Carolin Hildebrandt

An Overview of Recent Application of Medical Infrared Thermography in Sports Medicine in Austria

Medical infrared thermography (MIT) is used for analyzing physiological functions related to skin temperature. Technological advances have made MIT a reliable medical measurement tool. This paper provides an overview of MIT’s technical requirements and usefulness in sports medicine, with a special focus on overuse and traumatic knee injuries. Case studies are used to illustrate the clinical applicability and limitations of MIT. It is concluded that MIT is a non-invasive, non-radiating, low cost detection tool which should be applied for pre-scanning athletes in sports medicine.

The relationship between ACL injuries and physical fitness in young competitive ski racers: a 10-year longitudinal study

Background Epidemiological studies have shown a high incidence of anterior cruciate ligament (ACL) injuries among competitive alpine skiers. Little is known regarding modifiable risk factors in young skiers. There are still uncertainties in gender-related risk factors. Objective The purpose of this study was to determine the relationship between ACL injuries and internal risk factors. Methods Retrospective data analyses were performed based on a group of 175 female and 195 male alpine ski racers between the ages of 14 and 19 years. The athletes underwent physical testing annually from 1996 to 2006. Z score transformations normalised the age groups. Multivariate binary logistic regressions were calculated for men and women separately to detect significant predictors of ACL ruptures. t Tests were computed to reveal the differences in test scores between injured and non-injured athletes. Results A total of 57 (15%) ACL injuries occurred. The female−male risk ratio (RR) was higher in females (2.3, 95% CI 1.3 to 4.2). Z scores for relative leg force, ratio of absolute core flexion to extension force, relative core strength and reactive strength index were predictive variables for men. Z scores of all of these predictive variables except relative leg force were higher in the non-injured group. The ratios of absolute flexion to extension force and absolute core strength were predictive covariates for women. Z scores for absolute core strength were higher in the non-injured group. Conclusions The risk of ACL injury was greater in female athletes. The findings suggest that core strength is a predominant critical factor for ACL injuries in young ski racers.

The Application of Medical Infrared Thermography in Sports Medicine

Medical Infrared Thermography (MIT) is a non-radiating and contact-free technology to monitor physiological functions related to skin temperature control. The efficiency, safety and low cost of MIT make it a useful auxiliary tool for detecting and locating thermal abnormalities characterized by increases or decreases in skin surface temperature. It has been successfully utilized in the field of veterinary medicine to detect locomotion injuries in racehorses and to monitor their health status. However, research on human athletes with modern infrared sensor technology is more rare. Athletes are exposed to physical stress in training and during competition season. Overuse reactions and so-called “minor traumas” are very frequent; therefore, early detection is critical to avoid injuries. Research suggests that the most beneficial application of MIT is the screening of individuals for overuse injuries. In the following chapters, the use of MIT in clinical practice is presented with special focus on sports injuries and exercise-induced physiological functions. Case studies illustrate the clinical applicability.

The role of a relative age effect in the first winter Youth Olympic Games in 2012

Background Owing to the separation into age groups at the first winter Youth Olympic Games (YOG), athletes differed in age by up to two years, leading to a potential relative age effect (RAE). Objective The purpose of this study was to define the role of the RAE in the first winter YOG with regard to sex, type of sport and performance. Methods The birth dates and anthropometric data of all 1021 athletes (557 male, 464 female, 14–19 years old) participating in 15 sports were analysed. A χ2 test was used to assess the difference between the observed and expected birth distributions. ANOVA (analysis of variance) and Kruskal−Wallis analyses were used to investigate differences in anthropometrics. Results The birth date distribution of the overall sample was significantly different from an equal distribution, with an over-representation of athletes born shortly after the cut-off date (χ2=284.7, p<0.001). A significant RAE was found in both male (χ2=245.1, p<0.001) and female competitors (χ2=74.6, p<0.001). An analysis based on the type of sport showed an RAE in all categories (strength—χ2=229.9, p<0.001, endurance—χ2=60.4, p<0.001 and technique-related sports χ2=25.2, p=0.001). Relatively older competitors were also over-represented among medal winners (χ2=47.9, p<0.001). Relatively older male competitors were significantly taller (p=0.005) and heavier (p<0.001) than younger competitors. No differences were found in female competitors. Conclusions The results suggest that relative age had a highly significant influence on participation in various sports regardless of sex. A possible strategy to reduce the RAE would be a fixed quota for each birth year within the two-year age group across events.

The Role of a Relative Age Effect in the 12th Winter European Youth Olympic Festival in 2015

The aim of this study was to define the role of the relative age effect in the 12th Winter European Youth Olympic Festival 2015. The birth dates of all 899 participants and anthropometric data of 655 participants were analyzed. A significant relative age effect was present in the total sample and among the male athletes but not in the female athletes. Additionally, a significant relative age effect was present in strength- and endurance-related sports but not in technique-related sports. Statistically significantly more older athletes won medals. Relative age had a strong influence on participation in strength- and endurance-related sports as well as on performance.

Biological Maturity Status Strongly Intensifies the Relative Age Effect in Alpine Ski Racing.

The relative age effect (RAE) is a well-documented phenomenon in youth sports. This effect exists when the relative age quarter distribution of selected athletes shows a biased distribution with an over-representation of relatively older athletes. In alpine ski racing, it exists in all age categories (national youth levels up to World Cup). Studies so far could demonstrate that selected ski racers are relatively older, taller and heavier. It could be hypothesized that relatively younger athletes nearly only have a chance for selection if they are early maturing. However, surprisingly this influence of the biological maturity status on the RAE could not be proven, yet. Therefore, the aim of the present study was to investigate the influence of the biological maturity status on the RAE in dependence of the level of competition. The study investigated 372 elite youth ski racers: 234 provincial ski racers (P-SR; high level of competition) and 137 national ski racers (N-SR; very high level of competition). Anthropometric characteristics were measured to calculate the age at peak height velocity (APHV) as an indicator of the biological maturity status. A significant RAE was present among both P-SR and N-SR, with a larger effect size among the latter group. The N-SR significantly differed in APHV from the P-SR. The distribution of normal, early and late maturing athletes significantly differed from the expected normal distribution among the N-SR, not among the P-SR. Hardly any late maturing N-SR were present; 41.7% of the male and 34% of the female N-SR of the last relative age quarter were early maturing. These findings clearly demonstrate the significant influence of the biological maturity status on the selection process of youth alpine ski racing in dependence of the level of competition. Relatively younger athletes seem to have a chance of selection only if they are early maturing.

Influential Factors on the Relative Age Effect in Alpine Ski Racing.

The relative age effect (RAE), which refers to an over-representation of selected athletes born early in the selection year, was proven to be present in alpine ski racing in all age categories at both national and international levels. However, the influential factors on, or the causal mechanisms of, the RAE are still unknown. Therefore, the aim of the present study was to examine three possible influential factors on the relative age effect in alpine skiing: physical performance, anthropometric characteristics and biological maturational status. The study included the investigation of 282 elite Austrian youth ski racers and 413 non-athletes (comparison group) of the same age (10–13 years) and region. Six physical performance tests were performed, body mass and height were assessed, and the age at peak height velocity (APHV) was calculated. A significant RAE was present in the ski racers. No differences were shown in the physical performance characteristics or in the calculated APHV between the relative age quarters. These results suggest that ski racers born in the last quarter can counteract the relative age disadvantages if they already present the same level of physical performance and maturational status as those born at the beginning of the year. The height and weight of ski racers born at the beginning of the year were significantly higher compared to the non-athletes, and ski racers born in relative age quarter 1 were taller and heavier compared to the ski racers of the other quarters. This indicates that the anthropometric characteristics influence the selection process in alpine ski racing, and that relatively older athletes are more likely to be selected if they exhibit advanced anthropometric characteristics.

Injuries and illnesses in a cohort of elite youth alpine ski racers and the influence of biological maturity and relative age: a two-season prospective study

Background Studies on injuries and illnesses involving youth ski racers younger than 15 years are lacking in the literature. The aim of this study was prospectively to assess the incidence, prevalence, and severity of traumatic and overuse injuries, as well as illnesses of elite youth ski racers with regard to sex, biological maturity status, and relative age. Subjects and methods A prospective, longitudinal cohort design was used to monitor the anthropometrics, training characteristics, traumatic and overuse injuries, and illnesses of 82 elite youth ski racers (51 males, 31 females, age 9–14 years) over 2 consecutive years. The exact training exposure (skiing and athletic) was recorded. Relative age and estimated biological maturity status were assessed. Results Relatively low injury incidence or prevalence (traumatic, 0.86/1,000 hours of training; overuse, 0.28/1,000 hours) and comparably high illness prevalence (2.4/athlete) were reported. The knee was the most commonly affected body part (traumatic injuries 36.5%, overuse injuries 82%). A high number of bone fractures were revealed (46%), while no stress fractures occurred; 66% of the illnesses were respiratory tract infections. No differences were found between males and females, the differing maturity groups, or relative age quartiles. Early-maturing athletes had comparably low traumatic and overuse-injury rates. Relatively younger athletes had low traumatic injury rates. Conclusion The injury-prevention measures implemented in the training process of youth ski racers seem to contribute to a low incidence of injury. Biological maturity status should be considered in the training process to prevent injuries in late-maturing athletes.

Long-Term Athletic Development in Youth Alpine Ski Racing: The Effect of Physical Fitness, Ski Racing Technique, Anthropometrics and Biological Maturity Status on Injuries

Alpine ski racing is known to be a sport with a high risk of injuries. Because most studies have focused mainly on top-level athletes and on traumatic injuries, limited research exists about injury risk factors among youth ski racers. The aim of this study was to determine the intrinsic risk factors (anthropometrics, biological maturity, physical fitness, racing technique) for injury among youth alpine ski racers. Study participants were 81 youth ski racers attending a ski boarding school (50 males, 31 females; 9–14 years). A prospective longitudinal cohort design was used to monitor sports-related risk factors over two seasons and traumatic (TI) and overuse injuries (OI). At the beginning of the study, anthropometric characteristics (body height, body weight, sitting height, body mass index); biological maturity [status age at peak height velocity (APHV)]; physical performance parameters related to jump coordination, maximal leg and core strength, explosive and reactive strength, balance and endurance; and ski racing technique were assessed. Z score transformations normalized the age groups. Multivariate binary logistic regression (dependent variable: injury yes/no) and multivariate linear regression analyses (dependent variable: injury severity in total days of absence from training) were calculated. T-tests and multivariate analyses of variance were used to reveal differences between injured and non-injured athletes and between injury severity groups. The level of significance was set to p < 0.05. Relatively low rates of injuries were reported for both traumatic (0.63 TI/athlete) and overuse injuries (0.21 OI/athlete). Athletes with higher body weight, body height, and sitting height; lower APHV values; better core flexion strength; smaller core flexion:extension strength ratio; shorter drop jump contact time; and higher drop jump reactive strength index were at a lower injury risk or more vulnerable for fewer days of absence from training. However, significant differences between injured and non-injured athletes were only observed with respect to the drop jump reactive strength index. Regular documentation of anthropometric characteristics, biological maturity and physical fitness parameters is crucial to help to prevent injury in youth ski racing. The present findings suggest that neuromuscular training should be incorporated into the training regimen of youth ski racers to prevent injuries.

Limb symmetry index in competitive alpine ski racers: Reference values and injury risk identification according to age-related performance levels

Highlights • The suggested thresholds to define asymmetries should be defined for strength- and coordination-related tasks separately.• Youth ski racers showed greater limb asymmetries than elite skiers.• Limb dominance in unilateral leg extension strength is associated with injury risk in youth ski racers.• Asymmetries should be described as percentage values based on limb dominance rather than left/right leg dominance.