18th annual Congress of the ECSS 26th-29th June 2013, Barcelona, National Institute of Physical Education of Catalonia, Spain

TORQUE-ANGLE RELATIONSHIPS OF THE ELBOW FLEXORS AND EXTENSORS IN HEALTHY FEMALES
Pencheva, N., Kokova, M., Dencheva, S.
South-West University (Blagoevgrad, Bulgaria)

Introduction

The aims of this study are: (1) to obtain knowledge of the isometric torque-angle relationship of the elbow flexors and extensors; (2) to explore the impact of the elbow angle on the neuromuscular activity of the biceps brachii – long head (BB-LH) and triceps brachii – long head (TB-LH) by recording sEMG activity; and (3) to evaluate the correlations between the isometric flexor or extensor torque and RMS of the muscles tested.

Methods

Maximal isometric torque of flexors and extensors were measured (Biodex System 4) over a wide range of angles (15-150o) in ten females (21.2±1.4 years). Agonistic EMG activity and the level of coactivation for BB-LH and TB-LH were also measured. The curve fitting and statistics were performed by Prism software.

Results

The isometric torque-angle curves of flexors and extensors were modeled with 4th order polynomial function. The maximal torque of flexors (28.0±7.5 Nm) was generated at 90-105o position, while that of extensors (28.9±6.7 Nm) at 60-75o. The flexors/extensors torque ratio was lower, equal or higher than 100 % in the angular positions of 15-75o, 90o or 105-150o respectively. Agonistic EMG activity level of the BB-LH, as RMS, was correlated to measured torque of flexors, within the range of 75-150o (Spearman’s r=0.82), while that of TB-LH did not correlate with extensor’s torque. The antagonist activity for both muscles was low and did not result angle-dependent.

Discussion

In this study we found that the skew part (tail) of the non-linear, asymmetric torque-angle curve of flexors is situated in the left part of the measured range, while that of extensors, in the right one. These findings and the respective agonistic RMS-angle curves for BB-LH and TB-LH, seem to correspond at some extent to the force-length and to the moment arm-angle relationships (Ada et al., 2003; Pinter et al., 2010). However, the lack of correlation between extensor torque and activity of TB-LH can be explained by lower isometric functional capacity of the long head, which according to Murray ?t al. (2000) has shorter moment arm, as compared with that of BB-LH. Although, we found low and independent of elbow angle antagonistic activity of both muscles, it is hard to predict the size of crosstalk and the degree of underestimation of the maximal elbow torque, especially for extensors.

References

Ada L, Canning CG, Low ShL. (2003). Brain, 126, 724-731.
Murray WM, Buchanan ThS, Delp SL. (2000). J Biomech, 33 (8), 943-952.
Pinter IJ, Robbert MF, van Soest AJ, Smeets JB. (2010). J Electromyog Kinesiol, 20, 923-931.

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