Suspension trainers, sometimes also called slings, are popular exercise tools. A modification on the concept of gymnastics rings, slings like Redcord and TRX provide convenient ways to get a complete workout anywhere or a change of pace with your regular workout. Many people also use these tools for rehab and prehab.
Researchers recently examined the effect of Redcord slings on shoulder stability in a study published in the Journal of Strength and Conditioning Research.
Muscles like the serratus anterior and the middle and lower trapezius are important for shoulder health. To put it simply, they help keep your shoulder blade in a strong position, and in doing so, they allow your arms to function properly. However, in many athletes, especially those who spend a lot of time with a bar overhead, these muscles can become dysfunctional, leading to soreness or even injury.
In this study, researchers hypothesized that kinetic chain exercises performed on an unstable surface (specifically Redcord slings) would increase the activity of these stabilizers when compared to the same moves on a stable surface. The exercises were as follows:
- Half Push Up: A common exercise with suspension trainers, the half push up here means an incline push up with the upper body elevated. An example would be a push up done on a Smith machine with the bar fixed in place. It does not mean a normal push up on the floor with half the range of motion.
Half Push Up Exercise
- Knee Push Up: A basic kneeling push up. The Redcord handles were set to be just above floor level.
Knee Push Up Exercise
- Knee Prone Bridging Plus: This is an interesting name, for what is a plank on the knees and elbows. The “plus” part of the name refers to the scapular protraction and retraction in this position. A similar but easier version of what is sometimes called a scap push up.
Knee Prone Bridging Plus Exercise
- Pull Up: This one is not quite what you’re thinking. It’s a pull up starting from a laying position, sometimes called an inverted row or an Australian pull up. Essentially, it’s the opposite of a push up.
Pull Up Exercise
47 people performed these exercises while hooked up to EMG electrodes. The electrodes took readings from the three muscles of interest. They also measured activity in the prime movers of the shoulder joint to ensure that increased readings weren’t simply due to more intensity. The researchers noted that working the stabilizers in exclusion of the prime movers like the lats would be more effective for rehab purposes.
The results of this study demonstrate that the common use of slings for developing shoulder stability musculature is actually a big mistake. As it turns out, slings have pretty much the opposite effect. In every exercise the suspension trainer either had no real change to the three stabilizers or their activation dropped significantly. It was the prime movers that increased in activity as a result of the instability, in many cases, significantly so.
A big story of this study is pectoralis activation. In all of the pressing exercises, the increased need to keep the hands in place caused a major increase in the need for the pecs. So, for prehab and rehab of the scapular stabilizers studied in this article, stick to stable surfaces for the greatest effect. If you want a boost to the big muscles of your shoulders, especially the pecs, then slings are the way to go.
1. Kristof De Mey, et. al., “Shoulder Muscle Activation Levels During Four Closed Kinetic Chain Exercises With and Without Redcord Slings,” Journal of Strength and Conditioning Research, doi: 10.1519/JSC.0000000000000292