@article{SchaeferDechBittmann2021,
  author    = {Schaefer, Laura and Dech, Silas and Bittmann, Frank},
  title     = {Adaptive force and emotionally related imaginations},
  series = {Heliyon},
  volume    = {7},
  journal   = {Heliyon},
  number    = {8},
  publisher = {Elsevier},
  address   = {London},
  issn      = {2405-8440},
  doi       = {10.1016/j.heliyon.2021.e07827},
  pages     = {13},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{SchaeferBittmann2017,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Are there two forms of isometric muscle action?},
  series = {BMC sports science, medicine \& rehabilitation},
  volume    = {9},
  journal   = {BMC sports science, medicine \& rehabilitation},
  publisher = {BioMed Central},
  address   = {London},
  doi       = {10.1186/s13102-017-0075-z},
  year      = {2017},
  abstract  = {Background In isometric muscle function, there are subjectively two different modes of performance: one can either hold isometrically - thus resist an impacting force - or push isometrically - therefore work against a stable resistance. The purpose of this study is to investigate whether or not two different isometric muscle actions - the holding vs. pushing one (HIMA vs PIMA) - can be distinguished by objective parameters. Methods Ten subjects performed two different measuring modes at 80\% of MVC realized by a special pneumatic system. During HIMA the subject had to resist the defined impacting force of the pneumatic system in an isometric position, whereby the force of the cylinder works in direction of elbow flexion against the subject. During PIMA the subject worked isometrically in direction of elbow extension against a stable position of the system. The signals of pressure, force, acceleration and mechanomyography/-tendography (MMG/MTG) of the elbow extensor (MMGtri/MTGtri) and the abdominal muscle (MMGobl) were recorded and evaluated concerning the duration of maintaining the force level (force endurance) and the characteristics of MMG-/MTG-signals. Statistical group differences comparing HIMA vs. PIMA were estimated using SPSS. Results Significant differences between HIMA and PIMA were especially apparent regarding the force endurance: During HIMA the subjects showed a decisively shorter time of stable isometric position (19 ± 8 s) in comparison with PIMA (41 ± 24 s; p = .005). In addition, during PIMA the longest isometric plateau amounted to 59.4\% of the overall duration time of isometric measuring, during HIMA it lasted 31.6\% (p = .000). The frequency of MMG/MTG did not show significant differences. The power in the frequency ranges of 8-15 Hz and 10-29 Hz was significantly higher in the MTGtri performing HIMA compared to PIMA (but not for the MMGs). The amplitude of MMG/MTG did not show any significant difference considering the whole measurement. However, looking only at the last 10\% of duration time (exhaustion), the MMGtri showed significantly higher amplitudes during PIMA. Conclusion The results suggest that under holding isometric conditions muscles exhaust earlier. That means that there are probably two forms of isometric muscle action. We hypothesize two potential reasons for faster yielding during HIMA: (1) earlier metabolic fatigue of the muscle fibers and (2) the complexity of neural control strategies.},
  language  = {en}
}
@article{SchaeferBittmann2017,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Are there two forms of isometric muscle action? Results of the experimental study support a distinction between a holding and a pushing isometric muscle function},
  series = {BMC sports science, medicine \& rehabilitation},
  volume    = {9},
  journal   = {BMC sports science, medicine \& rehabilitation},
  publisher = {BioMed Central},
  address   = {London},
  issn      = {2052-1847},
  doi       = {10.1186/s13102-017-0075-z},
  pages     = {13},
  year      = {2017},
  abstract  = {Background: In isometric muscle function, there are subjectively two different modes of performance: one can either hold isometrically - thus resist an impacting force - or push isometrically -therefore work against a stable resistance. The purpose of this study is to investigate whether or not two different isometric muscle actions - the holding vs. pushing one (HIMA vs PIMA) - can be distinguished by objective parameters. Methods: Ten subjects performed two different measuring modes at 80\% of MVC realized by a special pneumatic system. During HIMA the subject had to resist the defined impacting force of the pneumatic system in an isometric position, whereby the force of the cylinder works in direction of elbow flexion against the subject. During PIMA the subject worked isometrically in direction of elbow extension against a stable position of the system. The signals of pressure, force, acceleration and mechanomyography/-tendography (MMG/MTG) of the elbow extensor (MMGtri/MTGtri) and the abdominal muscle (MMGobl) were recorded and evaluated concerning the duration of maintaining the force level (force endurance) and the characteristics of MMG-/MTG-signals. Statistical group differences comparing HIMA vs. PIMA were estimated using SPSS. Results: Significant differences between HIMA and PIMA were especially apparent regarding the force endurance: During HIMA the subjects showed a decisively shorter time of stable isometric position (19 +/- 8 s) in comparison with PIMA (41 +/- 24 s; p = .005). In addition, during PIMA the longest isometric plateau amounted to 59.4\% of the overall duration time of isometric measuring, during HIMA it lasted 31.6\% (p = .000). The frequency of MMG/MTG did not show significant differences. The power in the frequency ranges of 8-15 Hz and 10-29 Hz was significantly higher in the MTGtri performing HIMA compared to PIMA (but not for the MMGs). The amplitude of MMG/MTG did not show any significant difference considering the whole measurement. However, looking only at the last 10\% of duration time (exhaustion), the MMGtri showed significantly higher amplitudes during PIMA. Conclusion: The results suggest that under holding isometric conditions muscles exhaust earlier. That means that there are probably two forms of isometric muscle action. We hypothesize two potential reasons for faster yielding during HIMA: (1) earlier metabolic fatigue of the muscle fibers and (2) the complexity of neural control strategies.},
  language  = {en}
}
@article{DechBittmannSchaefer2021,
  author    = {Dech, Silas and Bittmann, Frank and Schaefer, Laura},
  title     = {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},
  series = {Diagnostics : open access journal},
  volume    = {11},
  journal   = {Diagnostics : open access journal},
  number    = {6},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2075-4418},
  doi       = {10.3390/diagnostics11060923},
  pages     = {23},
  year      = {2021},
  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.},
  language  = {en}
}
@article{DechBittmannSchaefer2020,
  author    = {Dech, Silas and Bittmann, Frank and Schaefer, Laura},
  title     = {Behavior of oxygen saturation and blood filling in the venous capillary system of the biceps brachii muscle during a fatiguing isometric action},
  series = {European Journal of Translational Myology},
  volume    = {30},
  journal   = {European Journal of Translational Myology},
  number    = {1},
  publisher = {Unipress},
  address   = {Padova},
  issn      = {2037-7460},
  doi       = {10.4081/ejtm.2019.8800},
  pages     = {79 -- 87},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{SchaeferBittmann2023,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Case report},
  series = {Frontiers in medicine},
  volume    = {9},
  journal   = {Frontiers in medicine},
  publisher = {Frontiers Media},
  address   = {Lausanne},
  issn      = {2296-858X},
  doi       = {10.3389/fmed.2022.879971},
  pages     = {10},
  year      = {2023},
  abstract  = {The increasing prevalence of Long COVID is an imminent public health disaster, and established approaches have not provided adequate diagnostics or treatments. Recently, anesthetic blockade of the stellate ganglion was reported to improve Long COVID symptoms in a small case series, purportedly by "rebooting" the autonomic nervous system. Here, we present a novel diagnostic approach based on the Adaptive Force (AF), and report sustained positive outcome for one severely affected Long COVID patient using individualized pulsed electromagnetic field (PEMF) at the area C7/T1. AF reflects the capacity of the neuromuscular system to adapt adequately to external forces in an isometric holding manner. In case, maximal isometric AF (AFiso(max)) is exceeded, the muscle merges into eccentric muscle action. Thereby, the force usually increases further until maximal AF (AFmax) is reached. In case adaptation is optimal, AFiso(max) is similar to 99-100\% of AFmax. This holding capacity (AFiso(max)) was found to be vulnerable to disruption by unpleasant stimulus and, hence, was regarded as functional parameter. AF was assessed by an objectified manual muscle test using a handheld device. Prior to treatment, AFiso(max) was considerably lower than AFmax for hip flexors (62 N = similar to 28\% AFmax) and elbow flexors (71 N = similar to 44\% AFmax); i.e., maximal holding capacity was significantly reduced, indicating dysfunctional motor control. We tested PEMF at C7/T1, identified a frequency that improved neuromuscular function, and applied it for similar to 15 min. Immediately post-treatment, AFiso(max) increased to similar to 210 N (similar to 100\% AFmax) at hip and 184 N (similar to 100\% AFmax) at elbow. Subjective Long COVID symptoms resolved the following day. At 4 weeks post-treatment, maximal holding capacity was still on a similarly high level as for immediately post-treatment (similar to 100\% AFmax) and patient was symptom-free. At 6 months the patient's Long COVID symptoms have not returned. This case report suggests (1) AF could be a promising diagnostic for post-infectious illness, (2) AF can be used to test effective treatments for post-infectious illness, and (3) individualized PEMF may resolve post-infectious symptoms.},
  language  = {en}
}
@article{SchaeferBittmann2022,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Case Study: Intra- and Interpersonal Coherence of Muscle and Brain Activity of Two Coupled Persons during Pushing and Holding Isometric Muscle Action},
  series = {Brain Sciences},
  volume    = {12},
  journal   = {Brain Sciences},
  edition   = {6},
  publisher = {MDPI Open Access Publishing},
  address   = {Basel, Schweiz},
  issn      = {2076-3425},
  doi       = {10.3390/brainsci12060703},
  pages     = {27},
  year      = {2022},
  abstract  = {Inter-brain synchronization is primarily investigated during social interactions but had not been examined during coupled muscle action between two persons until now. It was previously shown that mechanical muscle oscillations can develop coherent behavior between two isometrically interacting persons. This case study investigated if inter-brain synchronization appears thereby, and if differences of inter- and intrapersonal muscle and brain coherence exist regarding two different types of isometric muscle action. Electroencephalography (EEG) and mechanomyography/mechanotendography (MMG/MTG) of right elbow extensors were recorded during six fatiguing trials of two coupled isometrically interacting participants (70\% MVIC). One partner performed holding and one pushing isometric muscle action (HIMA/PIMA; tasks changed). The wavelet coherence of all signals (EEG, MMG/MTG, force, ACC) were analyzed intra- and interpersonally. The five longest coherence patches in 8-15 Hz and their weighted frequency were compared between real vs. random pairs and between HIMA vs. PIMA. Real vs. random pairs showed significantly higher coherence for intra-muscle, intra-brain, and inter-muscle-brain activity (p < 0.001 to 0.019). Inter-brain coherence was significantly higher for real vs. random pairs for EEG of right and central areas and for sub-regions of EEG left (p = 0.002 to 0.025). Interpersonal muscle-brain synchronization was significantly higher than intrapersonal one, whereby it was significantly higher for HIMA vs. PIMA. These preliminary findings indicate that inter-brain synchronization can arise during muscular interaction. It is hypothesized both partners merge into one oscillating neuromuscular system. The results reinforce the hypothesis that HIMA is characterized by more complex control strategies than PIMA. The pilot study suggests investigating the topic further to verify these results on a larger sample size. Findings could contribute to the basic understanding of motor control and is relevant for functional diagnostics such as the manual muscle test which is applied in several disciplines, e.g., neurology, physiotherapy.},
  language  = {en}
}
@article{SchaeferBittmann2018,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Coherent behavior of neuromuscular oscillations between isometrically interacting subjects},
  series = {Scientific Reports},
  volume    = {8},
  journal   = {Scientific Reports},
  publisher = {Macmillan Publishers Limited},
  address   = {London},
  issn      = {2045-2322},
  doi       = {10.1038/s41598-018-33579-5},
  pages     = {1 -- 10},
  year      = {2018},
  abstract  = {Previous research has shown that electrical muscle activity is able to synchronize between muscles of one subject. The ability to synchronize the mechanical muscle oscillations measured by Mechanomyography (MMG) is not described sufficiently. Likewise, the behavior of myofascial oscillations was not considered yet during muscular interaction of two human subjects. The purpose of this study is to investigate the myofascial oscillations intra- and interpersonally. For this the mechanical muscle oscillations of the triceps and the abdominal external oblique muscles were measured by MMG and the triceps tendon was measured by mechanotendography (MTG) during isometric interaction of two subjects (n = 20) performed at 80\% of the MVC using their arm extensors. The coherence of MMG/MTG-signals was analyzed with coherence wavelet transform and was compared with randomly matched signal pairs. Each signal pairing shows significant coherent behavior. Averagely, the coherent phases of n = 485 real pairings last over 82 ± 39 \% of the total duration time of the isometric interaction. Coherent phases of randomly matched signal pairs take 21 ± 12 \% of the total duration time (n = 39). The difference between real vs. randomly matched pairs is significant (U = 113.0, p = 0.000, r = 0.73). The results show that the neuromuscular system seems to be able to synchronize to another neuromuscular system during muscular interaction and generate a coherent behavior of the mechanical muscular oscillations. Potential explanatory approaches are discussed.},
  language  = {en}
}
@article{SchaeferDechAehleetal.2021,
  author    = {Schaefer, Laura and Dech, Silas and Aehle, Markus and Bittmann, Frank},
  title     = {Disgusting odours affect the characteristics of the adaptive force in contrast to neutral and pleasant odours},
  series = {Scientific Reports},
  volume    = {11},
  journal   = {Scientific Reports},
  publisher = {Springer Nature},
  address   = {London},
  issn      = {2045-2322},
  doi       = {10.1038/s41598-021-95759-0},
  pages     = {1 -- 16},
  year      = {2021},
  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.},
  language  = {en}
}
@article{SchaeferDechWolffetal.2022,
  author    = {Schaefer, Laura and Dech, Silas and Wolff, Lara L. and Bittmann, Frank},
  title     = {Emotional Imagery Influences the Adaptive Force in Young Women},
  series = {Brain Sciences},
  volume    = {12},
  journal   = {Brain Sciences},
  number    = {10},
  publisher = {MDPI},
  address   = {Basel, Schweiz},
  issn      = {2076-3425},
  doi       = {10.3390/brainsci12101318},
  pages     = {23},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{BittmannDechAehleetal.2020,
  author    = {Bittmann, Frank and Dech, Silas and Aehle, Markus and Schaefer, Laura},
  title     = {Manual Muscle Testing—Force Profiles and Their Reproducibility},
  series = {Diagnostics},
  volume    = {10},
  journal   = {Diagnostics},
  number    = {12},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2075-4418},
  doi       = {10.3390/diagnostics10120996},
  pages     = {30},
  year      = {2020},
  abstract  = {The manual muscle test (MMT) is a flexible diagnostic tool, which is used in many disciplines, applied in several ways. The main problem is the subjectivity of the test. The MMT in the version of a "break test" depends on the tester's force rise and the patient's ability to resist the applied force. As a first step, the investigation of the reproducibility of the testers' force profile is required for valid application. The study examined the force profiles of n = 29 testers (n = 9 experiences (Exp), n = 8 little experienced (LitExp), n = 12 beginners (Beg)). The testers performed 10 MMTs according to the test of hip flexors, but against a fixed leg to exclude the patient's reaction. A handheld device recorded the temporal course of the applied force. The results show significant differences between Exp and Beg concerning the starting force (padj = 0.029), the ratio of starting to maximum force (padj = 0.005) and the normalized mean Euclidean distances between the 10 trials (padj = 0.015). The slope is significantly higher in Exp vs. LitExp (p = 0.006) and Beg (p = 0.005). The results also indicate that experienced testers show inter-tester differences and partly even a low intra-tester reproducibility. This highlights the necessity of an objective MMT-assessment. Furthermore, an agreement on a standardized force profile is required. A suggestion for this is given.},
  language  = {en}
}
@article{SchaeferHoffBittmann2017,
  author    = {Schaefer, Laura and Hoff, Marco and Bittmann, Frank},
  title     = {Measuring system and method of determining the Adaptive Force},
  series = {European journal of translational myology},
  volume    = {27},
  journal   = {European journal of translational myology},
  number    = {3},
  publisher = {Unipress},
  address   = {Padova},
  issn      = {2037-7460},
  doi       = {10.4081/ejtm.2017.6479},
  pages     = {152 -- 159},
  year      = {2017},
  abstract  = {The term Adaptive Force (AF) describes the capability of adaptation of the nerve-muscle-system to externally applied forces during isometric and eccentric muscle action. This ability plays an important role in real life motions as well as in sports. The focus of this paper is on the specific measurement method of this neuromuscular action, which can be seen as innovative. A measuring system based on the use of compressed air was constructed and evaluated for this neuromuscular function. It depends on the physical conditions of the subject, at which force level it deviates from the quasi isometric position and merges into eccentric muscle action. The device enables - in contrast to the isokinetic systems - a measure of strength without forced motion. Evaluation of the scientific quality criteria of the devices was done by measurements regarding the intra- and interrater-, the test-retest-reliability and fatiguing measurements. Comparisons of the pneumatic device with a dynamometer were also done. Looking at the mechanical evaluation, the results show a high level of consistency (r²=0.94 to 0.96). The parallel test reliability delivers a very high and significant correlation (ρ=0.976; p=0.000). Including the biological system, the concordance of three different raters is very high (p=0.001, Cronbachs alpha α=0.987). The test retest with 4 subjects over five weeks speaks for the reliability of the device in showing no statistically significant differences. These evaluations indicate that the scientific evaluation criteria are fulfilled. The specific feature of this system is that an isometric position can be maintained while the externally impacting force rises. Moreover, the device can capture concentric, static and eccentric strength values. Fields of application are performance diagnostics in sports and medicine.},
  language  = {en}
}
@article{SchaeferLoefflerKleinetal.2021,
  author    = {Schaefer, Laura and L{\"o}ffler, Nils and Klein, Julia and Bittmann, Frank},
  title     = {Mechanomyography and acceleration show interlimb asymmetries in Parkinson patients without tremor compared to controls during a unilateral motor task},
  series = {Scientific Reports},
  volume    = {11},
  journal   = {Scientific Reports},
  publisher = {Springer Nature},
  address   = {Berlin},
  issn      = {2045-2322},
  doi       = {10.1038/s41598-021-81672-z},
  pages     = {15},
  year      = {2021},
  abstract  = {The mechanical muscular oscillations are rarely the objective of investigations regarding the identification of a biomarker for Parkinson's disease (PD). Therefore, the aim of this study was to investigate whether or not this specific motor output differs between PD patients and controls. The novelty is that patients without tremor are investigated performing a unilateral isometric motor task. The force of armflexors and the forearm acceleration (ACC) were recorded as well as the mechanomyography of the biceps brachii (MMGbi), brachioradialis (MMGbra) and pectoralis major (MMGpect) muscles using a piezoelectric-sensor-based system during a unilateral motor task at 70\% of the MVIC. The frequency, a power-frequency-ratio, the amplitude variation, the slope of amplitudes and their interlimb asymmetries were analysed. The results indicate that the oscillatory behavior of muscular output in PD without tremor deviates from controls in some parameters: Significant differences appeared for the power-frequency-ratio (p = 0.001, r = 0.43) and for the amplitude variation (p = 0.003, r = 0.34) of MMGpect. The interlimb asymmetries differed significantly concerning the power-frequency-ratio of MMGbi (p = 0.013, r = 0.42) and MMGbra (p = 0.048, r = 0.39) as well as regarding the mean frequency (p = 0.004, r = 0.48) and amplitude variation of MMGpect (p = 0.033, r = 0.37). The mean (M) and variation coefficient (CV) of slope of ACC differed significantly (M: p = 0.022, r = 0.33; CV: p = 0.004, r = 0.43). All other parameters showed no significant differences between PD and controls. It remains open, if this altered mechanical muscular output is reproducible and specific for PD.},
  language  = {en}
}
@article{SchaeferLoefflerKleinetal.2021,
  author    = {Schaefer, Laura and L{\"o}ffler, Nils and Klein, Julia and Bittmann, Frank},
  title     = {Mechanomyography and acceleration show interlimb asymmetries in Parkinson patients without tremor compared to controls during a unilateral motor task},
  series = {Scientific reports},
  volume    = {11},
  journal   = {Scientific reports},
  number    = {1},
  publisher = {Macmillan},
  address   = {London},
  issn      = {2045-2322},
  doi       = {10.1038/s41598-021-81672-z},
  pages     = {15},
  year      = {2021},
  abstract  = {The mechanical muscular oscillations are rarely the objective of investigations regarding the identification of a biomarker for Parkinson's disease (PD). Therefore, the aim of this study was to investigate whether or not this specific motor output differs between PD patients and controls. The novelty is that patients without tremor are investigated performing a unilateral isometric motor task. The force of armflexors and the forearm acceleration (ACC) were recorded as well as the mechanomyography of the biceps brachii (MMGbi), brachioradialis (MMGbra) and pectoralis major (MMGpect) muscles using a piezoelectric-sensor-based system during a unilateral motor task at 70\% of the MVIC. The frequency, a power-frequency-ratio, the amplitude variation, the slope of amplitudes and their interlimb asymmetries were analysed. The results indicate that the oscillatory behavior of muscular output in PD without tremor deviates from controls in some parameters: Significant differences appeared for the power-frequency-ratio (p=0.001, r=0.43) and for the amplitude variation (p=0.003, r=0.34) of MMGpect. The interlimb asymmetries differed significantly concerning the power-frequency-ratio of MMGbi (p=0.013, r=0.42) and MMGbra (p=0.048, r=0.39) as well as regarding the mean frequency (p=0.004, r=0.48) and amplitude variation of MMGpect (p=0.033, r=0.37). The mean (M) and variation coefficient (CV) of slope of ACC differed significantly (M: p=0.022, r=0.33; CV: p=0.004, r=0.43). All other parameters showed no significant differences between PD and controls. It remains open, if this altered mechanical muscular output is reproducible and specific for PD.},
  language  = {en}
}
@article{SchaeferBittmann2021,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Mechanotendography},
  series = {European journal of translational myology : European journal ; basic applied myology ; BAM online ; myology reviews},
  journal   = {European journal of translational myology : European journal ; basic applied myology ; BAM online ; myology reviews},
  number    = {31},
  publisher = {Unipress},
  address   = {Padova, Italien},
  issn      = {2037-7460},
  doi       = {10.4081/ejtm.2021.9553},
  pages     = {10},
  year      = {2021},
  abstract  = {The mechanotendography (MTG) is a method for analyzing the mechanical oscillations of tendons during muscular actions. The aim of this investigation was to evaluate the technical reliability of a piezo-based measurement system used for MTG. The reliability measurements were performed by using audio samples played by a subwoofer. The thereby generated pressure waves were recorded by a piezo-based measurement system. An audio of 40 Hz sine oscillations and four different formerly in vivo recorded MTG-signals were converted into audio files and were used as test signals. Five trials with each audio were performed and one audio was used for repetition trials on another day. The signals' correlation was estimated by Spearman (MCC) and intraclass correlation coefficients (ICC(3,1)), Cronbach's alpha (CA) and by mean distances (MD). All parameters were compared between repetition and randomized matched signals. The repetition trials show high correlations (MCC: 0.86 ± 0.13, ICC: 0.89 ± 0.12, CA: 0.98 ± 0.03), low MD (0.03 ± 0.03V) and differ significantly from the randomized matched signals (MCC: 0.15 ± 0.10, ICC: 0.17 ± 0.09, CA: 0.37 ± 0.16, MD: 0.19 ± 0.01V) (p = 0.001 - 0.043). This speaks for an excellent reliability of the measurement system. Presuming the skin above superficial tendons oscillates adequately, we estimate this tool as valid for the application in musculoskeletal system.},
  language  = {en}
}
@article{SchaeferBittmann2020,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Mechanotendography in Achillodynia shows reduced oscillation variability of pre-loaded Achilles tendon},
  series = {European Journal of Translational Myology (EJTM)},
  volume    = {30},
  journal   = {European Journal of Translational Myology (EJTM)},
  number    = {2},
  publisher = {Unipress},
  address   = {Padova},
  issn      = {2037-7460},
  doi       = {10.4081/ejtm.2020.8983},
  pages     = {247 -- 257},
  year      = {2020},
  abstract  = {The present study focuses on an innovative approach in measuring the mechanical oscillations of pre-loaded Achilles tendon by using Mechanotendography (MTG) during application of a short yet powerful mechanical pressure impact. This was applied on the forefoot from the plantar side in direction of dorsiflexion, while the subject stood on the ball of the forefoot on one leg. Participants with Achilles tendinopathy (AT; n = 10) were compared to healthy controls (Con; n = 10). Five trials were performed on each side of the body. For evaluation, two intervals after the impulse began (0-100ms; 30-100ms) were cut from the MTG and pressure raw signals. The intrapersonal variability between the five trials in both intervals were evaluated using the arithmetic mean and coefficient of variation of the mean correlation (Spearman rank correlation) and the normalized averaged mean distances, respectively. The AT-group showed a significantly reduced variability in MTG compared to the Con-group (from p = 0.006 to p = 0.028 for different parameters). The 95\% confidence intervals (CI) of MTG results were disjoint, whereas the 95\% CIs of the pressure signals were similar (p = 0.192 to p = 0.601). We suggest from this work that the variability of mechanical tendon oscillations could be an indicative parameter of an altered Achilles tendon functionality.},
  language  = {en}
}
@article{DechBittmannSchaefer2022,
  author    = {Dech, Silas and Bittmann, Frank and Schaefer, Laura},
  title     = {Muscle oxygenation and time to task failure of submaximal holding and pulling isometric muscle actions and influence of intermittent voluntary muscle twitches},
  series = {BMC Sports Science, Medicine and Rehabilitation},
  volume    = {55},
  journal   = {BMC Sports Science, Medicine and Rehabilitation},
  publisher = {Springer Nature},
  address   = {London},
  issn      = {1758-2555},
  doi       = {10.1186/s13102-022-00447-9},
  pages     = {1 -- 10},
  year      = {2022},
  abstract  = {Background Isometric muscle actions can be performed either by initiating the action, e.g., pulling on an immovable resistance (PIMA), or by reacting to an external load, e.g., holding a weight (HIMA). In the present study, it was mainly examined if these modalities could be differentiated by oxygenation variables as well as by time to task failure (TTF). Furthermore, it was analyzed if variables are changed by intermittent voluntary muscle twitches during weight holding (Twitch). It was assumed that twitches during a weight holding task change the character of the isometric muscle action from reacting (≙ HIMA) to acting (≙ PIMA). Methods Twelve subjects (two drop outs) randomly performed two tasks (HIMA vs. PIMA or HIMA vs. Twitch, n = 5 each) with the elbow flexors at 60\% of maximal torque maintained until muscle failure with each arm. Local capillary venous oxygen saturation (SvO2) and relative hemoglobin amount (rHb) were measured by light spectrometry. Results Within subjects, no significant differences were found between tasks regarding the behavior of SvO2 and rHb, the slope and extent of deoxygenation (max. SvO2 decrease), SvO2 level at global rHb minimum, and time to SvO2 steady states. The TTF was significantly longer during Twitch and PIMA (incl. Twitch) compared to HIMA (p = 0.043 and 0.047, respectively). There was no substantial correlation between TTF and maximal deoxygenation independently of the task (r = - 0.13). Conclusions HIMA and PIMA seem to have a similar microvascular oxygen and blood supply. The supply might be sufficient, which is expressed by homeostatic steady states of SvO2 in all trials and increases in rHb in most of the trials. Intermittent voluntary muscle twitches might not serve as a further support but extend the TTF. A changed neuromuscular control is discussed as possible explanation.},
  language  = {en}
}
@article{DechBittmannSchaefer2021,
  author    = {Dech, Silas and Bittmann, Frank and Schaefer, Laura},
  title     = {Muscle oxygenation level might trigger the regulation of capillary venous blood filling during fatiguing isometric muscle actions},
  series = {Diagnostics : open access journal},
  volume    = {11},
  journal   = {Diagnostics : open access journal},
  number    = {11},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2075-4418},
  doi       = {10.3390/diagnostics11111973},
  pages     = {17},
  year      = {2021},
  abstract  = {The regulation of oxygen and blood supply during isometric muscle actions is still unclear. Recently, two behavioral types of oxygen saturation (SvO(2)) and relative hemoglobin amount (rHb) in venous microvessels were described during a fatiguing holding isometric muscle action (HIMA) (type I: nearly parallel behavior of SvO(2) and rHb; type II: partly inverse behavior). The study aimed to ascertain an explanation of these two regulative behaviors. Twelve subjects performed one fatiguing HIMA trial with each arm by weight holding at 60\% of the maximal voluntary isometric contraction (MVIC) in a 90 \& DEG; elbow flexion. Six subjects additionally executed one fatiguing PIMA trial by pulling on an immovable resistance with 60\% of the MVIC with each side and same position. Both regulative types mentioned were found during HIMA (I: n = 7, II: n = 17) and PIMA (I: n = 3, II: n = 9). During the fatiguing measurements, rHb decreased initially and started to increase in type II at an average SvO(2)-level of 58.75 \& PLUSMN; 2.14\%. In type I, SvO(2) never reached that specific value during loading. This might indicate the existence of a threshold around 59\% which seems to trigger the increase in rHb and could explain the two behavioral types. An approach is discussed to meet the apparent incompatibility of an increased capillary blood filling (rHb) despite high intramuscular pressures which were found by other research groups during isometric muscle actions.},
  language  = {en}
}
@article{DechBittmannSchaefer2021,
  author    = {Dech, Silas and Bittmann, Frank and Schaefer, Laura},
  title     = {Muscle oxygenation level might trigger the regulation of capillary venous blood filling during fatiguing isometric muscle actions},
  series = {Diagnostics},
  volume    = {11},
  journal   = {Diagnostics},
  number    = {11},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2075-4418},
  pages     = {17},
  year      = {2021},
  abstract  = {The regulation of oxygen and blood supply during isometric muscle actions is still unclear. Recently, two behavioral types of oxygen saturation (SvO2) and relative hemoglobin amount (rHb) in venous microvessels were described during a fatiguing holding isometric muscle action (HIMA) (type I: nearly parallel behavior of SvO2 and rHb; type II: partly inverse behavior). The study aimed to ascertain an explanation of these two regulative behaviors. Twelve subjects performed one fatiguing HIMA trial with each arm by weight holding at 60\% of the maximal voluntary isometric contraction (MVIC) in a 90° elbow flexion. Six subjects additionally executed one fatiguing PIMA trial by pulling on an immovable resistance with 60\% of the MVIC with each side and same position. Both regulative types mentioned were found during HIMA (I: n = 7, II: n = 17) and PIMA (I: n = 3, II: n = 9). During the fatiguing measurements, rHb decreased initially and started to increase in type II at an average SvO2-level of 58.75 ± 2.14\%. In type I, SvO2 never reached that specific value during loading. This might indicate the existence of a threshold around 59\% which seems to trigger the increase in rHb and could explain the two behavioral types. An approach is discussed to meet the apparent incompatibility of an increased capillary blood filling (rHb) despite high intramuscular pressures which were found by other research groups during isometric muscle actions.},
  language  = {en}
}
@article{SchaeferBittmann2019,
  author    = {Schaefer, Laura and Bittmann, Frank},
  title     = {Muscular Pre-Activation Can Boost the Maximal Explosive Eccentric Adaptive Force},
  series = {Frontiers in Physiology},
  volume    = {10},
  journal   = {Frontiers in Physiology},
  publisher = {Frontiers Research Foundation},
  address   = {Lausanne},
  issn      = {1664-042X},
  doi       = {10.3389/fphys.2019.00910},
  pages     = {12},
  year      = {2019},
  abstract  = {The improvement of power is an objective in training of athletes. In order to detect effective methods of exercise, basic research is required regarding the mechanisms of muscular activity. The purpose of this study is to investigate whether or not a muscular pre-activation prior to an external impulse-like force impact has an effect on the maximal explosive eccentric Adaptive Force (xpAFeccmax). This power capability combines different probable power enhancing mechanisms. To measure the xpAFeccmax an innovative pneumatic device was used. During measuring, the subject tries to hold an isometric position as long as possible. In the moment in which the subjects' maximal isometric holding strength is exceeded, it merges into eccentric muscle action. This process is very close to motions in sports, where an adaptation of the neuromuscular system is required, e.g., force impacts caused by uneven surfaces during skiing. For investigating the effect of pre-activation on the xpAFeccmax of the quadriceps femoris muscle, n = 20 subjects had to pass three different pre-activation levels in a randomized order (level 1: 0.4 bar, level 2: 0.8 bar, level 3: 1.2 bar). After adjusting the standardized pre-pressure by pushing against the interface, an impulse-like load impacted on the distal tibia of the subject. During this, the xpAFeccmax was detected. The maximal voluntary isometric contraction (MVIC) was also measured. The torque values of the xpAFeccmax were compared with regard to the pre-activation levels. The results show a significant positive relation between the pre-activation of the quadriceps femoris muscle and the xpAFeccmax (male: p = 0.000, η2= 0.683; female: p = 0.000, η2= 0.907). The average percentage increase of torque amounted +28.15 ± 25.4\% between MVIC and xpAFeccmax with pre-pressure level 1, +12.09 ± 7.9\% for the xpAFeccmax comparing pre-pressure levels 1 vs. 2 and +2.98 ± 4.2\% comparing levels 2 and 3. A higher but not maximal muscular activation prior to a fast impacting eccentric load seems to produce an immediate increase of force outcome. Different possible physiological explanatory approaches and the use as a potential training method are discussed.},
  language  = {en}
}