How to Confuse Motor Control: Passive Muscle Shortening Af-ter Contraction in Lengthened Position Reduces the Muscular Hold-ing Stability in the Sense of Adaptive Force

Bittmann, Frank N.; Dech, Silas; Schaefer, Laura V.

doi:10.20944/preprints202303.0101.v1

Cited by 2 publications

(2 citation statements)

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“…[20] Hence, this adaptive holding capacity is considered as a special neuromuscular function which has to be differentiated from other strength capabilities. This is further supported by studies which indicated that AFiso maxin contrast to AF maxwas found to be especially sensitive to disruptive stimuli, e.g., in healthy individuals perceiving unpleasant odors/imagery, [23][24][25] generated slack of muscle spindles, [27,28] or in Long COVID patients. [50,51] A single case showed that also nociception might have a distinct reducing effect on the AFiso max , but not on AF max .…”

Section: Introductionmentioning

confidence: 69%

“…It assesses the muscular holding capacity by adapting to an increasing external load. [20][21][22][23][24][25][26][27][28] The AF not only tests for muscle strength but also for sensorimotor control which could be limited in OA patients due to nociceptive afferents. [4] From a neurophysiological perspective the sensorimotor control is specifically challenged during an adaptive holding task as AF, since muscle tension has to be adjusted immediately to a changing external load to maintain a given limb position.…”

Section: Introductionmentioning

confidence: 99%

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Adaptive Force of hamstring muscles is reduced in patients with knee osteoarthritis compared to asymptomatic controls

Schaefer,

Dech,

Carnarius

et al. 2023

Preprint

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Quadriceps strength deficits are known for patients with knee osteoarthritis (OA). Hamstring muscles has been less often investigated and findings are not as clear as for knee extensors. In regard of OA, the neuromuscular function in the sense of Adaptive Force (AF) has never been examined before. The maximal isometric AF (AFisomax) was previously considered to be especially vulnerable to disruptive stimuli and, therefore, was assumed to show deficits in OA patients. The present study investigated AF parameters (AFisomax and maximal AF (AFmax)) as well as the maximal voluntary isometric contraction (MVIC) of hamstring muscles bilaterally of 20 knee OA patients (ART) compared to 19 asymptomatic controls (CON). For each side, MVIC was captured before and after AF measurements. Five AF trials were performed using a pneumatically driven device. Participants should maintain an isometric position despite an increasing load of the device. After reaching AFisomax, the muscle merged into eccentric muscle action whereby the force increased further to AFmax. All torque parameters (normalized to body mass) were significantly lower in ART vs. CON for both sides with almost always very large effect sizes. MVIC deficits (difference between ART and CON) amounted −28% for the more and −30% for the less affected/asymptomatic side. AFmax showed deficits of −36% and −32% and AFisomax of −37% and −24%, respectively. The reduction of AFisomax was not as high as expected, especially related to MVIC or AFmax. The ratio AFmax to MVIC was significantly lower for the more affected side of ART (84 ± 17%) vs. CON (95 ± 7%). The force rise per degree of knee extension was significantly lower for ART vs. CON. The results suggest that in general hamstrings strength deficits are present in OA patients. The hypothesized stronger deficit in maximal holding capacity (AFisomax) in ART vs. CON was not confirmed. It is suggested this might presumably result from the seating measurement position. Knee strain relief might have been present thereby which could have reduced inhibitory nociceptive effects. Importantly, OA patients seem not to be able to generate as much of their possible maximal strength during eccentric action as controls and their force rise per degree of knee extension seems to be diminished. The role of force development especially under muscle lengthening should be considered in further studies to get more specific insights into this aspect of neuromuscular control.

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Section: Introductionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Adaptive Force of hamstring muscles is reduced in patients with knee osteoarthritis compared to asymptomatic controls

Schaefer,

Dech,

Carnarius

et al. 2023

Preprint

Self Cite

View full text Add to dashboard Cite

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Another Way to Confuse Motor Control: Manual Technique Supposed to Shorten Muscle Spindles Reduces the Muscular Holding Stability in the Sense of Adaptive Force in Male Soccer Players

2023

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Sensorimotor control can be impaired by slacked muscle spindles. This was shown for reflex responses and, recently, also for muscular stability in the sense of Adaptive Force (AF). The slack in muscle spindles was generated by contracting the lengthened muscle followed by passive shortening. AF was suggested to specifically reflect sensorimotor control since it requires tension-length control in adaptation to an increasing load. This study investigated AF parameters in reaction to another, manually performed slack procedure in a preselected sample (n = 13). The AF of 11 elbow and 12 hip flexors was assessed by an objectified manual muscle test (MMT) using a handheld device. Maximal isometric AF was significantly reduced after manual spindle technique vs. regular MMT. Muscle lengthening started at 64.93 ± 12.46% of maximal voluntary isometric contraction (MVIC). During regular MMT, muscle length could be maintained stable until 92.53 ± 10.12% of MVIC. Hence, muscular stability measured by AF was impaired after spindle manipulation. Force oscillations arose at a significantly lower level for regular vs. spindle. This supports the assumption that they are a prerequisite for stable adaptation. Reduced muscular stability in reaction to slack procedures is considered physiological since sensory information is misled. It is proposed to use slack procedures to test the functionality of the neuromuscular system, which is relevant for clinical practice.

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How to Confuse Motor Control: Passive Muscle Shortening Af-ter Contraction in Lengthened Position Reduces the Muscular Hold-ing Stability in the Sense of Adaptive Force

Cited by 2 publications

References 55 publications

Adaptive Force of hamstring muscles is reduced in patients with knee osteoarthritis compared to asymptomatic controls

Adaptive Force of hamstring muscles is reduced in patients with knee osteoarthritis compared to asymptomatic controls

Another Way to Confuse Motor Control: Manual Technique Supposed to Shorten Muscle Spindles Reduces the Muscular Holding Stability in the Sense of Adaptive Force in Male Soccer Players

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