Reliability of the muscle strength measurement and effects of the strengthening by an innovative exercise device for the abdominal trunk muscles

Abstract

OBJECTIVE:

We developed an innovative exercise device for the abdominal trunk muscles (ATMs) that has a built-in system to measure muscle strength. We aimed to examine the reliability of the strength measurement as well as the effect of strengthening using the device.

METHODS:

Twenty healthy adults participated in a reliability study of the muscle strength measurement. The first and second measurement were done in one day with an hour rest interval by raters 1 and 2, and the third by rater 1 following a one-week interval. We calculated the intraclass correlation coefficient (ICC). Another seven healthy men participated in a training program using the device, consisting of strengthening twice a week for 5 weeks. ATM strength was measured before and after the training period, and a positron emission tomography (PET) scan series was performed, consisting of examinations during rest before training (control condition) and during exercise after training (training condition).

RESULTS:

The intra-rater (ICC $=$ 0.95) and inter-rater (ICC $=$ 0.99) reliability of the strength measurement were excellent. ATM strength was significantly higher after training than before. ${}^{18}$ F-fluorodeoxyglucose accumulation within the diaphragm, abdominal rectus, abdominal external and internal oblique, transverse abdominal, and levator ani muscles was significantly higher in the training condition than in the control.

CONCLUSIONS:

Our innovative device showed excellent reliability to quantify ATM strength. Strengthening using the device increased strength and activated the abdominals, diaphragm, and pelvic floor muscles.