Original research
Kinetic chain influences on upper and lower trapezius muscle activation during eight variations of a scapular retraction exercise in overhead athletes

https://doi.org/10.1016/j.jsams.2012.04.008Get rights and content

Abstract

Objectives

To describe and compare the activation levels of the upper and lower trapezius muscle and study the influence of trunk and lower extremity position or movement during eight variations of a scapular retraction exercise.

Design

Descriptive study. Exercise performance was standardized and individualized based on height, age and body weight.

Methods

Individual muscle activation was captured by surface electromyography in thirty young healthy overhead athletes. Exercises were performed in front of a pulley apparatus.

Results

The mean values for upper trapezius and lower trapezius were 6.59% and 15.93% of maximum voluntary isometric contractions respectively. Main effects were found for “exercise” (F = 2.60; p = 0.037) and “muscle part” (F = 25.44; p < 0.001) in an ANOVA for repeated measures model showing higher lower trapezius muscle activation compared to the upper trapezius across exercises. An unipodal squat position on the contralateral leg increased trapezius muscle activation by 3.93% maximum voluntary isometric contraction (p = 0.019) compared to the conventional seated performance of the exercise. No differences between phases were found and no exercise activated a particular muscle part (upper trapezius or lower trapezius) to a greater extent in comparison with other exercises since no two-way interactions were found with p < 0.05.

Conclusions

All exercise variations may be useful in the early phases of scapular rehabilitation training because of their favorable trapezius muscle balance activation. Standing in a squat position on the contralateral leg can result in a slight increase in trapezius muscle activation. However, future comparative effectiveness studies are needed to identify the long-term training benefits of these exercises.

Introduction

Scapular dyskinesis and related shoulder impingement syndrome are common conditions, particularly in overhead athletes.1 Although various muscles contribute to the three-dimensional movements around the shoulder, a lack of activity in the lower trapezius (LT) has been observed in these people, often in combination with an excessive upper trapezius (UT) activation.2 This might contribute to excessive clavicle elevation on the thorax coupled with increased anterior tilt at the scapulothoracic joint which causes the rotator cuff to impinge during elevation.3 The UT and LT muscles play different roles around the scapula during dynamic activities. Whereas the UT does not appear to have a line of action for being a substantive upward rotator in healthy persons, the LT assists in producing scapulothoracic upward rotation.4 Furthermore, evidence indicates that the LT acts as a stabilizer at the scapulothoracic joint.4 Consequently, scapular muscle exercises characterized by high LT and low UT muscle activation are of interest in the rehabilitation of patients with secondary impingement.

Training the activation and strength of selective muscle parts is the most common clinical approach in the management of musculoskeletal disorders. Depending on different stages of rehabilitation, various exercises might improve scapular muscle performance. In general, rowing and scapular retraction exercises have been found to enhance scapular muscle performance because of their preferential trapezius muscle activation.5, 6, 7 In addition, the scapular retracted position has been found to reduce symptoms and increase muscle performance in patients with impingement symptoms.8, 9

Recent guidelines have pointed to the value of integrating shoulder girdle exercises into a global functional kinetic chain for multiple reasons.10, 11 In general, these recommendations are based on the principle of sport specificity emphasizing the core as the center of the body during upper extremity training. Furthermore, it is assumed to increase the activity in particular shoulder muscles compared to more artificially stabilized positions such as the prone, side-lying or seated position. Maenhout et al. have recently investigated the influence of the position of the lower extremity on scapular muscle activity and balance during closed kinetic chain push-up variations.12 In their research, they discovered that contralateral leg extension stimulates LT activity during a knee push up plus exercise. However, the influence of proximal body segments during scapular retraction exercises integrating the trunk and lower extremity has not yet been investigated. Therefore, the purpose of this study was to analyze UT and LT muscle activation levels in an overhead athletic population during eight variations of a high scapular retraction movement. It was hypothesized that differences between UT and LT muscle activation would be found in all exercises and that the kinetic chain, influenced by lower extremity position or movement, would have an effect on these activation levels.

Section snippets

Methods

The data were obtained from a group of 30 healthy overhead athletes (17 male, 13 female), including volleyball and tennis players, and swimmers (mean ± SD age, 20 ± 3.5 years; mean ± SD weight, 69.4 ± 10.5 kg; mean ± SD body height, 179 ± 0.11 cm; mean ± SD BMI, 22 ± 0.02). The participants were recruited from the student population in the local metropolitan area. Twenty-seven were right-handed and 3 were left-handed, and it was the dominant shoulder that was tested. Athletes were included if they were between

Results

Means and standard deviations were calculated across participants for normalized EMG activity of each muscle for all exercises (Table 3). The ANOVA model revealed that sphericity could not be assumed, and a Greenhouse–Geisser correction was used to interpret all results. No three-way interaction was found with p < 0.05. Subsequently, two-way interactions including the factor “exercise” were of interest, but none of them showed significant results. So, in none of the exercises the muscle

Discussion

Particular retraction exercise variations might have an influence on the recruitment patterns of specific shoulder muscles. However, the conventional focus on individual joint training has resulted in a limited knowledge of scapular muscle recruitment during exercises that activate the entire kinetic chain system. Therefore, we investigated UT and LT muscle activation during eight kinetic chain variations of a high scapular retraction exercise which is thought to be relevant in the

Conclusion

In view of the recent tendencies with respect to functional kinetic chain training, we investigated UT and LT muscle activation during a series of eight variations of the high scapular retraction exercise. The results show higher LT compared to UT muscle activation in all exercises. We can conclude that standing in a squat position on the contralateral leg stimulates higher trapezius muscle activation levels compared to a seated performance of the exercise suggesting kinetic chain influences on

Practical implications

  • Scapular retraction exercises seem useful for trapezius neuromuscular coordination training in overhead athletes because of their low upper trapezius muscle activation levels compared to those of the lower trapezius muscle.

  • Several kinetic chain variations might be useful because none of them result in excessive upper trapezius activation in healthy athletes.

Acknowledgements

As there has been no financial support for this project, the authors are grateful to the volunteers who participated in this study.

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