development of a device to measure and train flexibility

DEVELOPMENT OF A DEVICE TO MEASURE AND TRAIN FLEXIBILITY Bárbara Pessali-Marques; Gladys Onambélé-Pearson; Adrian Burden; Desney Richards; Islay McEwan. 1.Manchester Metropolitan University – Department of Exercise and Sport Science, United Kingdom.

Description The first version of the Equipment for Flexibility Test (EFT) was developed in the Biomechanics Laboratory of the Excellence in Sports Centre at Federal University of Minas Gerais, Belo Horizonte, Brazil. Improvements were done by Bárbara Pessali Marques and Alexandre Barros at Bastidores Conditioning Centre, Belo Horizonte, Brazil. The third version, here presented, was refined at Manchester Metropolitan University.

Introduction Flexibility is the capacity of a muscle to reach a range of motion in a joint (1, 2). The range of motion (ROM) is usually used to represent this capacity, which is commonly measured in degrees. The measurement of the ROM, however, does not explain the behaviour of the muscle-tendon unit (MTU) when stretched (3), therefore, it is necessary to measure variables other than the ROM considering the biomechanical and sensory properties; e.g. Maximum Torque, First Sensation of Stretch (Fig. 1), Stiffness, Energy (Fig. 2), Creep (Fig. 3), Stress Relaxation (Fig. 4).

In the initial position, the hip is considered to be at 0° of flexion and can move in a range up to 180°. The lever’s angular speed is maintained constantly at 5°/s (4) when the button is continuously pressed. For gravity correction, the weight of the participant’s limb is measured at 0° of hip flexion in the horizontal position. Therefore, the maximum gravity effect torque (MaxGET) is computed using the formulae:

Figure 2 - Stiffness and Energy (Pessali-Marques, 2014) Torque (Nm)

Figure 1 - Maximum ROM, Maximum Torque and First sensation of stretch. (Pessali-Marques, 2014)

The EFT is used to measure passive torque, passive ROM and FSS. It is used to test and to train the hamstrings flexibility through different stretching protocols. The equipment allows the measurement of the right and left lower limbs separately.

ROM(°)

Limb assisted by gravity reported torque = Measured torque – (MaxGET * sine (angle)) Time (s)

Figure 3 - Creep (adapted from Cabido et al 2014)

Limb resisted by gravity reported torque = Measured torque + (MaxGET * sine (angle))

Figure 4 - Stress relaxation (adapted from Taylor et al. 1990)

Objective Given the lack of adequate equipment to accurately measure the described biomechanical and sensory variables to understand the MTU behaviour during the stretch, especially in trained in flexibility populations such as dancers, the aim was to design and develop the Flexibility Equipment Test (FET). 1. Push button to control the ascend and descend of the lever. 2. The ankle support designed in a “U” shape to minimise hip external rotation. 3. Load cell (15 V – Líder Balanças - Brazil) to measure the MTU’s resistance force against stretch. 4. Amplifier (RW-ST01 Strain Gauge Transducer – SWOWO). 5. Support for the thigh to avoid hyperextension of the knee. 6. Participants1 control to signal the FSS: a tension in the hamstrings. 7. Potentiometer (TT Electronics 5k0 1 watt wire wound pot) to record the ROM. 8. Analogical/digital converter (NI USB-6008 National Instruments). 9. Computer: Dasylab program 11.0 (DasytecDaten System TechnikGmbH, Germany). 10. Motor (Parvalux motor and right angle gearbox). 11. Straps to fix the limb 12. Cushions for the neck and lumbar areas. 13. Adjustable sections according to participant’s limb length. 14. Lever Scholarship student of Capes – Brazil. 99999.002176/2015-07

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Conclusion The EFT enables a multidimensional approach of flexibility measurement through proper body positioning. It is the only equipment found in the literature (5) able to measure all the biomechanical and sensory variables that are necessary for the multidimensional evaluation of the flexibility and to understand the MTU behaviour during stretch protocols.

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References 1. Magnusson SP, et al Scan J Med & Sci Spo. 1997;7(4):195-202. 2. Alencar TAM & Matias KFS. Rev Bras Med Esp. 2010;16(3):230-4. 3. Weppler CH, et al. J Phy Ther 2010;90(3):438-49. 4. Blackburn JK. et al. J Elec Kin. 2004;14(6):683-91. 5. Pessali-Marques, B. Rev Mov. 2016; 9(4):552-632