An 8-week injury prevention exercise program combined with change-of-direction technique training limits movement patterns associated with anterior cruciate ligament injury risk.

Knee ligament sprains are common during change-of-direction (COD) maneuvers in multidirectional team sports. This study aimed to compare the effects of an 8-week injury prevention exercise program containing COD-specific exercises and a similar program containing linear sprint exercises on injury- and performance-related variables during a 135° COD task. We hypothesized that the COD-specific training would lead to (H1) stronger reductions in biomechanical variables associated with anterior cruciate ligament (ACL) injury risk during COD, i.e. knee abduction moment and angle, hip internal rotation angle and lateral trunk lean, and (H2) more effective improvements in COD performance according to the COD completion time, executed angle, ground contact time, and approach speed. Twenty-two sports science students (40% female) completed biomechanical assessments of COD movement strategies before and after participating in two supervised 25-min training sessions per week over 8 weeks. We observed significant 'training x group' interaction effects in support of H1: the COD-specific training but not the linear sprint training led to reduced peak knee abduction moments (interaction, p = 0.027), initial knee abduction (interaction, p < 0.001), and initial lateral trunk lean angles (interaction, p < 0.001) compared to baseline. Although the COD-specific training resulted in sharper executed angles (interaction, p < 0.001), the sprint-specific training group showed reduced COD completion (interaction, p = 0.037) and ground contact times (interaction, p < 0.001). In conclusion, a combination of generic and COD-specific injury prevention training resulted in COD technique adaptations that can help to avoid ACL injury-prone COD movements but may negatively affect COD speed.

Functional assessments for decision-making regarding return to sports following ACL reconstruction. Part II: clinical application of a new test battery.

PURPOSE: The purpose of this study was to utilize a novel functional test system to facilitate determining the time of return to sports following ACL reconstruction. METHODS: Sixty-nine patients with unilateral ACL reconstruction were included in this pilot study. All the patients performed a standardized test battery consisting of one- and two-legged stability tests, counter movement jumps, speedy jumps, plyometric jumps and a quick feed test. The first test was administered on average 170.7 ± 75.1 days post-operatively, and the retest was administered on average 239.1 ± 79.7 days post-operatively. The values of the subtests were compared with the normative data of healthy gender- and age-matched controls to determine the functional capacities of patients following ACL reconstruction. RESULTS: After the first and second test, 15.9 and 17.4 % of the patients met the criteria for a "return to non-competitive sports". One patient fulfilled the criteria for a "return to competitive sports" after the second test battery. The most limiting factor was a poor LSI value of <90 % if the dominant leg was involved and <80 % if the non-dominant leg was involved. CONCLUSION: This test battery demonstrates that, in terms of neuromuscular abilities, most patients, compared to healthy controls, are most likely not ready for a safe return to sports, even 8 months post-operatively. This should be considered in the future to determine when it is safe to return to sports and should avoid a premature return to competitive sports. LEVEL OF EVIDENCE: III.

[The assessment of biological maturation for talent selection - which method can be used?]. / Die Erhebung des biologischen Entwicklungsstandes für die Talentselektion - welche Methode eignet sich?

BACKGROUND: The biological maturity status plays an important role in sports, since it influences the performance level and the talent selection in various types of sport. More mature athletes are favorably selected for regional and national squads. Therefore, the biological maturity status should be considered during the talent selection process. In this context, the relative age effect (RAE), which exists when the relative age quarter distribution of selected sports groups shows a biased distribution with an over-representation of athletes born in the first months after the specific cut-off-date for the competition categories, represents another problem in the talent development. From an ethical point of view, discrimination of young talented kids does exist: the relatively younger athletes have little to no chance of reaching the elite level, despite their talents and efforts. The causal mechanisms behind the RAE are still unclear and have to be assessed. In this context, the biological maturation seems to be a possible influential factor for the existence of a RAE in sport, which has to be examined. Several methods for estimating the biological maturity status exist; however, they are often expensive and not practicable. Consequently, the aim of the present study was to assess the concordance of a simple, yet accurate method of estimating biological maturation (prediction equation of age at peak height velocity, APHV) of Mirwald and co-workers, and the gold standard method of estimating skeletal age (SA, the x-ray of the left wrist). METHODS: In total, 75 Austrian students (40♂, 35♀) aged 10 - 13 years, were examined. Thirty of the participants (17♂, 13♀) were students of a well-known Austrian ski boarding school, and 45 (23♂, 22♀) of a non-sportive secondary modern school of the same region. The participants included in the study had not experienced a rupture of the carpal bones of the left wrist. Parents and participants were informed of the study aims, requirements and risks before providing written informed consent. The study was performed according to the Declaration of Helsinki. The study was approved by the Board for Ethical Questions in Science (Nr.: 2/2014) and the Institutional Ethics Review Boards for Human Research. For the prediction equations, the body height, the body mass and the sitting height were examined 8. The actual CA at time of measurement, and the leg length as the difference between body height and sitting height were calculated. These parameters were used to predict MO as time before or after PHV for boys and girls using the prediction equations of Mirwald et al. 19. According to Malina and Koziel 8, the participants were classified as late, on time (average) or early maturing on the basis of their APHV relative to the sample mean and standard deviation separated by sex. Participants within plus/minus the standard deviation of the mean were considered on time; participants with APHV > mean + standard deviation were classified late, while those with APHV < mean - standard deviation were classified early. An expert in pediatric endocrinology evaluated the x-rays of the left-hand wrist with the Greulich-Pyle-Method for assessing SA, the most widely used method of determining SA 24. The difference between SA and CA were calculated (= difference SA-CA). Consistent with other studies, the participants were divided into three groups according to their maturity status: on time or average maturity status was a SA within ±1 year of CA, late maturating was a SA behind CA of more than 1 year, and early maturating was a SA in advance of CA of more than 1 year 5 19 25. The most accurate method used to compare two methods of measurement is the Bland-Altman plot and the 95 % limits of agreement 26 27 28. Bland-Altman plots of the difference between difference in APHV (from the literature mean) and difference SA-CA (y-axis) and the mean of difference in APHV and difference SA-CA (x-axis) were performed. Approximately 95 % of the points in the plot should lie within the limits; then the concordance between the two methods of measurement is given 28. Additionally, intraclass correlation coefficients (ICC(3,1); two-way-mixed, total agreement) were calculated between difference in APHV and difference SA-CA. Chi²-tests were used to assess the difference in the percentage of pupils classified as on time, early or late maturing between the classifications based on the SA and on APHV, respectively. The level of significance was set at p < 0.05 and for highly significant at p < 0.01. All of the calculations were performed using PASW Statistics V.21.0. RESULTS: Chi²-tests did not show any significant differences (p = 0.404) in the percentage of participants classified as on time, early or late maturing between the two classifications based on SA and on APHV, respectively, neither for the total sample, nor for the two groups ski racers and non-athletes. The Bland-Altman analysis showed that more than 95 % of the points in the plot lie within the limits; consequently, there is concordance between the two methods with regard to estimating biological maturation. The ICC(3,1) statistics showed a highly significant correlation: p = 0.002, ICC (95 % CI) = 0.48 (0.13 - 0.69). CONCLUSIONS: The prediction equations to determine APHV seem to be a valid method of assessing the biological maturity status of youths aged 10 - 13 years. The percentage of pupils classified as on time, early or late maturing did not differ significantly between the classifications based on the two methods. Also the Bland-Altman analysis proved the concordance between the two methods. The RAE could be influenced and strengthened by the biological age in sports in which advantages in maturity parameters are important. Athletes born early in the selection year, who are also at the same time advanced in maturity, might be advantaged in the selection process. However, since the prediction equations seem to be valid, this method can be used in the future in the talent selection process in order to not disadvantage late-maturing athletes, which in turn could result in the reduction of the occurrence of the RAE in various types of sports in the future. In talent selection processes the growth spurt and the implemented changes in proportions between core and the extremities are often not considered; although it was shown that during this period, athletes showed poor performances in physical fitness. Since physical fitness is an important criterion in talent selection processes, athletes who go through their individual peak growth spurt at the time of selection have disadvantages due to the diverse proportions. As a consequence, it seems important to know the athlete's APHV in order to consider the variations in physical performance caused by developmental changes. The prediction equations to determine APHV include the leg length and sitting height in order to consider the diverse proportions between core and extremities; hence, this method seems to be accurate and should be implemented in the talent selection process.

An isometric hand tester: quantifying motor function in the hand.

The aim of this study was to develop and assess an isometric hand tester to measure multiple strength parameters of the muscles of the hand. Nineteen men and 22 women took part in a first study and 17 men were tested in a second one. Five different tests were developed: wrist flexion, wrist extension, metacarpophalangeal joint flexion, thumb adduction and proximal and distal interphalangeal joint flexion. Reliability was tested with an intraclass correlation coefficient for single measures. When the results from men and women were analysed separately, all tests except metacarpophalangeal joint flexion and thumb adduction produced intraclass correlation coefficients greater than 0.7. Combining the genders gave intraclass correlation coefficients greater than 0.9 except for metacarpophalangeal joint flexion and thumb adduction. After adjustments, intraclass correlation coefficients for metacarpophalangeal joint flexion and thumb adduction were between 0.70 and 0.83 in the second study. The new isometric hand tests improve the measurement of intrinsic and extrinsic hand muscle strength.

[Influence of ski boots on balance performance]. / Einfluss des Skischuhs auf das Gleichgewichtsverhalten.

INTRODUCTION: Modern ski carving technique demands that skiers have a strong sense of balance and edge their skis with precision and feeling. Stiff ski boots facilitate the transfer of power to the ski but increase the difficulty of balancing. The aim of this study was to analyse the influence of ski boots on balance performance of alpine skiers. METHODS: 76 experienced skiers (female 33/male 43) and 76 ski racers of the Skigymnasium Stams (female 31/male 45) were tested on the MFT S 3 Check with and without ski boots. RESULTS: Ski boots significantly influenced balance. There were also significant differences between experienced skiers and ski racers, but gender differences were minimal. DISCUSSION: In addition to general conditioning, skiers should utilise general and ski-specific balance and sensomotor training which could help in ski injury prevention, especially knee injuries.

[S3-Check--evaluation and generation of normal values of a test for balance ability and postural stability]. / S3-Check--Evaluierung und Normwerteerhebung eines Tests zur Erfassung der Gleichgewichtsfähigkeit und Körperstabilität.

INTRODUCTION: Balance is very important in daily living, but there are practically no balance evaluation methods which fulfill scientific criteria and are available to the fitness community and other groups. The aims of this paper are to determine if the MFT-S3-Check, a system to measure balance, is scientifically objective, valid and reliable; and to establish norms for the MFT S 3-Check system. METHODS: Reliability was evaluated with 30 subjects in two testing sessions on two different days. Objectivity was determined by having two different test administrators test 10 subjects. Norms were generated from the data of over 5000 subjects (8 - 70 years of age). Validity was checked by comparing norms to data collected from 758 tests performed on ski racers (10 - 18 years of age). RESULTS: The objectivity and reliability tests for the sensor motor and stability indexes produced correlations which were moderate to very high. Norms were created for all age groups (female, male). The ski racers had significantly better values than the norms. DISCUSSION: The MFT S 3-Check fulfills the scientific criteria and is in use in fitness settings and in physiotherapy.

Frontal plane leg alignment and muscular activity during maximum eccentric contractions in individuals with and without patellofemoral pain syndrome.

PURPOSE: The role of frontal plane tibiofemoral alignment in subjects with patellofemoral pain syndrome (PFPS) is controversial and rarely discussed in the literature. As well, little research has been done on the effects of the hamstrings muscles on PFPS. The aim of the current study was to determine whether, in individuals with PFPS, frontal plane tibiofemoral alignment or muscular activity of the index knee's crossing muscles is altered during maximum eccentric leg press exercise. METHODS: This cross-sectional study involved 19 patients with PFPS and 19 control subjects who were matched according to gender, age, and physical activity. During eccentric leg press action, frontal plane tibiofemoral alignment was assessed with a motion analysis system based on skin markers. Simultaneously, surface-electromyography was used to assess the activity levels of the relevant knee crossing muscles. To assess the activity under functional conditions, a leg press with a footplate having variable stability was used for barefoot testing. RESULTS: The PFPS subjects did not have significantly different frontal plane leg alignment compared to controls. On electromyography (EMG), PFPS patients had significantly lower levels of hamstring activity during eccentric leg exercise. The differences between the two groups (%; absolute differences normalized EMG) ranged from 20% (semitendinosus; stable footplate; p=0.017) to 21% (biceps femoris; unstable footplate; p=0.019) and 32% (semitendinosus; unstable footplate; p=0.002). CONCLUSIONS: PFPS is not linked to altered frontal plane leg alignment during eccentric leg pressing. However, PFPS is associated with eccentric under-activation of the hamstrings, which may be a compensatory strategy that maintains patellofemoral joint pressure within bearable levels.

Specific fitness training and testing in competitive sports.

Improvements of athletic capacity in high-performance sport are mainly achieved through an increase of the quality of training. In physical preparation, the quality of training can be improved by developing highly specific means of training. The aim of this paper is to present three examples of how highly specific means of fitness training of world class athletes can be developed. The first example presents a test profile of specific motor abilities of top class tennis players, the second one deals with the improvement of specific strength training methods for ski jumpers, and the third deals with the development of specific training devices of Alpine ski racers.

Knee joint forces during downhill walking with hiking poles.

The aim of this study was to determine external and internal loads on the knee joint during downhill walking with and without hiking poles. Kinematic, kinetic and electromyographic data were collected from eight males during downhill walking on a ramp declined at 25 degrees. Planar knee joint moments and forces were calculated using a quasi-static knee model. The results were analysed for an entire pole-cycle as well as differentiated between single and double support phases and between each step of a pole-cycle. Significant differences between downhill walking with and without hiking poles were observed for peak and average magnitudes of ground reaction force, knee joint moment, and tibiofemoral compressive and shear forces (12-25%). Similar reductions were found in patellofemoral compressive force, the quadriceps tendon force and the activity of the vastus lateralis; however, because of a high variability, these differences were not significant. The reductions seen during downhill walking with hiking poles compared with unsupported downhill walking were caused primarily by the forces applied to the hiking poles and by a change in posture to a more forward leaning position of the upper body, with the effect of reducing the knee moment arm.

Comparisons of the ski turn techniques of experienced and intermediate skiers.

We compared selected kinematic variables for four different ski turn techniques performed by five experienced and five intermediate male skiers. The four ski turn techniques were the upstem turn, the downstem turn, the parallel turn and the parallel step turn. Each turn was divided into the initiation phase and the first and second steering phases. Most of the statistically significant differences (P < 0.05) between the two groups were found for the initiation phases of the four turns. Both the hip axis-hand axis angle and the edging angle of the uphill ski were significantly different between the two groups for the upstem turn at the beginning of the initiation phase. For the downstem turn, significant differences between the groups were found at the start of the initiation phase for the hip axis-hand axis angle, the shoulder axis-fall line angle, and the edging angle of the uphill ski. The standard deviation of the distance between the tips of the two skis over the second steering phase also differed significantly between the two groups. For the parallel step turn, significant differences were found at the start of the initiation phase for the edging angle of the downhill ski and the downhill ski to movement direction angle. Significant differences were also found for the edging angle of the downhill ski in the middle of the second steering phase and the shoulder axis to movement direction angle at the end of this phase. For the initiation phase of the parallel turn, significant differences were found for the timing of setting the ski pole, the uphill knee angle at the start of this phase and the range of the knee angle of the uphill leg from the start to the end of this phase. For this turn, significant differences between the two groups were also found for the edging angle of the downhill ski in the middle of the second steering phase and the shoulder axis to movement direction angle at the end of this phase. One of the reasons it was possible to identify a few significant differences only for the turns analysed, was the variability within the intermediate group: for most of the variables analysed, the standard deviation was much higher for the intermediate than for the experienced group.