TY  - JOUR
A1  - Mueller, Steffen
A1  - Mueller, Juliane
A1  - Stoll, Josefine
A1  - Mayer, Frank
T1  - Effect of six-week resistance and sensorimotor training on trunk strength and stability in elite adolescent athletes
BT  - a randomized controlled pilot trial
JF  - Frontiers in physiology
N2  - Intervention in the form of core-specific stability exercises is evident to improve trunk stability. The purpose was to assess the effect of an additional 6 weeks sensorimotor or resistance training on maximum isokinetic trunk strength and response to sudden dynamic trunk loading (STL) in highly trained adolescent athletes. The study was conducted as a single-blind, 3-armed randomized controlled trial. Twenty-four adolescent athletes (14f/10 m, 16 +/- 1 yrs.;178 +/- 10 cm; 67 +/- 11 kg; training sessions/week 15 +/- 5; training h/week 22 +/- 8) were randomized into resistance training (RT; n = 7), sensorimotor training (SMT; n = 10), and control group (CG; n = 7). Athletes were instructed to perform standardized, center-based training for 6 weeks, two times per week, with a duration of 1 h each session. SMT consisted of four different core-specific sensorimotor exercises using instable surfaces. RT consisted of four trunk strength exercises using strength training machines, as well as an isokinetic dynamometer. All participants in the CG received an unspecific heart frequency controlled, ergometer-based endurance training (50 min at max. heart frequency of 130HF). For each athlete, each training session was documented in an individual training diary (e.g., level of SMT exercise; 1RM for strength exercise, pain). At baseline (M1) and after 6 weeks of intervention (M2), participants' maximum strength in trunk rotation (ROM:63 degrees) and flexion/extension (ROM:55 degrees) was tested on an isokinetic dynamometer (concentric/eccentric 30 degrees/s). STL was assessed in eccentric (30 degrees/s) mode with additional dynamometer-induced perturbation as a marker of core stability. Peak torque [Nm] was calculated as the main outcome. The primary outcome measurements (trunk rotation/extension peak torque: con, ecc, STL) were statistically analyzed by means of the two-factor repeated measures analysis of variance (alpha = 0.05). Out of 12 possible sessions, athletes participated between 8 and 9 sessions (SMT: 9 +/- 3; RT: 8 +/- 3; CG: 8 +/- 4). Regarding main outcomes of trunk performance, experimental groups showed no significant pre-post difference for maximum trunk strength testing as well as for perturbation compensation (p > 0.05). It is concluded, that future interventions should exceed 6 weeks duration with at least 2 sessions per week to induce enhanced trunk strength or compensatory response to sudden, high-intensity trunk loading in already highly trained adolescent athletes, regardless of training regime.
KW  - core
KW  - training intervention
KW  - trunk stability
KW  - exercise
KW  - perturbation
Y1  - 2022
U6  - https://doi.org/10.3389/fphys.2022.802315
SN  - 1664-042X
VL  - 13
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Mueller, Juliane
A1  - Martinez-Valdes, Eduardo Andrés
A1  - Stoll, Josefine
A1  - Mueller, Steffen
A1  - Engel, Tilman
A1  - Mayer, Frank
T1  - Differences in neuromuscular activity of ankle stabilizing muscles during postural disturbances
BT  - a gender-specific analysis
JF  - Gait & posture
N2  - The purpose was to examine gender differences in ankle stabilizing muscle activation during postural disturbances. Seventeen participants (9 females: 27 +/- 2yrs., 1.69 +/- 0.1 m, 63 +/- 7 kg; 8 males: 29 +/- 2yrs., 1.81 +/- 0.1 m; 83 +/- 7 kg) were included in the study. After familiarization on a split-belt-treadmill, participants walked (1 m/s) while 15 right-sided perturbations were randomly applied 200 ms after initial heel contact. Muscle activity of M. tibialis anterior (TA), peroneus longus (PL) and gastrocnemius medialis (GM) was recorded during unperturbed and perturbed walking. The root mean square (RMS; [%]) was analyzed within 200 ms after perturbation. Co-activation was quantified as ratio of antagonist (GM)/agonist (TA) EMG-RMS during unperturbed and perturbed walking. Time to onset was calculated (ms). Data were analyzed descriptively (mean +/- SD) followed by three-way-ANOVA (gender/condition/muscle; alpha= 0.05). Perturbed walking elicited higher EMG activity compared to normal walking for TA and PL in both genders (p < 0.000). RMS amplitude gender comparisons revealed an interaction between gender and condition (F = 4.6, p = 0.049) and, a triple interaction among gender, condition and muscle (F = 4.7, p = 0.02). Women presented significantly higher EMG-RMS [%] PL amplitude than men during perturbed walking (mean difference = 209.6%, 95% confidence interval = -367.0 to -52.2%, p < 0.000). Co-activation showed significant lower values for perturbed compared to normal walking (p < 0.000), without significant gender differences for both walking conditions. GM activated significantly earlier than TA and PL (p < 0.01) without significant differences between the muscle activation onsets of men and women (p = 0.7). The results reflect that activation strategies of the ankle encompassing muscles differ between genders. In provoked stumbling, higher PL EMG activity in women compared to men is present. Future studies should aim to elucidate if this specific behavior has any relationship with ankle injury occurrence between genders.
KW  - Lower extremity
KW  - EMG
KW  - Perturbation
KW  - Split-belt treadmill
KW  - Ankle
Y1  - 2018
U6  - https://doi.org/10.1016/j.gaitpost.2018.01.023
SN  - 0966-6362
SN  - 1879-2219
VL  - 61
SP  - 226
EP  - 231
PB  - Elsevier
CY  - Clare
ER  - 
TY  - JOUR
A1  - Mueller, Steffen
A1  - Engel, Tilman
A1  - Müller, Juliane
A1  - Stoll, Josefine
A1  - Baur, Heiner
A1  - Mayer, Frank
T1  - Sensorimotor exercises and enhanced trunk function
BT  - a randomized controlled trial
JF  - International journal of sports medicine
N2  - The aim of this study was to investigate the effect of a 6-week sensorimotor or resistance training on maximum trunk strength and response to sudden, high-intensity loading in athletes. Interventions showed no significant difference for maximum strength in concentric and eccentric testing (p>0.05). For perturbation compensation, higher peak torque response following SMT (Extension: +24Nm 95%CI +/- 19Nm; Rotation: + 19Nm 95%CI +/- 13Nm) and RT (Extension: +35Nm 95%CI +/- 16Nm; Rotation: +5Nm 95%CI +/- 4Nm) compared to CG (Extension: -4Nm 95%CI +/- 16Nm; Rotation: -2Nm 95%CI +/- 4Nm) was present (p<0.05).
KW  - core
KW  - training intervention
KW  - prevention
KW  - perturbation
KW  - MiSpEx*
Y1  - 2018
U6  - https://doi.org/10.1055/a-0592-7286
SN  - 0172-4622
SN  - 1439-3964
VL  - 39
IS  - 7
SP  - 555
EP  - 563
PB  - Thieme
CY  - Stuttgart
ER  - 
TY  - JOUR
A1  - Müller, Juliane
A1  - Stoll, Josefine
A1  - Mueller, Steffen
A1  - Mayer, Frank
T1  - Dose-response relationship of core-specific sensorimotor interventions in healthy, well-trained participants
BT  - study protocol for a (MiSpEx) randomized controlled trial
JF  - Trials
N2  - Background: Core-specific sensorimotor exercises are proven to enhance neuromuscular activity of the trunk, improve athletic performance and prevent back pain. However, the dose-response relationship and, therefore, the dose required to improve trunk function is still under debate. The purpose of the present trial will be to compare four different intervention strategies of sensorimotor exercises that will result in improved trunk function. Discussion: The results of the study will be clinically relevant, not only for researchers but also for (sports) therapists, physicians, coaches, athletes and the general population who have the aim of improving trunk function.
KW  - Sensorimotor training
KW  - Perturbation
KW  - Exercise
KW  - MiSpEx
Y1  - 2018
U6  - https://doi.org/10.1186/s13063-018-2799-9
SN  - 1745-6215
VL  - 19
PB  - BMC
CY  - London
ER  - 
TY  - JOUR
A1  - Wochatz, Monique
A1  - Rabe, Sophie
A1  - Wolter, Martin
A1  - Engel, Tilman
A1  - Mueller, Steffen
A1  - Mayer, Frank
T1  - Muscle activity of upper and lower trapezius and serratus anterior during unloaded and maximal loaded shoulder flexion and extension
JF  - International Biomechanics
N2  - Altered scapular muscle activity is mostly described under unloaded and submaximal loaded conditions in impingement patients. However, there is no clear evidence on muscle activity with respect to movement phases under maximum load in healthy subjects. Therefore, this study aimed to investigate scapular muscle activity under unloaded and maximum loaded isokinetic shoulder flexion and extension in regard to the movement phase. Fourteen adults performed unloaded (continuous passive motion [CPM]) as well as maximum loaded (concentric [CON], eccentric [ECC]) isokinetic shoulder flexion (Flex) and extension (Ext). Simultaneously, scapular muscle activity was measured by EMG. Root mean square was calculated for the whole ROM and four movement phases. Data were analyzed descriptively and by two-way repeated measures ANOVA. CPMFlex resulted in a linear increase of muscle activity for all muscles. Muscle activity during CONFlex and ECCFlex resulted in either constant activity levels or in an initial increase followed by a plateau in the second half of movement. CPMExt decreased with the progression of movement, whereas CONExt and ECCExt initially decreased and either levelled off or increased in the second half of movement. Scapular muscle activity of unloaded shoulder flexion and extension changed under maximum load showing increased activity levels and an altered pattern over the course of movement.
KW  - shoulder
KW  - scapular muscle activity
KW  - isokinetic testing
KW  - electromyography
Y1  - 2017
U6  - https://doi.org/https://doi.org/10.1080/23335432.2017.1364668
VL  - 4
IS  - 2
SP  - 68
EP  - 76
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Khajooei, Mina
A1  - Lin, Chiao-I
A1  - Mayer, Frank
A1  - Mueller, Steffen
T1  - Muscle activity and strength in maximum isokinetic legpress testing with unstable footplates in active individuals
JF  - Isokinetics and exercise science : official journal of the European Isokinetic Society
N2  - BACKGROUND: Compensating unstable situations is an important functional capability to maintain joint stability, to compensate perturbations and to prevent (re-)injury. Therefore, reduced maximum strength and altered neuromuscular activity are expected by inducing instability to load test situations. Possible effects are not clear for induced instability during maximum legpress tests in healthy individuals. OBJECTIVE: To compare isokinetic legpress (LP) strength and lower-leg muscle activity using stable (S) and unstable (UN) footplates. METHODS: 16 males (28 +/- 4 yrs, 179 +/- 7 cm, 75 +/- 8 kg) performed five maximum LP in concentric (CON) and eccentric (ECC) mode. The maximum force (Fmax) and muscle activity were measured under conditions of S and UN footplates. The tested muscles comprised of the tibialis anterior (TA), peroneus longus (PL) and soleus (SOL) and their activity were quantified against the MVIC of each muscle respectively. RESULTS: The main finding revealed a significant reduction in Fmax under UN condition: 11.9 +/- 11.3% in CON and 23.5 +/- 47.8% in ECC (P < 0.05). Significant findings were also noted regarding the RMS derived values of the EMG of PL and TA. CONCLUSION: Unstable LP reduced force generation and increased the activity of PL and TA muscles which confirmed greater neuromuscular effort to compensate instability. This may have some implications for resistance testing and training coupled with an unstable base in the prevention and rehabilitation of injury to the neuromusculoskeletal system.
KW  - Tibialis anterior
KW  - peroneus longus
KW  - soleus
KW  - instability
Y1  - 2019
U6  - https://doi.org/10.3233/IES-182206
SN  - 0959-3020
SN  - 1878-5913
VL  - 27
IS  - 3
SP  - 177
EP  - 183
PB  - IOS Press
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Wochatz, Monique
A1  - Tilgner, Nina
A1  - Mueller, Steffen
A1  - Rabe, Sophie
A1  - Eichler, Sarah
A1  - John, Michael
A1  - Völler, Heinz
A1  - Mayer, Frank
T1  - Reliability and validity of the Kinect V2 for the assessment of lower extremity rehabilitation exercises
JF  - Gait & posture
N2  - Research question: The purpose of this study was to evaluate the test-retest reliability of lower extremity kinematics during squat, hip abduction and lunge exercises captured by the Kinect and to evaluate the agreement to a reference 3D camera-based motion system. Methods: Twenty-one healthy individuals performed five repetitions of each lower limb exercise on two different days. Movements were simultaneously assessed by the Kinect and the reference 3D motion system. Joint angles and positions of the lower limb were calculated for sagittal and frontal plane. For the inter-session reliability and the agreement between the two systems standard error of measurement (SEM), bias with limits of agreement (LoA) and Pearson Correlation Coefficient (r) were calculated. Results: Parameters indicated varying reliability for the assessed joint angles and positions and decreasing reliability with increasing task complexity. Across all exercises, measurement deviations were shown especially for small movement amplitudes. Variability was acceptable for joint angles and positions during the squat, partially acceptable during the hip abduction and predominately inacceptable during the lunge. The agreement between systems was characterized by systematic errors. Overestimations by the Kinect were apparent for hip flexion during the squat and hip abduction/adduction during the hip abduction exercise as well as for the knee positions during the lunge. Knee and hip flexion during hip abduction and lunge were underestimated by the Kinect. Significance: The Kinect system can reliably assess lower limb joint angles and positions during simple exercises. The validity of the system is however restricted. An application in the field of early orthopedic rehabilitation without further development of post-processing techniques seems so far limited.
KW  - Reproducibility
KW  - Agreement
KW  - Markerless motion capture system
KW  - Telerehabilitation
Y1  - 2018
U6  - https://doi.org/10.1016/j.gaitpost.2019.03.020
SN  - 0966-6362
SN  - 1879-2219
VL  - 70
SP  - 330
EP  - 335
PB  - Elsevier
CY  - Clare
ER  - 
TY  - JOUR
A1  - Engel, Tilman
A1  - Mueller, Juliane
A1  - Kopinski, Stephan
A1  - Reschke, Antje
A1  - Mueller, Steffen
A1  - Mayer, Frank
T1  - Unexpected walking perturbations: Reliability and validity of a new treadmill protocol to provoke muscular reflex activities at lower extremities and the trunk
JF  - Journal of biomechanics
N2  - Instrumented treadmills offer the potential to generate standardized walking perturbations, which are particularly rapid and powerful. However, technical requirements to release adequate perturbations regarding timing, duration and amplitude are demanding. This study investigated the test-retest reliability and validity of a new treadmill perturbation protocol releasing rapid and unexpected belt perturbations to provoke muscular reflex responses at lower extremities and the trunk. Fourteen healthy participants underwent two identical treadmill walking protocols, consisting of 10 superimposed one-sided belt perturbations (100 ms duration; 2 m/s amplitude), triggered by a plantar pressure insole 200 ms after heel contact. Delay, duration and amplitude of applied perturbations were recorded by 3D-motion capture. Muscular reflex responses (within 200 ms) were measured at lower extremities and the trunk (10-lead EMG). Data was analyzed descriptively (mean +/- SD). Reliability was analyzed using test-retest variability (TRV%) and limits of agreement (LoA, bias +/- 1.96*SD). Perturbation delay was 202 14 ms, duration was 102 +/- 4 ms and amplitude was 2.1 +/- 0.01 m/s. TRV for perturbation delay, duration and amplitude ranged from 5.0% to 5.7%. LoA reached 3 +/- 36 ms for delay, 2 +/- 13 ms for duration and 0.0 +/- 0.3 m/s for amplitude. EMG amplitudes following perturbations ranged between 106 +/- 97% and 909 +/- 979% of unperturbed gait and EMG latencies between 82 +/- 14 ms and 106 +/- 16 ms. Minor differences between preset and observed perturbation characteristics and results of test-retest analysis prove a high validity with excellent reliability of the setup. Therefore, the protocol tested can be recommended to provoke muscular reflex responses at lower extremities and the trunk in perturbed walking. (C) 2017 Elsevier Ltd. All rights reserved.
KW  - Perturbation
KW  - Stumbling
KW  - Gait
KW  - Treadmill
KW  - Reliability
KW  - MiSpEx
Y1  - 2017
U6  - https://doi.org/10.1016/j.jbiomech.2017.02.026
SN  - 0021-9290
SN  - 1873-2380
VL  - 55
SP  - 152
EP  - 155
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Wochatz, Monique
A1  - Rabe, Sophie
A1  - Wolter, Martin
A1  - Engel, Tilman
A1  - Mueller, Steffen
A1  - Mayer, Frank
T1  - Reproducibility of scapular muscle activity in isokinetic shoulder flexion and extension
JF  - Journal of electromyography and kinesiology
N2  - Repetitive overhead movements have been identified as a main risk factor to develop shoulder complaints with scapular muscle activity being altered. Reliable assessment of muscle activity is essential to differentiate between symptomatic and asymptomatic individuals. Therefore, the present study aimed to investigate the intra-and inter-session reliability of scapular muscle activity during maximal isokinetic shoulder flexion and extension. Eleven asymptomatic adults performed maximum effort isokinetic shoulder flexion and extension (concentric and eccentric at 60 degrees/s) in a test-retest design. Muscle activity of the upper and lower trapezius and serratus anterior was assessed by sEMG. Root Mean Square was calculated for whole ROM and single movement phases of absolute and normalized muscle activity. Absolute (Bland-Altman analysis (Bias, LoA), Minimal detectable change (MDC)) and relative reliability parameters (Intraclass correlation coefficient (ICC), coefficient of variation (CV)/test-retest variability (TRV)) were utilized for the evaluation of reproducibility. Intra-session reliability revealed ICCs between 0.56 and 0.98, averaged CVs of 18% and average MDCs of 81 mV. Inter-session reliability resulted in ICCs between 0.13 and 0.93, averaged TRVs of 21%, average MDCs of 15% and systematic and random error between -8 +/- 60% and 12 +/- 36%. Scapular muscle activity assessed in overhead movements can be measured reliably under maximum load conditions, though variability is dependent on the movement phase. Measurement variability does not exceed magnitudes of altered scapular muscle activities as reported in previous studies. Therefore, maximum load application is a promising approach for the evaluation of changes in scapular control related to pathologies. (C) 2017 Elsevier Ltd. All rights reserved.
Y1  - 2017
U6  - https://doi.org/10.1016/j.jelekin.2017.04.006
SN  - 1050-6411
SN  - 1873-5711
VL  - 34
SP  - 86
EP  - 92
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Huang, Hongshi
A1  - Guo, Jianqiao
A1  - Yang, Jie
A1  - Jiang, Yanfang
A1  - Yu, Yuanyuan
A1  - Mueller, Steffen
A1  - Ren, Gexue
A1  - Ao, Yingfang
T1  - Isokinetic angle-specific moments and ratios characterizing hamstring and quadriceps strength in anterior cruciate ligament deficient knees
JF  - Scientific reports
N2  - This study is intended to find more effective and robust clinical diagnostic indices to characterize muscle strength and coordination alternation following anterior cruciate ligament (ACL) rupture. To evaluate angle-specific moments and hamstring (H)/quadriceps (Q) ratios, 46 male subjects with unilateral chronic ACL-rupture performed isokinetic concentric (c), eccentric (e) quadriceps and hamstring muscle tests respectively at 60 degrees/s. Normalized moments and H/Q ratios were calculated for peak moment (PM) and 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees knee flexion angles. Furthermore, we introduced single-to-arithmetic-mean (SAM) and single-to-root-mean-square (SRMS) muscle co-contraction ratios, calculating them for specific angles and different contraction repetitions. Normalized PM and 40 degrees specific concentric quadriceps, concentric hamstring strength in the ACL-deficient knee were reduced significantly (P <= 0.05). Concentric angle-specific moments together with Qe/Qc ratios at 40 degrees (d = 0.766 vs. d = 0.654) identify more obvious differences than peak values in ACL ruptured limbs. Furthermore, we found SRMS-QeQc deficits at 40 degrees showed stronger effect than Qe/Qc ratios (d = 0.918 vs. d = 0.766), albeit other ratio differences remained basically the same effect size as the original H/Q ratios. All the newly defined SAM and SRMS indices could decrease variance. Overall, 40 degrees knee moments and SAM/ SRMS ratios might be new potential diagnosis indices for ACL rupture detection.
Y1  - 2017
U6  - https://doi.org/10.1038/s41598-017-06601-5
SN  - 2045-2322
VL  - 7
PB  - Nature Publ. Group
CY  - London
ER  -