Assessment of the Adaptive Force of Elbow Extensors in Healthy Subjects Quantified by a Novel Pneumatically Driven Measurement System with Considerations of Its Quality Criteria

Abstract

Adaptive Force (AF) reflects the capability of the neuromuscular system to adapt adequately to external forces with the intention of maintaining a position or motion. One specific approach to assessing AF is to measure force and limb position during a pneumatically applied increasing external force. Through this method, the highest (AFmax), the maximal isometric (AFisomax) and the maximal eccentric Adaptive Force (AFeccmax) can be determined. The main question of the study was whether the AFisomax is a specific and independent parameter of muscle function compared to other maximal forces. In 13 healthy subjects (9 male and 4 female), the maximal voluntary isometric contraction (pre- and post-MVIC), the three AF parameters and the MVIC with a prior concentric contraction (MVICpri-con) of the elbow extensors were measured 4 times on two days. Arithmetic mean (M) and maximal (Max) torques of all force types were analyzed. Regarding the reliability of the AF parameters between days, the mean changes were 0.31–1.98 Nm (0.61%–5.47%, p = 0.175–0.552), the standard errors of measurements (SEM) were 1.29–5.68 Nm (2.53%–15.70%) and the ICCs(3,1) = 0.896–0.996. M and Max of AFisomax, AFmax and pre-MVIC correlated highly (r = 0.85–0.98). The M and Max of AFisomax were significantly lower (6.12–14.93 Nm; p ≤ 0.001–0.009) and more variable between trials (coefficient of variation (CVs) ≥ 21.95%) compared to those of pre-MVIC and AFmax (CVs ≤ 5.4%). The results suggest the novel measuring procedure is suitable to reliably quantify the AF, whereby the presented measurement errors should be taken into consideration. The AFisomax seems to reflect its own strength capacity and should be detected separately. It is suggested its normalization to the MVIC or AFmax could serve as an indicator of a neuromuscular function.

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

“…In case the neuromuscular system has to adapt to a varying external force in the described holding manner or during muscle lengthening, it is reasonable to assume that the requirements regarding the neuromuscular control could be even higher 36 , 37 . Therefore, it might be beneficial to investigate the Adaptive Force (AF) to challenge the neuromuscular control in a special way 38 , 39 . The AF reflects the holding capability to adapt adequately to external forces with the intention to maintain a given position or motion 38 , 40 , 41 .…”

“…Therefore, it might be beneficial to investigate the Adaptive Force (AF) to challenge the neuromuscular control in a special way 38 , 39 . The AF reflects the holding capability to adapt adequately to external forces with the intention to maintain a given position or motion 38 , 40 , 41 . One specific way to execute the AF is to hold a given position against a rising external load.…”

“…This necessitates a sound functionality of the sensorimotor control. If the neuromuscular system is not able to match the increasing external force isometrically, the muscle starts to lengthen in the course of the external force increase 38 . Therefore, the AF can be realized during an isometric or an eccentric muscle action.…”

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

“…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.…”

“…Thereby, the muscle's force increases further up to its maximum (AFecc max ). It has been shown that the maximal holding capacity (AFiso max ) is normally lower (~80%) than the maximal strength of a muscle [ 11 ]. This behavior and additional hints [ 12 , 13 ] suggest the ability to hold could be an independent quality of neuromuscular function.…”