Association between lower extremity muscle strength and acute ankle injury in youth team-sports athletes

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY-NC-ND 4.0 https://creativecommons.org/licenses/by-nc-nd/4.0/ Association between lower extremity muscle strength and acute ankle injury in youth team-sports athletes © 2021 Elsevier Accepted version (Final draft) Hietamo, J.; Pasanen, K.; Leppänen, M.; Steffen, K.; Kannus, P.; Heinonen, A.; Mattila, V.; Parkkari, J. Hietamo, J., Pasanen, K., Leppänen, M., Steffen, K., Kannus, P., Heinonen, A., Mattila, V., & Parkkari, J. (2021). Association between lower extremity muscle strength and acute ankle injury in youth team-sports athletes. Physical Therapy in Sport, 48, 188-195. https://doi.org/10.1016/j.ptsp.2021.01.007 2021 1 Hietamo, J., Pasanen, K., Leppänen, M., Steffen, K., Kannus, P., Heinonen, A., Mattila, V., & Parkkari, J. 1 (2021). Association between lower extremity muscle strength and acute ankle injury in youth team2 sports athletes. Physical Therapy in Sport, 48, 188-195 3 4 ABSTRACT 5 Objectives: To investigate lower extremity muscle strength as risk factor for an acute ankle injury 6 in youth athletes. 7 Design: Cohort study. 8 Setting: Basketball and floorball clubs. 9 Participants: 188 youth (≤21) male and 174 female athletes. 10 Main outcome measures: 1RM leg press, maximal concentric isokinetic quadriceps and 11 hamstrings as well as maximal isometric hip abductor strength were measured and athletes were 12 followed for an acute ankle injury up to three years. Cox regression models were used in statistical 13 analyses. 14 Results: In males, greater 1RM leg press and maximal quadriceps strength increased the risk of any 15 type of acute ankle injury (Hazard ratio [HR] for 1 SD increase, 1.63 [95% CI, 1.12‒2.39] and 1.43 16 [95% CI, 1.01‒2.01], respectively). In females, greater 1RM leg press and difference between legs 17 in hip abduction strength increased the risk of acute non-contact ankle injury (HR for 1 SD increase, 18 1.44 [95% CI, 1.03‒2.02] and 1.44 [95% CI, 1.03‒2.00], respectively). However, ROC curve 19 analyses showed AUC:s of 0.57-0.64 indicating “fail” to “poor” combined sensitivity and specifity 20 of these tests. 21 Conclusion: Greater strength in both sexes along with asymmetry in hip abductor strength in 22 females increased the risk of acute ankle injury. 23 2 24 Keywords: SPORT INJURY; INJURY RISK; YOUTH SPORT 25 1. INTRODUCTION 26 Incidence of ankle injury is high in youth team sports (Borowski, Yard, Fields, & Comstock, 2008; 27 Emery, Carolyn A., Meeuwisse, & Hartmann, 2005; Olsen, O-E, Myklebust, Engebretsen, & Bahr, 28 2006; Powell & Barber-Foss, 2000). Lateral ankle sprain is observed most frequently (Sankey, 29 Brooks, Kemp, & Haddad, 2008; Starkey, 2000; Woods, Hawkins, Hulse, & Hodson, 2003a). 30 Ankle sprain can lead to a marked loss of practicing and playing time (Cloke, Spencer, Hodson, & 31 Deehan, 2009) and often evolve persistent pain, weakness and chronic instability possibly resulting 32 in lower sport activity levels or even change of sports (Anandacoomarasamy & Barnsley, 2005). 33 Identifying risk factors that are modifiable and clinically easy to test are essential 34 before planning injury prevention programs (Bahr & Krosshaug, 2005). The role of lower extremity 35 (LE) muscle strength as a risk factor for sport injury is controversial. Lower quadriceps and 36 hamstrings strength or strength imbalances between these muscles have shown to increase the risk 37 of anterior cruciate ligament injury and hamstring strain (Croisier, Ganteaume, Binet, Genty, & 38 Ferret, 2008; Myer et al., 2009; Soderman, Alfredson, Pietila, & Werner, 2001) although contrary 39 results also exist (Bennell et al., 1998; Uhorchak et al., 2003). In our previously published study, 40 lower hip abduction strength increased the risk of acute knee injury in youth male athletes (Hietamo 41 et al., 2020). 42 There are several studies investigating ankle dorsiflexion, plantar flexion, inversion, 43 eversion, dorsiflexion and plantar flexion strength as well as strength ratios between these as risk 44 factors for ankle injury (Beynnon, Renstrom, Alosa, Baumhauer, & Vacek, 2001; Wang, Chen, 45 Shiang, Jan, & Lin, 2006; Willems, T. M. et al., 2005; Willems, Tine Marieke et al., 2005). 46 However, based on kinetic chain theories, impairments of proximal core and hip muscle function 47 3 are suggested to increase the likelihood of uncontrolled joint displacements distally and occurrence 48 of distal LE injury (Leetun, Ireland, Willson, Ballantyne, & Davis, 2004; Willson, Dougherty, 49 Ireland, & Davis, 2005). Lower hip abduction strength has found to associate with chronic ankle 50 sprains (Friel, McLean, Myers, & Caceres, 2006), but in another study, no association between hip 51 muscle strength and the risk of non-contact lateral ankle sprain was reported in high school athletes 52 (McHugh, Tyler, Tetro, Mullaney, & Nicholas, 2006). In addition, alterations in knee kinematics in 53 jump landing task have found in subjects with chronic ankle instability (Gribble & Robinson, 2009) 54 and neuromuscular training including quadriceps and hamstrings strengthening exercises have 55 shown to decrease the risk of acute ankle injury in youth athletes (Emery, C. A. & Meeuwisse, 56 2010; Olsen, Odd-Egil, Myklebust, Engebretsen, Holme, & Bahr, 2005). Therefore, lower 57 quadriceps and hamstrings strength may also be considered as risk factors for acute ankle injury. 58 The purpose of this study was thus to investigate selected LE muscle strength 59 variables as potential risk factors for an acute ankle injury in youth male and female team-sport 60 athletes. We hypothesized that lower muscle strength increases the risk of these injuries. 61 62 63 64 65 66 67 68 69 4 70 2. METHODS 71 2.1. Study design and participants 72 This study is part of the Predictors of Lower Extremity Injuries in Team Sports (PROFITS) study 73 (Pasanen et al., 2015). The study was conducted in accordance with the Declaration of Helsinki and 74 was approved by the Ethics Committee of the Pirkanmaa Hospital District, Tampere, Finland (ETL75 code R10169). The participants signed a written informed consent before entering the study 76 (including parental consent for participants under the age of 18). 77 Junior-aged (≤21 yrs) basketball and floorball athletes were recruited from 9 78 basketball and 9 floorball teams from 6 sports clubs from Tampere city district. All athletes played 79 at the two highest junior or adult league levels. Altogether 214 male (102 basketball and 112 80 floorball) and 189 female (107 basketball and 82 floorball) athletes entered the study during the 81 preseason (April‒May) in 2011, 2012 or 2013. Each athlete completed a baseline questionnaire 82 including questions about age, sex, previous injuries and playing level. Standing height (cm) and 83 body mass (kg) were recorded and muscle strength tests performed. After baseline tests, injury 84 registration continued until the end of April 2014. Twenty-four male and 11 female athletes were 85 excluded due to ongoing injury. Athletes were considered as injured if they report injuries at 86 baseline questionnaire or were not able to fully participate in muscle strength tests. In addition, 2 87 male and 4 female athletes were excluded, because they were not official members of the teams 88 leading to a total of 188 (88%) male and 174 (92%) female athletes in the final analysis (Fig. 1). 89 The demographic data and ankle injury history of athletes are presented in (Table 1). 90 2.2. Muscle strength tests 91 5 The muscle strength tests were part of a baseline test battery used to investigate potential 92 anatomical, biomechanical and neuromuscular risk factors for injuries. The complete test protocol 93 with standardised warm-up procedures before each test is described elsewhere (Pasanen et al., 94 2015). 95 2.2.1. Maximal one-repetition leg press strength 96 A seated leg press machine (Technogym®, Gambettola, Italy) was used to measure a combined 97 maximal extension strength of LE muscles. The distance between feet was 20 cm and end of shoes 98 were 10 cm above from the lowest end of the foot plate. The back of the seat was set on 30° angle 99 relative to the floor. A vertical bar was placed at the point where the knees reached the target knee 100 angle of 80° (Fig. 2). The target knee angle was measured with a goniometer (HiRes, Baseline® 101 Evaluation Instruments, White Plains, NY, USA). A standardized warm-up protocol consisted three 102 sets with gradually increasing weights (Pasanen et al., 2015). The one-repetition maximum (1RM) 103 leg press test protocol started with 80‒150 kg. Appropriate starting weights for each athlete were 104 decided individually by asking about athlete’s experience of weight training in seated leg press 105 machine. At the starting point athlete’s legs were extended and the weights were then lowered until 106 the knees form the correct angle and then returned at the starting position as hard as possible. After 107 each successful trial, the weights were increased by maximum 30 kg after the first trials and by 108 minimum 10 kg after the last trials for the next attempt. Recovery period between the attempts was 109 2 minutes (Verdijk, van Loon, Meijer, & Savelberg, Hans H C M., 2009) and the test ends when 110 1RM was reached. Body mass normalized value was used in the analysis. Similar test has been 111 proved to be reliable tool for measuring muscle strength (Levinger et al., 2009). 112 2.2.2. Maximal isokinetic quadriceps and hamstrings strength 113 Maximal concentric isokinetic quadriceps and hamstrings strength was measured at first study year 114 (2011) in non-commercial dynamometer (name hidden). At the second study year (2012) the 115 6 dynamometer was replaced by Biodex Multi-Joint System Pro dynamometer (Biodex System 4, 116 Biodex Medical Systems, Inc., Shirley, NY, USA). The test procedure was the same either of the 117 dynamometers used. The test range of motion was 90° through 15° of knee flexion with an angular 118 velocity of 60°/s (Fig. 2). A standardized test protocol (Pasanen et al., 2015) with gradually 119 increasing intensity were performed and the final test includes three repetitions with maximum 120 strength. The maximal strength was reported as peak torque (N‧m) recorded and body mass 121 normalized value was used in the analysis. The strength difference between legs as well as 122 hamstrings-to-quadriceps (HQ) strength ratio were calculated. Isokinetic strength testing has been 123 established as reliable tool for assessing muscle strength (Brosky JA Jr, Nitz, Malone, Caborn, & 124 Rayens, 1999). 125 To evaluate the reproducibility of measurements between the used two dynamometers, 126 twelve 14‒15 years old male soccer athletes (24 legs) were tested with both dynamometers by 127 different testers who collected the data. Intraclass correlation coefficient (ICC) value (3,k) was 0.81 128 (95% CI, 0.43‒0.93) for isokinetic quadriceps and 0.79 (95% CI, 0.47‒0.91) for isokinetic 129 hamstring strength measurement indicating good test-retest reliability of the tests. 130 2.2.3. Maximal hip abductor strength 131 Maximal isometric hip abductor strength (kg) was tested with a hand-held dynamometer (Hydraulic 132 Push-Pull Dynamometer, Baseline® Evaluation Instruments, White Plains, NY, USA). The test was 133 perfomed with the athlete lying legs extended in a supine position on bench. The pelvis and the 134 contralateral thigh were fixed with a belt and the athlete hold his or her arms across the chest during 135 the test. The dynamometer was positioned approximately 2 cm proximal the lateral ankle malleolus 136 with the leg in neutral position and the foot in slight dorsiflexion (Fig. 2). The dynamometer was 137 applied in a fixed position and the athlete hold muscle contraction against the dynamometer for 138 approximately two seconds (make-test). After one test trial the athlete performed two maximal 139 7 contractions with a 10 second rest between the attempts (Johnson, Mille, Martinez, Crombie, & 140 Rogers, 2004). The highest result was recorded and body mass normalized value was used in the 141 analysis. The strength difference between legs was also calculated. Similar procedure has been 142 showed to be reliable for assessing hip abductor strength (Thorborg, Petersen, Magnusson, & 143 Holmich, 2010). 144 2.3. Injury and exposure registration 145 During a follow-up period (May 2011‒April 2014), all acute ankle injuries were registered by two 146 study physicians. They contacted the teams once a week to check possible new injuries and after 147 each injury reported, the injured athlete was interviewed by telephone using the structured 148 questionnaire (Pasanen et al., 2015). Injury definition was modified from definition by Fuller and 149 colleagues (Fuller et al., 2006). An injury was recorded if the athlete was unable to fully participate 150 in matches or training during the next 24 hours. Only injuries which occurred in a teams’ scheduled 151 training sessions or matches were included in this study. The injuries were classified as contact (ie. 152 direct contact or strike to the involved ankle) or non-contact (ie. no direct contact to the involved 153 ankle). 154 During the follow-up, the coach of each team recorded athletes’ participation in 155 trainings and matches. Athlete attendance in a training session (yes/no), duration of a training 156 session (h) and attendance in each period of a match (yes/no) were recorded individually on a team 157 diary. The diaries were returned after each follow-up month and the individual monthly exposure 158 time (h) were registered for all athletes. If an acute ankle injury occurred, the exposure hours of that 159 month were estimated by dividing the days from the beginning of the month to the injury date by all 160 days of the month and then by multiplying the result by the athlete’s registered exposure hours of 161 that month. 162 2.4. Statistical analysis 163 8 Descriptive data are presented as the mean ± standard deviation (SD) or the median and 164 interquartile range (IQR) depending on the normality of distribution of variables. An independent165 samples t test was used to compare group differences for normally distributed variables and the 166 Mann-Whitney U test for non-normally distributed variables. Depending on the distribution of the 167 variables, Pearson’s and Spearman’s correlation coefficients were used to evaluate linear correlation 168 between two variables. Injury incidences were calculated as the number of injuries per 1000 player169 hours and reported with 95% CIs: ([Incidence rate – 1.96 * Standard error of incidence rate] * 170 1000 hours) to ([Incidence rate + 1.96 * Standard error of incidence rate] * 1000 hours). Recurrent 171 injuries were included in incidence calculations. 172 Considering the study procedure, Cox regression models were chosen to analyse 173 strength variables using the athlete or the leg as a unit of analysis. The unit of analysis was defined 174 according to the strength variable representing either the characteristic of the athlete or of the leg 175 (Bahr & Holme, 2003b). The outcomes were a new acute (contact or non-contact) ankle injury and 176 a new acute non-contact ankle injury. Exposure time (h) from the start of the follow-up until the 177 first injury or the end of the follow-up were included in the models. Sports club was included in all 178 models as random effect and the leg in the models using it as the unit of analysis. Unadjusted and 179 adjusted models with predefined adjustement factors were made separately for male and female 180 athletes. The adjustement factors that might mostly influence to the risk of ankle injury were 181 selected in the following order: previous acute ankle injury, age, height, sport and playing at adult 182 level. These adjustement factors were included in the models according to the number of injuries in 183 each model, using estimation of 10 injuries needed per included variable (Peduzzi, Concato, 184 Feinstein, & Holford, 1995). In the models using the athlete as the unit of analysis, previous injuries 185 of ipsilateral or contralateral side were included, and in the models using the leg as a unit of 186 analysis, only injuries of ipsilateral side were included. 187 15 Regardless of significant associations between the muscle strength and ankle injury in 325 our study, substantial overlap between the test results in injured and uninjured athletes existed 326 leading “fail” to “poor” combined sensitivity and specifity for the strength tests meaning that the 327 tests can correctly classify <70% of injured and uninjured athletes. Therefore, in clinical practice, 328 the muscle strength tests as measured in the present study cannot be recommended alone as injury 329 screening tools for acute ankle injury in youth athletes. 330 Study strengths and limitations 331 This study had several strengths. First, all the data was collected prospectively. Second, the 332 accuracy of ankle injury data collection was good, because study physicians contacted coaches once 333 a week. Third, individually collected exposure data enabled the use of Cox regression in statistical 334 analyses (Bahr & Holme, 2003). Finally, the strength risk factors were measured with standard and 335 simple procedures easy to use in clinical practice. 336 One main limitation of the study was that we measured only muscle strength, but 337 ankle injury is likely a result of the complex interaction between many internal (athlete-related) and 338 external (environmental) risk factors (Bahr & Krosshaug, 2005; Meeuwisse, 1994). However, we 339 took into analyses several other potential risk factors as adjustement factors. Another main 340 limitation was, that strength measurements were not repeated and thus the strength values might 341 have been changed during the 3-year follow-up. In addition, we did not take the influence of lever 342 arm (limb length) into account for 1RM leg press and hip abduction strength measurements 343 (Bakken et al., 2018; McHugh et al., 2006). Finally, because the study cohort comprised of youth 344 floorball and basketball athletes, the findings may not be applicable to adult athletes or athletes 345 from other youth sports. 346 347 348 16 349 5. CONCLUSION 350 Our 3-year prospective study showed that greater 1RM leg press and maximal quadriceps strength 351 increased the risk of any type of acute ankle injury in youth male athletes while greater 1RM leg 352 press strength and greater difference between legs in maximal hip abduction strength increased the 353 risk of acute non-contact ankle injury in youth female athletes. 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