Disgusting odours affect the characteristics of the Adaptive Force in contrast to neutral and pleasant odours

Abstract

The olfactomotor system is especially investigated by examining the sniffing in reaction to olfactory stimuli. The motor output of respiratory-independent muscles was seldomly considered regarding possible influences of smells. The Adaptive Force (AF) characterizes the capability of the neuromuscular system to adapt to external forces in a holding manner and was suggested to be more vulnerable to possible interfering stimuli due to the underlying complex control processes. The aim of this pilot study was to measure the effects of olfactory inputs on the AF of the hip and elbow flexors, respectively. The AF of 10 subjects was examined manually by experienced testers while smelling at sniffing sticks with neutral, pleasant or disgusting odours. The reaction force and the limb position were recorded by a handheld device. The results show, inter alia, a significantly lower maximal isometric AF and a significantly higher AF at the onset of oscillations by perceiving disgusting odours compared to pleasant or neutral odours (p < 0.001). The adaptive holding capacity seems to reflect the functionality of the neuromuscular control, which can be impaired by disgusting olfactory inputs. An undisturbed functioning neuromuscular system appears to be characterized by a proper length tension control and by an earlier onset of mutual oscillations during an external force increase. This highlights the strong connection of olfaction and motor control also regarding respiratory-independent muscles.

Adaptive Force and emotionally related imaginations – preliminary results suggest a reduction of the maximal holding capacity as reaction to disgusting food imagination

“…Since this method is similar to the one described in Schaefer et al (2021) [ 10 ], the following descriptions are partly adopted.…”

“…ZF4526901TS7) was already used in Bittmann et al. [ 8 ] and Schaefer et al (2021) [ 10 ]. It consists of strain gauges (co. Sourcing map, model: a14071900ux0076, precision: 1.0 ± 0.1%, sensitivity: 0.3 mV/V) and kinematic sensor technology (Bosch BNO055, 9-axis absolute orientation sensor, sensitivity: ±1%) to record the reaction force, the accelerations and angular velocity (gyrometry) during the MMT.…”

“…The above mentioned refined assessment is based on the concept of Adaptive Force (AF) which was introduced by the research group around Bittmann [ 7 , 8 , 9 , 10 , 11 ]. The AF is defined as the neuromuscular function which is necessary to maintain a given position or movement despite an external force impact.…”

“…This behavior and additional hints [ 12 , 13 ] suggest the ability to hold could be an independent quality of neuromuscular function. Moreover, the maximal holding AF (AFiso max ) seems to be more variable and possibly vulnerable regarding interfering influences like pleasant or unpleasant olfaction [ 10 ]. This may be due to the nature of neurophysiological motor control during a holding action [ 12 , 13 ].…”

“…Since negative imaginations are considered to cause negative emotions [ 30 ] (disgust), we presume an inhibitory effect on the motor output. We assume outcomes comparable to those of a similar pilot study concerning the influence of positive and negative experienced odors [ 10 ]. Based on those previous findings, it is hypothezised the AFiso max is reduced by disgusting vs. tasty imaginations.…”