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Hot on the Press

It’s the same in all gyms around the world. The bench press plays a major role in the exercise regime of many gym goers. It is an exercise that is used to strengthen the pectoralis major and anterior deltoid muscle groups with varying levels of assistance from the triceps depending on the position of the elbow in relation to the shoulder. The bench press is a compound exercise requiring movement at the shoulder girdle and elbow providing strength and power in the "push" muscles along with cosmetic toning of the chest and shoulders.

However, there is a down side. Bench press would have to be one of the most common contributors of shoulder pain in the gym. Why does such a commonly used exercise have the potential to create so many problems?

This article will attempt to identify some of the risk factors involved with this exercise and explore the current methods of management employed to improve safety during its execution.

We really cannot proceed any further without reviewing some mechanics of the shoulder. We all know that the shoulder joint is the most mobile joint in the body. It allows vast amounts of movement in all planes. This produces the first problem. To achieve that range, the shoulder joint has to be mechanically unstable - we sacrifice structural stability for mobility. The shoulder joint is often referred to as a ball and saucer rather than a ball and socket. Only a third of the head of humerus is in contact with the much smaller saucer.(see figure one).

Figure 1. Bony relationships of the shoulder girdle (Frank Netter – Human Atlas)

Problem number two - we cannot have dense ligaments supporting the joint as these would also reduce the available range of motion. Nature’s solution to these issues of instability was to provide dynamic stabilising muscles to hold the joint surfaces together. These stabilisers are collectively known as the rotator cuff. Basically they are designed to maintain joint position (i.e. the relationship of the ball to the saucer) during all movements at the shoulder joint by actively hugging the 2 bony surfaces together. (See figures two and three).

Figure 2. Rotator Cuff – Posterior View (Frank Netter – Human Atlas) Figure 3. Rotator Cuff – Anterior View (Frank Netter – Human Atlas)

Lets now see what our bench press exercise does to this joint complex. By lying on a flat bench we immobilise an integral part of the shoulder girdle - the scapula. The scapula plays a vital role in the function of the shoulder - by impairing its mobility we place further stress on the ball and saucer.

Second issue - using a bar prevents the shoulder moving through a natural arcing movement as the hands are locked in position. Compared to a dumbell press, the bench press with a bar changes the axis of movement of the press requiring further adjustment within the joint tissues.

So OK things are looking pretty grim for the shoulder before we start. Lets now take the bar down toward the chest. There is a common rule of biomechanics know as the convex - concave rule - this rule basically states that during joint motion the convex surface of a joint will slide in the opposite direction of the motion of the limb. In this case therefore the ball slides forward as the upper arm moves backward towards the bench. At the bottom of the movement the ball is trying to escape out of the front of the saucer. This is the most vulnerable part of the press. The muscles of the rotator cuff are required to drag the head of humerus backward into the socket (see figure four).

Figure 4. Convex Concave Rule (Frank Netter – Human Atlas)

To make matters worse as pectoralis major attempts to initiate the press during the next upward phase - the angle of the tendon insertion will result in further forward movement of the head of humerus placing more stress on the front of the joint. It is therefore not surprising that the cuff tissues receive such a hard time in this phase of the bench press.

As indicated by figure four, the rotator cuff must work collectively to draw the head of humerus into the scapula to protect the vulnerable joint tissues from damage ( note the angle of pull of subscapularis and supraspinatus along with the posterior cuff muscles). Traditionally when conditioning these muscles we use exercises that involve lateral rotation to provide the conditioning necessary to improve the function of the cuff. These exercises stress the infraspinatus and teres minor muscles which are indeed vital contributors to joint stability (figure five).

Figure 5. Dumbell Lateral Rotation - In side lying

It is evident in these schematic drawings (figure four) however, that subscapularis at the front of the joint also plays an integral role in providing joint stability. How often though do we neglect this muscle during our conditioning of the cuff? It is my opinion that we place most of the emphasis on the lateral rotators and ignore the benefits of training subscapularis into internal rotation (figure six).

Figure 6

Another often overlooked factor is that the key to all these stability exercises is to ensure the head of humerus is correctly positioned during the full range. Often with rotator cuff dysfunction you will observe a forward position of the head of humerus indicating an inability of the cuff to maintain joint position. If this positional fault remains during the corrective exercises we are conditioning the cuff to maintain this faulty alignment which will ultimately result in further joint problems. The client must be taught to gently draw the head of humerus back into the socket of the shoulder and maintain this position during the rotational movements selected for conditioning.

This specific retraining of cuff control will assist in improved stability during such exercises as the bench press. Other methods of controlling some of these issues include encouraging the use of dumbells to allow a freer, more natural movement at the shoulder girdle and limiting the range of motion as the bar approaches the chest to avoid excessive forward glide of the head of humerus.

Bench press can still play its major role with respect to upper body conditioning – however we do have to be aware of some of the common pit falls.