The long and short of residual force enhancement non-responders

Power, Geoffrey A.; Hinks, Avery; Mashouri, Parastoo; Contento, Vincenzo S.; Chen, Jackey

doi:10.1007/s00421-020-04511-5

Cited by 7 publications

(4 citation statements)

References 13 publications

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“…This is way more difficult in in vivo muscle-tendon unit contractions and flexion on the joint level not necessarily always lead to stretch of the muscle (Aeles & Vanwanseele, 2019). Thus, it is not surprising that in vivo experiments on voluntary muscle action show a less clear picture in their observations, and-as mentioned above-even identify participants that do not respond to active lengthening with increased force at all (Power et al, 2020;Seiberl et al, 2015). Seiberl et al speculated that either "[…] non-responders lack certain muscle physiological abilities to generate enhanced force or […] they are limited in performance during and after lengthening as a result of neural inhibitions or insufficient task specific motor control" (Seiberl et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Residual force enhancement in humans: Is there a true non‐responder?

et al. 2021

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When an active muscle is stretched and kept isometrically active, the resulting force is enhanced compared to a purely isometric reference contraction at the same muscle length and activity; a generally accepted muscle property called residual force enhancement (rFE). Interestingly, studies on voluntary muscle action regularly identify a significant number of participants not showing rFE. Therefore, the aim was to unmask possible confounders for this non‐responsive behavior. Ten participants performed maximum voluntary isometric plantarflexion contractions with and without preceding stretch. Contractions were accompanied by the assessment of voluntary activation using the twitch‐interpolation technique. The same test protocol was repeated four additional times with a least on day rest in‐between. Additionally, at the first and fifth sessions, a submaximal tetanic muscle‐stimulation condition was added. At both muscle‐stimulation sessions mean rFE higher 10% (p < 0.028) was found. In contrast, during voluntary muscle action, individual participants showed inconsistent rFE across sessions and only one session (#3) had significant rFE (5%; p = 0.023) in group means. As all participants clearly had rFE in electrical stimulation conditions, structural deficits cannot explain the missing rFE in voluntary muscle action. However, we also did not find variability in voluntary activation levels or muscle activity as the confounding characteristics of “non‐responders.”

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Section: Introductionmentioning

confidence: 99%

Residual force enhancement in humans: Is there a true non‐responder?

et al. 2021

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“…Most notably, spinal excitability is reduced in stretch-hold compared to fixed-end isometric contractions 45 , and this effect is likely modulated by the inhibitory Golgi tendon organ-evoked reflex, which is elevated in the force-enhanced state 19 . Since this inhibitory reflex is activated by muscle-tendon unit stretch, the large-magnitude joint excursion (70°) that we used was likely a large contributor to the loss of rFE when scaling from the single fibre to the joint level, and the appearance of non-responders 17 .…”

Section: Discussionmentioning

confidence: 99%

“…While rFE is always observed in single muscle fibres from human and animal preparations 5–8,12 , rFE is not always observed in vivo during voluntary contractions, with some participants producing up to 34% rFE in the knee extensors, but others producing no rFE 13–17 . This phenomenon of voluntary rFE ‘non-responders’ appears to be at least partly driven by neural factors 17 , as spinal excitability 18,19 has been shown to be reduced in the rFE state, and non-responders are eliminated during electrically evoked contractions in vivo 16,20 . This non-responder phenomenon raises the question of how rFE scales from the single fibre to the joint level in the same participants; however, this comparison has yet to be directly investigated.…”

Section: Introductionmentioning

confidence: 99%

Residual force enhancement decreases when scaling from the single muscle fibre to joint level in humans

Hinks,

Jacob,

Patterson

et al. 2024

Preprint

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Residual force enhancement (rFE), defined as increased isometric force following active lengthening compared to a fixed-end isometric contraction at the same muscle length and level of activation, is present across all scales of muscle. While rFE is always present at the cellular level, often rFE ‘non-responders’ are observed during joint-level voluntary contractions. We compared rFE between the joint level and single fibre level (vastus lateralis biopsies) in 16 young males.In-vivovoluntary knee-extensor rFE was measured by comparing steady-state isometric torque between a stretch-hold (maximal activation at 150°, stretch to 70°, hold) and a fixed-end isometric contraction, with ultrasonographic recording of vastus lateralis fascicle length (FL). Fixed-end contractions were performed at 67.5°, 70°, 72.5°, and 75°; the joint angle that most closely matched FL of the stretch-hold contraction’s isometric steady-state was used to calculate rFE. The starting and ending FLs of the stretch-hold contraction were expressed as % optimal FL, determined via torque-angle relationship. In single fibre experiments, the starting and ending fibre lengths were matched relative to optimal length determined fromin-vivotesting, yielding an average sarcomere excursion of ∼2.2-3.4µm. There was a greater magnitude of rFE at the single fibre (∼20%) than joint level (∼5%) (P=0.004), with ‘non-responders’ only observed at the joint level. By comparing rFE across scales within the same participants, we show the development of the rFE non-responder phenomenon is upstream of rFE’s cellular mechanisms, with rFE only lost rather than gained when scaling from single fibres to the joint level.

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“…We used electrical stimulation to prevent neural inhibition, which might change depending on rotation magnitude and muscle–tendon unit length. In addition, an unresolved issue is still the potential neural contribution to non-responders to rFE 76 . However, one limitation is that the electrical stimulated contractions we have used in our experiment differ from voluntary contractions with their asynchronous and varied firing frequencies 64 .…”

Section: Discussionmentioning

confidence: 99%

The effect of stretch–shortening magnitude and muscle–tendon unit length on performance enhancement in a stretch–shortening cycle

Groeber

Stafilidis

Baca

2021

Sci Rep

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Stretch-induced residual force enhancement (rFE) is associated with increased performance in a stretch–shortening cycle (SSC). Although the influence of different range of motions and muscle–tendon unit lengths has been investigated in pure stretch-hold experiments in vivo, the contribution to a SSC movement in human muscles remains unclear. In two sessions, 25 healthy participants performed isometric reference (ISO), shortening hold (SHO) and SSC contractions on an isokinetic dynamometer. We measured the net knee-joint torque, rotational mechanical work, knee kinematics and fascicle behavior (m. vastus lateralis) of the upper right leg. In session 1 the SHO- and SSC-magnitude was changed respectively (SHO: 50°–20°, 80°–20° and 110°–20°; SSC: 20°–50°–20°, 20°–80°–20° and 20°–110°–20°) and in session 2 the muscle–tendon unit length (SHO: 50°–20°, 80°–50° and 110°–80°; SSC: 20°–50°–20°, 50°–80°–50° and 80°–110°–80°; straight leg = 0°). In both sessions, rotational work was significantly (p < 0.05) increased in the SSC compared to the SHO contractions (in the range of 8.1–17.9%). No significant difference of joint torque was found in the steady-state for all SSC-magnitudes compared to the corresponding SHO contractions in session 1. In session 2, we found only significantly (p < 0.05) less depressed joint torque in the SSC at the longest muscle–tendon unit length compared to the corresponding SHO condition, without any differences in knee kinematics and fascicle behavior. Therefore, the physiological relevance of rFE might be particularly important for movements at greater muscle–tendon unit lengths.

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The long and short of residual force enhancement non-responders

Cited by 7 publications

References 13 publications

Residual force enhancement in humans: Is there a true non‐responder?

Residual force enhancement in humans: Is there a true non‐responder?

Residual force enhancement decreases when scaling from the single muscle fibre to joint level in humans

The effect of stretch–shortening magnitude and muscle–tendon unit length on performance enhancement in a stretch–shortening cycle

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