Preventive Neuromuscular Training for Young Female Athletes: Comparison of Coach and Athlete Compliance Rates

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1 Journl of Athletic Trining 2016;51(12): doi: / Ó by the Ntionl Athletic Triners Assocition, Inc originl reserch Preventive Neuromusculr Trining for Young Femle Athletes: Comprison of Coch nd Athlete Complince Rtes Di Sugimoto, PhD, ATC, CSCS* ; Crl G. Mttcol, PhD, ATC, FNATA ; Hether M. Bush, PhD ; Stci M. Thoms, MS ; Kim D. Brber Foss, MS, ATC ; Gregory D. Myer, PhD* #; Timothy E. Hewett, PhD** *The Micheli Center for Sports Injury Prevention, Wlthm, MA; Division of Sports Medicine, Deprtment of Orthopedics, Boston Children s Hospitl, MA; Deprtment of Rehbilittion Sciences, College of Helth Sciences nd Deprtment of Biosttistics, College of Public Helth, University of Kentucky, Lexington; The SPORT Center, Division of Sports Medicine, Cincinnti Children s Hospitl Medicl Center, OH; Deprtments of Peditrics nd Orthopedic Surgery, University of Cincinnti, OH; #Deprtment of Orthopedics, University of Pennsylvni, Phildelphi; **Myo Clinic Biomechnics Lbortories nd Sports Medicine Center, Deprtments of Orthopedics, Physicl Medicine nd Rehbilittion nd Physiology & Biomedicl Engineering, Myo Clinic, Rochester nd Minnepolis, MN Context: Fewer thletic injuries nd lower nterior crucite ligment injury incidence rtes were noted in studies of neuromusculr trining (NMT) interventions tht hd high complince rtes. However, severl groups hve demonstrted tht preventive NMT interventions were limited by low complince rtes. Objective: To descriptively nlyze coch nd thlete complince with preventive NMT nd compre the complince between study rms s well s mong school levels nd sports. Design: Rndomized, controlled clinicl tril. Setting: Middle nd high school thletic progrms. Prticipnts or Other Prticipnts: A totl of 52 tems, comprising 547 femle thletes, were rndomly ssigned to the experimentl or control group nd followed for 1 thletic seson. Intervention(s): The experimentl group (n ¼ 30 tems [301 thletes]: 12 bsketbll tems [125 thletes], 6 soccer tems [74 thletes], nd 12 volleybll tems [102 thletes]) prticipted in n NMT progrm imed t reducing trumtic knee injuries through trunk-stbiliztion nd hip-strengthening progrm. The control group (n ¼ 22 tems [246 thletes]: 11 bsketbll tems [116 thletes], 5 soccer tems [68 thletes], nd 6 volleybll tems [62 thletes]) performed resistive rubber-bnd running progrm. Min Outcome Mesure(s): Complince with the ssigned intervention protocols (3 times per week during the preseson [men ¼ 3.4 weeks] nd 2 times per week in-seson [men ¼ 11.9 weeks] of coches [coch complince] nd thletes [thlete complince]) ws mesured descriptively. Using n independent t test, we compred coch nd thlete complince between the study rms. A 2-wy nlysis of vrince ws clculted to compre differences between coch nd thlete complince by school level (middle nd high schools) nd sport (bsketbll, soccer, nd volleybll). Results: The protocols were completed t men rte of times per week during the preseson nd times per week in-seson. A totl of 88.4% of thletes completed 2/3 of the intervention sessions. Coch complince ws greter in the experimentl group thn in the control group (P ¼.014). Coch complince did not differ by sport but ws greter t the high school thn the middle school (P ¼.001) level. Athlete complince did not differ by study rm, sport, or school level. Conclusions: Athletes received instruction in bout 50% of ech protocol. Nerly 90% of thletes performed more thn 2/3 of the ssigned NMT interventions. The ssigned intervention ws performed more often in the experimentl rm compred with the control rm. Coches t the high school level complied with the given protocol more thn middle school coches did. Athletes complied well with the protocol, but coches did not, especilly t the middle school level. Key Words: thletic injuries, knee, nterior crucite ligment, high school, middle school Key Points Coches prcticed only 50% of the ssigned neuromusculr trining (NMT) intervention sessions. Nerly 90% of thletes complied with more thn 2/3 of the NMT interventions. Busy competition schedules nd lck of vilble time during the seson might hve hindered complince with the protocol mong coches, especilly t the middle school level. Identifying pplicble strtegies for successful implementtion of preventive NMT nd mintining high complince rtes mong coches re key.

2 Adherence nd complince re terms often used to describe the bility to follow given tsks. For neuromusculr trining (NMT) intervention studies, complince with the protocol is n importnt vrible when determining the success nd usefulness of these progrms. 1 Mny groups 2 15 hve mesured the effect of NMT complince in reducing knee-injury rtes. Using prospective, cluster-rndomized controlled design, other investigtors 16 ssessed complince in 52 young femle soccer tems ( totl of 1055 plyers) who prticipted in comprehensive soccer specific wrm-up progrm clled 11þ. Athletes who displyed high level of complince showed 35% lower overll injury incidence compred with thletes who displyed n intermedite complince level. Similrly, thletes with high level of complince experienced 39% lower incidence of cute soccer injuries thn thletes with intermedite complince levels. Authors 1 who compred nterior crucite ligment (ACL) incidence rtes mong 6 NMT studies (using binry incidence rte rtio nlysis) found tht those who demonstrted high level of complince hd 73% lower ACL incidence rte thn those with low complince levels. Their tertile incidence rte rtio nlysis identified n ACL incidence rte in those with high level of complince tht ws 82% lower thn those with moderte or lower levels of complince. Both nlyses demonstrted the effect of NMT complince on ACL incidence rtes. Although pst reserchers 1,16 studied the effect of complince with NMT intervention on thletic injuries, few groups 7 11,17,18 did not report NMT complince in the originl mnuscripts. Other uthors 2,3 cited low NMT complince s limittion of their experiments tht hindered outcomes. Reporting of complince nd the effect of NMT complince re not well documented, re often neglected in nlysis, nd re not emphsized in most study designs. There is no stndrd reporting method for complince rte in NMT reserch, which my be why this fctor is not often reported. Therefore, we sought to nlyze 2 types of complince mesures: complince of coches with the given study protocol nd complince of thletes with the given NMT interventions. The current study with 2 rms (experimentl versus control group) ws performed s secondry nlysis to determine the prophylctic effectiveness of preventive NMT on knee injuries in young femle thletes. Our min purpose ws to nlyze complince with preventive NMT protocol in coches nd thletes by (1) descriptively nlyzing coch nd thlete complince with the study protocol, (2) exmining coch nd thlete complince between the study rms, nd (3) compring coch nd thlete complince bsed on school level nd sport. METHODS Study Design A prospective cluster-rndomized controlled tril ws used to exmine the effects of trunk- nd hip-focused NMT on knee injuries in young femle thletes. The clusters were girls soccer, volleybll, nd bsketbll tems in middle nd high schools. Ech tem ws rndomly ssigned to either n experimentl group (core integrtive NMT) or control group (speed nd gility trining). The smple-size estimtion nd rndomiztion were performed independently by sttisticin who mintined the concelment; ll other reserch tem members, including the principl investigtor, outcome ssessors, reserch ssistnts, nd intervention providers, were blinded. In ddition, the current tril followed n intention-to-tret (ITT) protocol. The ITT protocol ssured tht none of the prticipnts ws excluded once it ws rndomized. 19 The purpose of the ITT protocol is to preserve the rndom lloction of the tril 20 nd void bis ssocited with nonrndom loss of prticipnts. 21 Prticipnts Athletes nd coches from totl of 52 tems (547 thletes), consisting of femle bsketbll (23 tems, 241 thletes), soccer (11 tems, 142 thletes), nd volleybll (18 tems, 164 thletes) tems t public middle nd high schools greed to prticipte in this study. To reduce bis, coches nd thletes were blinded to the rndomiztion. Trining Protocol Both interventions were initited in the preseson nd continued until the end of postseson ply. The individuls providing the llocted interventions were minly coching stff (n ¼ 39, 83.0%) but lso severl certified thletic triners (n ¼ 4, 8.5%) nd specilly trined undergrdute college students (n ¼ 4, 8.5%) in sports medicine ssocited progrms. All intervention providers ttended mndtory eduction nd trining sessions before nd during the intervention. These sessions for the experimentl nd control intervention providers took plce seprtely to mintin blinding nd consisted of 60-minute overview of exercise demonstrtions nd injury-trcking nd reporting methods. The core integrtive NMT progrm involved series of exercises designed to trget trunk stbiliztion nd improve hip strength nd power; the specific exercises were previously documented. 22 They included lower extremity strengthening, jump-lnding mneuvers, nd trunk stbiliztion s derived from previous reserchers 2,7,9,23,24 who demonstrted decresed incidence rtes nd improved neuromusculr control fter their use. The core integrtive NMT level of intensity, difficulty, nd techniques were progressed throughout the seson. The intervention providers were sked to implement the progrm (13 exercises, single set, 4 15 repetitions depending on the exercise) for 15 to 30 minutes 3 times per week during the preseson. Once tems begn the in-seson regimen, the core integrtive NMT ws shortenedto10to15minutes2timesperweek(7exercises, single set, 3 10 repetitions depending on the exercise). The durtion nd frequency of the speed nd gility trining were the sme s for the core integrtive NMT progrm. The speed nd gility trining used rubber bnd (medium strength; Jump Strength Inc, Youngstown, OH), which ws secured round the prticipnt s wist to provide resistnce. Then she ws sked to run forwrd nd bckwrd while tension ws plced on the rubber bnd to provide resistnce. This trining method ws reported to enhnce sprint strt speed nd increse stride frequency in young femle thletes. 25 The speed nd gility trining consisted of 8 to 10 different styles of rubber-bnd running, including bckwrd nd high-knees techniques t slow, moderte, nd fst speeds. The speed nd gility trining ws implemented in the control group s plcebo nd to reduce bis between groups, especilly when other interventions t the sme school were different. 0 Volume 51 Number 12 December 2016

3 Tble 1. Exmple of Individul Athlete Complince Form Session 1 Session 2 Session 3 Session 4 Session 5 Individul Complince Athlete A [ [ [ [ 4 Athlete B [ [ [ [ [ 5 Athlete C [ [ [ 3 Complince Trcking The intervention providers were sked to record ech prticipnt s ttendnce nd completion of exercises t the end of ech session. If prticipnt did not finish the ssigned exercises in session, this ws defined s not being complint for tht session. The study coordintor contcted ech intervention provider weekly nd collected the complince informtion through e-mil using n Excel (version 2010; Microsoft Corp, Redmond, WA) spredsheet ttchment. When the complince informtion ws not obtined, the study coordintor mde subsequent request to the intervention provider. Tble 2. Demogrphic Informtion for Experimentl nd Control Groups Definition of Complince Rte Clcultion The complince clcultion strted with the first intervention session of the preseson nd continued through the lst intervention session of the in-seson. Ech intervention provider s complince ws exmined bsed on the study protocol (3 times per week during the preseson nd 2 times per week in-seson) nd how mny times the intervention ws delivered. The coch complince rte ws defined s follows: Coch complince (%) ¼ Summtion of intervention sessions delivered during preseson nd in-seson/summtion of mximum intervention sessions tht could be delivered ccording to the study protocol. Individul thlete complince ws believed to be the most reflective vrible of NMT ctivity enggement. The individul thlete complince form is shown in Tble 1 nd ws completed by intervention providers ech time the intervention ws delivered. The individul thlete complince ws clculted s follows: Athlete complince (%) ¼ Proportion of individuls on roster who ttended nd completed more thn 2/3 of intervention sessions tht were delivered by intervention providers during preseson nd in-seson. We selected the cutoff vlue of 2/3 of intervention sessions becuse previous uthors 1 indicted tht once complince with NMT decresed by 2/3, NMT ws not prophylcticlly effective. 4 Sttisticl Anlysis All tems were rndomized, nd chrcteristics of ech group (core integrtive versus speed nd gility trining) re listed in Tble 2. Independent t tests were performed for height, weight, body mss index, nd ge. The level for the independent t test ws set priori t.05. Group, Tems (Athletes) Chrcteristic Vrible Experimentl Control Sport, no. Averge 30 (244) 22 (195) Bsketbll 12 (97) 11 (92) Soccer 6 (57) 5 (44) Volleybll 12 (90) 6 (59) Physicl chrcteristics, men 6 SD Height, cm Weight, kg Body mss index Age, y Age distribution, y Pubertl sttus Prepubertl 22 7 Pubertl Postpubertl Previous knee injuries? Yes No Previous knee surgeries? Yes 1 1 No Previous prticiption in injury-prevention progrm? Yes No Previous prticiption in performnce-enhncement progrm? Yes No P Vlue

4 Figure. Study flow digrm. For im 1, we used descriptive sttistics to nlyze coch nd thlete complince rtes between the study rms. To exmine im 2, independent t tests were performed to exmine differences in coch nd thlete complince rtes between the study rms, nd the priori level ws set t.05. To ttin im 3, both complince rtes were nlyzed bsed on school level (middle or high school) nd sport (bsketbll, soccer, or volleybll) using 2-wy nlysis of vrince. Bonferroni post hoc tests were employed to djust for multiple comprisons. RESULTS A totl of 28 tems (12 bsketbll, 6 soccer, nd 12 volleybll tems) were ssigned to the core integrtive NMT group nd 22 tems (11 bsketbll, 5 soccer, nd 6 volleybll tems) were ssigned to the speed nd gility trining group (Figure). Group Demogrphic Descriptive Sttistics Demogrphic descriptive sttistics for the groups re found in Tble 2. Height, weight, body mss index, nd ge did not differ on pretest mesures. Aim 1: Coch Complince With Protocol Coch complince with the given protocol ws 52.5% %. The intervention ws implemented t men rte of times per week during the preseson nd times per week in-seson. Aim 1: Athlete Complince With Intervention Athlete complince with the intervention ws 87.8% %. During the study, 88.4% of thletes completed more thn 2/ 3 of ll the intervention sessions. Aim 2: Coch Complince Between the Experimentl nd Control Groups Coch complince ws greter in the core integrtive NMT group thn in the speed nd gility trining group (P ¼.014; Tble 3). Coch complince during the preseson did not differ between groups; however, greter complince ws recorded in-seson for the core integrtive NMT group compred with the speed nd gility trining group (P ¼.022; Tble 3). Aim 2: Athlete Complince Between the Experimentl nd Control Groups Athlete complince did not differ Tble 3. Intervention Sessions Performed nd Coch Complince in Experimentl nd Control Groups Group, Men 6 SD Vrible Experimentl Control P Vlue Seson Intervention sessions, No. (%) ( ) ( ).014 Preseson Totl Sessions/wk Complince, % In-seson Totl Sessions/wk Complince, % P, Volume 51 Number 12 December 2016

5 Tble 4. Athlete Complince in Experimentl nd Control Groups Group, Men 6 SD (%) Experimentl Control P Vlue between the core integrtive NMT nd speed nd gility trining groups (P ¼.602; Tble 4). Aim 3: Coch Complince Bsed on School Level nd Sport There ws no interction between school level nd sport (P ¼.348; Tble 5) nd no min effect of sport (P ¼ 0.867; Tble 5). However, coch complince ws greter in middle schools thn in high schools (P ¼.001; Tble 5). Aim 3: Athlete Complince Bsed on School Level nd Sport There ws no interction of school level nd sport (P ¼.833; Tble 6) nd no min effect of school level (P ¼.359; Tble 6) or sport (P ¼.733; Tble 6). DISCUSSION The min purpose of our study ws to nlyze coch nd thlete complince with interventions designed to reduce trumtic knee injuries in young femle thletes. Coch complince with the protocol ws 52.5% %, which is men rte of times per week during the preseson nd times per week in-seson. The study protocol ws to provide the ssigned intervention 3 times per week during the preseson nd 2 times per week in-seson. The rte of the intervention s instructed by the coch ws unexpectedly lower. Low levels of complince with NMT protocols were documented in pst investigtions. 2,3 One strtegy used in previous work to enhnce complince with NMT ws to hve noncoching personnel tke supervisory role in the interventions. 2 In our study, most of those who provided the intervention were coches (n ¼ 39, 83%); 8 intervention providers were noncoching stff members (4 certified thletic triners nd 4 undergrdute college students). Thus, we ssessed whether the tems under the noncoching intervention providers demonstrted higher complince. However, complince with the ssigned intervention did not differ for coch versus noncoch intervention providers (57.3% % led by coches versus 53.3% % led by noncoches, P ¼.638). One certified thletic triner in this study mentioned tht the ssigned intervention ws sometimes omitted t the coches discretion even though the thletic triner ws vilble to deliver the prescribed intervention. This comment exemplified tht some coches chose not to Tble 5. Intervention Sessions Performed nd Coch Complince By School Level nd Sport, Men 6 SD Sport Vrible Middle High Bsketbll Totl, No Complince, % Soccer Totl, No Complince, % Volleybll Totl, No Complince, % follow the protocol nd tht coches hve strong uthority to determine how prctice time is used. Therefore, gining coches understnding through communiction is key to successful implementtion of the protocol. The different levels of coch complince between the study rms were not expected. In this study, the speed nd gility trining intervention served the purpose of shm trining becuse the rndomiztion ws performed t the tem level but not t the school level. Previous reserchers 25 reported n increse in sprint strt speed fter the speed nd gility trining progrm. The exercises incorported in the speed nd gility trining progrm plced more emphsis on the performnce spects of trining, so we expected better coch complince with this group. However, the core integrtive NMT intervention ws prcticed totl of 20.4 times in the experimentl group compred with 15.7 times by the speed nd gility trining group during seson (Tble 3), nd the difference ppers to stem from the in-seson complince rtes. The core integrtive NMT intervention ws performed pproximtely 15 times inseson (men of 1.3 times per week; Tble 2), yet the speed nd gility trining intervention ws implemented only 11 times in-seson (men of 1.0 time per week; Tble 3). Given the lck of difference in the number of interventions implemented between the study rms during the preseson, the in-seson complince rte difference likely influenced the overll seson complince rtes (Tble 3). According to our reserch ssocites working on site, few coches commented tht limited prctice schedules did not llow them to follow the study protocol (3 times per week during the preseson nd 2 times per week in-seson), especilly in-seson. The resons for the limited prctice schedules vried, but the most common reson ws tight competition schedules. For instnce, when 2 competitions were scheduled during weekdys, only 3 dys were vilble to perform the prescribed intervention, but 1 or 2 of those dys were often used for rest nd recovery, which mde following the in-seson protocol (2 times per week) difficult. For this reson, we crried out n extr nlysis to investigte if the number of thletic competitions between the study rms differed. Indeed, the speed nd gility trining group hd more thletic competitions ( totl of 24.0) compred with the core integrtive NMT group ( totl of 22.4; Tble 7). Therefore, more thletic competitions might hve reduced opportunities to perform the speed nd gility trining intervention in the control rm, which in turn might hve led to the higher level of coch complince in the experimentl rm. In ddition, coch complince levels were different between the school levels but not different by sport (Tble 5). The lower coch complince levels t middle schools cross ll sports might be due to fewer prctice opportu- School The interction ws not significnt (P ¼.348). The min effect for school level ws significnt (P ¼.001), but the min effect of sport ws not significnt (P ¼.867). Tble 6. Athlete Complince By School Level nd Sport, Men 6 SD (%) School Sport Middle High Bsketbll Soccer Volleybll Neither the interction (P ¼.833) or the min effect of school level (P ¼.733) or sport (P ¼.359) ws significnt.

6 Tble 7. Athletic Competitions of Experimentl nd Control Groups, Men 6 SD Number of Competitions Experimentl Control P Vlue Averge Bsketbll Soccer Volleybll P,.05. Group nities compred with high schools during the preseson. In this study, few middle school soccer nd volleybll coches mentioned tht they did not hve dequte time to perform the ssigned interventions during the preseson. Specificlly, the preseson durtion of the soccer nd volleybll tems t the middle school level ws pproximtely 2 weeks compred with 4 weeks for the bsketbll tems, which reflected the observed results within the middle schools (Tble 5). The sme explntion might be pplicble to the differences in coch complince between the middle nd high schools. The high school preseson is generlly longer thn tht in middle school, so high school coches might hve hd more time nd opportunities to perform the ssigned interventions. On the other hnd, middle school coches preferred not to spend limited prctice time nd opportunities on the study interventions. In short, it ppered tht vilble time during the seson plys criticl role for coches. The nlysis of coch complince between the study rms showed the sme tendencies. The tight schedules nd greter number of competitions seemed to limit opportunities to perform the speed nd gility trining in the control rm. Therefore, securing vilble time is nother importnt spect to enhncing complince with study protocol nd implementtion of preventive NMT. Athlete complince did not differ between the study rms (Tble 4). Nerly 90% of thletes who were enrolled in this clinicl tril prticipted in more thn 2/3 of the intervention sessions given, regrdless of school level or sport (Tble 6). The min resons for missing the ssigned NMT were being lte for prctices nd being sick or injured. Our results offer importnt clinicl implictions: when the intervention ws provided by the coching stff, most thletes followed their instructions. Authors 2,3 of severl previous preventive NMT studies hve pointed out tht complince is limittion. However, becuse most thletes tend to perform prescribed interventions, key to enhncing preventive NMT complince is to enhnce coch complince nd dherence to the intervention. Reserchers 26 who investigted vribles influencing the implementtion of preventive NMT reported tht coching experience nd the presence of dditionl supporting stff (such s n thletic triner or strength nd conditioning specilist) my influence prticiption. Thus, the presence of supporting helth cre providers is criticl element in preventive NMT implementtion nd execution. In ddition, these uthors 26 found tht performnce enhncement, eductionl requirements, nd policy chnges by thletic ssocitions were key to implementing preventive NMT intervention nd mintining high complince mong coches. Steffen et l 27 recently compred 2 preventive NMT delivery methods: (1) set of eductionl workshops for coches nd on-site ssistnce from physiotherpists nd (2) unsupervised Web site-bsed eduction for coches. Preventive NMT exercises were prcticed lmost twice s much by tems whose coches took the eductionl workshops nd hd ssistnce from physiotherpists compred with tems whose coches hd ccess to the unsupervised Web site-bsed eduction. Also, thletes who dhered to the preventive NMT exercises t the higher level hd 57% lower injury incidence. 27 Our study hd severl methodologic concerns tht need to be reported. First, the cluster rndomiztion resulted in lmost equl numbers of bsketbll nd soccer tems between the rms; however, rndomiztion ws not idel in volleybll. Only 6 tems were llocted to the speed nd gility trining group compred with 12 tems in the core integrtive NMT group (Figure). Second, cross-contmintion between the trining groups occurred. Severl thletes were recruited to more dvnced tems during the intervention period, which resulted in severl prticipnts experiencing both interventions. Becuse the nlysis ws performed under the ITT principle, we nlyzed the dt ccording to the tem of initil lloction. CONCLUSIONS This project focused on nlyzing 2 types of complince: complince of intervention providers with following study protocol (coch complince) nd complince of individul thletes with performing ssigned NMT (thlete complince). Coch complince with the study protocol ws pproximtely 50% nd ws greter in the experimentl rm thn in the control rm. High school coches were more complint thn middle school coches. Coch complince did not differ mong sports. Nerly 90% of thletes complied with more thn 2/3 of the interventions, regrdless of study rm, school level, or sport, which indictes tht thletes cn follow given intervention. Busy competition schedules nd lck of vilble time during sesons might hve contributed to the lower complince level of coches. Becuse previous reserchers identified n inverse dose-response reltionship between preventive NMT complince nd trumtic knee (ie, ACL) injury, 1,14,28 future investigtors need to focus on finding prcticl strtegies to mke NMT prt of regulr prctice regimens. This will llow coches to comply with nd dhere to preventive NMT, which my protect young thletes from injury. ACKNOWLEDGMENTS This study ws supported by grnts R01-AR nd R01- AR from the Ntionl Institute of Helth nd the Ntionl Institute of Arthritis nd Musculoskeletl nd Skin Diseses. REFERENCES 1. Sugimoto D, Myer GD, Bush HM, Klugmn MF, Medin McKeon JM, Hewett TE. Complince with neuromusculr trining nd nterior crucite ligment injury risk reduction in femle thletes: met-nlysis. J Athl Trin. 2012;47(6): Myklebust G, Engebretsen L, Brekken IH, Skjolberg A, Olsen OE, Bhr R. Prevention of nterior crucite ligment injuries in femle tem hndbll plyers: prospective intervention study over three sesons. Clin J Sport Med. 2003;13(2): Volume 51 Number 12 December 2016

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