Strategies to Reduce ACL Injury Risk in Youth Athletes – Part 2 (Strength Training)

In part 1 of our series on reducing ACL injuries in adolescent athletes, I discussed the mechanisms leading to the injury itself and warm-up strategies to reduce injury risk (https://rebelmovement.org/2019/04/25/strategies-to-reduce-injury-risk-in-youth-athletes-part-1/).

Part 2 will discuss strength training, including:

– what does the research state on strength training and injury?

– what are some fundamental resistance exercises that an adolescent athlete should be introduced to and perform?

– what is a proper way to regress / progress a strength exercise?

Let’s dive in…

Strength Training

 In my opinion, the introduction of sports into a youth’s life should coincide with an introduction to strength training. You may be thinking, “my (insert age) child should be lifting weights? Isn’t that dangerous?” It’s actually quite the opposite. Under proper supervision, a strength training program may offer an adolescent athlete a multitude of physical, emotional, and psychological benefits (Faigenbaum, 2009). Overall, it appears that 8-12 weeks of resistance training can improve overall strength by 30-50% in youth athletes (Dehab & McCambridge, 2009).

(Faigenbaum, 2009)

For the sake of scope, let’s focus our attention on the effects of strength training for reducing injury risk in this population. So what does the research tell us? One of the earliest studies completed on strength training and injury rate was by Hejna (1982). High school athletes were divided into three groups: weight training during the pre-season and in-season, weight training year-round, and a control, non-strength training group. The researchers found that athletes who participated in weight training had an injury rate of 26.2%, while the control group’s injury rate was 72.4%. If an injury were to occur, the control group took approximately 2.4 times longer to rehabilitate from injury compared to their strength training counterparts.

After 8 weeks of resistance and plyometric training, 27 female high school athletes demonstrated improvements in neuromuscular and biomechanical movement qualities that suggest these athletes were at less risk for ACL injury (Lephart, 2005). Specifically, the athletes demonstrated increases in quadriceps strength during dynamometer testing and greater muscular activity in the gluteus medius bilateral vertical jump (Lephart, 2005). Additionally, athletes displayed increased hip and knee flexion during the jump-landing maneuver (Lephart, 2005). In a meta-analysis by Sugimoto (2015), across 14 reviewed studies, strength interventions reduced the risk of ACL injury by 68% in youth female athletes. A larger meta-analysis by Lauersen, Bertelsen, & Andersen (2014) provide additional evidence for strength training to reduce injury risk, as “strength training reduced sports injuries to less than 1/3 and overuse injuries could be almost halved”. So the question becomes, what specific strength exercises should youth athletes complete? From multiple investigations, it appears that even the addition of bodyweight exercises can have a significant impact on injury risk. Keep in mind that bodyweight exercises are a form of resistance training! Walden (2012) incorporated unilateral/bilateral squats, glute bridges, lunges, planks, and jump-landings, resulting in a 64% reduction in ACL injury. Similar exercises were incorporated into a warm-up for female youth soccer athletes, resulting in a 77% reduction in knee injury rate (Kiani, 2010).

(Walden, 2012)

The basis of strength training for adolescent athletes is mastering basic movement patterns that are transferable to a multitude of more complex resistance exercises. We want to ensure that our athletes are not adding strength to dysfunction, which can lead to many future issues. A requisite for every adolescent (and any athlete for that matter) is demonstrating proper form in the following “fundamental” exercises: hip-hinge / Romanian deadlift, body-weight squat, forward/backward lunge, push-up, pull-up/inverted row, and over-head press.

In addition to form, proper exercise progression is a must for younger athletes, as these motor patterns are very much malleable and quickly receptive to adaptation, for better or worse. Here’s an example of a squat exercise progression that I have found quite successful with youth athletes:

1) hip-hinge

2) body-weight squat (may add box behind athlete)

3) squat with a PVC pipe

4) goblet and/or resistance band squat

5) unloaded barbell back/front squat

6) loaded barbell back/front squat

Again, I cannot stress the following enough: do not add strength to dysfunction. If your athlete cannot adequately perform a barbell squat, there is no benefit to adding further load to this movement. Similar progressions can be made for any upper or lower body compound exercise. Sometimes that will include the use of resistance bands or partners (e.g. assisted pull-ups), TRX equipment (single-leg squats, inverted rows), or the training center itself (wall assisted push-ups). To reap the most benefits of strength training program, youth athletes should be participating in a strength program at twice per week at a minimum (Behm, 2008). It is beyond the scope of this post to discuss the physiological adaptations to resistance training, but athletes need to be consistent in their training to obtain build resiliency within the musculoskeletal system. Loading the system in a sensible and progressive manner throughout our young athletes’ sporting careers will provide the opportunity for maximal performance, but more importantly, will keep them on the field.

If you’re looking to dive deeper into the literature regarding strength training for adolescent athletes, I highly recommend these position papers:

National Strength and Conditioning Association – https://www.ncbi.nlm.nih.gov/pubmed/19620931

Canadian Society for Exercise Physiology – https://www.ncbi.nlm.nih.gov/pubmed/18461111

UK Strength and Conditioning Association – https://www.ncbi.nlm.nih.gov/pubmed/24055781

References

Behm, D. G., Faigenbaum, A. D., Falk, B., & Klentrou, P. (2008). Canadian Society for Exercise Physiology position paper: resistance training in children and adolescents. Applied Physiology, Nutrition, and Metabolism33(3), 547-561.

Dahab, K. S., & McCambridge, T. M. (2009). Strength training in children and adolescents: raising the bar for young athletes?. Sports Health1(3), 223-226.

Faigenbaum, A. D., Kraemer, W. J., Blimkie, C. J., Jeffreys, I., Micheli, L. J., Nitka, M., & Rowland, T. W. (2009). Youth Resistance Training: Updated Position Statement Paper From the National Strength and Conditioning Association. Journal of Strength and Conditioning Research,23(Supplement 5), S60-S79. doi:10.1519/jsc.0b013e31819df407

Hejna, W. F., Rosenberg, A., Buturusis, D. J., & Krieger, A. (1982). The Prevention of Sports Injuries in High School Students Through Strength Training. National Strength Coaches Association Journal,4(1), 28-31. doi:10.1519/0199-610x(1982)0042.3.co;2

Kiani, A. (2010). Prevention of Soccer-Related Knee Injuries in Teenaged Girls. Archives of Internal Medicine,170(1), 43-49. doi:10.1001/archinternmed.2009.289

Lauersen, J. B., Bertelsen, D. M., & Andersen, L. B. (2014). The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. British Journal of Sports Medicine48(11), 871-877.

Lephart, S. M., Abt, J. P., Ferris, C. M., Sell, T. C., Nagai, T., Myers, J. B., & Irrgang, J. J. (2005). Neuromuscular and biomechanical characteristic changes in high school athletes: a plyometric versus basic resistance program. British Journal of Sports Medicine39(12), 932-938.

Sugimoto, D., Myer, G. D., Foss, K. D., & Hewett, T. E. (2015). Specific exercise effects of preventive neuromuscular training intervention on anterior cruciate ligament injury risk reduction in young females: Meta-analysis and subgroup analysis. British Journal of Sports Medicine,49(5), 282-289. doi:10.1136/bjsports-2014-093461

Walden, M., Atroshi, I., Magnusson, H., Wagner, P., & Hagglund, M. (2012). Prevention of acute knee injuries in adolescent female football players: Cluster randomised controlled trial. BMJ,May 3(344). doi:10.1136/bmj.e3042

 

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