During resistance training protocols, it is frequently suggested that people target the scapular stabilizing musculature (middle and lower trapezius and serratus anterior) while minimizing shoulder prime mover activation (upper trapezius and large glenohumeral muscles) in their training regime, particularly in overhead athletes with scapular dyskinesis. In order to increase the activation levels in the stabilizing muscles without drastically increasing the activation in the prime movers, unstable surfaces are frequently used while performing closed kinetic chain exercises (CKC). However, the specific influence of Redcord slings (RS) as an unstable surface tool on the shoulder muscle activation levels has not been investigated very often, regardless these results may be used for adequate exercise selection. For this reason, the authors conducted a controlled laboratory study on 47 healthy subjects (22 ± 4.31 yr; 176 ± 0.083 cm; 69± 8.57 kg) during four CKC exercises without and with RS: half push-up, knee push-up, knee prone bridging plus, and pull-up. When using RS, serratus anterior muscle activation decreased during the knee push-up and knee prone bridging plus exercise. In addition, a drastic increase in pectoralis major muscle activation was found during the half push-up and knee prone bridging plus exercise. As a result, the use of RS does not necessarily suggest that higher levels of scapular stabilizer muscle activation will be achieved.
The findings of the study indicate that RS could be an appropriate training tool when used within a general strengthening program, but shouldn’t be chosen to the exclusion of a stable base of support when training for specific scapular stabilization purposes.