The pH heterogeneity in human calf muscle during neuromuscular electrical stimulation

Stutzig, Norman; Rzanny, R.; Moll, Kevin; Gussew, Alexander; Reichenbach, Jürgen R.; Siebert, Tobias

doi:10.1002/mrm.26329

Cited by 8 publications

(10 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In our experiments, we can almost exclude the possibility that the pH decreased to values of 6.2 within a time period of 0.8 s (Stutzig et al, 2017). Thus, it seems that the main cause of fatigue that we observed and simulated is based on elevated [P i ], which influences both actomyosin cross-bridge force generation and myofibrillar Ca 2+ sensitivity.…”

Section: On the Effects Of Phosphate Accumulation And Myofibrillar Camentioning

confidence: 53%

Exhaustion of Skeletal Muscle Fibers Within Seconds: Incorporating Phosphate Kinetics Into a Hill-Type Model

et al. 2020

Self Cite

View full text Add to dashboard Cite

Section: On the Effects Of Phosphate Accumulation And Myofibrillar Camentioning

confidence: 53%

Exhaustion of Skeletal Muscle Fibers Within Seconds: Incorporating Phosphate Kinetics Into a Hill-Type Model

et al. 2020

Self Cite

View full text Add to dashboard Cite

“…Due to the imprecisely defined muscular contributors to the spectra in our study, it can be assumed that the high pH component represents a contamination of signal from the soleus, which already was discussed in our paper (1). As illustrated by the changes in T 2 *-w images between pre-and postfatigue (Supporting Figs.…”

mentioning

confidence: 67%

Interpretation of pH‐heterogeneity in human muscle induced by neuromuscular electrical stimulation

Stutzig

Rzanny

Moll

et al. 2016

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

We thank M. Jubeau and J. Gondin for their interest in our work (1). We are grateful that they have pointed our attention to their recent work on neuromuscular electrical stimulation (NMES) (2), which we unintentionally missed during the preparation of our manuscript (1). Both studies, however, differ on crucial points. In contrast to the nonlocalized volume-selection utilizing coil sensitivity, as used in our study, they applied a chemical shift image sequence with a better defined volume selection at the expense of temporal resolution (43.5 s (2) vs. 5 s (1)), which induces substantial temporal averaging over shifting metabolite peaks. Further differences exist with regard to the investigated muscle and stimulation pattern. Nevertheless, our interpretation that the identified pH compartments correspond to different fiber types was supported by their observation of pH-heterogeneity in spectra of homogeneous muscle regions with outer volume contaminations between 9% to 10%.The main difference to the work of Jubeau et al. and the novelty of our study is that we maximized the NMESinduced pH-heterogeneity by a short and strong stimulation (PCr depletion was completed after the first 50 s (1) vs. 400 s in (2)), which would likewise explain the substantially higher shifts of the acidic pH-component (pH < 6.4) in our study. Thus, spectroscopic series were acquired with the best possible time resolution (5 s) while accepting compromises with regard to signal localization and signal-to-noise ratio (SNR). Under these conditions, we observed a split of Pi into three Pi components in all volunteers, which thus far only was detected for voluntary muscle contractions (3). Because it can be assumed that proton enrichment by glycolytic activity and proton exchange are competitive processes, the lower stimulation intensity in the approach of Jubeau et al. may be responsible for smaller pH differences and for the absence of an additional split. Their presentation of the vastus lateralis spectra during NMES stimulation (middle spectrum in the bottom block Figure 1 in Jubeau et al.(2)) lets us assume that the linewidth of the Pi-1 component is larger than for Pi-2, possibly indicating a superposition of two nonresolved components. Unfortunately, we did not find indications of linewidths in their paper.Due to the imprecisely defined muscular contributors to the spectra in our study, it can be assumed that the high pH component represents a contamination of signal from the soleus, which already was discussed in our paper (1). As illustrated by the changes in T 2 *-w images between pre-and postfatigue (Supporting Figs. S9-S12 in Stutzig et al. (1)), these changes are limited to the medial gastrocnemius muscle, and thus no pH-changes are expected in the soleus and the lateral gastrocnemius, whereas all dynamic series apart from one indicate at least a small acidic shift compared to the resting pH ( Fig. 7 in Stutzig et al. (1)). We assume that individual differences are responsible for the prominent shift of two volunteers showing pH o...

show abstract

“…Another explanation is the single fiber force reduction due to inorganic phosphate accumulation (Stutzig et al. 2017). …”

Section: Discussionmentioning

confidence: 99%

“…1979) while cellular inorganic phosphate reduces contractility (Stutzig et al. 2017), the maximum CE force generation capacity cannot be assigned to either or . , was set to the identified value of for computational reasons and the parameters , , , were identified at subsequent stages of the fatigue protocol (Fig.…”

Section: Methodsmentioning

confidence: 99%

Model-based analysis of fatigued human knee extensors

Penasso

Thaller

2018

Eur J Appl Physiol

View full text Add to dashboard Cite

This study investigated the effect of isometrically induced fatigue on Hill-type muscle model parameters and related task-dependent effects. Parameter identification methods were used to extract fatigue-related parameter trends from isometric and ballistic dynamic maximum voluntary knee extensions. Nine subjects, who completed ten fatiguing sets, each consisting of nine 3 s isometric maximum voluntary contractions with 3 s rest plus two ballistic contractions with different loads, were analyzed. Only at the isometric task, the identified optimized model parameter values of muscle activation rate and maximum force generating capacity of the contractile element decreased from to Hz and from to N, respectively. For all tasks, the maximum efficiency of the contractile element, mathematically related to the curvature of the force–velocity relation, increased from to . The model parameter maximum contraction velocity decreased from to m/s and the stiffness of the serial elastic element from to N/mm. Thus, models of fatigue should consider fatigue dependencies in active as well as in passive elements, and muscle activation dynamics should account for the task dependency of fatigue.

show abstract

The pH heterogeneity in human calf muscle during neuromuscular electrical stimulation

Abstract: It is suggested that NMES is able to induce pH heterogeneity in the medial gastrocnemius, and that the single Pi peaks represent the different muscle fiber types of the skeletal muscle. Magn Reson Med 77:2097-2106, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Cited by 8 publications

References 53 publications

Exhaustion of Skeletal Muscle Fibers Within Seconds: Incorporating Phosphate Kinetics Into a Hill-Type Model

Exhaustion of Skeletal Muscle Fibers Within Seconds: Incorporating Phosphate Kinetics Into a Hill-Type Model

Interpretation of pH‐heterogeneity in human muscle induced by neuromuscular electrical stimulation

Model-based analysis of fatigued human knee extensors

Contact Info

Product

Resources

About