Hamstring injury is common in sprinting sports and injury recurrence remains a major concern. The aim of this thesis is to explore the biomechanical characteristics of athletes following sprint related hamstring injury. We conducted 1) An examination of already published research on biomechanical deficits following hamstring injury in athletes who had returned to sport by means of a systematic review and meta-analysis; 2) A detailed examination of sprinting following hamstring injury in athletes who had returned to sport muscle activity using 3D motion capture and surface EMG; 3) An examination of high intensity eccentric loading performance in previously injured athletes using low density, high surface area surface EMG and measures of force; 4) An analysis of hamstring muscle recovery until return to sport following hamstring injury using low density, high surface area surface EMG and measures of force via case reports in two elite athletes. Previous research indicates that athletes who had returned to sport following hamstring injury continue to display deficits in force production, especially during slow eccentric contractions. The observational studies indicate that athletes run with significantly asymmetric movements about the pelvis and hip that would place their hamstrings under increased length during the terminal swing phase of sprinting. Furthermore, significant alterations in late swing EMG ratios suggest relatively reduced activity in the previously injured biceps femoris. Spatial activation of the hamstring appears altered in previously injured athletes, with reduced relative activation of the proximal muscle and reduced median frequency values in the medial muscle compared to control limbs. Asymmetries in activation patterns are also noted in the pre-return to sport phase. Previous hamstring injury is associated with significant alterations in force production, movement symmetry and muscle activation patterns following return to sport highlighting the complexity of this injury and the need for advanced rehabilitation screening approaches.

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Bakgrund: Det är viktigt att kliniskt kunna avgöra om idrottaren är tillräckligt rehabiliterad för att återgå till full träning och matchspel eftersom otillräcklig rehabilitering är den största riskfaktorn för återskada i hamstrings. Därför skulle ett test med enkel utrustning behöva komplettera den kliniska undersökningen. Syfte: Studiens syfte är att undersöka vilket samband som finns mellan genomförandet av Nordic hamstring strength test och Asklings hamstring test utifrån skattning av smärta och obehag i samband med testen. Huruvida deltagarnas tilltro till att prestera sitt yttersta i en 90 min fotbollsmatch påverkas efter testerna samt att beskriva obehag och smärta efter testerna för spelare som varit skadad eller inte under senaste sex månaderna. Metod: 22 fotbollsspelare fick skatta sin tilltro till sin egen förmåga att prestera sitt yttersta i en 90 min fotbollsmatch samt skatta obehag och smärta med VAS i samband med testerna. Hamstring Outcome Score användes för att få en helhetssyn av deltagarnas funktion och skadehistoria kring hamstring. Spearman’s rho och Wilcoxon’s teckenrang test användes för att analysera resultatet. Resultat: Korrelationen mellan Asklings hamstring test och Nordic hamstring strength test var moderat (0,4-0,6) dock signifikant på <0,05. Majoriteten av spelarna sänkte sin tilltro efter testerna. De yngre spelarna har varit skadade senast men det är de äldsta spelarna som har dragit på sig flest skador. Slutsatser: Vidare forskning på ett större antal deltagare behövs för att avgöra om Nordic hamstring strength test skulle kunna användas som ett kompletterande test till den kliniska undersökningen. / Backgroud: It’s important to clinically determine whether the athlete is ready to return to full training and match play as inadequate rehabilitation are the major risk factor for reinjury in the hamstrings. Therefore, a test with simple equipment is needed to complement the clinical examination. Purpose: The study aims to investigate the relationship between the implementation of the Asklings hamstring test and the Nordic hamstring strength test based on the estimation of pain and discomfort during the tests. Whether the participants’ confidences to perform their best in a 90 minutes soccer game is affected by the tests, and describe pain and discomfort after the tests for those who had or had not been injured during the last six months. Methods: 22 football players had to rate their confidence in their own ability to perform their best in a 90 minutes football game, and estimate the discomfort and pain using VAS during the tests. Hamstring Outcome Score was used to obtain a holistic view of the participants’ function and injury history about hamstrings. Spearman’s Rho and Wilcoxon’s Rank Sum test was used to analyze the results. Result: There is a moderate correlation (0,4-0,6) between Askling hamstring test and Nordic hamstring strength test with a significance level of p<0,05. The majority of the players lowered their confidence after the tests. The younger players have been injured most recently but the oldest players have had the most injuries. Conclusion: Further research with a larger number of participants is needed to determine whether Nordic hamstring strength test could be used as a complementary test to the clinical examination.