Swimmers depend on accessory breathing muscles for adequate ventilation. Pectoralis minor is an accessory breathing muscle. The daily repetition of gleno-humeral flexion and medial rotation results in adaptive shortening of Pectoralis, a common phenomenon in competitive swimmers. If Pectoralis minor is shortened the scapula is in an anteriorly tipped position. This anteriorly tipped position will affect scapula kinematics as well as the strength of Pectoralis minor to function as an accessory breathing muscle. One of the risk factors contributing to shoulder dysfunction in competitive swimmers is an altered scapular position.
The study aimed to determine if lateral costal breathing dissociation exercises in conjunction with scapular retraining exercises had an effect on the position of the scapula in competitive swimmers.
A comparative parallel group longitudinal design was used in this study. During a six week supervised intervention period the intervention group (n=28) and control group (n=30) did retraining of the scapula stabilisers and stretching of Pectoralis minor. The intervention group did breathing dissociation exercises to facilitate lateral costal breathing. No specific breathing exercises were facilitated within the control group. Pectoralis minor length and thoracic expansion had been measured. The function of the scapula stabilisers was evaluated. The resting as well as dynamic scapula positions were evaluated. Evaluations were done at baseline, six weeks and five months post intervention.
Treatment groups were compared with respect to change from baseline to six weeks and baseline to five months in PMI, FVC and thoracic expansion utilizing analysis of covariance (ANCOVA) with covariates baseline reading. The intervention group showed an increase in the Pectoralis minor Index (PMI) of 0.5 (left & right) and the control group reflected an increase of 0.5 (left) and 0.7 (right).
The intervention group reflected continuous improvement in PMI and the control group showed deterioration. In addition to the PMI upper thoracic, expansion decreased and lower thoracic expansion increased in the intervention group. The control group showed a decrease in upper and lower thoracic expansion. Groups were compared with respect to change from baseline to six weeks and five months respectively for categorical parameters, muscle function and scapula position (resting and dynamic) using Fisher’s exact test. After six weeks the intervention group showed significantly (p<0.04) less winging of the distal third of the scapula on the left side when compared to the control group. After five months the scapula showed significantly less tipping (p<0.02) during gleno-humeral flexion, on the left side.
The McNemar test for symmetry had been applied to determine if any within group changes occurred. Within the intervention group ten of the thirteen markers used to determine the resting position of the scapula, reflected significant improvement compared to the six markers in the control group. Only the intervention group reflected remarkable improvement in function of the lower fibres of Trapezius muscle. Serratus anterior and middle fibres of Trapezius muscles showed significance within group improvement in function for both groups. The scapula showed significantly less dysrhythmia within the intervention group on the left and right sides (p< 0.0209) when compared to the control group.
After five months the resting scapula position reflected deterioration for both groups. Dysrhythmia and winging of the scapula deteriorated from six weeks to five months for both groups. The muscle function of the lower fibres of Trapezius showed significance within group changes for both groups from six weeks to five months. The ability to contract Serratus anterior and the middle fibres of Trapezius agonistically was maintained from six weeks to five months. However the eccentric control and ability to contract the muscle without fatigue within the Serratus anterior and middle fibres of Trapezius showed deterioration from six weeks to five months for both groups.
Conclusion: The increase in PMI and increase in lower thoracic expansion for the intervention group could favour swimmers to breathe more effectively. An increase in Pectoralis minor length resulted in a more posteriorly tipped scapula. This better positioned scapula promotes optimum function of the lower fibres of Trapezius. Contracting from a stable scapula, Pectoralis minor can fulfil its function as an accessory breathing muscle more effectively.