How to test Rotator Cuff strength in throwing athletes.
The ICC T20 World Cup is underway and thousands of throwing actions will take place over the next 4 weeks.
Did you know, at peak rotation, maximum humeral internal rotation velocity during throwing may reach 7500 to 7700 degrees per second (Seroyer et al 2010)? That’s approximately 4 times faster than a helicopter's rotor spins.
It’s no wonder then that some of the cricketers taking part in the ICC T20 World Cup this month need to have strong and functional rotator cuff muscles to generate and tolerate the forces involved in throwing.
How do the rotator cuff muscles work when throwing?
The above from Oyama 2012 illustrates the complexity of the throwing action and the demand on the tissues.
From this we can see that the shoulder forces acting on the shoulder work in a deceleration - acceleration - deceleration pattern. It may also be surprising to see that the rotator cuff works mostly to compress the shoulder joint and provide stability during these movements, and only generates a small amount of acceleration forces when required.
Often the assumption is that the strength is required in these muscles to create the movement at shoulder for the throw, but research has long shown that the predominant activation of these muscles is in the generating of stability to support the shoulder joint, often experiencing 50kg+ worth of force (Seroyer et al 2010).
Jobe et al 1983
How do you know if your athlete has enough strength?
Now that we understand the forces involved and how the rotator cuff works in throwing, how do we assess whether the people we work with have enough capacity to tolerate it?
Typically health professionals have used manual muscle testing to test strength, although many studies suggest that there are limitations to the accuracy of this testing with some research suggesting accuracy levels of 52% (van Niekerk 2017).
Other testing methods might include repetition maximum or isometric hold testing for time. While these methods can provide an objective result they typically assess the endurance strength capacity of certain shoulder movements and may not give insight into the capacity to generate the high force and high-speed requirements in the throwing movement.
That’s why AxIT is your best option for assessing shoulder strength in throwers.
The Athletic Shoulder Test is a useful test of shoulder girdle strength with research suggesting clients should generate between 13-28% of their bodyweight in force depending on the position.
AxIT allows you to collect data on rotator cuff maximum strength (peak force) and power (rate of force development) in almost any shoulder position, providing versatility in understanding exactly where your client's deficiencies and discrepancies might be in their throwing performance.
In-built data allows you to compare your client's shoulder strength to evidence-based references to give context around whether they are weak or strong in a certain movement, and intuitive visuals track their progression over time to show the effectiveness of your shoulder strengthening programs.
It can also be used to monitor important shoulder strength ratios to improve the way your client's shoulder functions. For example Boettcher et al 2020 found that the shoulder External Rotation / Internal Rotation strength ratio in a neutral position was approximately 70% bilaterally for 68 elite swimmers, while Cools et al 2016 found the ratio to be almost 1:1 at 90° of shoulder abduction in their study of overhead athletes.
Using these ratios can be helpful in identifying exactly which parts of the rotator cuff needs to be strengthened in your client.
AxIT Pull-IT makes it easy to collect accurate isometric rotator cuff strength data.
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