Exercises for decreasing the likelihood of ACL knee injuries in female athletes: article review
Posted on 19th February 2014 by Jack Magill
Introduction
Anterior cruciate ligament (ACL) injuries are one of the most common knee injuries. In fact, approximately 1/3500 people in the United States, of the general population, will experience an ACL tear in a given year. The incidence of the injury increases if the person is an athlete. Of the athletic population, females that participate in sports that require jumping, cutting, and landing at high speeds, experience the greatest amount of ACL injuries. Typically, this injury requires orthopedic surgery and 6-8 months of rehabilitation.
Myer GD, Ford KR, Brent JL, Hewett TE. The Effects of Plyometric vs. Dynamic Stabilization and Balance Training on Power, Balance, and Landing Force in Female Athletes. Journal of Strength and Conditioning Research.2006;20(2):345-353.
So, what did they look at?
The purpose of this study was to compare the effects of maximum effort plyometric jumping vs. dynamic stabilization and balance training on power, balance, and landing force, in female athletes. In other words, will increasing core strength or increasing performance in jumping exercises, decrease forces on the knee that cause ACL injuries?
Nineteen female volleyball players were divided into two training groups; a plyometric group and a balance group. The focus of the plyometric group included an emphasis on performing jumping movements with maximum effort and power, and also performing cutting techniques with quick reactions and maximal feedback. The athletes were instructed to perform maximum effort jumps without knee valgus (knee bending in towards other leg) with a focus on improving efficiency and power of the jump. The balance group was instructed on methods to dampening landing force through bending at the hip and knee without knee valgus, their balance exercises were performed by progressing from stable ground to unstable surfaces. Each group performed their exercises three times a week for eight weeks.
What was measured?
At the end of the training, the forces that go through the knee were measured using a single leg hop test. The forces that were assessed were forces that either pushed the subjects knee forward and backward or from side to side, as well as the total force of landing on the ground. These forces were compared to the baseline forces taken at the initiation of the study.
The results
Both groups demonstrated different effects of training on the forces through the knee, during the single leg hop. The balance group reduced their total landing force on the ground by 7% while the plyometric increased their force by 7.6%. Both groups were able to decrease the forces that moved their knee from side to side. However, neither group’s training changed the forces that move the knee forward or backward.
So what does this mean?
The results of this study indicated that performing exercises that focus on balance and increasing core strength could reduce the amount of landing force after performing a maximal jump. Also, plyometric jumping training and balance training can reduce the amount of side to side forces on the knee, during landing. Therefore, by incorporating both of these training protocols, a female volleyball athlete can reduce the stresses on her knees, after jumping, and reduce the likelihood of sustaining an ACL injury.
Strengths and limitations
I found this study to be very interesting and it had a number of strengths. The authors provided a detailed progression of the exercises with duration and intensities of the protocol. This type of presentation makes the incorporation of this study to practice rather easy. Also, the authors used a number of charts that illuminated the effects of the training. The major limitations of this study was that population was rather small and very specific, making the application of the results questionable to other populations. Also, some of the training exercises were very high level and would not be appropriate for inexperienced participants.
