The 2 Laws of Torque: Application for Swimming

By Sean Kao

I want to preface this article by giving all credit to Dr. Kelly Starrett. I am simply regurgitating what he has stated about the laws of torque, and making it applicable to the swimming population. Some controversy regarding the “Laws of Torque” have emerged in recent years, but I believe there are some points that can be beneficial to the swimming community.

The laws of torque: What is it?

Torque is simply moment arm multiplied by muscle force, or a rotational force. Kelly’s definition may be slightly ambiguous because he is referring to generating torque specifically within the hip and shoulder capsule to eliminate capsular slack within the socket, which tend.

There are two laws that Dr. Starrett refers to:

1) Maintaining an external rotation force during flexion in the hip or shoulder joint (ex. Squat, overhead press, push-up)

2) Maintaining an internal rotation force during extension in the hip or shoulder joint (ex. Exit phase of freestyle/butterfly, straight-arm pull-down)

Application to swimmers

The Hip

Breaststroke is an anomaly to Kelly’s law of torque, because hip internal rotation (knees in, ankle out) is required during the loading phase of the kick. Therefore, one of the most common faults I see in swimmers (especially breaststrokers) during a squat, is eversion of the foot (pinky toe coming up), which then could lead to knee valgus (knees coming in). Although necessary in the pool to generate maximal propulsion during a breaststroke kick, such habits may lead to injury over time in the weight room. The photo below shows a common squat fault in breaststrokers:

Picture1

To correct this, Kelly’s law of torque can be applied. If eversion of the foot is spotted during a squat, athletes should apply hip external rotation and think about screwing their feet outwards into the ground. This will allow the foot to maintain full contact to the ground. The key here is to screw your feet into the ground without your feet actually moving. To apply “torque” into the ground, the angle of the feet become imperative. Although no two squats will look exactly the same, athletes should aim to squat with a toe-out angle of roughly 10-30 degrees. As Dr. Starrett would state, any toe-out angle greater than 30 degrees will cause an “energy leak”. In addition, research has shown that squatting with hip external rotation greater than 30 degrees seems to decrease hip adductor activity which could also lead to an inefficient squat (Pereira 2010). The photo below shows how foot eversion should be corrected:

Picture2

The Shoulder

This “law” is probably more applicable to swimming as it pertains to the freestyle and butterfly stroke itself. Although I have not seen any research to back this, I believe the best swimmers in the world have found a way to swim that is the most biomechanically efficient and safe. They do this by applying Kelly’s second law of torque which states that athletes must “generate an internal rotation force when the arms are in extension”. In layman’s terms, their hand exits the water with their pinky first and lead with the pinky for the first ¼ to ½ of the recovery phase of the stroke.

4 swimmers come to mind when I say this: Nathan Adrian, Ian Thorpe, Katie Ledecky, and Michael Phelps. Check out the photos and notice how they all internally rotate during shoulder extension.

Picture3

Again, although I have not seen any research that backs the efficacy on this topic regarding shoulder stability, I believe there is something to be said about it when gold medalists and world-record holders are swimming in this fashion. Because of the prevalence of shoulder injuries, it would be interesting to conduct a longitudinal study on swimmers who internally rotate vs externally rotates during shoulder extension and observe the frequency of shoulder injuries over time.

Perhaps the inclusion of this “law” in resistance exercises can also assist swimmers in setting a stroke specific motor pattern. For example, athletes can consciously internally rotate their shoulder during a straight arm lat-pulldown or tricep kickback. To apply internal rotation to the shoulders to develop stability, both the shoulder and elbows should be in extension. For example, during the push-up the shoulder is in extension but the elbow is in flexion, therefore and external rotational force should be applied through the hands in the ground.

It is important to note that inclusion of this swimming technique is only one component to preventing shoulder injuries and developing maximal force. Proper periodization, strength training, sleep, and diet are major components in preventing shoulder injuries across the entire swimming population.

References

Pereira, G. R., Leporace, G., Chagas, D. D., Furtado, L. F., Praxedes, J., & Batista, L. A. (2010). Influence of Hip External Rotation on Hip Adductor and Rectus Femoris Myoelectric Activity During a Dynamic Parallel Squat. Journal of Strength and Conditioning Research, 24(10), 2749-2754. doi:10.1519/jsc.0b013e3181c6a139

Starrett, K., & Cordoza, G. (2015). Becoming a supple leopard: the ultimate guide to resolving pain, preventing injury, and optimizing athletic performance. Las Vegas: Victory Belt Publishing Inc.