How to Activate Scapular Posterior Tilt? ~Exercise Strategies Focusing on the Lower Trapezius and Serratus Anterior~

Among the periscapular muscles,
the lower trapezius (LT) and serratus anterior (SA) in particular
are involved in scapular posterior tilt, upward rotation, and external rotation,
playing a crucial role in the stability and function of the shoulder joint.

Weakness or dysfunction of these muscles
can increase the risk of various shoulder joint disorders,
such as shoulder impingement, rotator cuff tears,
and shoulder instability.

For professionals,
selecting exercise therapies that effectively activate and
strengthen the muscles involved in scapular posterior tilt
is extremely important
in the prevention and rehabilitation of shoulder joint disorders.

Therefore, in this article,
we would like to consider
exercise strategies for effectively activating the lower trapezius and serratus anterior.

1. Relationship between muscle activity of the lower trapezius and serratus anterior and trunk stabilization

Ha et al. (2012)
conducted a study comparing the muscle activity of the
lower trapezius (LT) and serratus anterior (SA) during different arm elevation exercises.

In this study,
targeting 20 healthy individuals (10 men, 10 women),
the electromyography of the LT and SA was measured during the following four types of exercises.

1. Wall-assisted arm lift (WAL): An exercise where you stand facing a wall and lift your arms while keeping your forearms against the wall.

2. Prone arm lift (PAL): An exercise where you lie face down and lift your arms diagonally upward.

3. Back-rocking arm lift (BRAL): An exercise where you lift your arms straight up while rocking backward from a quadruped position.

4. Back-rocking diagonal arm lift (BRDAL): An exercise where you lift your arms diagonally upward while rocking backward from a quadruped position.

The results
revealed that back-rocking diagonal arm elevation (BRDAL) was most effective for LT activation,
and back-rocking arm elevation (BRAL) was most effective for SA activation,
respectively.

It is thought that performing
back-rocking, where you lift your arms while slowly moving your hips toward your heels from a quadruped position,
and the resulting trunk stabilization,
may have promoted the selective activation of the LT and SA.

In a state where the trunk is unstable,
other periscapular muscles may act compensatorily,
potentially inhibiting the isolated contraction of the LT and SA.

With back-rocking,
it is believed that by stabilizing the trunk, compensatory activity of other muscles is suppressed,
effectively enhancing the activity of the LT and SA.

2. Scapular position and muscle fiber direction

The difference in LT and SA activation between BRDAL and BRAL
is thought to be related to
the scapular abduction angle and the direction of the muscle fibers.

In BRDAL, the scapula is in a position of approximately 145° abduction,
which maximizes LT activity.
This position aligns with the direction of the LT muscle fibers,
thought to promote more efficient muscle contraction.

On the other hand, in BRAL, the scapula is abducted to 180°.
This position is at the end range of scapular abduction,
and is considered the position where scapular posterior tilt is maximized.
Also, since the SA muscle fibers are in a shortened position during BRAL,
it is thought that more efficient muscle contraction is promoted.

3. Summary

To effectively activate the LT and SA involved in scapular posterior tilt,
performing back-rocking
while keeping the trunk stable is considered effective.

Especially

• LT: Bear Rocking Diagonal Arm Lift (BRDAL)

• SA: Bear Rocking Arm Lift (BRAL)

are each effective.

When selecting these exercise therapies,
it is important to consider
the position of the scapula and the direction of the muscle fibers.

Please use this as a reference for
stabilizing the shoulder joint
accompanied by scapular posterior tilt
by activating the lower trapezius (LT) and serratus anterior (SA).

*The literature referenced and cited here is as follows: