Tobias Hein

Using the variability of continuous relative phase as a measure to discriminate between healthy and injured runners

Several studies have used variability of continuous relative phase (CRP) to investigate overuse injuries, since low variability is thought to be related to running injuries. This study investigates whether the analysis of CRP variability leads to additional information about possible differences or similarities between healthy and injured runners. Further, a decision about future applications of CRP variability should be based on the ability to implement and interpret data. 18 healthy female runners (CO) and 18 female runners who suffered from iliotibial band syndrome (ITBS) were evaluated by calculating CRP variability for 4 coupling pairs. Besides analyzing continuous variability of CRP, we also averaged it for the whole stance phase and for four predefined stance phase intervals. Confidence intervals were displayed and independent t-tests for comparing the two groups were conducted. During initial and terminal stance phase as well as after heel-off an increase in CRP variability was detected for both groups of runners. In contrast, the foot flat period was characterized by stable joint coordination and a decrease in variability. This paper presents possible interpretations of CRP variability but no statistically significant differences in CRP variability were found between the two groups of runners. Despite the missing statistical significance, a relationship between high CRP variability and injury seems to be conceivable, since the injured runners demonstrated an increased variability for all couplings in the first half of the stance phase. Further application of CRP variability in biomechanical research is essential to determine whether a relationship exists between injury and coordination variability.

Prospective analysis of intrinsic and extrinsic risk factors on the development of Achilles tendon pain in runners

There are currently no generally accepted, consistent results that clearly characterize factors causing Achilles tendon pain (AT) in runners. Therefore, we carried out a prospective study to evaluate the multifactorial influence of clinical, biomechanical (isometric strength measurements and three‐dimensional kinematics) and training‐related risk factors on the development of AT. Two hundred sixty‐nine uninjured runners were recruited and underwent an initial examination. One hundred forty‐two subjects completed their participation by submitting training information on a weekly basis over a maximal period of 1 year. Forty‐five subjects developed an overuse injury, with 10 runners suffering from AT. In an uninjured state, AT runners already demonstrated decreased knee flexor strength and abnormal lower leg kinematics (sagittal knee and ankle joint) compared with a matched control group. A relationship between years of running experience or previous overuse injuries and the development of new symptoms could not be established. The interrelationship of biomechanical and training‐specific variables on the generation of AT is evident. A combination of alterations in lower leg kinematics and higher impacts caused by fast training sessions might lead to excessive stress on the Achilles tendon during weight bearing and thus to AT in recreational runners.

Short-Term Exercise-Induced Changes in Hydration State of Healthy Achilles Tendons Can Be Visualized by Effects of Off-Resonant Radiofrequency Saturation in a Three-Dimensional Ultrashort Echo Time MRI Sequence Applied at 3 Tesla

Off‐resonant RF saturation influences signal intensity dependent on free and bound water fractions as well as the macromolecular content. The extent of interaction between these compartments can be evaluated by using the off‐resonance saturation ratio (OSR). Combined with UTE sequences quantification of OSR even in tendinous tissues with extremely fast signal decay is possible. The aim of this prospective study was to investigate short‐term exercise‐induced effects of hydration state of the Achilles tendon by means of OSR and tendon volume.

Evaluation of a six-week whole-body vibration intervention on neuromuscular performance in older adults.

Abstract Perchthaler, D, Grau, S, and Hein, T. Evaluation of a 6-week whole-body vibration intervention on neuromuscular performance in older adults. J Strength Cond Res 29(1): 86–95, 2015—Research in the field of whole-body vibration (WBV) for the enhancement of neuromuscular performance is becoming increasingly popular. However, additional understanding of optimal WBV training protocols is still necessary to develop optimal and effective training and prevention concepts, especially for elderly people. The intention of this study was to evaluate a 6-week WBV intervention program based on optimal vibration loads adapted from the literature on lower-limb strength parameters and performance, as well as on perceived exertion according to a subjective rating. A total of 21 older adults were allocated randomly into either a WBV training or control group (CO). Before and after the intervention period, jump height was measured during a countermovement jump. In addition, isolated isokinetic maximal knee extension and flexion strength, mean power, and work were recorded using a motor-driven dynamometer. Borgs scale for rating of perceived exertion was used to evaluate the intensity of WBV exercises within each training session. After the intervention period, jump height increased by 18.55% (p < 0.001) in the WBV group, whereas values of the CO remained unchanged. There were no statistically significant differences in isokinetic maximal strength, mean power, or work values in knee extension or flexion (all p > 0.05). Finally, the subjective perceived exertion of the WBV exercises and respective training parameters ranged between moderate rating levels of 7 and 13 of Borgs scale. Our data show that WBV is a feasible and safe training program for elderly people to increase multijoint strength performance of the lower limbs during a countermovement jump. This could help to determine the potential of WBV programs in training of the elderly to prevent age-related reduction of neuromuscular performance.

Diagnostic value of T1 and T2* relaxation times and off‐resonance saturation effects in the evaluation of achilles tendinopathy by MRI at 3T

To evaluate and compare the diagnostic value of T1, T2* relaxation times and off‐resonance saturation ratios (OSR) in healthy controls and patients with different clinical and morphological stages of Achilles tendinopathy.

Influence of Physical Activity on T1 and T2*Relaxation Times of Healthy Achilles Tendons at 3T

To evaluate longitudinal (T1) and transverse (T2*) relaxation times at different Achilles tendon locations (insertion, mid‐portion, and musculotendinous area) in a cohort of subjects with variable tendon straining activity, but without any signs of tendinopathy.

Anthropometric influences on dynamic foot shape: Measurements of plantar three-dimensional foot deformation

Purpose: Advances in scanner technology enable the capture of feet during walking. Knowledge of dynamic deformation is essential for fundamental research and application-oriented improvements in terms of comfortable and functional footwear. The core hypothesis of our study is that there is a relationship between dynamic foot measures and the anthropometric dimensions age, gender and body mass index. Methods: We measured the dynamic foot shape of 129 subjects (77 female, 52 male) with a plantar dynamic scanner system. During stance phase we captured maximum values (MaxDyn) and changes (ΔDyn) of length, width, and height measures as well as angles and indices of feet. We identified relationships between foot measures and anthropometric dimensions by two statistical methods: analysis of variance (ANOVA) between matched groups and multiple regression analysis within whole sample size. Results: MaxDyn values of foot width measures are higher in overweight subjects. Most important predictors of MaxDyn are static measures and gender, regarding values that characterise the longitudinal arch as well as lateral ball length. More dynamic deformation was found in ball and arch angle as well as medial ball length and ball width of overweight subjects and in width measures of women. Multiple regression analysis detects body weight as an important predictor for changes in foot width measures as well as arch height and angle. Conclusion: The ability to collect foot measures during natural walking is the basis for the following findings. First, our study confirms that static foot measures can be used as basic design criteria for footwear. Second, our study points out the influence of factors like gender and body weight on dynamic foot morphology. Consideration of these additional factors can essentially improve design methods and particularly the fit of footwear.

The effects of gender, age, and body mass on dynamic foot shape and foot deformation inchildren and adolescents

Purpose: The aim of the present study is to identify influences of gender, age, and body mass on the dynamic foot morphology and foot deformation of maturing feet. Only advancements in scanner technology enable recording of foot morphology during walking. Methods: Static and dynamic foot morphology of 2554 participants (6–16 years) were measured with DynaScan4D. Different foot measures corresponding to measures used in last construction were defined. Influences of gender, age, and body mass were calculated within the whole sample by multiple linear regression analysis and within matched groups by Students t-test. Results: The results of multiple linear regression analysis show similar patterns in boys and girls. The explained variance (R2) of the differences between static and dynamic foot morphology is low. R2 is higher for the maximum dynamic foot measures where the respective static value mainly predicts the dynamic value. Relative maximum dynamic values of foot height, width, and girth are higher in overweight, younger, and male participants. The deformation of the instep height and the angle of the fifth toe differ between overweight and normal weight participants. Between boys and girls as well as children and adolescents there are differences in the deformation of the ball area. Conclusion: There are effects of gender, age, and body mass on dynamic foot morphology and deformation. The differences are small regarding the high variability. Thus, dynamic adjustments are applicable without customising to gender, age, and body mass. However, it is important to account for the high variability and for static and dynamic situations. This should be discussed with focus on use of resilient materials. These results can improve footwear design and thus contribute to healthy foot development.

Do lower extremity kinematics and training variables affect the development of overuse injuries in runners? - a prospective study

Background The incidence of running injuries appears to be multifactorial, e.g. with regard to training errors or kinematics of the lower extremity [1,2]. To date, studies examining differences between healthy and injured runners are mainly retrospective, and therefore not able to determine whether these differences are the cause or effect of injury. The goal of this prospective study is to evaluate whether the development of overuse injuries in initially healthy subjects is caused by alterations in lower extremity kinematics and/or training habits.

The influence of footwear and ankle kinematics on the development of overuse injuries in runners. A prospective study

Running is a popular recreational activity that has many benefits for the cardiovascular system. Despite the positive effects on the human body, between 20% and 80% of all runners suffer from an overuse injury every year (van Gent et al. 2007). The incidence of running injuries appears to be multi-factorial. Training errors, such as weekly mileage or training surfaces (Macera et al. 1989), and alterations in ankle kinematics are often considered to influence the occurrence of overuse injuries in runners (Willems et al. 2006). Supported footwear is propagated to reduce an increased amount of rearfoot motion to minimize the risk of overuse injury (Krauss et al. 2010), but evidence to substantiate this is still needed (Richards et al. 2009).