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Abstract Decreased adductor muscle strength has been shown to be a risk factor for the development of future groin injury. The purpose of this study was therefore to examine standard values of isometric adductor muscle strength in Swedish male soccer and to map any differences in muscle strength between non-injured players and previously injured players. Twenty-one male soccer players were included in the study. A handheld dynamometer was used to record maximal isometric adductor muscle strength. The average value for isometric adductor muscle strength for all included players was 2,709 N/kg [± 0,37 SD]. Average values for non-injured and previously injured players were 2,716 N/kg [± 0,41 SD] and 2,537 N/kg [± 0,25 SD] respectively. The average value for the contralateral, non-injured side within the previously injured players was 2,86 N/kg [± 0,43 SD]. The difference in muscle strength between previously injured players and non-injured players was not statistically significant (p = .162). Conversely the difference between the non-injured side and the injured side in previously injured players was statistically significant (p = .018). Future studies should focus on including players of different levels to conclude whether the differences observed in this study is present regardless of the level of play.

Bakgrund En handhållen dynamometer (HHD) är ett kliniskt användbart mätverktyg för att mäta muskelstyrka. På Akademiska sjukhuset i Uppsala finns en HHD av märket MicroFET2® (Hoggan Scientific). Det finns ett fåtal studier gjorda som undersöker intrabedömarreliabiliteten vid mätningar av isometrisk muskelstyrka av knäledens muskelgrupper med denna dynamometer. Syfte Syftet med studien var att undersöka den absoluta och relativa reliabiliteten vid mätningar av maximal muskelstyrka i knäledens muskelgrupper med en HHD. Metod Psykometrisk design med test-retest förfarande. Totalt undersöktes 24 friska vuxna vid två mättillfällen med 6–8 dagars mellanrum. Den relativa reliabiliteten presenterades med Intraclass correlation coefficient (ICC 2,1). Den absoluta reliabiliteten presenteras i standard error of measurement (SEM), SEM% samt smallest detectable change (SDC). Resultat Resultaten visade mycket hög relativ reliabilitet för knäledens extensioner (ICC = 0,950,96) och för knäledens flexorer (ICC = 0,94–0,96). SEM varierade mellan 33,58N-34,81N för knäledens extensorer och 14,16N-17,16N för knäledens flexorer. SDC varierade mellan 93,08N–96,49N för knäledens extensorer och 39,25N-47,57N för knäledens flexorer. Konklusion Resultaten indikerar att HHD har mycket hög relativ reliabilitet för bedömning av styrka i knäledens stora muskelgrupper hos ett bekvämlighetsurval med friska vuxna människor.  Den relativa och absoluta reliabiliteten bedömdes överlag vara i enlighet med tidigare studier. För implementering i klinik behöver framtida studier utvärdera absolut och relativ reliabilitet på specifika patientpopulationer. / Background Hand held dynamometry (HHD) is a practical device for testing muscle strength. There is currently a HHD (MicroFET2® - Hoggan Scientific) available at Uppsala University hospital. Few reliability studies excist where the objective is to examine the intra-rater reliability of isometric maximal knee-strength using this device. Objective To examine the absolute and relative reliability of isometric maximal knee-strength using a MicroFET2. Method Psychometric design through test-retest with 6–8 days between measures on 24 healthy adults. The relative reliability expressed as Intra-class correlation coefficient (ICC 2,1) and the absolute reliability as standard error of measurement (SEM), SEM%, and smallest detecatble change (SDC). Results The results of this study showed very good reliability for both knee extensors (ICC = 0,950,96) and knee flexors (ICC = 0,94–0,96). Regarding the absolute reliability SEM ranged from 33,58N-34,81N for knee extensors and 14,16N-17,16N for knee flexors. SDC ranged from 93,08N-96,49N for knee extensors and 39,25N-47,57N for knee flexors. Conclusion The results indicate that HHD has a very good relative reliability for assessing strength in the large muscle groups of the knee joint when examined on a group of healty adults. The relative and absolute reliability was generally in accordance when compared with previous studies. Before being implemented in praxis, future studies need to evaluate absolute and relative reliability on specific patient populations.

Inledning: Muskelstyrka i höftregionen är en viktig fysisk färdighet inom fotboll dels ur ett prestationsperspektiv, dels för skadeprevention. Trots detta saknas normativa isometriska styrkevärden för höftadduktorer och - abduktorer hos damfotbollsspelare. Syfte: Syftet med denna tvärsnittsstudie var att undersöka den isometriska höftstyrkan i adduktion, unilateralt och bilateralt, samt höftabduktion unilateralt med en handhållen dynamometer hos skadefria damfotbollsspelare. Metod: 29 friska damfotbollsspelare på elitnivå inkluderades i studien. Den isometriska höftstyrkan mättes vid ett tillfälle på försäsongen med en handhållen dynamometer. Höftadduktion och -abduktion mättes unilateralt i en sidliggande position och den bilaterala höftadduktorstyrkan mättes i ett squeeze-test i en ryggliggande position. Ett tillägg av en extern fixation av dynamometern applicerades vid testtillfället. Resultat: Styrkevärden (medelvärde, SD ±) var: höftabduktion dominant ben 1,94 ± 0,3 Nm/kg, icke-dominant ben 1,81± 0,3 Nm/kg, höftadduktion dominant ben 1,61 ± 0,3 Nm/kg, icke-dominant ben 1,51 ± 0,3 Nm/kg, squeeze-test 4,11 ± 0,5 N. Styrkekvot adduktion/abduktion var 0,83 dominant ben och 0,84 icke-dominant ben. Det dominanta benet var signifikant starkare (p<0,05) i både höftadduktion och -abduktion, 7 % respektive 8 %. Konklusion: För damfotbollsspelare var det dominanta benet signifikant starkare i både höftadduktion och -abduktion. Höftabduktorerna var signifikant starkare än adduktorerna i både det dominanta och icke-dominanta benet med en styrkekvot adduktorerna/abduktorerna på 0,83 respektive 0,84. / Introduction: Hip strength is an important physical factor in soccer for both performance and for injury prevention. Despite this normative isometric strength values are lacking for hip adduction and abduction in healthy women’s soccer players. Aim: The aim of this cross-sectional study was to examine the isometric hip strength in adduction, unilateral and bilateral, and hip abduction unilateral with a handheld dynamometer in healthy women's soccer players. Methods: 29 healthy female elite soccer players were included in the study. The isometric hip strength was measured one time in the pre-season with a hand-held dynamometer. Hip adduction and abduction were measured unilaterally in a side lying position and the bilateral hip adductor strength was measured in a squeeze test in a supine position. An addition of an external fixation of the dynamometer was applied during testing. Results: Strength values (mean, SD ±) were: hip abduction dominant leg 1,94 ± 0,3 Nm/kg, non-dominant leg 1,81± 0,3 Nm/kg, hip adduction dominant leg 1,61 ± 0,3 Nm/kg, non-dominant leg 1,51 ± 0,3 Nm/kg, squeeze-test 4.11 ± 0.5 N. The strength ratio of adduction/abduction were 0,83 dominant leg and 0,84 non-dominant leg. The dominant leg was significantly stronger (p<0,05) in both hip abduction and adduction, 7 % and 8 %, respectively. Conclusion: For women’s soccer players the dominant leg was significantly stronger in both hip abduction and adduction. The hip abductors were significantly stronger than the adductors in both the dominant and non-dominant leg with a strength ratio adductor/abductor 0,83 and 0,84 respectively.