Simon Walker

The latest hypothesis regarding the source of enhanced neural activation from resistance training is the reticulospinal rather than the corticospinal tract, based on invasive animal and emerging human data. The present study employed a six-week isometric resistance training intervention in a randomized controlled design to address this knowledge gap. Thirty-nine healthy, untrained males (age ~23 y, sustained contraction group n = 13, explosive contraction group n = 9, control group n = 17) underwent neuromuscular and electrophysiological testing and completed all study requirements. Maximal isometric torque (MVC) and rate of torque development (RTD) were measured during a familiarization session as well as before and after the six-week period. Transcranial magnetic stimulation was used to assess motor-evoked potential (MEP) area and silent period duration while subjects contracted to 10% of MVC. Loud sound (120 dB) was used to modulate MEP area and reaction time to visual stimuli during the StartReact test. Only the intervention groups demonstrated significant improvements in MVC (27%) and RTD (60%) (both P < 0.01), along with reduced MEP area (− 21%) and silent period duration (− 23%) (both P < 0.01). The sustained contraction group showed reduced modulation of reaction time and increased MEP suppression due to loud sound. Short-term resistance training seemed to reduce cortical inhibition and corticospinal excitability in both training groups. The study showed conflicting changes in measures purported to evaluate reticulospinal functioning. It is recommended to examine different forms of resistance training and longer training exposure in future.

Age‐related declines in neuromuscular performance are well documented; however, the cortical processes underlying these changes remain unclear. This systematic review and meta‐analysis compared younger and older adults across key transcranial magnetic stimulation measures of corticospinal and intracortical function, including corticospinal excitability, cortical silent period, intracortical facilitation and intracortical inhibition. Age‐related differences in maximal voluntary strength were also quantified as a secondary outcome. A comprehensive literature search identified 52 eligible studies from 1682 records. Methodological quality was evaluated using a modified Downs and Black checklist, and the certainty of evidence was assessed using the GRADE approach. A random‐effects model was applied to calculate standardised mean differences (SMDs) with 95% confidence intervals (CIs). Compared to younger adults, older adults produced lower maximal isometric voluntary force (SMD = −0.76) and exhibited reduced resting motor evoked potential amplitudes (SMD = −0.55) and intracortical facilitation (SMD = −0.27). These age‐related differences were not observed during active contractions. Cortical silent period duration was longer in older adults (SMD = 0.39). No age‐related differences were found in short‐ or long‐interval intracortical inhibition. These findings indicate that ageing is associated with reduced resting corticospinal and intracortical excitability, prolonged cortical silent periods and lower maximal voluntary strength. As neural and strength outcomes were analysed independently, a causal relationship cannot be established, but the parallel pattern points to central neural alterations as plausible targets for future interventions aimed at mitigating age‐related neuromuscular decline.

This study examined lower‐extremity power using countermovement jump (CMJ) height and estimated peak power across the lifespan with five Finnish datasets. The pooled dataset included 24 804 males and 5413 females aged 6–75 years. CMJ height (cm) was measured on a contact mat from flight time(s), and peak power (W) was estimated using equations for adults and children and expressed also relative to body mass (W/kg). Five‐year age groups were formed for mean comparison. CMJ height and peak power increased throughout childhood and adolescence. From ages 11 to 15, males exhibited greater CMJ height and peak power than females. Based on mean values, CMJ height peaked at ages 16–20 and peak power at 21–25 in males, while both peaked at 21–25 in females. Males maintained their level until 26–30 years, whereas females showed a decline after the peak. Segmented regression models indicated earlier peaks for CMJ height (18 years in males, 17 in females) and slightly later peaks for peak power (21 years in males, 19 in females). Before the peaking age, annual relative increases calculated over 11–15 years were 5.6% versus 3.1% for CMJ height and 4.7%–7.6% vs. 4.0%–7.3% for peak power (males vs. females). After the peaking age, annual declines calculated over 52–58 years were 0.9% for CMJ height and 0.3%–0.7% for peak power in both sexes. The results provide insights into life‐course patterns and the transitional period of late adolescence and early adulthood, when jumping performance peaks and evidence is limited.

The cortico-reticulospinal tract is now thought to be an important regulator of voluntary force, but there is a shortage of accepted measures assessing its excitability. Here, we used transcranial magnetic stimulation to elicit ipsilateral motor-evoked potentials (iMEPs) in a large group of healthy males and females. We demonstrated good-to-excellent reproducibility across all iMEP characteristics (including latency, amplitude, and presence) in both sexes. iMEPs are, thus, a useful tool to assess cortico-reticulospinal excitability.

This study investigated sex differences in neuromuscular responses during dynamic balance perturbations and isometric maximal voluntary contractions (IMVCs) by examining if menstrual cycle (MC) phase and the fluctuations in endogenous hormones influence the observation of sex differences. Twenty‐seven young adults (17 males: 28.5 ± 6.4 years; 10 females: 31.2 ± 6.5 years) were measured twice: females were measured at the early‐follicular (EF) phase, that is 2–4 days after onset of bleeding, and at the mid‐luteal phase (LUT), coinciding with peak levels of progesterone. Males were measured twice with 7–14 days between measurements. During dynamic balance perturbations, H‐reflex and V‐wave (neural drive) responses were recorded from the posterior perturbations at four latencies (40 ms, 70 ms, 100 ms, and 130 ms) coinciding with short‐ (SLR), medium‐ (MLR), and long‐ (LLR) latency responses and voluntary activation. Further, IMVC and its associated neural drive were assessed. Sex differences in either the H‐reflex ( P  = 0.217) or the V‐wave ( P  = 0.475) were not observed during balance perturbation tasks when females at EF were compared to males. However, when the measurements were conducted at LUT, a significant sex difference was revealed in both H‐reflex ( P  = 0.029) and V‐wave ( P  = 0.049) responses. Similarly, in neural drive during IMVC, no sex differences were observed at EF ( P  = 0.440), but a significant sex difference at LUT was observed ( P  = 0.024). Our results suggest that hormonal fluctuation in two distinct MC phases lead to females having lower neural responses during dynamic balance and voluntary force generation tasks at LUT compared to males.

The neural mechanisms underlying resistance training (RT) adaptations remain incompletely understood, particularly the contribution of cortico‐reticular and reticulospinal tracts (RSTs), which have rarely been examined in humans. One factor that may critically shape these adaptations is training pace, an overlooked yet physiologically relevant variable, as externally paced and self‐paced contractions impose distinct demands on cortical and subcortical motor circuits. This study examined (1) how RT affects RST excitability and (2) whether different types of RT produce distinct changes in descending motor pathway excitability. Thirty healthy participants were randomized to metronome‐paced RT (MP‐RT), self‐paced RT (SP‐RT) or control. Cortical and corticospinal excitability were assessed with transcranial magnetic stimulation, while cortico‐reticulospinal and RST excitability were measured using the ipsilateral to contralateral motor‐evoked potential amplitude ratio (ICAR) and the StartReact effect. Training consisted of dumbbell exercises performed three times weekly for three weeks, with repeated neurophysiological testing. Both RT protocols improved one‐repetition maximum and maximal voluntary force ( P < 0.001). SP‐RT resulted in greater increases in the StartReact effect ( P < 0.001), rate of force development (0.0453) and cortico‐reticulospinal excitability (ICAR; P = 0.0351), whereas MP‐RT elicited larger increases in corticospinal excitability ( P = 0.00420) and greater reductions in short‐interval intracortical inhibition ( P < 0.001). This study provides the first evidence in humans that RT modifies cortico‐reticular and RST excitability. Importantly, adaptations were pacing‐dependent: SP‐RT selectively targets cortico‐reticular circuit and RST, whereas MP‐RT engaged corticospinal and inhibitory intracortical circuits. This pathway‐specific plasticity underscores training modality as critical determinant of neural adaptation, with implications for rehabilitation and performance. image Key points: This study examined the effects of resistance training (RT) on descending motor pathways using transcranial magnetic stimulation and the StartReact protocol. Given the inaccessibility of the reticulospinal tract in humans, its excitability was inferred indirectly via the StartReact effect and ipsilateral to contralateral MEP amplitude ratio (ICAR), offering novel insight into cortico‐reticulospinal modulation. Both metronome‐paced and self‐paced RT increased muscle strength but induced distinct neural adaptations. Self‐paced RT engaged cortico‐reticular and reticulospinal pathways, as indicated by elevated ICAR and StartReact effect values, while metronome‐paced RT increased corticospinal excitability and reduced intracortical inhibition. These findings demonstrate, for the first time in humans, that RT pacing can differentially modulate corticospinal and reticulospinal excitability, two parallel descending motor systems with distinct roles. This selective pathway engagement suggests that training tempo is not merely behavioural but a physiologically meaningful factor for directing neuroplasticity.

Cross‐education refers to strength gains in the untrained limb following unilateral training, typically attributed to corticospinal adaptations. These changes are modest and may not fully explain interlimb transfer in older adults. This study assessed cortico‐reticular and reticulospinal tract excitability in young and older adults using a multimodal neurophysiological approach to determine whether subcortical pathways contribute when corticospinal plasticity is age limited. Thirteen older (67 ± 5 years) and 12 young adults (26 ± 6 years) completed two weeks of unilateral elbow flexor strength training. Strength, cortical excitability, and reticulospinal function were evaluated in the untrained limb using single‐ and paired‐pulse TMS, StartReact, and behavioral measures. Both younger and older adults showed significant strength gains in the untrained arm (young: +22%, older: +20%), with no group × time interaction ( p = 0.556). Corticospinal excitability, assessed via stimulus–response curves (100%–170% aMT), remained unchanged ( p = 0.624). Intracortical facilitation increased at Week 2 ( p = 0.011), while short‐interval intracortical inhibition did not change ( p = 0.269). Reaction times were significantly reduced across groups ( p < 0.001), and the rate of force development increased at retention ( p = 0.019), consistent with enhanced reticulospinal excitability. Cross‐activation of the ipsilateral motor cortex increased at all time points in young adults ( p < 0.001), but only at retention in older adults ( p < 0.001). Voluntary activation improved exclusively in older adults ( p < 0.001). Cross‐education was mediated by subcortical mechanisms, notably increased reticulospinal excitability. Cortical adaptations are modest and age‐independent. The bilateral organization of the reticulospinal system positions it as a promising target for interventions to enhance contralateral motor output through unilateral training.

The present study examined the effects of self-selected music on exercise tolerance and related physiological responses during endurance cycling. Recreationally active adults (N = 29) completed two time-to-exhaustion (TTE) trials at ~80% of peak power output under counterbalanced conditions: music (self-selected, 120–140 bpm) and no-music. Participants cycled longer with music (M = 35.61, SD = 14.01 min) than without (M = 29.80, SD = 11.47 min), t(28) = 3.62, p = .001, dz = 0.67. Heart-rate (HR) analyses (N = 27) showed greater cumulative cardiovascular load under music (AUC +15.4% vs no-music; t(26) = 2.40, p = .024), and a small isotime HR increase (+2.9 bpm, ~+1.9%; t(26) = 2.75, p = .011). Music also extended the time participants tolerated suprathreshold effort, both in absolute (p < .001) and proportional (p = .005) terms. Total energy expenditure was higher with music (+69 kJ; +17%; t(28) =3.34, p =.002), whereas energy-expenditure rate did not differ (+0.11 kJ·min⁻¹; p =.652); post-exercise lactate was unaffected after controlling for TTE (cond. +0.32–0.39 mmol·L⁻¹; p ≥ .265). Aerobic fitness (VO₂peak) did not moderate the ergogenic effect (r =−.28, p =.135). Despite longer performance and higher cumulative exposure, terminal responses (end %HRmax, %VO₂peak, RPE, lactate) were similar (all p > .15). Qualitative data contextualized the participant experience. Results support the notion that self-selected music facilitates tolerance of sustained effort without commensurate increases in momentary cardiovascular strain, consistent with a cognitive rather than metabolic mechanism supporting prolonged tolerance of high-intensity work.

Objectives: This study examined the effects of step-reduction and subsequent step-recovery and exercise rehabilitation on systemic metabolism in older adults. Methods: Participants were 66 eligible participants from the ENDURE randomised controlled trial allocated to an intervention group (n=32; 25 % male) or control group (n=34; 21 % male). The intervention group was instructed to limit their daily steps to a maximum of 2000 for two weeks (Period I), followed by a four-week exercise rehabilitation program (Period II) involving twice-weekly sessions of whole-body resistance and bicycle ergometer-based endurance training. Fasting blood samples were collected at baseline, after Period I, and after Period II. Systemic metabolism was assessed using high-throughput proton nuclear magnetic resonance spectroscopy. Data were normalised using Box-Cox transformation and analysed with linear mixed-effects models including random intercepts. Results: Period I and Period II had largely opposing effects on systemic metabolism. For instance, compared to the control group, Period one led to increases in VLDL-phospholipids (0.54 SD, P = 0.005), VLDL-cholesterols (0.41 SD, P = 0.012) and VLDL-triglycerides (0.79 SD, P = 0.002), and decreases in HDL-phospholipids (−0.31 SD, P = 0.037) and HDL-cholesterols (−0.47 SD, P = 0.011), alongside an increase in HDL-triglycerides (0.64 SD, P = 0.011). These changes reversed during Period II. Glycoprotein acetylation biomarker GlycA levels were unaffected by either intervention. Conclusions: These findings suggest that short-term inactivity does not markedly influence the inflammatory state but adversely affects lipoprotein metabolism and glycolytic pathways; however, these changes are reversible through the resumption of physical activity.