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Coaches Blog

Sam's Blog is a bi-weekly addition to the US Youth Soccer Blog. Sam Snow is the Coaching Director for US Youth Soccer.

 

Technique and Injury

Sam Snow

A coach from the Midwest had these comments and question about a soccer injury.

"I've had a client come to me with some injury/rehab issues attributed to ball striking and playing the long ball. This is a U-14 elite player with over developed quads, extremely tender hamstrings and poor gait. Her physical therapist and I are trying to find some research on this and then document our process. I've been doing a lot of work with players on ball striking and athletic development which is why they came to me, but I've never seen such poor mechanics and extreme injury at such a young age.
Are there any resources on this matter?"

I then posed the question to Dr. Don Kirkendall of FIFA F-MARC. He is also a regular presenter at the US Youth Soccer adidas Workshop. Here's his reply:

"I am not sure what injury they are asking about as 'tender hamstrings' doesn't tell me much. This could be part of the recovery process from a strain injury, delayed soreness from unaccustomed activity, or microtrauma from such processes as overstretch or weakness or the poor technique. Without a better description, I'd only be speculating.

An imbalance between quad and hamstring strength is an issue on a number of fronts. Most of the discussion is around injury which the Physical Therapist of this email would be aware of. But poor hamstring strength could also impair technique.

Some of it might be bound up in the male/female differences in kicking. Men approach the ball faster than women and then have a slower angular knee extension velocity than women. Thus women make up for the slow approach by extending the leg faster in an attempt to gain ball velocity. But this puts the knee at risk for extension injury. Could stronger hamstrings help? A good question. Hamstring strengthening has been advocated for reducing strain injury, especially at the highest levels of play in men, and been very successful.

On the strength-skill interaction, during ballistic movements, the hamstring muscles contract to prevent over/hyper extension of the knee. Weak hamstring muscles, which slow down terminal knee extension during kicking, could lead to a number of different sources of knee pain during kicking. So, the player would alter the kicking motion to compensate for the weak hamstring muscles and avoid the pain. She might try to approach faster and use less knee extension. Or she could be kicking mostly from the hip and not rapidly extending the knee. Or she could be doing everything else well right up until the point in the kicking cycle when it's time to extend the knee forcefully. Both would reduce the stress across the knee near forceful extension and avoid pain, but her ability at 'striking and playing the long ball' would be reduced. Try kicking hard with a straight leg.

Of course, there could be structural or other soft tissue issues at the knee that could be the source of pain and poor technique.

Here is a male/female comparison of kicking kinematics that Bill Barfield did that might be helpful. 
There may be references at the end they might find helpful."