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The link between emotions and motor control has been discussed for years. The measurement of the Adaptive Force (AF) provides the possibility to get insights into the adaptive control of the neuromuscular system in reaction to external forces. It was hypothesized that the holding isometric AF is especially vulnerable to disturbing inputs. Here, the behavior of the AF under the influence of positive (tasty) vs. negative (disgusting) food imaginations was investigated. The AF was examined in n = 12 cases using an objectified manual muscle test of the hip flexors, elbow flexors or pectoralis major muscle, performed by one of two experienced testers while the participants imagined their most tasty or most disgusting food. The reaction force and the limb position were measured by a handheld device. While the slope of force rises and the maximal AF did not differ significantly between tasty and disgusting imaginations (p > 0.05), the maximal isometric AF was significantly lower and the AF at the onset of oscillations was significantly higher under disgusting vs. tasty imaginations (both p = 0.001). A proper length tension control of muscles seems to be a crucial functional parameter of the neuromuscular system which can be impaired instantaneously by emotionally related negative imaginations. This might be a potential approach to evaluate somatic reactions to emotions.
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.
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.
The objective of the study is to develop a better understanding of the capillary circulation in contracting muscles. Ten subjects were measured during a submaximal fatiguing isometric muscle action by use of the O2C spectrophotometer. In all measurements the capillary-venous oxygen saturation of hemoglobin (SvO2) decreases immediately after the start of loading and levels off into a steady state. However, two different patterns (type I and type II) emerged. They differ in the extent of deoxygenation (–10.37 ±2.59 percent points (pp) vs. –33.86 ±17.35 pp, P = .008) and the behavior of the relative hemoglobin amount (rHb). Type I reveals a positive rank correlation of SvO2 and rHb (? = 0.735, P <.001), whereas a negative rank correlation (? = –0.522, P <.001) occurred in type II, since rHb decreases until a reversal point, then increases averagely 13% above the baseline value and levels off into a steady state. The results reveal that a homeostasis of oxygen delivery and consumption during isometric muscle actions is possible. A rough distinction in two types of regulation is suggested.
The objective of the study is to develop a better understanding of the capillary circulation in contracting muscles. Ten subjects were measured during a submaximal fatiguing isometric muscle action by use of the O2C spectrophotometer. In all measurements the capillary-venous oxygen saturation of hemoglobin (SvO2) decreases immediately after the start of loading and levels off into a steady state. However, two different patterns (type I and type II) emerged. They differ in the extent of deoxygenation (–10.37 ±2.59 percent points (pp) vs. –33.86 ±17.35 pp, P = .008) and the behavior of the relative hemoglobin amount (rHb). Type I reveals a positive rank correlation of SvO2 and rHb (? = 0.735, P <.001), whereas a negative rank correlation (? = –0.522, P <.001) occurred in type II, since rHb decreases until a reversal point, then increases averagely 13% above the baseline value and levels off into a steady state. The results reveal that a homeostasis of oxygen delivery and consumption during isometric muscle actions is possible. A rough distinction in two types of regulation is suggested.
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.
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.
The link between emotions and motor function has been known for decades but is still not clarified. The Adaptive Force (AF) describes the neuromuscular capability to adapt to increasing forces and was suggested to be especially vulnerable to interfering inputs. This study investigated the influence of pleasant an unpleasant food imagery on the manually assessed AF of elbow and hip flexors objectified by a handheld device in 12 healthy women. The maximal isometric AF was significantly reduced during unpleasant vs. pleasant imagery and baseline (p < 0.001, dz = 0.98–1.61). During unpleasant imagery, muscle lengthening started at 59.00 ± 22.50% of maximal AF, in contrast to baseline and pleasant imagery, during which the isometric position could be maintained mostly during the entire force increase up to ~97.90 ± 5.00% of maximal AF. Healthy participants showed an immediately impaired holding function triggered by unpleasant imagery, presumably related to negative emotions. Hence, AF seems to be suitable to test instantaneously the effect of emotions on motor function. Since musculoskeletal complaints can result from muscular instability, the findings provide insights into the understanding of the causal chain of linked musculoskeletal pain and mental stress. A case example (current stress vs. positive imagery) suggests that the approach presented in this study might have future implications for psychomotor diagnostics and therapeutics.
The link between emotions and motor function has been known for decades but is still not clarified. The Adaptive Force (AF) describes the neuromuscular capability to adapt to increasing forces and was suggested to be especially vulnerable to interfering inputs. This study investigated the influence of pleasant an unpleasant food imagery on the manually assessed AF of elbow and hip flexors objectified by a handheld device in 12 healthy women. The maximal isometric AF was significantly reduced during unpleasant vs. pleasant imagery and baseline (p < 0.001, dz = 0.98–1.61). During unpleasant imagery, muscle lengthening started at 59.00 ± 22.50% of maximal AF, in contrast to baseline and pleasant imagery, during which the isometric position could be maintained mostly during the entire force increase up to ~97.90 ± 5.00% of maximal AF. Healthy participants showed an immediately impaired holding function triggered by unpleasant imagery, presumably related to negative emotions. Hence, AF seems to be suitable to test instantaneously the effect of emotions on motor function. Since musculoskeletal complaints can result from muscular instability, the findings provide insights into the understanding of the causal chain of linked musculoskeletal pain and mental stress. A case example (current stress vs. positive imagery) suggests that the approach presented in this study might have future implications for psychomotor diagnostics and therapeutics.
Isometric muscle function
(2022)
The cumulative dissertation consists of four original articles. These considered isometric muscle ac-tions in healthy humans from a basic physiological view (oxygen and blood supply) as well as possibilities of their distinction. It includes a novel approach to measure a specific form of isometric hold-ing function which has not been considered in motor science so far. This function is characterized by an adaptation to varying external forces with particular importance in daily activities and sports.
The first part of the research program analyzed how the biceps brachii muscle is supplied with oxygen and blood by adapting to a moderate constant load until task failure (publication 1). In this regard, regulative mechanisms were investigated in relation to the issue of presumably compressed capillaries due to high intramuscular pressures (publication 2).
Furthermore, it was examined if oxygenation and time to task failure (TTF) differs compared to an-other isometric muscle function (publication 3). This function is mainly of diagnostic interest by measuring the maximal voluntary isometric contraction (MVIC) as a gold standard. For that, a person pulls on or pushes against an insurmountable resistance. However, the underlying pulling or pushing form of isometric muscle action (PIMA) differs compared to the holding one (HIMA).
HIMAs have mainly been examined by using constant loads. In order to quantify the adaptability to varying external forces, a new approach was necessary and considered in the second part of the research program. A device was constructed based on a previously developed pneumatic measurement system. The device should have been able to measure the Adaptive Force (AF) of elbow ex-tensor muscles. The AF determines the adaptability to increasing external forces under isometric (AFiso) and eccentric (AFecc) conditions. At first, it was questioned if these parameters can be relia-bly assessed by use of the new device (publication 4). Subsequently, the main research question was investigated: Is the maximal AFiso a specific and independent variable of muscle function in comparison to the MVIC? Furthermore, both research parts contained a sub-question of how results can be influenced.
Parameters of local oxygen saturation (SvO2) and capillary blood filling (rHb) were non-invasively recorded by a spectrophotometer during maximal and submaximal HIMAs and PIMAs.
These were the main findings: Under load, SvO2 and rHb always adjusted into a steady state after an initial decrease. Nevertheless, their behavior could roughly be categorized into two types. In type I, both parameters behaved nearly parallel to each other. In contrast, their progression over time was partly inverse in type II. The inverse behavior probably depends on the level of deoxygenation since rHb increased reliably at a suggested threshold of about 59% SvO2. This triggered mechanism and the found homeostatic steady states seem to be in conflict with the concept of mechanically compressed capillaries and consequently with a restricted blood flow. Anatomical configuration of blood vessels might provide one hypothetical explanation of how blood flow might be maintained. HIMA and PIMA did not differ regarding oxygenation and allocation to the described types. The TTF tended to be longer during PIMA.
As a sub-question, oxygenation and TTF were compared between (HIMA) and intermittent voluntary muscle twitches during a weight holding task. TTF but not oxygenation differed significantly
(Twitch > HIMA). A changed neuromuscular control might serve as a speculative explanation of how the results can be explained. This is supported by the finding that the TTF did not correlate significantly with the extent of deoxygenation irrespective of the performed task (HIMA, PIMA or Twitch).
Other neuromuscular aspects of muscle function were considered in second part of the re-search program. The new device mentioned above detected different force capacities within four trials at two days each. Among AF measurements, the functional counterpart of a concentric muscle action merging into an isometric one was analyzed in comparison to the MVIC.
Based on the results, it can be assumed that a prior concentric muscle action does not influence the MVIC. However, the results were inconsistent and possibly influenced by systematic errors. In con-trast, maximal variables of the AF (AFisomax and AFeccmax) could be measured in a reliable way which is indicated by a high test-retest reliability. Despite substantial correlations between force variables, the AFisomax differed significantly from MVIC and AFmax, which was identical with AFeccmax in almost all cases. Moreover, AFisomax revealed the highest variability between trials.
These results indicate that maximal force capacities should be assessed separately. The adaptive holding capacity of a muscle can be lower compared to a commonly determined MVIC. This is of relevance since muscles frequently need to respond adequately to external forces. If their response does not correspond to the external impact, the muscle is forced to lengthen. In this scenario, joints are not completely stabilized and an injury may occur. This outlined issue should be addressed in future research in the field of sport and health sciences.
At last, the dissertation presents another possibility to quantify the AFisomax by use of a handheld device applied in combination with a manual muscle test. This assessment delivers a more practical way for clinical purposes.