One unique aspect of swimming mechanics is that the power comes from the muscles of the shoulder girdle. In most sports, there is a ground reaction force and power is transmitted from the legs through the trunk and scapula and out the arms.
In swimming, however, the body is being pulled over the arms. Thus the arms are the propulsive mechanism, and the shoulders are quite vulnerable, e specially if the scapula cannot act as a stable base for the glenohumeral control muscles
Unfortunately, approximately half of competitive swimmers develop shoulder pain severe enough to cause them to alter their training schedule at some point during their swimming career. In a survey of 532 collegiate swimmers and 395 master swimmers, not only did approximately half the swimmers have a history of 3 or more weeks of shoulder pain that forced them to alter their training, but more than half of the injured swimmers also had a recurrence. These data point to the need for long-term intervention in the competitive swimmer.
In a separate unpublished survey of 233 competitive swimmers on 17 collegiate teams, the location of pain was queried, as were the positions during the stroke of the most intense pain.
Anterior-superior region of the shoulder was identified in 44% of the swimmers as the area of pain. Diffuse pain was identified in 26% of the swimmers, with lesser frequencies reported for the anterior-inferior region of the shoulder (14% of the swimmers), posterior-superior region (10% of the swimmers), and posterior-inferior region (4% of the swimmers).
Swimming Freestyle Stroke
The basic arm mechanics—with the arm position marking different phases of the freestyle stroke—are as follows
- Arm enters the water and extends forward in front of the shoulder.
- The underwater pull-through starts with the early pull-through phase, which is marked by the initiation of the backward arm movement. The palm and forearm should face the backward direction with the fingertips pointing down for as long as possible.
- The point at which the humerus is perpendicular to the body is called the mid pull-through. Subsequent to mid pull-through is the late pull through. The hand continues back and passes next
to the hip until it exits the water, leading with the elbow. After the arm exits the water, the recovery phase begins, when the arm is swung above the water to bring the arm into position to pull once again.
In swimmers with normal shoulders, the serratus anterior continually fires above 20% of its maximum.
This muscle appears to be stabilizing the scapula in a protracted position as the arm pulls the body over itself.
Demonstrates significantly less muscle action during a large portion of pull-through. Although the serratus anterior diminishes its action during pull-through, the rhomboids increase their activity.
It may be that, in an attempt to stabilize the scapula during the absence of the serratus anterior, the primary muscles availableare the rhomboids. Yet the action of the rhomboids (retraction and downward rotation of the scapula) is the exact opposite of the serratus anterior (protraction and upward
rotation). This may well be positioning the acromion to impinge on the rotator cuff.
As a clinician, one application of this research information is to ensure there is both a strengthening and endurance component for the serratus anterior and the subscapularis in a swimmer’s conditioning program. Another application is to watch for the initial signs of fatigue in these muscles, as that may be the start of a chain of injury.
Swimming Butterfly Mechanics
Butterfly stroke typically consisting more of an S -shaped pulling pattern
The butterfy stroke is a bilateral activity, as opposed to a reciprocal, unilateral pattern in the freestyle and backstroke. Swimmers who press the chest down such that the hands and arms are above the torso are generally in a more risky shoulder position in the early pull through because this leads to the humeral hyperextension (the humerus is behind the axis of the body).
During late pull-through and the beginning of the recovery phase, there is also a chance for the shoulder to beat risk. At the beginning of the late pull-through, the arms are bent and the hands are underneath the hips. The arms then extend, with the hands sweeping outward and the arms lifting upward to exit the water and transition into the recovery phase.
There is potential for the humerus to be internally rotated during the arm exit and early recovery
phase. A swimmer should not overemphasize the end of late pull-through and lift the hands out of the water too high; instead, he or she should keep his or her hands as close to the surface of the water as possible in the early recovery phase.
This action, followed by lunging forward on arm entry, canstress the spine and lower back
The two muscles with clinically relevant muscle firing changes in the painful shoulder during the butterfly are the serratus anterior and the teres minor.
In swimmers with painful shoulders the hand entry is wider than that of the swimmers with
normal shoulders. With the wider hand entry, the scapula does not need as much upward rotation or protraction, as evidenced by the decreased activity in the serratus anterior.
Teres minor also reveals significantly less action, most likely caused by the altered scapular and humeral position less action in the serratus anterior.
This muscle is not firing enough to stabilize the scapula or to assist with the pulling of the body over the arm. The decreased firing may be attributable to fatigue. In the normal shoulders, the serratus
anterior constantly fires above 20% (which, as previously discussed, leaves it susceptible to fatigue).
In the painful population, the serratus anterior may have become fatigued,
hence the markedly depressed muscle activity and the resultant unstable scapula.
With an unstable or “floating” scapula, the teres minor is unable to control the humeral rotation caused by the powerful pectoralis major. Therefore, these two muscles (the serratus anterior and the teres minor), which are attached to the scapula, lack the synergistic interplay to assist with propulsion and balance the rotatory humeral motion
End of the recovery phase, the teres minor also exhibits decreased muscle activity in the swimmer with a
painful shoulder. This is most likely because the muscle is preparing for the wider hand entry, and thus does not require as much action
Swimming Backstroke Mechanics
Backstroke is similar to the freestyle stroke in that the arms stroke reciprocally and are supported by a trunk rotation and a leg kick. Obviously, the major difference between the backstroke and the freestyle is that the backstroke is performed supine.
In the backstroke, the shoulder is vulnerable to injury similarly to the freestyle arm becomes submerged and the hand and arm press toward the feet. End of the late pull-through, the elbow straightens out with a slight downward press before lifting out of the water to start the recovery phase.
The timing of the body rotation as it relates to the arm entry and early pull-through is important.
Common symptoms of a late body rotation are a hand entry that crosses inside the shoulder width and a hand entry In this situation, in which the arm stroke leads the body rotation, the humerus is hyperextended.
A deep, early pull-through can lead to a humeral hyperextension because the body is not rotated enough or soon enough.
If a swimmer is experiencing shoulder pain in the early pull-through phase of backstroke and the swimmer is observed to have a straight arm and deep initial pull, then some stress on the shoulder may be relieved with a suggestion to keep the pull more shallow and the arm closer to the body
At the end of the late pull-through, when the hand exits the water, it is important that the hand exit the water with the thumb first.
Lifting the arm out with the pinky first will result in excessive humeral internal rotation. This will increase the pinching of the supraspinatus on the undersurface of the acromion. The hand then rotates during
mid-recovery so that the hand can enter the water with the pinky first and the palm rotated out
The muscles most active during the powerful pull-through are the teres minor and the
subscapularis and obviously, these two muscles were not designed for power
Even during the peak moments of pulling, the latissimus dorsi reveals 30% less action than does
the teres minor and the subscapularis in swimmers with normal shoulders.
During pull-through, the teres minor and subscapularis are constantly active at approximately 30%
maximum voluntary contraction. Thus it appears that these two rotator cuff muscles are functioning as power drivers as well as endurance muscles
At the same time as the depressed activity in the teres minor in the backstrokers with painful shoulders, the rhomboids also exhibit less action.
Apparently, the scapula is not retracted properly in early recovery and hence there may be less clearance for the humeral head under the acromion.
Swimming Breaststroke Mechanics
The breaststroke is the oldest of all competitive swim strokes, and it is unique in that the arms do not exit the water. In this stroke, the legs are more of the propeller or power drivers than are the arms. It appears that the least number of complaints of shoulder pain appear to occur with the breaststroke
The issue of body rotation along with humeral hyperextension is minimal.
This stroke uses a bilateral arm motion in which the arms reach forward and then sweep outward (the beginning of the pull-through), while the elbows begin to flex.
When the hands are in line with the mid-chest, the hands move inward in a circular pattern
until they meet in front of the chest and are thrust forward (recovery) once again.
Because the arms remain in front of the body at all times, the shoulders are not at high risk in
the breaststroke and kicking motion most frequently used in competition is the whip kick, a symmetric, bilateral action
During pull-through, breaststroke swimmers with painful shoulders demonstrate an increase in activity in the subscapularis and the latissimus dorsi.
The increased subscapularis activity, along with a decrease in the action of the teres minor, leads to a relative increase in internal rotation.
The increased internal rotation places the arm in a position that is vulnerable to impingement. The increase in latissimus dorsi action may assist with humeral head depression to relieve the impingement