The Significance of Maximal Squat Strength for Neuromuscular Knee Control in Elite Handball Players: A Cross-Sectional Study.

Both weak muscle strength and impaired neuromuscular control has previous been suggested as risk factors for future traumatic knee injury. However, data on the relationship between these two factors are scarce. Thus, the aim of this study was to investigate the relationship and influence of the one repetition maximum (1RM) barbell squat strength on dynamic knee valgus in elite female and male handball players. In this cross-sectional study 22 elite handball players (7 females) were included. A unilateral drop jump (VDJ) test was used for the assessment of frontal plane dynamic knee valgus. Players also performed a one repetition maximum (1RM) barbell squat test, expressed relative to bodyweight (r1RM), to assess maximal strength, which were dichotomized to analyze 'weak' versus 'strong' players according to median. Correlations were noted between r1RM in squat and knee valgus angle for both the non-dominant (r = -0.54; p = 0.009) and dominant leg (r = -0.46, p = 0.03). The odds of knee valgus were eight times higher, for the dominant leg, in the weak group compared to the strong group (p = 0.03) and 27 times higher, for the non-dominant leg (p = 0.002). The outcome of the present study suggests that maximum squat strength plays an important role when it comes to neuromuscular control of the knee, and that weak handball players are at higher risk of knee valgus compared to strong players during jumping activity.

Development of a Novel Nordic Hamstring Exercise Performance Test Device: A Reliability and Intervention Study.

There is evidence that a knee flexor exercise, the Nordic hamstring exercise (NHE), prevents hamstring injuries. The purpose of this study was therefore to develop, and to determine the reliability of, a novel NHE test device and, further, to determine the effectiveness of a 10-week low volume NHE program on NHE performance. Twenty female football (soccer) players, aged 16-30 years, participated in this study. From a kneeling position on the device, with the ankles secured under a heavy lifting sling, participants leaned forward in a controlled manner as far as possible (eccentric phase) and then returned to the starting position (concentric phase). A tape measure documented the forward distance achieved by the participants in cm. Participants completed three separate occasions to evaluate test-retest reliability. Additionally, 14 players performed a low volume (1 set of 5 repetitions) NHE program once weekly for 10 weeks. No significant test-retest differences in NHE performance were observed. The intra-class correlation coefficient was 0.95 and the coefficient of variation was 3.54% between tests. Mean improvement in the NHE performance test by the players following training was 22% (8.7 cm), p = 0.005. Our test device reliably measured NHE performance and is easy to perform in any setting. Further, NHE performance was improved by a 10-week low volume NHE program. This suggests that even a small dose (1 set of 5 repetitions once weekly) of the NHE may enhance NHE performance.

Short-term effects of postural taping on pain and forward head posture: a randomized controlled trial.

BACKGROUND: Balance Body Tape (BBT) is a recently developed taping-method with the aim to reduce pain and improve posture through change in movement behavior. However, the potential effects of a treatment with BBT are scarcely documented. Therefore, the aim with this study was to investigate the effect of a three-week Balance body tape-treatment on the intensity of perceived neck, shoulder and back pain and forward head posture. METHODS: In this RCT study, subjects (n = 26), who reported being university students or having a sedentary work and experiencing pain in neck, back or shoulders, were randomized to either an intervention (n = 12) or control group (n = 14). The intervention group received a three-week treatment with BBT, the control group received no treatment. A questionnaire regarding pain, including a Numeric Rating Scale (NRS) measuring pain intensity, and a Photographic posture analysis measurement (PPAM) regarding the craniovertebral (CV) angle were assessed before and after the intervention for both groups. Wilcoxon's signed rank test and Mann-Whitney U test was used to assess intra- and between group differences respectively. The relationship between pain intensity and CV angle was assessed using Spearman's correlation. RESULTS: No difference in demographic and physical characteristics between the groups were noted at baseline (p > 0.05). Pain intensity at baseline was 5 for the intervention group and 4 for the control group (p = 0.330). At follow up, the intervention group reported a lower score (NRS = 2.5, p = 0.003) whereas the control group had no significant difference in pain intensity (NRS = 3, p = 0.086). No significant change was found in the CV angle (p = 0.058) and no correlation was found between NRS and the CV angle (r = 0.102, p = 0.619). CONCLUSION: A short treatment period with BBT may, compared to no treatment, have a small reducing effect on pain intensity in neck, back and/or shoulders. However, no effect was found on forward head posture in this study. TRIAL REGISTRATION: Registered retrospectively on 08/11/2021. NCT05111704 . Trial registration page link.

Postural orientation, what to expect in youth athletes? A cohort study on data from the Malmö Youth Sport Study.

BACKGROUND: Studies investigating postural orientation in uninjured youth athletes are scarce. Understanding how postural orientation during functional performance tests change with age in uninjured athletes has the potential to enhance awareness of changes in performance after injury and to set realistic goals for injured athletes. Thus, the aim of this study was to explore postural orientation during functional tasks at early adolescence, and changes in postural orientation from early to middle adolescence and relate this to sex, type of sport and right leg lean body mass (RLLBM). METHODS: In this cohort study 144 (38% female) youth athletes (mean age 13.5 years, SD 0.3) were included at baseline and 86 of these at follow up 2 years later. Four functional performance tests were visually evaluated for Postural Orientation Errors (POEs) with an ordinal scale, ranging from 0 (good) to 2 (poor), yielding a maximum total POE score of 51, and RLLBM by dual energy X-ray absorptiometry. RESULTS: Improvements were observed in the total POE score from baseline to follow-up, median difference - 10 and - 7 (p < 0.001) for female and male athletes, respectively. At follow-up, female athletes had lower total POE score (median 18) than males (median 24) (p = 0.01). There were no differences in POE scores between sports type (team, individual, aesthetic) (p = 0.20-0.98) and no relationship between total POE score and RLLBM (rs = 0.09, p = 0.42). CONCLUSIONS: POEs appear to be quite common in young athletic population, but improvements are achieved over time. At mid-adolescence, female athletes seem to have less POEs than males. Neither sport type nor RLLBM seem to influence postural orientation.

Vertical drop jump landing depth influences knee kinematics in female recreational athletes.

OBJECTIVES: To examine whether different vertical drop jump (VDJ) landing depth (small versus deep) and stance width (wide versus narrow) may alter movement biomechanics in female recreational athletes. The purpose was also to identify whether leg muscle strength is a predictive factor for knee control during a VDJ. DESIGN: Cross-sectional. SETTING: Biomechanics laboratory. PARTICIPANTS: Eighteen women aged between 18 and 30 years. MAIN OUTCOME MEASURES: Three VDJ tests were used for biomechanical analysis: 1) small "bounce" jump (BJ), 2) deep "countermovement" jump with wide (CMJW) and 3) narrow foot position (CMJN). Subjects also performed an isometric knee-extension strength test, dichotomized to 'weak' versus 'strong' subjects according to median and quartiles. RESULTS: There were greater knee valgus angles during landing for both the CMJW and CMJN test compared to the BJ test (p ≤ 0.05). Differences in knee valgus between weak and strong subjects were significant for the BJ test (p = 0.044) but not for any of the other tests. CONCLUSIONS: VDJ landing depth influences knee kinematics in women. Landing depth may therefore be considered when screening athletes using the VDJ test. Also, muscle strength seems to influence the amount of knee valgus angles, but the difference was not statistically significant (except for the BJ test) in this small cohort.