Neuromuscular organization during balance-correcting responses induced with platform-translation and upper body cable-pull perturbation methods

Balance-correcting responses are fast, accurate, and functionally-and directionally-specific. However, there remains a lack of clarity in the literature as to how balance-correcting re-sponses are organized, perhaps due to use of various perturbation methods. This study investi-gated the differences in neuromuscular organization of balance-correcting responses induced with platform-translation (PLAT) and upper body cable-pull (PULL) methods. Healthy males (n = 15; age: 24.3 +/- 3.0 years) underwent unexpected forward and backward PLAT and PULL perturba-tions of equivalent intensity. EMG of leg, thigh, and trunk anterior and posterior muscles was recorded bilaterally during forward-stepping trials. Muscle activation latencies were calculated with respect to perturbation initiation. Repeated measures ANOVAs tested for differences in muscle activation latencies between perturbation methods and body sides (anterior/posterior muscles, swing/stance limb sides); Holm-Bonferroni sequentially rejective procedure adjusted alpha during multiple comparisons. Anterior muscle activation latencies were similar between methods (-210 ms). During PLAT trials, posterior muscles demonstrated symmetrical distal-proximal activation between 70 ms and 260 ms, bilaterally. During PULL trials, stance-limb side posterior muscles demonstrated proximal-distal activation 70-130 ms; the activation la-tencies (-80 ms) were not different between the stance-limb side posterior muscles. Previous examinations of method comparisons have examined results across publications, and generally have not accounted for different stimulus characteristics. This study revealed markedly different neuromuscular organization of balance-correcting responses to two different perturbation methods that utilized, importantly, equivalent perturbation intensity. Interpretation of functional balance recovery responses requires clear understanding of the intensity and nature of the perturbation.

Automated summary

Balance-correcting responses are fast, accurate, and functionally-and directionally-specific. However, there remains a lack of clarity in the literature as to how balance-correcting responses are organized, perhaps due to use of various perturbation methods. This study investigated the differences in neuromuscular organization of balance-correcting responses induced with platform-translation (PLAT) and upper body cable-pull (PULL) methods.