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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 (weak median vs strong median). 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 weak median group compared with the strong median group in females (p 0.011). A relative 1RM squat 1.05 kg (105% of bodyweight) was established as the best cutoff 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.

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Reduced isometric hip-abductor strength predisposed competitive male soccer players to noncontact lateral ankle sprains.

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The positive effect of physical activity and exercise on bone mass is well documented in several studies comparing with sedentary subjects. Recent studies have reported that cardiovascular fi tness and weight-bearing exercise affect bone mass benefi cially. Although it is widely accepted that muscle strength is signifi cantly correlated with bone mass, little is known about anaerobic power and its relation to bone mass. Therefore, the purpose of this study was to analyse the relation between bone mass and anaerobic power in professional jumpers. Thirty professional men jumpers (long, high and triple jumping) with no history of bone disease participated in this study (mean±SD, aged 21.27±3.52 years, height 182±6 cm, weight 69.93±6.01 kg). Bone mineral content (BMC) and bone mineral density (BMD) were measured by dual-energy x-ray absorptiometry. Femoral neck and trochanter BMC and BMD for right and left sides and also lumbar spines were assessed. Sargent jump test was performed by athletes and records were converted to anaerobic power using Lewis formulae. Pearson correlation test was used to analyse data. Results of this study showed a positive relationship between femoral neck and trochanter BMC and anaerobic power (r=0.557, p<0.05). Similar result was found for femoral neck and trochanter BMD and anaerobic power (r=0.446, p<0.05). In conclusion, long-term jumping, is associated with markedly increased BMC and BMD at the femoral neck and trochanter and it can be accounted as one of the important environmental factors to determine femoral BMC and BMD in elite jumpers.

RESULTS: There were no significant difference between groups or between lower extremity dominance for concentric knee extension and flexion peak torque, total work and work fatigue index. However, peak torque agonist/antagonist ratio was lower (p = 0.032) in AS than SS group for both dominant (AS = 46.5±4.7%; SS = 52.2 ± 5.8%) and non-dominant (AS = 47.8 ± 3.9%; SS = 53.5 ± 6.0%) lower extremities. CONCLUSION:Peak torque agonist/antagonist ratio was greater in SS than AS short distance elite swimmers during knee extension-flexion isokinetic test. These results suggest the need for designing training programs to improve strength balance between hamstrings and quadriceps muscles of front crawl and backstroke short distance elite swimmers PURPOSE: Compare the VO2 response during walking on land vs walking in water at selected water depths in normal and over weight female subjects. METHODS:Eighteen subjects aged 45±13 yrs, body mass of 80±18 kg and body mass index (BMI) of 29.0±6.2 kg/m 2 were divided into two groups (n = 9) based on BMI <26 (LOBMI, body mass = 65.4±6.3 kg, BMI = 23.5±1.5) and BMI >30 (HIBMI, body mass = 95.84±14.8 kg, BMI = 34.6±3.2 kg/m 2 ). Each group walked on a land treadmill (land) in 24° C air and on three separate days in a water treadmill (ATM, Hydroworx tm ) at 30° C. Sessions consisted of six 5-min walking bouts of 2. 41, 3.22, 4.02, 4.83, 5.63 and 6.44 Km per hour. Water depth was at the xiphoid (xip), 10 cm below (-10 cm), and 10 cm above xip (+10 cm). Heart rate (HR) and relative VO2 (ml/kg/min) were recorded during the final three min and averaged. RESULTS:Although VO2 increased (P<0.05) with speed on land LOBMI (12.55±2.04 ml/kg/min) was similar to HIBMI (11.21±2.03). In water, regardless of depth LOBMI VO2 was greater (p<0.05) than HIBMI (+10cm: 13.16 vs 9.94; xip:15.46 vs 12.51; -10cm: 17.44 vs 13.77 ml/kg/min) across all speeds. CONCLUSIONS:These results suggest that BMI influences energy expenditure in water. The potential influence of greater buoyancy in overweight subjects suggest an index of adiposity (ie., body fat%) may prove to be an effective predictor of energy expenditure during walking in shallow water.

The purpose of this study was to determine the validity and reliability of the Persian version of the Vividness of the Movement Imagery Questionnaire 2 (VMIQ-2). In the fi rst stage validity and reliability and in the second stage concurrent validity questionnaire VMIQ-2 by a Persian version of the Movement Imagery Questionnaire revised was evaluated. In the fi rst stage of this study, 125 male and 96 female athletes of different levels of competition and in the second stage, 20 male and 30 female athletes from the two levels of competitive and non-competitive sports were studied. For the main component analysis, factor analysis and to confi rm the structure of the questionnaire varimax rotation was used. The Kronbakh α applied for measuring the reliability between subscales and the correlation method was used for determining the relationship between subscales, structure determination of validity and also to determine the validity of two simultaneous questionnaires MIQ-R and VMIQ-2. The results showed that about 47% of the questions related to the variance VMIQ were covered. Values of α coeffi cients for subscales of visual external and internal imagery, kinesthetic imagery and total scale, was respectively r=0. 86, r=0.89, r=0.91 and r=0.95, that suggests the existence of a high reliability in the subscales and overall scale vividness of movement imagery. Regarding its validity, the results showed that this questionnaire has concurrent validity (−0.70) and acceptable convergent validity of the construction between its subscales (p<0.001). It can be concluded that the Persian version of VMIQ-2 has the suitable validity and reliability.on 30 April 2019 by guest. Protected by copyright.