Biology subjects

Piasecki, J.

Publications and source records attributed to Piasecki, J..

6 recordsLinked to original sources

bioRxiv2026

Motor unit discharge properties are modestly influenced by menstrual cycle-related fluctuations in sex hormone concentrations

Concentrations of estradiol (E2) and progesterone (P4), the main female sex hormones, exhibit large fluctuations across the menstrual cycle. Due to their receptors throughout the central nervous system, both hormones have the potential to influence motor function by influencing ionotropic and metabotropic inputs to motor pools, which can be estimated through the neural codes extracted from motor unit discharge patterns. To address key methodological limitations in prior menstrual cycle research on motor output, we established the Motor Units and Sex Hormones (MUSH) collaboration. The objective of this multi-site investigation was to determine whether endogenous fluctuations in estradiol and progesterone influence human motor unit activity. We hypothesized that motor unit discharge rates and persistent inward current (PIC)-related contributions to discharge would be greatest during the late follicular phase, when estradiol concentrations were highest. Fifty females completed a comprehensive protocol involving menstrual cycle and ovulation tracking, serum hormone measurement, and high-density surface electromyographic recordings during isometric contractions to quantify motor unit activity in the early follicular, late follicular, and mid luteal phases. After exclusion of 10 females with either atypical hormone concentration profiles or insufficient motor unit yield, 40 remained in the final analysis. There were significant changes in several motor unit discharge variables between menstrual cycle phases and significant associations with hormone concentrations. Increased estradiol was associated with higher peak discharge rates and ascending discharge rate nonlinearity, while increased progesterone was associated with higher peak discharge rates, more discharge rate hysteresis and ascending discharge rate nonlinearity. Despite reaching statistical significance, the magnitudes of these effects (i.e., effect sizes) were small. Overall, these findings indicate that fluctuations in sex hormones influence motor unit behavior, but the effects are subtle, highlighting the need for well-powered and methodologically rigorous menstrual cycle research. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/699975v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@2eb2c0org.highwire.dtl.DTLVardef@1d98359org.highwire.dtl.DTLVardef@13e772borg.highwire.dtl.DTLVardef@1bb27_HPS_FORMAT_FIGEXP M_FIG C_FIG KEY POINTSO_LIThere are small but detectable differences in motor unit discharge rates between menstrual cycle phases, which are predicted by within-participant fluctuations in estradiol and progesterone. C_LIO_LIDischarge rate patterns that provide estimates of neuromodulatory and inhibitory input suggest that estradiol and progesterone can influence spinal cord circuitry differently than has previously been documented in the brain, highlighting an understudied aspect of female neurophysiology. C_LIO_LIVariability in menstrual cycles and associate hormones makes large-scale, rigorous studies especially valuable in female neuromuscular research. C_LI

neuroscience↗

bioRxiv2025

Menstrual cycle phase alters corticospinal excitability and spike-timing-dependent plasticity in healthy females

The known fluctuations in ovarian hormone concentrations across the eumenorrheic menstrual cycle contribute to modulations in cortical excitability and inhibition. However, how such changes affect spike-timing-dependent plasticity (STDP) has not been systematically studied. This research aimed to determine the effect of the menstrual cycle on corticospinal excitability and STDP. Twelve eumenorrheic female participants (age: 25 {+/-} 5 years), visited the lab in three menstrual cycle phases: early follicular (EF), late follicular (LF), and mid-luteal (ML). Visits comprised of corticospinal excitability (motor evoked potential [MEP]/Mmax), short-intracortical inhibition (SICI), and intracortical facilitation (ICF) measures, recorded in the resting first dorsal interosseous. Followed by a paired associative stimulation (PAS) protocol, utilising ulnar nerve and transcranial magnetic stimulation (25 ms interstimulus interval) to elicit neuroplasticity. To assess the time course of STDP, measurements were repeated at 15 and 30-minutes post PAS. Corticospinal excitability (MEP/Mmax) was greater in the LF phase (p[≤]0.002) compared to EF and ML, with no phase effects observed for SICI or ICF (p[≥]0.112). PAS elicited an increase in MEP/Mmax across all phases at 15-minutes (112 {+/-} 5, 115 {+/-} 5, and 113 {+/-} 7% baseline, p[≤]0.010), whereas at 30-minutes only ML was facilitated (126 {+/-} 7% baseline, p=0.029). The present data demonstrates facilitatory STDP can be induced with PAS across the tested menstrual cycle phases, but responses are prolonged and potentiated in the ML phase. Additionally, increased corticospinal excitability in the LF phase is likely due to intrinsic changes within the descending tract, as no changes in intracortical neurotransmission were observed.

neuroscience↗

bioRxiv2024

Sex differences in the cardiopulmonary and neuromuscular response to high-intensity interval exercise

Sex differences exist in the integrative response to exercise, however, these are typically researched during constant-load exercise. Interval exercise involves high-intensity efforts interspersed with recovery periods to repeatedly stress physiological systems, and it is currently unknown whether the response to this form of exercise differs between sexes. Ten males and ten females (age: 25{+/-}3 years) completed two experimental visits. First, an incremental treadmill exercise test was performed to obtain submaximal (lactate threshold) and maximal ([Formula] O2peak) data. Thereafter, visit two involved 4 x 3-min running intervals at 90% of the final incremental test velocity (v[Formula] O2peak), with 90 secs rest between intervals. Before exercise and after each interval, maximal voluntary contraction (MVC), quadriceps potentiated twitch (Qtw.pot), and voluntary activation (VA) were recorded. The rates of oxygen uptake ([Formula] O2), carbon dioxide production ([Formula] CO2) and ventilation ([Formula] E) were continuously recorded throughout. There was no sex difference in relative [Formula] O2peak (males: 47.2{+/-}6.0 vs. females: 44.4{+/-}5.8 ml.kg- 1.min-1, p=0.292). When expressed relative to peak values, there were no sex differences in the [Formula] O2 or [Formula] CO2 response to the interval task (p[≥]0.781). Females had greater [Formula] E, [Formula] E/[Formula] O2, and [Formula] E/[Formula] CO2 values during the first two intervals (p[≤]0.046). There were no sex differences in the reductions in MVC, Qtw.pot, and VA during the interval task (p[≥]0.150), however females had lesser reductions in Qtw.pot values post-exercise (-24{+/-}9 vs. -15{+/-}8%, p=0.044). Sex differences exist in the physiological response to interval exercise. Compared to males, females experienced greater hyperpnoea during the initial stages, and had lesser decreases in contractile function post-exercise.

physiology↗

bioRxiv2023

Sex disparities in age-related neuromuscular decline: unveiling female susceptibility from early to late elderly

BackgroundFemales typically have a longer lifespan than males which is not matched by an improved healthspan, with older females having higher rates of frailty, characteristic of a sex specific degradation of the neuromuscular system. Several motor unit (MU) characteristics show sex-specific behaviour during mid-level contractions in healthy younger people, highlighting a potential influence of hormonal differences that may be augmented in older age. The purpose of this study was to investigate sex differences in physical performance and MU features of the aged human vastus lateralis (VL) from early to late elderly. MethodsThis study included 21 healthy older males (mean {+/-} SD, range: 67.2 {+/-} 7.6, 56 - 81 yrs) and 17 healthy older females (69.5 {+/-} 5.2, 60 - 78 yrs). Intramuscular electromyography data were collected from VL during standardised submaximal sustained contractions. Muscle size and physical performance characteristics were also measured. Multiple mixed-effects linear regression models with age considered were conducted and statistical significance was accepted when p<0.05. ResultsWhen compared to males, early to late elderly females had smaller cross-sectional area of VL (p<0.001), lower knee extensor torque (p<0.001) and poorer force steadiness (p=0.036), as well as higher MU firing rate (FR) (p=0.025) and greater MU FR variability (p=0.031). With progression from early to late elderly, both sexes showed decreased functional capacity at a similar rate. ConclusionFunctional deterioration occurs to a similar extent in both sexes from early to late elderly. However, throughout the majority of the elderly period males demonstrate a greater muscle size, strength, and functional performance. Older females have greater MUFR variability and worse force steadiness than older males. These findings help to address the lack of MU data in older females, and suggest earlier interventions are needed in older females to prevent functional deterioration and reduce the health-sex paradox within ageing humans.

physiology↗

bioRxiv2023

Menstrual cycle associated alteration of vastus lateralis motor unit function

Estrogen and progesterone are the primary female sex hormones and have net excitatory and inhibitory effects, respectively, on neuronal function. Fluctuating concentrations across the menstrual cycle has led to several lines of research in relation to neuromuscular function, yet evidence from animal and cell culture models have yet to be demonstrated in human motor units (MU) coupled with quantification of circulating hormones. Intramuscular electromyography (iEMG) was applied to record MU potentials (MUP) and corresponding MUP trains (MUPT) from the vastus lateralis of eumenorrheic females during the early follicular, ovulation and mid luteal phases of the menstrual cycle, alongside assessments of neuromuscular performance. Multi-level regression models were applied to explore effects of time and of contraction level. Statistical significance was accepted as p<0.05. Knee extensor maximum voluntary contraction (MVC), jump power, force steadiness, and balance did not differ across the menstrual phases (all p>0.4). Firing rate of low threshold MU (10% MVC) was reduced during phases of high progesterone ({beta}=-0.82Hz, p<0.001), with no difference in MUPs analysed from 25% MVC contractions. MUPs were more complex during ovulation and mid luteal phase (p<0.03), with no change in neuromuscular junction transmission instability (p>0.3). Assessments of neuromuscular performance did not differ across the menstrual cycle. The suppression of low threshold MU firing rate during periods of increased progesterone may suggest a potential inhibitory effect and an alteration of recruitment strategy, however this had no discernible effect on performance. These findings highlight contraction level dependent modulation of VL MU function over the eumenorrheic cycle.

physiology↗

bioRxiv2021

Motor unit recruitment strategies of the vastus lateralis according to sex

AimDespite men exhibiting greater muscle strength and fatigibility than women, it remains unclear if there are sex-based differences in muscle recruitment strategies e.g. motor unit (MU) recruitment and modulation of firing rate (FR) at normalised forces and during progressive increases in force. MethodsTwenty-nine healthy male and thirty-one healthy female participants (18-35 years) were studied. Intramuscular electromyography was used to record individual motor unit potentials (MUPs) and near fibre MUPs from the vastus lateralis (VL) during 10% and 25% maximum isometric voluntary contractions (MVC), and spike-triggered averaging was used to obtain motor unit number estimates (MUNE) of the VL. Multilevel mixed-effects linear regression models were used to investigate the effects of sex at each contraction level. ResultsMen exhibited greater muscle strength (p<0.001) and size (p<0.001) than women, with no difference in force steadiness at 10% or 25% MVC. Women had smaller MUs and higher FR at 10% MVC (both p<0.02), similar to that at 25% MVC in MU size (p=0.062) and FR (p=0.031). However, both sexes showed similar increases in MU size and FR when moving from low-to mid-level contractions. There were no sex differences in any near fibre MUP parameters or in MUNE. ConclusionIn the vastus lateralis, women produce muscle force via different neuromuscular recruitment strategies to men which is characterised by smaller MUs discharging at higher rates. However, similar strategies are employed to increase force production from low to moderate contractions. These findings of similar proportional increases between sexes support the use of mixed sex cohorts in studies of this nature. Key pointsO_LIIncreases in muscle force production are mediated by motor unit (MU) recruitment, and MU firing rate (FR). C_LIO_LIWomen are underrepresented in studies of human neuromuscular research and markedly differ to men in a number of aspects of neuromuscular function, yet little is known of the recruitment strategies of each. C_LIO_LIHere we demonstrate men and women have similar vastus lateralis MU number estimates, yet women recruit smaller MUs with higher FR than men at normalised contraction levels. However, increases in force are achieved via similar trajectories of MU recruitment and MU FR in men and women. C_LIO_LIAlthough men and women exhibit divergent neuromuscular recruitment strategies to achieve normalised forces, increases in force are achived similarly and support the inclusion of mixed sex cohorts in studies of this nature. C_LI

physiology↗