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Updated: Mar 19, 2020

Due to huge burden caused by injuries and rehabilitation processes to professional athletes, there is an increasing need and interest for objective monitoring of functional rehabilitation processes from muscle injuries. There has been an estimation, made already in 1984, that 3–5 million injuries occur annually among competitive and recreational athletes in the United States alone. From Muscle injuries hamstring injuries are named one of the major problems, especially in sports that require sprinting, jumping or kicking, so e.g. in all ball games and athletics. Training-related hamstring injury rates are constantly increasing (Ekstrand et al. 2016). Ekstrand et al. 2016 reported 4 % annual increase in hamstring injuries in European men football leagues between 2001-2015. Currently 22 % of the players sustain at least one hamstring injury during a season. Strength deficits and bilateral right-left asymmetries have been reported to increase hamstring injury risk (Croisier et al. 2008). Knapik et al. 1991 reported a higher risk of injury in athletes with asymmetries in knee flexor strength or hip flexibility greater than 15% between the right and left sides. Also abnormal ratio between quadriceps and hamstring muscle groups (Q/H ratio), typically meaning too weak hamstrings, is a factor to increase hamstring strain injuries (Delextrat et al. 2010). In addition, a previous injury or fatigue may increase the injury risk (Ekstrand et al. 2011). Injuries affect the way our nervous system coordinates the movements. Following an injury, movement patterns are altered to avoid using a muscle that may have a strain, contusion, or tendinitis. By the time the muscle recuperates, a movement pattern has been developed that neglects this particular muscle or uses it less. The body has become familiar with this movement pattern and has no reason to change back (Cook 2003, 40). One-third of the injuries will recur with the greatest risk during the initial 2 weeks following return to sport (Orchard & Seward 2002). The high recur number suggests that most rehabilitation plans at the moment are inadequate and / or athletes return prematurely. Therefore, new methods to objectively monitor recovery from muscle injuries and to try to avoid them as much as possible, are more than welcome.

Right-leg balance and traffic light system to visualize muscle asymmetries In Myontec we wanted to create a solution for muscle asymmetry evaluation using EMG. The general idea behind this was; with wearable system you are free from movement restrictions and can investigate your movement patterns and typical behaviors of your muscles in sport specific movements and during typical training routines and that gives you the true information about the movement patterns. We know that movements patterns result from habits, typical activities, leg dominance and previous injuries (Cook 2003, 29). With use of Mbody we are able to show you movement patterns inhabited by your body, your strengths and weaknesses, that you can then concentrate on improving and possibly avoid injuries because of corrective actions taken on time. On the other hand, if you are recovering from muscle injury, Mbody shows you the progress in your rehabilitation program and helps objectively in decision making about return to sport. Lastly, you can add EMG to your typical conditioning test patterns to give you further information about your training progress. We took all above and created a traffic light system. Our traffic light system gives warnings from muscle group based left-right asymmetries with very visual color system providing you with the following information.

• Green when asymmetry between right and left leg muscle groups is < 9 % (45,5% … 54,5%) meaning that everything is ok and muscle groups are well balanced. • Yellow between 9 – 18 % (41% … 59%) difference between right and left sides. There is a clear trend towards asymmetry but the amount of asymmetry is still reasonably light. • Red when there is substantial asymmetry of > 18 % (outside 41% … 59%) between left and right muscle groups and its origin should be defined and corrected actions sought in order to avoid injuries.

Authors: Merja Hoffrén-Mikkola, PhD (biomechanics), Content Developer, Myontec Pekka Tolvanen, M.Sc. (Physics), Product Manager, Founder of Myontec

REFERENCES Cook G. (2003). Athletic body in balance: Optimal movement skills and conditioning for performance. Human Kinetics. Champaign, IL, USA. Croisier J., Ganteaume S., Binet J., Genty M. & Ferret J. (2008). Strength imbalances and prevention of hamstring injury in professional soccer players. American Journal of Sports Medicine 36 (8); 1469-1475. Delextrat A., Gregory J. & Cohen D. (2010). The use of functional H:Q ratio to assess fatigue in soccer. International Journal of Sports Medicine 31(3); 192-197. Ekstrand J., Hägglund M. & Walden M. (2011). Injury incidence and injury patterns in professional football: the UEFA injury study. British Journal of Sports Medicine 45(7); 553-558. Ekstrand J., Waldén M. & Hägglund M. (2016). Hamstring injuries have increased by 4% annually in men’s professional football, since 2001: a 13-year longitudinal analysis of the UEFA Elite Club injury study. Br J Sports Med. doi:10.1136/bjsports-2015095359. Knapik J.J., Bauman C.L., Jones B.H., Harris J.M. & Vaughan L. (1991). Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes. Am J Sports Med 19 (1); 76-81. Orchard J. & Seward H. (2002). Epidemiology of injuries in the Australian Football League, seasons 1997-2000. Br J Sports Med 36; 39-44.

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