Two of the most discussed aspects associated with injury risk reduction during the season are: 1) lower limb symmetry and 2) force absorption qualities. We used a Hop and Stop test of bilateral force production / force absorption, and the results showed a tremendous gain in symmetry in both the hopping and leaping exercises. We classified the hopping test as an evaluation of force production, as we were not concerned with the stability of the landing, but rather just how far they were able to hop (or how much force they were capable of generating). The leaping test was a measure of force absorption, as we were concerned with the players ability to “stick” the landing and come to a balanced stop within on second. We compared the leap distance to the hop distance and were able to come up with a projected limb confidence and symmetry measure. We considered this an important aspect for us to include in our assessment for its relation to injury risk in soccer players. Here is the graph of the test on over 100 players in 2009 that went through single legged training 10 week program.
When compared to our traditional double legged program (squats, cleans, double legged stair and box plyometrics, etc.) this group seemed to have much better gains in regards to symmetry and force absorption, but not as great of gains in force production. Our program goals are two fold in regards to this type of training as we are looking for both symmetry and force absorption qualities to reduce the risk of injury, as well as speed, agility and vertical attributes to improve athletic performance. The graphs below indicate that the double legged group improved in the force producing, physical performance skills while the single legged group improved their symmetry and hopefully had a reduction in injury risk.
The program we have created over the last few years has been built around the key premise that we need to keep as much strength as possible to maintain speed and power, while incorporating as much stability as possible protect the knees from injury. From this we have learned that both single and double legged activities are necessary. During the spring we will be alternating between double legged exercises and single legged exercises in each workout. But we have to be careful not to increase the volume to a level where the athlete will be sore from the the workout as fatigue seems to be a major factor in injury risk during the spring soccer season as we have seen in 2004 survey of high school soccer players.
Since implementing single legged training in with our standard double legged training we have reduced the risk of ACL injury to 1 in every 227 girls or 10x lower then the average in our region during the high school season. We will discuss the exact protocol for introducing this in future blog posts this season and it is also well documented in our our speed and strength manuals: Speed & Agility Foundations and Athletic Strength Foundations.
This spring we will typically use simple single legged exercises that give us the most bang for our athleticism buck. We choose exercises like single legged hopping, hop turns, box step up jump to stick, single legged pulling, rowing and pressing and single legged TRX lunges and jump lunges. The focus is put more on maximum effort and control verses that of increased load and we are extremely pleased with the results to this point.
Keep checking back to the blog in the weeks to come as we will use an entire post to focus on our progression through one of these single legged exercises.