IMU- and TENS-based work and power calculation methods in hip flexion resistance training

Abstract

Purpose: The study is the first part of a series presenting the primary results of multijoint hip flexion resistance training biomechanical investigation. The series evaluates the exercise in the context of possible implementation in hip flexors shortening and hypertension. The described exercise was designed to use muscle hypertrophy as a solution for pelvis stabilizing muscles’ imbalance. This study aims to evaluate the work performed and power generated during hip flexion resistance training using two established methods and investigate the potential of IMU sensors as a cost-effective tool for measuring individual performance and progress in non-laboratory settings. Methods: The study was conducted with the use of training equipment constructed according to patent P.435615 allowing for the application of downward directed force to feet while performing hip flexion. Thirteen healthy students (7 females and 6 males, body-height 176.00 ± 12.54 cm, body-mass 73.69 ± 18.08 kg, age: 21.77 ± 1.09 years) took part in the training session using three different additional loads (0, 2.5, and 5 kg). Techniques applied in the study included optical kinematics capture, strain gauges, and inertial sensors. Results: The average work of (TENS/IMU) were 56.57 ± 12.00 / 58.13 ± 13.07 - 76.54 ± 13.88 / 74.40 ± 13.93 J and an average power of 23.22 ± 6.43 / 23.65 ± 7.12 - 31.51 ± 9.42 / 31.62 ± 10.60 W were calculated for the additional load of 0 kg and 5 kg respectively. The correlation between values calculated with two tested methods was high both for power (R= .85 P< .001) and work (R= .86 P< .001). Conclusions: Referenced data indicate a good correlation between the two methods but prove the need for further improvement of IMU-based method precision. It also allowed to determine a potential baseline of 15kg additional load for 1RM tests maximal value.