Work

The relationship and agreement between systemic and local breakpoints in locomotor and non-locomotor muscles during single-leg cycling

Year: 2025

Type: article

Abstract: Introduction: There is a well-established relationship between the respiratory compensation point (RCP) and local muscular breakpoints determined from near-infrared spectroscopy (NIRS) and electromyography (EMG). However, these breakpoints have not yet been compared both in locomotor and non-locomotor muscles simultaneously in single-leg cycling exercise. Therefore, the aim of the study was to investigate the relationship and agreement between systemic and local breakpoints in locomotor and non-locomotor muscles. Method: ) with their right leg were included in the analysis. Ventilation and gas exchange were recorded to determine RCP. Surface EMG (sEMG) and NIRS signals were measured from both vasti lateralis muscles and breakpoints were determined from root mean Q square sEMG and deoxygenated hemo- and myoglobin signal m[HHb]. Results: There was no significant difference in the power output at RCP (127.3 ± 21.8 W) and local muscular breakpoints both from the locomotor (m[HHb]: 119.7 ± 23.6 W, sEMG: 126.6 ± 26.0 W) and non-locomotor (m[HHb]: 117.5 ± 17.9 W, sEMG: 126.1 ± 28.4 W) muscles. Breakpoints also showed significant (p < 0.01) correlations (r = 0.67-0.90, ICC = 0.80-0.94) to each other with weaker correlations in the non-locomotor muscle (r = 0.66-0.86, ICC = 0.74-0.90). Despite the strong correlations, high individual variability and weak limits of agreement (up to -32.5-46.5 W) and substantial absolute differences (10.2-16.7 W) were observed which indicates that these breakpoints cannot be used interchangeably. Discussion: These findings offer further insights into the mechanistic relationship between local and systemic physiological response to exercise with increasing workload. We conclude that, despite strong correlations, local muscular breakpoints do not have to coincide with systemic boundaries of physiological domains.

Source: Frontiers in Physiology

DOI: 10.3389/fphys.2025.1465344

Authors: Markus Tilp, Nina Mosser, Gudrun Schappacher-Tilp, Annika Kruse, Philipp Birnbaumer, Gerhard Tschakert

Institutions: University of Graz, FH JOANNEUM University of Applied Sciences

Language: English

Topic: Cardiovascular and exercise physiology

Subfield: Complementary and alternative medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $3,801