Can tests of physical fitness predict traumatic knee injury in youth female athletes? A prospective cohort study.

OBJECTIVES: To compile a battery of test including various aspects of physical fitness that could be used on the field and to assess whether any of these tests are associated with future traumatic knee injuries in youth female team sports athletes. DESIGN: Prospective cohort. SETTING: Sport setting. PARTICIPANTS: Female athletes (n = 117, age 15-19 years), from Swedish sport high schools, active in soccer, handball, or floorball. MAIN OUTCOME MEASURES: Differences in pre-injury tests values of 11 physical fitness tests in injured versus non-injured athletes, assessed as number of traumatic knee injuries over one season. RESULTS: 28 athletes sustained 34 traumatic knee injuries. Athletes who sustained an injury had a shorter distance on the Yo-Yo IR1 test at baseline than those without an injury (mean difference -193 m, CI -293- -65 m). None of the other tests, assessed for muscular strength, endurance, power, flexibility and dynamic knee valgus, differed between injured and non-injured athletes. CONCLUSIONS: Youth female athletes with lower intermittent endurance capacity, assessed with the Yo-Yo IR1, seemed to be at greater risk of traumatic knee injury. Neither hop performance, flexibility, dynamic knee valgus nor isolated strength tests at baseline could distinguish between injured and non-injured youth female athletes at follow-up.

FIDES Athlete Development Programme: project background and study protocol of an embedded multiple case study.

Most sports science research revolves around male subjects. As a result, most of the knowledge and practices within sports are male-centric. Failing to take the biological, psychological and social (biopsychosocial) particularities of females into account is believed to hinder optimal sports participation, development and performance, with potential negative effects on the health and well-being of females. To close the knowledge gap and alleviate these issues, we aim to develop and evaluate a 12-video educational intervention that addresses female-specific subject matter: the FIDES Athlete Development Programme. The study is designed as an embedded multiple case study where at least 1320 Swedish female athletes aged 13-16 will participate, in addition to their parents and their coaches. The girls will be recruited through their sports clubs, with half being exposed to the FIDES Athlete Development Programme and the other half serving as control cases. The primary outcomes are well-being and sporting experience. To further increase our understanding of the intervention and its implications, interviews and focus group interviews with a reference group of girls and focus group interviews with a randomly selected subsample of coaches and parents will also be performed. The project is approved by the Swedish ethics committee (number: 2023-05264-01) and will be carried out in compliance with the Declaration of Helsinki. Results from the project will be published open access in peer-reviewed journals, at national and international conferences, in mass media, and a PhD thesis. The anonymised data will be made openly available in a data repository.

A test battery for evaluation of muscle strength, balance and functional performance in subjects with chronic ankle instability: a cross-sectional study.

BACKGROUND: Studies investigating ankle condition in subjects with chronic ankle instability (CAI) using an on-the-field test battery are scarce. Understanding which tests that are most challenging for these subjects has the potential to set realistic goals in rehabilitation and return-to-sports criteria. Thus, the primary aim of this study was to investigate CAI subjects regarding strength, balance and functional performance with an easily used test battery that required minimal equipment. METHODS: This study was conducted with a cross-sectional design. A total of 20 CAI subjects, engaged in sports, and 15 healthy subjects serving as a control group, were tested for assessment of strength, balance and functional performance. A test battery was developed accordingly; isometric strength in inversion and eversion, the single leg stance test (SLS), single leg hop for distance (SLHD) and side hop test. The limb symmetry index was calculated to determine whether a side-to-side lower limb difference could be classified as normal or abnormal. The sensitivity of the test battery was also calculated. RESULTS: The subjects were 20% weaker on the injured side compared with the non-injured side in eversion (p < 0.01) and 16% weaker in inversion (p < 0.01) (Table 2). For the SLS test, the mean score of the injured side was 8 points (67%) higher (more foot lifts) compared to the non-injured side (p < 0.01). The mean distance of the SLHD was 10 cm (9%) shorter for the injured side compare to the non-injured side (p = 0.03). The mean number of side hop was 11 repetitions (29%) fewer for the injured side compare to the non-injured side (p < 0.01). Six of the 20 subjects obtained abnormal LSI values in all five tests whereas none obtained normal values in all tests. The sensitivity of the test battery was 100%. CONCLUSION: Deficits in muscle strength, balance and functional performance appear to be present in CAI subjects with the largest impairments in balance and side hop performance, which stresses the need for return to sport criteria for this group of subjects. TRIAL REGISTRATION: Registered retrospectively on 24/01/2023. NCT05732168.

Jump height as performance indicator for the selection of youth football players to national teams.

BACKGROUND: Different jump tests such as the Countermovement Jump (CMJ), Abalakov Jump (AJ) and Standing Long Jump (SLJ) are often used in practice to evaluate muscular power and functional performance in football. These tests are also used in different selection processes and talent identification, but the significance of the tests for the selection of youth players to national teams are relatively unknown. The aim of this study was to compare jump ability between youth football players selected or not selected for the national team. METHODS: In this cross-sectional study, 22 players (aged 17±2 years), 11 national players (NP) and 11 non-national players (NNP) were evaluated in three different jump tests; CMJ, AJ and SLJ. Mean scores for the tests were analyzed and compared. RESULTS: Significant differences were found between the groups regarding jump height in favor of the NP group in both the CMJ (NP 39.9±5.0 cm vs. NNP 34.2±4.9 cm, P=0.013) and the AJ (NP 47.1±5.4 vs. NNP 40.9±4.7, P=0.010). No group difference was found regarding jump length in SLJ (NP 246.2±17.9 vs. NNP 232.9±16.5, P=0.084). CONCLUSIONS: The results suggest that tests, measuring jump height, could be used as a performance indicator and part of the selection process of youth football players to national teams, whereas the use of jump length could be questioned.

Weaker lower extremity muscle strength predicts traumatic knee injury in youth female but not male athletes.

BACKGROUND: The role of lower extremity (LE) muscle strength for predicting traumatic knee injury in youth athletes is largely unknown. AIMS: The aim was to investigate the influence of LE muscle strength on traumatic knee injury in youth female and male athletes. METHODS: 225 athletes (40% females) from sport senior high schools in Sweden were included in this case-control study. The athletes recorded any traumatic knee injury that had occurred during their high-school period in a web-based injury form. A one repetition maximum (1RM) barbell squat test was used to measure LE muscle strength. The 1RM was dichotomised to analyse 'weak' versus 'strong' athletes according to the median (weakmedian vs strongmedian). RESULTS: 63 traumatic knee injuries, including 18 ACL injuries, were registered. The majority of injured female athletes were in the weak group compared with the strong group (p=0.0001). The odds of sustaining a traumatic knee injury and an ACL injury was 9.5 times higher and 7 times higher, respectively, in the weakmedian group compared with the strongmedian group in females (p ≤0.011). A relative 1RM squat ≤1.05 kg (105% of bodyweight) was established as the best cut-off value to distinguish high versus low risk of injury in female athletes. No strength-injury relationships were observed for the male athletes (p ≥0.348). CONCLUSIONS: Weaker LE muscle strength predicted traumatic knee injury in youth female athletes, but not in males. This suggests that LE muscle strength should be included in injury screening in youth female athletes.