint angle. However, unlike the latissimus dorsi, the other muscles all seem to retain leverage for shoulder extension even when the arm is elevated above 120 degrees.

• Teres major — the shoulder extensor moment arm of the teres major changes with shoulder elevation angle in a similar way to the moment arm of the latissimus dorsi, but the steepness of the curve and the absolute moment arm lengths are greater.
• Teres minor — the way that the shoulder extensor moment arm of the teres minor changes with shoulder elevation angle is unclear. Some research has reported that it increases linearly with increasing shoulder elevation, while other research suggests that it decreases.
• Posterior deltoid — the shoulder extensor moment arm of the posterior deltoid decreases clearly with increasing shoulder elevation angle, being greatest at low degrees of shoulder elevation.
• Pectoralis major (costal region) — the costal region of the pectoralis major develops a small shoulder extension moment arm once the arm is elevated above 45 degrees.

Practical implications

In practice, only the inferior (pelvic) region of the latissimus dorsi has a shoulder extension moment arm above 120 degrees of shoulder elevation. Even so, at lower levels of shoulder elevation, the superior (thoracic) region has the longest moment arm length. The latissimus dorsi shoulder extension moment arm lengths of all regions peak between 30 and 60 degrees. Thus, it seems likely that shoulder extension exercises that involve peak force between 30–60 degrees of shoulder elevation will target the superior (thoracic) region of the latissimus dorsi, while exercises that involve peak force above 120 degrees will be somewhat effective for the inferior (pelvic) region.

(2) SHOULDER ADDUCTION

Effects of joint angle on the whole latissimus dorsi

Taking all three regions together, the shoulder adduction moment arm of the latissimus dorsi changes with shoulder elevation angle, peaking at 70 degrees of shoulder elevation. Above and below this level, the shoulder adduction moment arm is much shorter, but it is still present.

Effects of joint angle on latissimus dorsi regions

Looking at each region of the latissimus dorsi separately provides a different picture. Firstly, it is clear that the superior (thoracic) region contributes to shoulder adduction to a far smaller extent than the middle (lumbar) and inferior (pelvic) regions. Secondly, the regions peak at different joint angles. The middle (lumbar) region peaks at 65 degrees, the superior (thoracic) region peaks at 70 degrees, and the inferior (pelvic) region peaks at 75 degrees of shoulder elevation.

Effects of joint angle on other muscles

When moving the shoulder in the frontal plane, many muscles are involved. The anterior and middle deltoids and two of the rotator cuff muscles (the supraspinatus and infraspinatus) are the primary shoulder abductors, while the pectoralis major, latissimus dorsi, teres major, and subscapularis are the primary shoulder adductors. The posterior deltoid and teres minor function as shoulder adductors when the shoulder is below 45–60 degrees of elevation, but as shoulder abductors when the shoulder is above this point. The shoulder adduction moment arms of the other muscles that adduct the shoulder each alter with joint angle.

• Teres major — the shoulder adduction moment arm of the teres major changes with shoulder elevation angle in an identical way to the moment arm of the latissimus dorsi.
• Subscapularis — the shoulder adduction moment of the subscapularis behaves similarly to the the latissimus dorsi, albeit more extremely. The subscapularis has minimal leverage at low degrees of shoulder elevation, but leverage increases sharply towards 90 degrees of shoulder elevation, before decreasing again.
• Posterior deltoid and teres minor — the posterior deltoid and teres minor are only shoulder adductors when the arm is below 45–60 degrees of shoulder elevation.
• Pectoralis major — the pectoralis major (all regions) displays a peak shoulder adduction moment arm length when the arms are by the sides, and the moment arm decreases linearly as the arm is elevated, reaching zero before the arms are at shoulder height.

Practical implications

In practice, it seems likely that shoulder adduction exercises that involve peak force at 65–75 degrees of shoulder elevation will be most effective for training the latissimus dorsi, although this will cause preferential development of the middle (lumbar) and inferior (pelvic) regions.

WORKING SARCOMERE LENGTHS

The working sarcomere lengths of the latissimus dorsi have been investigated, and differ between (1) movements involving spinal and shoulder motion, and between (2) thoracic and lumbopelvic regions of the muscle. Even so, when standing in the anatomical position, the sarcomere lengths of both regions are close to their optimal length, lying on the plateau region.

Considering spinal motion, recent research suggests that both the thoracic and lumbopelvic regions of the latissimus dorsi work on the final part of the ascending limb and the plateau region of the length-tension relationship during both extension and axial rotation of the spine. Yet, they work through the ascending limb, the plateau, and the descending limb in lateral flexion. Also, the lumbopelvic region displays a greater range of working sarcomere lengths, starting earlier on the ascending limb (1.64 vs. 2.41μm) and finishing slightly later on the descending limb (3.30 vs. 3.21μm). Even so, the role of the latissimus dorsi in performing lateral spine flexion is likely quite small.

Considering shoulder motion, recent research suggests that the thoracic and lumbopelvic regions of the latissimus dorsi work predominantly on the plateau region and descending limb of the length-tension relationship during both shoulder adduction and extension. During such movements, the thoracic region of the muscle displays a greater range of working sarcomere lengths, starting in approximately the same place near the start of the plateau region but reaching further down the descending limb. This indicates that shoulder adduction and extension movements involving a stretched position may be useful for developing both regions of the latissimus dorsi, but they may develop the thoracic region to a slightly greater extent. Yet, since the thoracic region has no shoulder extension moment arm at long muscle lengths, shoulder adduction exercises may be the better option for this region.

Practical implications

In practice, this suggests that the latissimus dorsi does not readily suffer active insufficiency in shoulder movements. Also, it seems that the latissimus dorsi can experience stretch-mediated hypertrophy from shoulder adduction or extension, although effects differ between regions. Targeting the thoracic region with exercises involving long muscle lengths is best done with shoulder adduction; targeting the lumbopelvic region is likely feasible by shoulder extension.

SUSCEPTIBILITY TO MUSCLE DAMAGE

Research that has studied the effects of a standard workout on a number of muscle groups has found that the latissimus dorsi takes longer to recover from a standardized workout than some but not all other muscles. The ability of the muscle to recover will depend upon its (1) voluntary activation percentage, (2) muscle fiber type, and (3) working sarcomere lengths.

Unfortunately, it seems that no studies have yet assessed the voluntary activation potential of the latissimus dorsi. We must therefore estimate its capability based on its size, although this is not always a good predictor. In comparison with many other muscles, the latissimus dorsi is quite large, being among the largest muscles in the upper body after the deltoids, the triceps brachii, and the pectoralis major. Yet, it is still smaller than many of the prime movers of the lower body. Since the triceps brachii is slightly larger and can achieve fairly high levels of voluntary activation, it is likely that the latissimus dorsi can attain similarly high levels. Even so, it is important to note that this is purely an estimate, rather than a measurement.

Research that has compared the muscle fiber type of several muscles suggests that the latissimus dorsi is comprised of broadly equal amounts of slow twitch and fast twitch muscle fibers, and lies approximately in the middle between more slow twitch and more fast twitch muscles. Yet, other studies that have assessed only the fiber type of the latissimus dorsi suggest that the muscle displays a tendency to be more fast twitch than slow twitch. Currently, it is therefore unclear whether the latissimus dorsi has a balanced fiber type proportion, like many of the lower body prime movers, or a fast twitch fiber type proportion, like the arm and chest muscles.

As explained above, the latissimus dorsi can reach the descending limb during movements that involve normal physiological ranges of motion for either the shoulder or spine. This increases the amount of passive tension that can be produced by the muscle fibers, which increases the amount of damage that they experience.

Practical implications

In practice, our knowledge of the factors that influence recovery time for the latissimus dorsi is incomplete. The only data that exist relate to the working sarcomere lengths, which reach the descending limb and thus increase the potential for muscle damage. Even so, current measurements of recovery time indicate that the latissimus dorsi takes a moderate amount of time to be repaired after a workout, suggesting that it is more easily damaged than the least susceptible muscle groups (which include the quadriceps and calves) but less easily damaged than the most susceptible muscle groups (which include the pectoralis major, biceps, and triceps).

What is the takeaway?

The latissimus dorsi is a large muscle that is involved a wide range of movements for the shoulder and spine. Training it has a major impact on the size of the back musculature. The latissimus dorsi can be further subdivided into (1) superior (thoracic), (2) middle (lumbar), and (3) inferior (pelvic) regions, which means that multiple exercises are likely necessary to cause maximum hypertrophy of this muscle group.

Shoulder extension exercises that involve peak force between 30–60 degrees of shoulder elevation (close-grip rows with accommodating resistance) can be used to target the superior (thoracic) region. In contrast, shoulder extension exercises that involve peak force at high levels of shoulder elevation (machine pull-overs) will target the inferior (pelvic) region. Shoulder adduction exercises involving peak force at 65–75 degrees of shoulder elevation (wide-grip pull-downs with accommodating resistance) will target the middle (lumbar) and inferior (pelvic) regions.

Technically, training the latissimus dorsi at long muscle lengths can trigger stretch-mediated hypertrophy in all regions, because the sarcomeres of all of its regions reach the descending limb in shoulder adduction and extension exercises. However, since the latissimus dorsi has its longest moment arm lengths at fairly low levels of shoulder elevation, it is likely that other muscles are greater contributors to shoulder adduction and extension movements when the latissimus dorsi is elongated.

When elongating the latissimus dorsi in shoulder extension and adduction exercises, the amount of sarcomere stretch is slightly greater for the thoracic region. Yet, the total lack of an internal moment arm in high degrees of shoulder elevation prevents the thoracic region from being targeted effectively at long muscle lengths by shoulder extension. Shoulder extension exercises with high forces at long muscle lengths (machine pull-overs) will therefore only cause stretch-mediated hypertrophy in the inferior (pelvic) region. Shoulder adduction exercises with high forces at long muscle lengths (wide-grip lat pull-downs, but only where the machine involves peak forces at the top of the exercise) should still trigger stretch-mediated hypertrophy in all regions, albeit only to the extent that the latissimus dorsi is able to contribute to the exercise instead of other muscle groups.

The factors that might influence recovery time for the latissimus dorsi are unclear. Direct measurements show that the latissimus dorsi takes a moderate amount of time to repair after a workout, being more easily-damaged than many leg muscles, but less-easily damaged than the arm muscles.