@article{AppiahDwomohMuellerMayer2018,
  author    = {Appiah-Dwomoh, Edem Korkor and M{\"u}ller, Steffen and Mayer, Frank},
  title     = {Reproducibility of Static and Dynamic Postural Control Measurement in Adolescent Athletes with Back Pain},
  series = {Rehabilitation Research and Practice},
  volume    = {2018},
  journal   = {Rehabilitation Research and Practice},
  publisher = {Hindawi},
  address   = {New York},
  issn      = {2090-2875},
  doi       = {10.1155/2018/8438350},
  pages     = {1 -- 8},
  year      = {2018},
  abstract  = {Static (one-legged stance) and dynamic (star excursion balance) postural control tests were performed by 14 adolescent athletes with and 17 without back pain to determine reproducibility. The total displacement, mediolateral and anterior-posterior displacements of the centre of pressure in mm for the static, and the normalized and composite reach distances for the dynamic tests were analysed. Intraclass correlation coefficients, 95\% confidence intervals, and a Bland-Altman analysis were calculated for reproducibility. Intraclass correlation coefficients for subjects with (0.54 to 0.65), (0.61 to 0.69) and without (0.45 to 0.49), (0.52 to 0.60) back pain were obtained on the static test for right and left legs, respectively. Likewise, (0.79 to 0.88), (0.75 to 0.93) for subjects with and (0.61 to 0.82), (0.60 to 0.85) for those without back pain were obtained on the dynamic test for the right and left legs, respectively. Systematic bias was not observed between test and retest of subjects on both static and dynamic tests. The one-legged stance and star excursion balance tests have fair to excellent reliabilities on measures of postural control in adolescent athletes with and without back pain. They can be used as measures of postural control in adolescent athletes with and without back pain.},
  language  = {en}
}
@article{HirschmuellerKonstantinidisBauretal.2011,
  author    = {Hirschm{\"u}ller, Anja and Konstantinidis, Lukas and Baur, Heiner and M{\"u}ller, Steffen and Mehlhorn, Alexander and Kontermann, Julia and Grosse, Ulrich and S{\"u}dkamp, Norbert P. and Helwig, Peter},
  title     = {Do changes in dynamic plantar pressure distribution, strength capacity and postural control after intra-articular calcaneal fracture correlate with clinical and radiological outcome?},
  series = {Injury : international journal of the care of the injured},
  volume    = {42},
  journal   = {Injury : international journal of the care of the injured},
  number    = {10},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0020-1383},
  doi       = {10.1016/j.injury.2010.09.040},
  pages     = {1135 -- 1143},
  year      = {2011},
  abstract  = {Fractures of the calcaneus are often associated with serious permanent disability, a considerable reduction in quality of life, and high socio-economic cost. Although some studies have already reported changes in plantar pressure distribution after calcaneal fracture, no investigation has yet focused on the patient's strength and postural control. Method: 60 patients with unilateral, operatively treated, intra-articular calcaneal fractures were clinically and biomechanically evaluated >1 year postoperatively (physical examination, SF-36, AOFAS score, lower leg isokinetic strength, postural control and gait analysis including plantar pressure distribution). Results were correlated to clinical outcome and preoperative radiological findings (Bohler angle, Zwipp and Sanders Score). Results: Clinical examination revealed a statistically significant reduction in range of motion at the tibiotalar and the subtalar joint on the affected side. Additionally, there was a statistically significant reduction of plantar flexor peak torque of the injured compared to the uninjured limb (p < 0.001) as well as a reduction in postural control that was also more pronounced on the initially injured side (standing duration 4.2 +/- 2.9 s vs. 7.6 +/- 2.1 s, p < 0.05). Plantar pressure measurements revealed a statistically significant pressure reduction at the hindfoot (p = 0.0007) and a pressure increase at the midfoot (p = 0.0001) and beneath the lateral forefoot (p = 0.037) of the injured foot. There was only a weak correlation between radiological classifications and clinical outcome but a moderate correlation between strength differences and the clinical questionnaires (CC 0.27-0.4) as well as between standing duration and the clinical questionnaires. Although thigh circumference was also reduced on the injured side, there was no important relationship between changes in lower leg circumference and strength suggesting that measurement of leg circumference may not be a valid assessment of maximum strength deficits. Self-selected walking speed was the parameter that showed the best correlation with clinical outcome (AOFAS score). Conclusion: Calcaneal fractures are associated with a significant reduction in ankle joint ROM, plantar flexion strength and postural control. These impairments seem to be highly relevant to the patients. Restoration of muscular strength and proprioception should therefore be aggressively addressed in the rehabilitation process after these fractures.},
  language  = {en}
}
@article{BaurHirschmuellerMuelleretal.2011,
  author    = {Baur, Heiner and Hirschm{\"u}ller, Anja and M{\"u}ller, Steffen and Mayer, Frank},
  title     = {Neuromuscular activity of the peroneal muscle after foot orthoses therapy in runners},
  series = {Medicine and science in sports and exercise : official journal of the American College of Sports Medicine},
  volume    = {43},
  journal   = {Medicine and science in sports and exercise : official journal of the American College of Sports Medicine},
  number    = {8},
  publisher = {Lippincott Williams \& Wilkins},
  address   = {Philadelphia},
  issn      = {0195-9131},
  doi       = {10.1249/MSS.0b013e31820c64ae},
  pages     = {1500 -- 1506},
  year      = {2011},
  abstract  = {BAUR, H., A. HIRSCHMULLER, S. MULLER, and F. MAYER. Neuromuscular Activity of the Peroneal Muscle after Foot Orthoses Therapy in Runners. Med. Sci. Sports Exerc., Vol. 43, No. 8, pp. 1500-1506, 2011. Purpose: Foot orthoses are a standard option to treat overuse injury. Biomechanical data providing mechanisms of foot orthoses' effectiveness are sparse. Stability of the ankle joint complex might be a key factor. The purpose was therefore to analyze neuromuscular activity of the musculus peroneus longus in runners with overuse injury symptoms treated with foot orthoses. Methods: A total of 99 male and female runners with overuse injury symptoms randomized in a control group (CO) and an orthoses group (OR) were analyzed on a treadmill at 3.3 m.s(-1) before and after an 8-wk foot orthoses intervention. Muscular activity of the musculus peroneus longus was measured and quantified in the time domain (initial onset of activation (T-ini), time of maximal activity (T-max), total time of activation (T-tot)) and amplitude domain (amplitude in preactivation (A(pre)), weight acceptance (A(wa)), push-off (A(po))). Results: Peroneal activity in the time domain did not differ initially between CO and OR, and no effect was observed after therapy (T-ini: CO = -0.88 +/- 0.09, OR = -0.88 +/- 0.08 / T-max: CO = 0.14 +/- 0.06, OR = 0.15 +/- 0.06 / T-tot: CO = 0.40 +/- 0.09, OR = 0.41 +/- 0.09; P > 0.05). In preactivation (Apre), muscle activity was higher in OR after intervention (CO = 0.97 +/- 0.32, 95\% confidence interval = 0.90-1.05; OR = 1.18 +/- 0.43, 95\% confidence interval = 1.08-1.28; P = 0.003). There was no group or intervention effect during stance (A(wa): CO = 2.33 +/- 0.66, OR = 2.33 +/- 0.74 / A(po): CO = 0.80 +/- 0.41, OR = 0.88 +/- 0.40; P > 0.05). Conclusions: Enhanced muscle activation of the musculus peroneus longus in preactivation suggests an altered preprogrammed activity, which might lead to better ankle stability providing a possible mode of action for foot orthoses therapy.},
  language  = {en}
}
@article{CasselMuellerCarlsohnetal.2012,
  author    = {Cassel, Michael and M{\"u}ller, Steffen and Carlsohn, Anja and Baur, Heiner and Jerusel, N. and Mayer, Frank},
  title     = {Intra- and interrater variability of sonographic investigations of patella and achilles tendons},
  series = {Sportverletzung, Sportschaden : Grundlagen, Pr{\"a}vention, Rehabilitation},
  volume    = {26},
  journal   = {Sportverletzung, Sportschaden : Grundlagen, Pr{\"a}vention, Rehabilitation},
  number    = {1},
  publisher = {Thieme},
  address   = {Stuttgart},
  issn      = {0932-0555},
  doi       = {10.1055/s-0031-1281839},
  pages     = {21 -- 26},
  year      = {2012},
  abstract  = {Background: Clinical examinations of tendon disorders routinely include ultrasound examinations, despite the fact that availability of data concerning validity criteria of these measurements are limited. The present study therefore aims to evaluate the reliability of measurements of Achilles- and Patella tendon diameter and in the detection of structural adaptations. Materials and Methods: In 14 healthy, recreationally active subjects both asymptomatic Achilles (AT) and patella tendons (PT) were measured twice by two examiners in a test-retest design. Besides the detection of anteroposterior (a.p.-) and mediolateral (m.l.-) diameters, areas of hypoechogenicity and neovascularisation were registered. Data were analysed descriptively with calculation of test-retest variability (TRV), intraclass-correlation coefficient (ICC) and Bland and Altman's plots with bias and 95\% limits of agreement (LOA). Results: Intra- and interrater differences of AT- and PT-a.p.-diameter varied from 0.2 - 1.2 mm, those of AT- and PT-m.l-diameter from 0.7-5.1 mm. Areas of hypoechogenicity were visible in 24\% of the tendons, while 15\% showed neovascularisations. Intrarater AT-a.p.-diameters showed sparse deviations (TRV 4.5-7.4\%; ICC 0.60-0.84; bias -0.05-0.07 mm; LOA-0.6-0.5 to -1.1 - 1.0 mm), while interrater AT- and PT-m.l.-diameters were highly variable (TRV 13.7-19.7\%; ICC 0.11-0.20; bias -1.4-4.3 mm; LOA-5.5-2.7 to -10.5 - 1.9 mm). Conclusion: Our results suggest that the measurement of AT- and PT-a.p.-diameters is a reliable parameter. In contrast, reproducibility of AT- and PT-m.l.-diameters is questionable. The study corroborates the presence of hypoechogenicity and neovascularisation in asymptomatic tendons.},
  language  = {de}
}
@article{MuellerMayerBauretal.2011,
  author    = {M{\"u}ller, Steffen and Mayer, Patrizia and Baur, Heiner and Mayer, Frank},
  title     = {Higher velocities in isokinetic dynamometry a pilot study of new test mode with active compensation of inertia},
  series = {Isokinetics and exercise science : official journal of the European Isokinetic Society},
  volume    = {19},
  journal   = {Isokinetics and exercise science : official journal of the European Isokinetic Society},
  number    = {2},
  publisher = {IOS Press},
  address   = {Amsterdam},
  issn      = {0959-3020},
  doi       = {10.3233/IES-2011-0398},
  pages     = {63 -- 70},
  year      = {2011},
  abstract  = {Isokinetic dynamometry is a standard technique for strength testing and training. Nevertheless reliability and validity is limited due to inertia effects, especially for high velocities. Therefore in a first methodological approach the purpose was to evaluate a new isokinetic measurement mode including inertia compensation compared to a classic isokinetic measurement mode for single and multijoint movements at different velocities. Isokinetic maximum strength measurements were carried out in 26 healthy active subjects. Tests were performed using classic isokinetic and new isokinetic mode in random order. Maximum torque/force, maximum movement velocity and time for acceleration were calculated. For inter-instrument agreement Bland and Altman analysis, systematic and random error was quantified. Differences between both methods were assessed (ANOVA alpha = 0.05). Bland and Altman analysis showed the highest agreement between the two modes for strength and velocity measurements (bias: < +/- 1.1\%; LOA: < 14.2\%) in knee flexion/extension at slow isokinetic velocity (60 degrees/s). Least agreement (range: bias: -67.6\% +/- 119.0\%; LOA: 53.4\% 69.3\%) was observed for shoulder/arm test at high isokinetic velocity (360 degrees/s). The Isokin(new) mode showed higher maximum movement velocities (p < 0.05). For low isokinetic velocities the new mode agrees with the classic mode. Especially at high isokinetic velocities the new isokinetic mode shows relevant benefits coupled with a possible trade-off with the force/torque measurement. In conclusion, this study offers for the first time a comparison between the 'classical' and inertia-compensated isokinetic dynamometers indicating the advantages and disadvantages associated with each individual approach, particularly as they relate to medium or high velocities in testing and training.},
  language  = {en}
}
@article{HirschmuellerBaurMuelleretal.2011,
  author    = {Hirschm{\"u}ller, Anja and Baur, Heiner and M{\"u}ller, Steffen and Helwig, Peter and Dickhuth, Hans-Hermann and Mayer, Frank},
  title     = {Clinical effectiveness of customised sport shoe orthoses for overuse injuries in runners a randomised controlled study},
  series = {British journal of sports medicine : the journal of sport and exercise medicine},
  volume    = {45},
  journal   = {British journal of sports medicine : the journal of sport and exercise medicine},
  number    = {12},
  publisher = {BMJ Publ. Group},
  address   = {London},
  issn      = {0306-3674},
  doi       = {10.1136/bjsm.2008.055830},
  pages     = {959 -- 965},
  year      = {2011},
  abstract  = {Background and objectives Treatment of chronic running-related overuse injuries by orthopaedic shoe orthoses is very common but not evidence-based to date. Hypothesis Polyurethane foam orthoses adapted to a participant's barefoot plantar pressure distribution are an effective treatment option for chronic overuse injuries in runners. Design Prospective, randomised, controlled clinical trial. Intervention 51 patients with running injuries were treated with custom-made, semirigid running shoe orthoses for 8 weeks. 48 served as a randomised control group that continued regular training activity without any treatment. Main outcome measures Evaluation was made by the validated pain questionnaire Subjective Pain Experience Scale, the pain disability index and a comfort index in the orthoses group (ICI). Results There were statistically significant differences between the orthoses and control groups at 8 weeks for the pain disability index (mean difference 3.2; 95\% CI 0.9 to 5.5) and the Subjective Pain Experience Scale (6.6; 2.6 to 10.6). The patients with orthoses reported a rising wearing comfort (pre-treatment ICI 69/100; post-treatment ICI 83/100) that was most pronounced in the first 4 weeks (ICI 80.4/100). Conclusion Customised polyurethane running shoe orthoses are an effective conservative therapy strategy for chronic running injuries with high comfort and acceptance of injured runners.},
  language  = {en}
}
@article{MuellerStollCasseletal.2017,
  author    = {M{\"u}ller, Steffen and Stoll, Josefine and Cassel, Michael and Mayer, Frank},
  title     = {Trunk Muscle Activity during Drop Jump Performance in Adolescent Athletes with Back Pain},
  series = {Frontiers in physiology},
  volume    = {8},
  journal   = {Frontiers in physiology},
  publisher = {Frontiers Research Foundation},
  address   = {Lausanne},
  issn      = {1664-042X},
  doi       = {10.3389/fphys.2017.00274},
  year      = {2017},
  abstract  = {In the context of back pain, great emphasis has been placed on the importance of trunk stability, especially in situations requiring compensation of repetitive, intense loading induced during high-performance activities, e.g., jumping or landing. This study aims to evaluate trunk muscle activity during drop jump in adolescent athletes with back pain (BP) compared to athletes without back pain (NBP). Eleven adolescent athletes suffering back pain (BP: m/f: n = 4/7; 15.9 ± 1.3 y; 176 ± 11 cm; 68 ± 11 kg; 12.4 ± 10.5 h/we training) and 11 matched athletes without back pain (NBP: m/f: n = 4/7; 15.5 ± 1.3 y; 174 ± 7 cm; 67 ± 8 kg; 14.9 ± 9.5 h/we training) were evaluated. Subjects conducted 3 drop jumps onto a force plate (ground reaction force). Bilateral 12-lead SEMG (surface Electromyography) was applied to assess trunk muscle activity. Ground contact time [ms], maximum vertical jump force [N], jump time [ms] and the jump performance index [m/s] were calculated for drop jumps. SEMG amplitudes (RMS: root mean square [\%]) for all 12 single muscles were normalized to MIVC (maximum isometric voluntary contraction) and analyzed in 4 time windows (100 ms pre- and 200 ms post-initial ground contact, 100 ms pre- and 200 ms post-landing) as outcome variables. In addition, muscles were grouped and analyzed in ventral and dorsal muscles, as well as straight and transverse trunk muscles. Drop jump ground reaction force variables did not differ between NBP and BP (p > 0.05). Mm obliquus externus and internus abdominis presented higher SEMG amplitudes (1.3-1.9-fold) for BP (p < 0.05). Mm rectus abdominis, erector spinae thoracic/lumbar and latissimus dorsi did not differ (p > 0.05). The muscle group analysis over the whole jumping cycle showed statistically significantly higher SEMG amplitudes for BP in the ventral (p = 0.031) and transverse muscles (p = 0.020) compared to NBP. Higher activity of transverse, but not straight, trunk muscles might indicate a specific compensation strategy to support trunk stability in athletes with back pain during drop jumps. Therefore, exercises favoring the transverse trunk muscles could be recommended for back pain treatment.},
  language  = {en}
}
@article{CasselIntziegianniRischetal.2017,
  author    = {Cassel, Michael and Intziegianni, Konstantina and Risch, Lucie and M{\"u}ller, Steffen and Engel, Tilman and Mayer, Frank},
  title     = {Physiological Tendon Thickness Adaptation in Adolescent Elite Athletes},
  series = {Frontiers in physiology},
  volume    = {8},
  journal   = {Frontiers in physiology},
  publisher = {Frontiers},
  address   = {Lausanne},
  issn      = {1664-042X},
  doi       = {10.3389/fphys.2017.00795},
  pages     = {1 -- 8},
  year      = {2017},
  abstract  = {Increased Achilles (AT) and Patellar tendon (PT) thickness in adolescent athletes compared to non-athletes could be shown. However, it is unclear, if changes are of pathological or physiological origin due to training. The aim of this study was to determine physiological AT and PT thickness adaptation in adolescent elite athletes compared to non-athletes, considering sex and sport. In a longitudinal study design with two measurement days (M1/M2) within an interval of 3.2 ± 0.8 years, 131 healthy adolescent elite athletes (m/f: 90/41) out of 13 different sports and 24 recreationally active controls (m/f: 6/18) were included. Both ATs and PTs were measured at standardized reference points. Athletes were divided into 4 sport categories [ball (B), combat (C), endurance (E) and explosive strength sports (S)]. Descriptive analysis (mean ± SD) and statistical testing for group differences was performed (α = 0.05). AT thickness did not differ significantly between measurement days, neither in athletes (5.6 ± 0.7 mm/5.6 ± 0.7 mm) nor in controls (4.8 ± 0.4 mm/4.9 ± 0.5 mm, p > 0.05). For PTs, athletes presented increased thickness at M2 (M1: 3.5 ± 0.5 mm, M2: 3.8 ± 0.5 mm, p < 0.001). In general, males had thicker ATs and PTs than females (p < 0.05). Considering sex and sports, only male athletes from B, C, and S showed significant higher PT-thickness at M2 compared to controls (p ≤ 0.01). Sport-specific adaptation regarding tendon thickness in adolescent elite athletes can be detected in PTs among male athletes participating in certain sports with high repetitive jumping and strength components. Sonographic microstructural analysis might provide an enhanced insight into tendon material properties enabling the differentiation of sex and influence of different sports.},
  language  = {en}
}
@article{AppiahDwomohMuellerMayer2019,
  author    = {Appiah-Dwomoh, Edem Korkor and M{\"u}ller, Steffen and Mayer, Frank},
  title     = {Is there an association between variables of static and dynamic postural control in adolescent athletes with back pain?},
  series = {German Journal of Exercise and Sport Research},
  volume    = {49},
  journal   = {German Journal of Exercise and Sport Research},
  number    = {2},
  publisher = {Springer},
  address   = {New York},
  issn      = {2509-3142},
  doi       = {10.1007/s12662-019-00573-6},
  pages     = {150 -- 155},
  year      = {2019},
  abstract  = {An association between static and dynamic postural control exists in adults with back pain. We aimed to determine whether this association also exists in adolescent athletes with the same condition. In all, 128 athletes with and without back pain performed three measurements of 15s of static (one-legged stance) and dynamic (star excursion balance test) postural control tests. All subjects and amatched subgroup of athletes with and without back pain were analyzed. The smallest center of pressure mediolateral and anterior-posterior displacements (mm) and normalized highest reach distance were the outcome measures. No association was found between variables of the static and dynamic tests for all subjects and the matched group with and without back pain. The control of static and dynamic posture in adolescent athletes with and without back pain might not be related.},
  language  = {en}
}
@article{WochatzEngelMuelleretal.2020,
  author    = {Wochatz, Monique and Engel, Tilman and M{\"u}ller, Steffen and Mayer, Frank},
  title     = {Alterations in scapular kinematics and scapular muscle activity after fatiguing shoulder flexion and extension movements},
  series = {Medicine and science in sports and exercise : MSSE},
  volume    = {52},
  journal   = {Medicine and science in sports and exercise : MSSE},
  number    = {17},
  publisher = {Lippincott Williams \& Wilkins},
  address   = {Philadelphia},
  issn      = {0195-9131},
  doi       = {10.1249/01.mss.0000676540.02017.2c},
  pages     = {274 -- 274},
  year      = {2020},
  abstract  = {Repetitive overhead motions in combination with heavy loading were identified as risk factors for the development of shoulder pain. However, the underlying mechanism is not fully understood. Altered scapular kinematics as a result of muscle fatigue is suspected to be a contributor. PURPOSE: To determine scapular kinematics and scapular muscle activity at the beginning and end of constant shoulder flexion and extension loading in asymptomatic individuals. METHODS: Eleven asymptomatic adults (28±4yrs; 1.74±0.13m; 74±16kg) underwent maximum isokinetic loading of shoulder flexion (FLX) and extension (EXT) in the sagittal plane (ROM: 20- 180°; concentric mode; 180°/s) until individual peak torque was reduced by 50\%. Simultaneously 3D scapular kinematics were assessed with a motion capture system and scapular muscle activity with a 3-lead sEMG of upper and lower trapezius (UT, LT) and serratus anterior (SA). Scapular position angles were calculated for every 20° increment between 20-120° humerothoracic positions. Muscle activity was quantified by amplitudes (RMS) of the total ROM. Descriptive analyses (mean±SD) of kinematics and muscle activity at begin (taskB) and end (taskE) of the loading task was followed by ANOVA and paired t-tests. RESULTS: At taskB activity ranged from 589±343mV to 605±250mV during FLX and from 105±41mV to 164±73mV during EXT across muscles. At taskE activity ranged from 594±304mV to 875±276mV during FLX and from 97±33mV to 147±57mV during EXT. Differences with increased muscle activity were seen for LT and UT during FLX (meandiff= 141±113mV for LT, p<0.01; 191±153mV for UT, p<0.01). Scapula position angles continuously increased in upward rotation, posterior tilt and external rotation during FLX and reversed during EXT both at taskB and taskE. At taskE scapula showed greater external rotation (meandiff= 3.6±3.7°, p<0.05) during FLX and decreased upward rotation (meandiff= 1.9±2.3°, p<0.05) and posterior tilt (meandiff= 1.0±2.1°, p<0.05) during EXT across humeral positions. CONCLUSIONS: Force reduction in consequence of fatiguing shoulder loading results in increased scapular muscle activity and minor alterations in scapula motion. Whether even small changes have a clinical impact by creating unfavorable subacromial conditions potentially initiating pain remains unclear.},
  language  = {en}
}