Performance during seated balancing is often used to assess trunk neuromuscular control, including evaluating impairments in back pain populations. Balancing in less challenging environments allows for flexibility in control, which may not depend on health status but instead may reflect personal preferences. To make assessment less ambiguous, trunk neuromuscular control should be maximally challenged. Thirty-four healthy subjects balanced on a robotic seat capable of adjusting rotational stiffness. Subjects balanced while rotational stiffness was gradually reduced. The rotational stiffness at which subjects could no longer maintain balance, defined as critical stiffness (kCrit), was used to quantify the subjects’ trunk neuromuscular control. A higher kCrit reflects poorer control, as subjects require a more stable base to balance. Subjects were tested on three days separated by 24 hours to assess test–retest reliability. Anthropometric (height and weight) and demographic (age and sex) influences on kCrit and its reliability were assessed. Height and age did not affect kCrit; whereas, being heavier (p < 0.001) and female (p = 0.042) significantly increased kCrit. Reliability was also affected by anthropometric and demographic factors, highlighting the potential problem of inflated reliability estimates from non-control related attributes. kCrit measurements appear reliable even after removing anthropometric and demographic influences, with adjusted correlations of 0.612 (95%CI: 0.433–0.766) versus unadjusted correlations of 0.880 (95%CI: 0.797–0.932). Besides assessment, trainers and therapists prescribing exercise could use the seated balance task and kCrit to precisely set difficulty level to a percentage of the subject's stability threshold to optimize improvements in trunk neuromuscular control and spine health.
Bibliographical noteFunding Information:
This publication was made possible in part by grant number U19 AT006057 from the National Center for Complementary and Integrative Health (NCCIH) at the National Institutes of Health based in the US . Its contents are solely the responsibility of the authors and do not necessarily represent the official views of NCCIH . Dr. Sal y Rosas Celi was supported by Dirección de Gestión de la Investigación at the PUCP based in Peru through grant DGI-2017-496 . The authors wish to thank Cody Priess for designing and developing the robotic platform used to assess trunk neuromuscular control.
All Science Journal Classification (ASJC) codes
- Orthopedics and Sports Medicine
- Biomedical Engineering