Power Up to Prevent Injuries

Exercise is a vital part of a healthy lifestyle.  Exercise and sports injuries, on the other hand, can be painful, frustrating, time-consuming and expensive for both lay persons and elite athletes.  Therefore, prevention of injuries which could limit activity is a major issue.  One measure that has been found to be successful, cost-effective and accessible to the general public and athletes alike is strength training.  We aren’t talking about power lifting.  Simple exercises, often using just one’s own body weight, can have a significant impact on the strength of the muscles and ability of joints to work efficiently. 

A review of literature published in 2018 reported on multiple studies that have shown the injury prevention benefits of strength training.  They reported on the combined results of 6 studies that together included almost 8000 participants and over 150 observed injuries.      

The 2003 study published in the Scandinavian Journal of Medicine and Science in Sports provided a basic hamstring strengthening program for 30 adult elite soccer players.  Participants were divided into 2 groups, one who received extra training 1-2 times a week for 10 weeks focused on strengthening the hamstring muscle.  Meanwhile, the other group did their normal training routines only.   They reported that all team members attended all training sessions during the observational period of 10 months.  Those in the extra training group trained to failure (rather than do a set number of repetitions, they continued to exhaustion) and increased the average volume per week during the study.  

At the conclusion of the season, there was a clear difference between the groups.  Only 3 of 15 in the extra training group experienced a hamstring injury compared to 10 of the control group!  Additionally, “there were significant increases in strength and speed in the training group.”   

Another study on this topic utilized a randomized controlled trial published in the American Journal of Sports Medicine in 2015.  This study also provided a basic hamstring strengthening program, specifically the nordic hamstring exercise (NHE).  The NHE is an exercise where a person begins in a kneeling position with the feet being held in place by a bar or a workout partner.  They then slowly lower their body forward by extending the knee while keeping their back straight.  When they can hold it no longer, they extend their hands to catch themselves.  Study participants were 648 amateur soccer players. Players from 40 teams were divided into 2 groups.  The control group would do normal training while the other group was asked to perform 25 sessions of NHE in a 13-week period in addition to their normal training.  Researchers held evaluation meetings and designed a website to facilitate compliance of the exercise program.  The study reported over 90% compliance with the exercise regimen.  Subjects were followed for the 2013 calendar year and injuries reported.  Overall , 36 players (6.2%) reported hamstring injuries.  However, there was a significant difference between the NHE group and the control group.  Injury incidence rate among the NHE group was only 0.25 while the control group was 0.8! 

A third study also focused on a randomized controlled trial that was directed at preventing hamstring injuries among soccer players by strengthening the muscle.  Fifty Danish professional and amateur male soccer teams were divided between an intervention group (461 players) and a control group (481 players).  The intervention group participated in a 10-week training program that gradually increased in intensity.  Researchers in this study then implemented maintenance sessions once a week throughout the season.  At the end of the season, 52 players in the control group had experienced acute hamstring injuries compared to only 15 in the intervention group!   New injury rates per 100 player seasons were 3.1 for the intervention group and 13.1 for the control group.  It also appears that the benefits are not only for new injuries.  Recurrent injury rates for the intervention group were only 7.1 while the control group rate was 45.8! 

A difference was also seen in a 2012 study published in the British Medical Journal focused on adolescent female soccer players and the prevention of ACL knee injuries.  Over 4500 players aged 12-17 were divided into 2 groups by their team and followed for the 2009 season (7 months).  Of the 230 Swedish teams, 121 were assigned to the intervention group and 109 to the control group.  The intervention group added a 15-20 minute neuromuscular warm-up program twice a week to their regular training routines.  The program was designed to target core stability, balance and proper knee alignment.  It included traditional strength training such as squats and bench press, along with exercises to challenge coordination, and joint proprioception (body’s ability to sense movement, action, and location), such as pelvic lifts, lunges and jump/landing technique.  As with the previous studies, the difficulty level was gradually increased during the study.  Once again, there was a difference between the intervention group and control with 7 ACL knee injuries compared to 14 in the control group! 

Another study evaluating soccer players that was included in the review was published in the Journal of Strength and Conditioning Research in 2016.  Researchers examined the impact of strength training on 52 young (13-14 years) elite soccer players.  Half of the players had two to three 90-minute sessions of strength training added to their weekly training program for 3 weeks, followed by a 1-week recovery time.  This was repeated four times for a total of 12 weeks of strength training sessions.  Not only did those who had the strength training experience fewer injuries (4 compared to 13 in the control group), they also showed significant improvement in sprint running and jumping tests.   

The final study in the review investigated exercise intervention on anterior knee pain (AKP) among a group of UK army recruits who were undertaking a grueling physical conditioning program.  The study involved 39 male and 11 female training groups in the initial phase of army recruit training.  A total of 759 recruits were assigned to the intervention group and 743 to the control group.  Those in the intervention group completed 4 strengthening and 4 stretching exercises in addition to their regular daily physical training, while the control group continued with the existing training protocols.  During the 14-week training program there were 36 new cases of anterior knee pain among the control group compared with only 10 in the intervention group.  Researchers concluded that the simple stretching and strengthening exercises not only “resulted in a substantial and safe reduction in the incidence of AKP” among their military recruits, but that the same type of exercises “could also be beneficial for preventing this common injury among nonmilitary participants in recreational physical activity.” 

When evaluating these studies as a group, researchers were able to draw some interesting conclusions. 

• A 10% increase in the number of strength training repetitions was associated with a 4.3 percentage point risk reduction. 
• All studies evaluated demonstrated a significant reduction in sports injuries. 

• Strength training programs reduced sports injuries by an average of 66%. 
• The studies included in the review support the concept that overuse injuries occur when tissues are chronically overloaded.  Therefore, they suggest rather than simply reducing training, that preventative actions be taken, to include preconditioning, variation in exercises and loads and carry-over of improved coordination/technique from a strength training prevention program, 
• Although five of the six included studies enrolled populations of football players, both the included evidence and the literature point towards plausible and general mechanisms that make these findings externally valid 
• In addition to being very safe, these interventions have—through more than one mechanism—proven prevention results seldom achieved by other exercise interventions or fields of medicine. 

Writers of the review suggest individuals start with learning the exercises and proper technique before increasing weight and intensity.  They note: “Preliminary phases may seem irrelevant to eager athletes/clubs, however we consider the initial phases of injury prevention to be a critical investment, especially as injuries inevitably constitute delays and setbacks in relation to the very same goals as the original sport participation.”  Further, they suggest that off-season or other less demanding periods of training could be a great time to begin strength training prevention programs.   

Writers also caution that heavy weight training should not be done as a warm-up to other athletic activities as the fatigue could hinder performance and increase the risk of injuries.  Instead, they recommend a “rest period between maximal efforts [of] approximately 72 hours for beginners, with experienced and physiologically adapted athletes likely needing shorter recovery times.” 

They also note that children and adolescents do not warrant vastly different approaches.  They can benefit from strength training even at young ages.  However, when dealing with younger individuals, it is especially important they receive qualified instruction, competent supervision and their intensity progression is tailored to their individual needs.   

Talk to your chiropractor about strengthening exercises that might be appropriate for your health status and activity goals.  As experts in the musculoskeletal system, they are well versed in the proper alignment and working of the various joints, as well as what muscles can help, or hinder, a joint from working properly.  This knowledge can help you prevent injuries, recover when they do occur and may even improve your performance.  If you do not have a chiropractor, you can find a TCA member doctor at tnchiro.com. 

 

RESOURCES: 

Lauersen JB, Andersen TE, Andersen LB  Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries: a systematic review, qualitative analysis and meta-analysis  British Journal of Sports Medicine 2018;52:1557-1563.  

 Askling C, Karlsson J, Thorstensson A. Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload. Scand J Med Sci Sports 2003;13:244–50. 

 van der Horst N, Smits DW, Petersen J, et al. The preventive effect of the Nordic hamstring exercise on hamstring injuries in amateur soccer players: a randomized controlled trial. Am J Sports Med  2015;43:1316–23. 

Petersen J, Thorborg K, Nielsen MB, et al. Preventive effect of eccentric training on acute hamstring injuries in men’s soccer: a cluster-randomized controlled trial. Am J Sports Med 2011;39:2296–303. 

Waldén M, Atroshi I, Magnusson H, et al. Prevention of acute knee injuries in adolescent female football players: cluster randomized controlled trial. BMJ 2012;344:e3042. 

Coppack RJ, Etherington J, Wills AK. The effects of exercise for the prevention of overuse anterior knee pain: a randomized controlled trial. Am J Sports Med 2011;39:940–8. 

Zouita S, Zouita AB, Kebsi W, et al. Strength training reduces injury rate in elite young soccer players during one season. J Strength Cond Res 2016;30:1295–3 

Wikipedia Nordic hamstring curl entry accessed 6/20/2023 

WebMD Editorial Contributors “What is Proprioception?” reviewed by Brennan, Dan on Nov 27, 2021.  Accessed 6/20/23