TY - JOUR A1 - Schaefer, Laura A1 - Carnarius, Friederike A1 - Dech, Silas A1 - Bittmann, Frank T1 - Repeated measurements of Adaptive Force BT - maximal holding capacity differs from other maximal strength parameters and preliminary characteristics for non-professional strength vs. endurance athletes JF - Frontiers in physiology N2 - The Adaptive Force (AF) reflects the neuromuscular capacity to adapt to external loads during holding muscle actions and is similar to motions in real life and sports. The maximal isometric AF (AFisoₘₐₓ) was considered to be the most relevant parameter and was assumed to have major importance regarding injury mechanisms and the development of musculoskeletal pain. The aim of this study was to investigate the behavior of different torque parameters over the course of 30 repeated maximal AF trials. In addition, maximal holding vs. maximal pushing isometric muscle actions were compared. A side consideration was the behavior of torques in the course of repeated AF actions when comparing strength and endurance athletes. The elbow flexors of n = 12 males (six strength/six endurance athletes, non-professionals) were measured 30 times (120 s rest) using a pneumatic device. Maximal voluntary isometric contraction (MVIC) was measured pre and post. MVIC, AFisoₘₐₓ, and AFₘₐₓ (maximal torque of one AF measurement) were evaluated regarding different considerations and statistical tests. AFₘₐₓ and AFisoₘₐₓ declined in the course of 30 trials [slope regression (mean ± standard deviation): AFₘₐₓ = −0.323 ± 0.263; AFisoₘₐₓ = −0.45 ± 0.45]. The decline from start to end amounted to −12.8% ± 8.3% (p < 0.001) for AFₘₐₓ and −25.41% ± 26.40% (p < 0.001) for AFisoₘₐₓ. AF parameters declined more in strength vs. endurance athletes. Thereby, strength athletes showed a rather stable decline for AFmax and a plateau formation for AFisoₘₐₓ after 15 trials. In contrast, endurance athletes reduced their AFₘₐₓ, especially after the first five trials, and remained on a rather similar level for AFisomax. The maximum of AFisoₘₐₓ of all 30 trials amounted 67.67% ± 13.60% of MVIC (p < 0.001, n = 12), supporting the hypothesis of two types of isometric muscle action (holding vs. pushing). The findings provided the first data on the behavior of torque parameters after repeated isometric–eccentric actions and revealed further insights into neuromuscular control strategies. Additionally, they highlight the importance of investigating AF parameters in athletes based on the different behaviors compared to MVIC. This is assumed to be especially relevant regarding injury mechanisms. KW - Adaptive Force KW - maximal isometric Adaptive Force KW - holding capacity KW - neuromuscular control KW - strength vs. endurance athletes KW - injury mechanisms KW - repeated adaptive isometric–eccentric muscle action KW - holding (HIMA) and pushing (PIMA) isometric muscle action Y1 - 2023 U6 - https://doi.org/10.3389/fphys.2023.1020954 SN - 1664-042X VL - 14 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Schaefer, Laura A1 - Dech, Silas A1 - Wolff, Lara L. A1 - Bittmann, Frank T1 - Emotional Imagery Influences the Adaptive Force in Young Women BT - Unpleasant Imagery Reduces Instantaneously the Muscular Holding Capacity JF - Brain Sciences N2 - 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. KW - Adaptive Force KW - maximal isometric Adaptive Force KW - holding capability KW - neuromuscular adaptation KW - motor control KW - pleasant and unpleasant imagery KW - emotions KW - emotional imagery KW - manual muscle test Y1 - 2022 U6 - https://doi.org/10.3390/brainsci12101318 SN - 2076-3425 VL - 12 IS - 10 PB - MDPI CY - Basel, Schweiz ER - TY - JOUR A1 - Schaefer, Laura A1 - Dech, Silas A1 - Bittmann, Frank T1 - Adaptive force and emotionally related imaginations BT - Preliminary results suggest a reduction of the maximal holding capacity as reaction to disgusting food imagination JF - Heliyon N2 - 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. KW - Adaptive Force KW - Isometric Adaptive Force KW - Holding capacity KW - Holding KW - isometric muscle action KW - Imaginations KW - Emotions KW - Motor control KW - Functional weakness KW - Manual muscle test Y1 - 2021 U6 - https://doi.org/10.1016/j.heliyon.2021.e07827 SN - 2405-8440 VL - 7 IS - 8 PB - Elsevier CY - London ER -