TY  - JOUR
A1  - Lesinski, Melanie
A1  - Prieske, Olaf
A1  - Borde, Ron
A1  - Beurskens, Rainer
A1  - Granacher, Urs
T1  - Effects of Different Footwear Properties and Surface Instability on Neuromuscular Activity and Kinematics During Jumping
JF  - Journal of strength and conditioning research : the research journal of the NSCA
N2  - The purpose of this study was to examine sex-specific effects of different footwear properties vs. barefoot condition during the performance of drop jumps (DJs) on stable and unstable surfaces on measures of jump performance, electromyographic (EMG) activity, and knee joint kinematics. Drop jump performance, EMG activity of lower-extremity muscles, as well as sagittal and frontal knee joint kinematics were tested in 28 healthy male (n = 14) and female (n = 14) physically active sports science students (23 6 2 years) during the performance of DJs on stable and unstable surfaces using different footwear properties (elastic vs. minimal shoes) vs. barefoot condition. Analysis revealed a significantly lower jump height and performance index (Delta 7-12%; p < 0.001; 2.22 <= d = 2.90) during DJs on unstable compared with stable surfaces. This was accompanied by lower thigh/shank muscle activities (Delta 11-28%; p < 0.05; 0.99 <= d = 2.16) and knee flexion angles (Delta 5-8%; p < 0.05; 1.02 <= d = 2.09). Furthermore, knee valgus angles during DJs were significantly lower when wearing shoes compared with barefoot condition (Delta 22-32%; p < 0.01; 1.38 <= d = 3.31). Sex-specific analyses indicated higher knee flexion angles in females compared with males during DJs, irrespective of the examined surface and footwear conditions (Delta 29%; p < 0.05; d = 0.92). Finally, hardly any significant footwear-surface interactions were detected. Our findings revealed that surface instability had an impact on DJ performance, thigh/shank muscle activity, and knee joint kinematics. In addition, the single factors "footwear" and "sex" modulated knee joint kinematics during DJs. However, hardly any significant interaction effects were found. Thus, additional footwear-related effects can be neglected when performing DJs during training on different surfaces.
KW  - shoe
KW  - drop jump
KW  - EMG
KW  - knee
KW  - biomechanics
Y1  - 2018
U6  - https://doi.org/10.1519/JSC.0000000000002556
SN  - 1064-8011
SN  - 1533-4287
VL  - 32
IS  - 11
SP  - 3246
EP  - 3257
PB  - Lippincott Williams & Wilkins
CY  - Philadelphia
ER  - 
TY  - JOUR
A1  - Müller, Steffen
A1  - Mayer, Patrizia
A1  - Baur, Heiner
A1  - Mayer, Frank
T1  - Higher velocities in isokinetic dynamometry a pilot study of new test mode with active compensation of inertia
JF  - Isokinetics and exercise science : official journal of the European Isokinetic Society
N2  - 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.
KW  - Strength testing
KW  - concentric
KW  - validity
KW  - trunk
KW  - knee
KW  - shoulder
Y1  - 2011
U6  - https://doi.org/10.3233/IES-2011-0398
SN  - 0959-3020
VL  - 19
IS  - 2
SP  - 63
EP  - 70
PB  - IOS Press
CY  - Amsterdam
ER  -