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Brazilian Journal of Physical Therapy

versão impressa ISSN 1413-3555versão On-line ISSN 1809-9246

Resumo

CHAGAS, Mauro H. et al. Exploratory factor analysis for differentiating sensory and mechanical variables related to muscle-tendon unit elongation. Braz. J. Phys. Ther. [online]. 2016, vol.20, n.3, pp.240-247.  Epub 22-Mar-2016. ISSN 1413-3555.  http://dx.doi.org/10.1590/bjpt-rbf.2014.0152.

Background

Stretching exercises are able to promote adaptations in the muscle-tendon unit (MTU), which can be tested through physiological and biomechanical variables. Identifying the key variables in MTU adaptations is crucial to improvements in training.

Objective

To perform an exploratory factor analysis (EFA) involving the variables often used to evaluate the response of the MTU to stretching exercises.

Method

Maximum joint range of motion (ROMMAX), ROM at first sensation of stretching (FSTROM), peak torque (torqueMAX), passive stiffness, normalized stiffness, passive energy, and normalized energy were investigated in 36 participants during passive knee extension on an isokinetic dynamometer. Stiffness and energy values were normalized by the muscle cross-sectional area and their passive mode assured by monitoring the EMG activity.

Results

EFA revealed two major factors that explained 89.68% of the total variance: 53.13% was explained by the variables torqueMAX, passive stiffness, normalized stiffness, passive energy, and normalized energy, whereas the remaining 36.55% was explained by the variables ROMMAX and FSTROM.

Conclusion

This result supports the literature wherein two main hypotheses (mechanical and sensory theories) have been suggested to describe the adaptations of the MTU to stretching exercises. Contrary to some studies, in the present investigation torqueMAX was significantly correlated with the variables of the mechanical theory rather than those of the sensory theory. Therefore, a new approach was proposed to explain the behavior of the torqueMAX during stretching exercises.

Palavras-chave : multivariate analysis; biomechanical properties; hamstring muscles; stretching exercises; stretch tolerance; movement.

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