Extraction of material parameters for the simulation of heat treatments of cast aluminium alloys through unified models

The objective of this work, which is part of the IDEAL (Integrated Development Routes for Optimized Cast Aluminium Components) project, financed by the EU in frame work 6 and born in collaboration with the automobile and foundry industries, is to simulate creep behavior of aluminum cast samples subjected to high temperature. In this paper a two-state variables unified model is applied in order to simulate creep behavior and time-dependent metallurgical changes. The fundamental assumption of the unified theory is that creep and viscoplasticity, which are both irreversible strains developed because of dislocations motion in the material structure, can be modelled through the implementation of a similar plastic strain velocity law, generally called flow rule. The paper shows how to obtain the material data needed for the simulation of the stress-strain behavior of aluminum at high temperature. As an example, the analysis of several tests performed at various temperatures and strain rates on a particular aluminum alloy, is presented as well. Furthermore, the one dimensional code developed during this project is illustrated and a simulation is run using the material data obtained through the mentioned experimental study. The results obtained for the simulation of tensile tests and of creep tests are compared with experimental curves, showing a good agreement

Greater understanding of normal hip physical function may guide clinicians in providing targeted rehabilitation programmes

Objectives: This study investigated tests of hip muscle strength and functional performance. The specific objectives were to: (i) establish intra- and inter-rater reliability; (ii) compare differences between dominant and non-dominant limbs; (iii) compare agonist and antagonist muscle strength ratios; (iv) compare differences between genders; and (v) examine relationships between hip muscle strength, baseline measures and functional performance. Design: Reliability study and cross-sectional analysis of hip strength and functional performance. Methods: In healthy adults aged 18-50. years, normalised hip muscle peak torque and functional performance were evaluated to: (i) establish intra-rater and inter-rater reliability; (ii) analyse differences between limbs, between antagonistic muscle groups and genders; and (iii) associations between strength and functional performance. Results: Excellent reliability (intra-rater ICC = 0.77-0.96; inter-rater ICC = 0.82-0.95) was observed. No difference existed between dominant and non-dominant limbs. Differences in strength existed between antagonistic pairs of muscles: hip abduction was greater than adduction (p < 0.001) and hip ER was greater than IR (p < 0.001). Men had greater ER strength (p = 0.006) and hop for distance (p < 0.001) than women. Strong associations were observed between measures of hip muscle strength (except hip flexion) and age, height, and functional performance. Conclusions: Deficits in hip muscle strength or functional performance may influence hip pain. In order to provide targeted rehabilitation programmes to address patient-specific impairments, and determine when individuals are ready to return to physical activity, clinicians are increasingly utilising tests of hip strength and functional performance. This study provides a battery of reliable, clinically applicable tests which can be used for these purposes

Screening to Detect Hip and Groin Problems in Elite Adolescent Football (Soccer) Players – Friend or Foe?

Injury prevention strategies in team settings should not overlook early detection and secondary prevention. Monitoring systems may be an effective approach to detect common and troublesome injuries, such as hip and groin pain in football (soccer) players. The purpose of this International Perspective is to share our experiences with monitoring hip and groin pain in youth academy football and discuss challenges that surfaced. We consider why players may not accurately report pain, their perceptions of groin pain, and whether all groin pain is clinically meaningful. # Level of Evidence

Injuries in youth football and the relationship to player maturation: an analysis of time-loss injuries during four seasons in an English elite male football academy

A better insight into injuries in elite youth football may inform prevention strategies. The purpose of this prospective cohort study was to investigate the frequency, incidence and pattern of time-loss injuries in an elite male football academy, exploring injuries in relation to age and maturation status. Across four consecutive playing seasons, playing exposure and injuries to all academy players (U’9 to U’21) were recorded by club medical staff. Maturation status at the time of injury was also calculated for players competing in U’13 to U’16 aged squads. Time-loss injury occurrence and maturation status at time of injury were the main outcome measures. A total of 603 time-loss injuries were recorded, from 190 different players. Playing exposure was 229,317 hours resulting in an overall injury rate of 2.4 p/1000h, ranging from 0.7 p/1000h (U’11) to 4.8 p/1000h (u’21). Most injuries were traumatic in mechanism (73%). The most common injury location was the thigh (23%) and the most common injury type was muscle injury (29%) combining to provide the most common injury diagnosis; thigh muscle injury (17%). In U’13-U’16 players, a higher number of injuries to early-maturing players were observed in U’13-U’14 players, whilst more injuries to U’15-U’16 players occurred when classed as ‘on-time’ in maturity status. Maturation status did not statistically relate to injury pattern, however knee bone (not-fracture) injuries peaked in U’13 players whilst hip/groin muscle injuries peaked in U’15 players

Hip abduction weakness in elite junior footballers is common but easy to correct quickly: a prospective sports team cohort based study

Background: Hip abduction weakness has never been documented on a population basis as a common finding in a healthy group of athletes and would not normally be found in an elite adolescent athlete. This study aimed to show that hip abduction weakness not only occurs in this group but also is common and easy to correct with an unsupervised home based program. Methods: A prospective sports team cohort based study was performed with thirty elite adolescent under-17 Australian Rules Footballers in the Australian Institute of Sport/Australian Football League Under-17 training academy. The players had their hip abduction performance assessed and were then instructed in a hip abduction muscle training exercise. This was performed on a daily basis for two months and then they were reassessed.Results: The results showed 14 of 28 athletes who completed the protocol had marked weakness or a side-to-side difference of more than 25% at baseline. Two months later ten players recorded an improvement of ≥ 80% in their recorded scores. The mean muscle performance on the right side improved from 151 Newton (N) to 202 N (p<0.001) while on the left, the recorded results improved from 158 N to 223 N (p<0.001). Conclusions: The baseline values show widespread profound deficiencies in hip abduction performance not previously reported. Very large performance increases can be achieved, unsupervised, in a short period of time to potentially allow large clinically significant gains. This assessment should be an integral part of preparticipation screening and assessed in those with lower limb injuries. This particular exercise should be used clinically and more research is needed to determine its injury prevention and performance enhancement implications

Hip strength and range of motion: normal values from a professional football league

To determine the normal profiles for hip strength and range of motion (ROM) in a professional football league in Qatar, and examine the effect of leg dominance, age, past history of injury, and ethnicity on these profiles.Cross-sectional cohort study.Participants included 394 asymptomatic, male professional football players, aged 18-40 years. Strength was measured using a hand held dynamometer with an eccentric test in side-lying for hip adduction and abduction, and the squeeze test in supine with 45° hip flexion. Range of motion measures included: hip internal and external rotation in 90° flexion, hip IR in prone, bent knee fall out and hip abduction in side-lying. Demographic information was collected and the effect on the profiles was analysed using linear mixed models with repeated measures.Strength values (mean±SD) were: adduction=3.0±0.6Nm/kg, abduction=2.6±0.4Nm/kg, adduction/abduction ratio=1.2±0.2, Squeeze test=3.6±0.8N/kg. Range of motion values: internal rotation in flexion=32±8°, external rotation=38±8°, internal rotation in prone=38±8°, bent knee fall out=13±4.4cm, abduction in side-lying=50±7.3°. Leg dominance had no clinically relevant effect on these profiles. Multivariate analysis demonstrated that age had a minor influence on squeeze strength (-0.03N/kg/year), external rotation (-0.30°/year) and abduction range (-0.19°/year) but past history of injury, and ethnicity did not.Normal values are documented for hip strength and range of motion that can be used as reference profiles in the clinical assessment, screening, and management of professional football players. Leg dominance, recent past injury history and ethnicity do not need to be accounted for when using these profiles for comparison purposes