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unstable load training

How to improve overhead stability using unstable load training

Created by Mikey Lau


4 minute read

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This blog post is a part of a series where we summarise the current literature on anything health, fitness and well-being related. These are research articles that can give you a better insight into different ways that you can train your clients to get better results - faster. Be sure to sign up to our weekly newsletter to get the latest exclusive contents and offers.

Williams, et al. (2018)

Shoulder injuries are prevalent in overhead-dominant sports such as baseball, softball and tennis. The rotator cuff is usually placed under high eccentric stress during such events. Therefore, athletes would need to consider an effective injury prevention programme to reduce the likelihood of being 'out-of-action'. Many methodologies exist for stability training with some research to show its use to prevent injuries. The rationale behind such training is to provide a stimulus to increase muscle activation, joint stiffness, and to improve bio-motor abilities associated with stability.

Common methods of training involve exercising on unstable surfaces such as the BOSU or Swiss-ball. Another way to incorporate instability into a training regime is recognised as unstable load training (ULT). This combines equipment such as barbells, kettle-bells, plates and resistance bands to generate instability. Typically, ULT involves suspending the weights using resistance bands at the ends of a barbell.

It was proposed that this form of training could increase muscle fibre, motor and spindle recruitment. Though there's a lack of research supporting this claim, other studies have shown that ULT on squats could increase activation of the rectus abdominis, external oblique, and soleus compared to other forms of stable training.

The authors of this study aimed to determine any differences between stable and unstable load training. They’ve hypothesised that ULT will increase muscle activation of all prime movers and stabilisers with an increase in anterior/posterior movement of the centre of pressure (COP). In addition, they hypothesised that an unstable load on a flexible barbell will have a greater effect size compared to an unstable load on a regular barbell.


  • A within-subject study comparing 3 conditions across 12 recreationally active males.
  • Exclusion criteria: shoulder pain within 6 months, pain with overhead press or a history of shoulder dislocation.
  • The loads prescribed for the overhead press was 50% of the subject's 1-repetition max (1RM).
  • The 3 conditions: standard barbell and plates (SS), a standard barbell with hanging kettle-bells (US) and an earthquake barbell with suspended kettle-bells (EQ).
  • Surface electromyography (sEMG) was used to measure the level of muscle activation.
  • Collected over 2 sessions where subjects were asked to abstain from any exercise 48 hours prior.
  • On the first day, a 1RM test was conducted for the overhead press with a standard barbell and plates.
  • The subjects performed 10 reps of each condition at least a week after the first session.


It was discovered that EQ significantly increased muscle activation for the biceps brachii, erector spinae, latissimus dorsi, pectoralis major, rectus abdominis, rhomboid and the serratus anterior compared to SS whilst SU produced significantly greater activation of the erector spinae and latissimus dorsi compared to SS. Additionally, EQ significantly increased COP compared to both SU and SS.

The findings agreed with the author's hypothesis that EQ would increase prime mover and stabiliser activation. Interestingly, activation between prime movers did not differ between conditions, but stabilisers were significantly more active in the EQ condition.

In short, the findings of this paper suggest the use of ULT as a viable method to train stabilisers around the upper-body musculature involved in overhead pressing

Practical applications

Unstable load training could be included to introduce instability within a client's programme. The use of the earthquake bar with suspended loads generates significantly greater activation of such stabilisers. However, a lighter load of about 50% of the client’s 1RM was suggested to elicit such a response.


The subjects were recreationally active. This presented some issues as they could have various levels of experience with resistance training. In turn, performance could be reflected in the results. The small sample size may not reflect the true population.


Williams, M., Hendricks, D., Dannen, M., Arnold, A., and Lawrence, M. (2018). Activity of Shoulder Stabilizers and Prime Movers During an Unstable Overhead Press. Journal of Strength and Conditioning Research, 34(1). pp. 73-78.

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