Oliver Hayman

Muscle damage severity decreases after repeated eccentric exercise bouts (the repeated bout effect [RBE]), but whether accompanying neural and neuromuscular changes contribute to protection or arise secondary to reduced damage remains unclear. This systematic review and meta-analysis compared neurophysiological and neuromuscular responses between initial and repeated eccentric bouts in healthy adults. Eight databases were searched from November 1990 to January 2025, and Hedges’ g was calculated where outcomes were comparable. Given the small number of contributing studies, all pooled analyses were considered exploratory. Twelve studies met the inclusion criteria. Twitch/evoked force showed recovery-compatible point estimates at 24 h (g = 1.02, 95% CI −0.03–2.06) and 48 h (g = 0.50, 95% CI 0.08–0.92). Voluntary activation findings were mixed. TMS-derived voluntary activation produced positive single-study estimates at 24 h (g = 1.10, 95% CI 0.29–1.92) and 48 h (g = 1.06, 95% CI 0.26–1.87), whereas pooled ITT-derived estimates were imprecise at 24 h (g = 0.36, 95% CI −0.92–1.63) and recovery-compatible but based on only two studies at 48 h (g = 0.44, 95% CI 0.03–0.85). M-wave/Mmax showed no consistent between-bout pattern. Corticospinal, intracortical, spinal, reticulospinal, motor-unit and EMG findings were limited, inconsistent or directionally unclear. Neural and neuromuscular changes accompany the RBE, but whether they contribute to protection or reflect reduced damage remains unresolved. Peripheral contractile outcomes showed the most consistent recovery-compatible pattern, whereas evidence concerning central activation and motor-unit behaviour remained limited or inconsistent.

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.

Purpose: Long-distance running induces marked increases in inflammation and muscle damage. Tart cherries (TC) have become a popular nutritional strategy for exercise recovery, particularly for attenuation of markers associated with muscle damage and inflammation. Research question. The aim of this study was to examine the effect of a yet-to-be-explored cultivar (Vistula) of TC on recovery following a marathon. Methods: Thirty-five recreationally trained marathon runners (mean ± SD age, stature, and mass were 40 ± 10 years old, 176.5 ± 10.2 cm, and 78.8 ± 13.8 kg, respectively) completed an undulating marathon course. Participants were randomised to receive either freeze-dried TC powder or calorie-matched placebo (17 TC, 18 placebo) for 7 days, with the marathon on day 5 of supplementation. Maximal voluntary contractions (MVC), counter movement jumps (CMJ), muscle soreness (DOMS), plasma creatine kinase (CK), and high-sensitive C-reactive protein (hs-CRP) were assessed before, immediately after, and at 24- and 48-h post marathon. Results: There were significant changes over time for all variables ( p < 0.001) indicating muscle damage. There were no treatment or interaction effects for MVC, CMJ, DOMS, and CK ( p > 0.2). However, there was a treatment effect for hs-CRP, where the TC group experienced lower levels of hs-CRP (mean ± SD during recovery: TC 7.9 ± 3.5, placebo 12.5 ± 5.1 mg/L, p = 0.031). Conclusions: The marathon caused changes in muscle damage and inflammation indices. Despite no functional or soreness differences, the TC group showed lower inflammation levels, offering insights into Vistula tart cherries for recovery.

Unfamiliar eccentric exercise causes muscle damage, but repeating the same exercise later substantially reduces symptoms—an adaptive phenomenon known as the repeated bout effect (RBE). We investigated the neural contributions to this response. We observed lower motor unit discharge variability and smaller increases in firing rate after the repeated bout. These findings provide evidence that motor unit-level neural adjustments are a critical component of the RBE, offering a new perspective on this protective adaptation.

The behavior of motor units during high-intensity fatiguing contractions with limited oxygen supply is poorly investigated. Here, we show that during fatiguing exercise with blood flow restriction, motor units are recruited at lower force levels with inhibition of relatively lower-threshold motor units and increased activity of relatively higher-threshold motor units. These changes in motor unit behavior might represent an acute neural adaptation to produce force during high-intensity contractions with limited oxygen supply.

Synaptic input to the motoneuron pool is altered during fatiguing muscle contractions. In humans, the corticospinal tract is often studied, with equivocal findings regarding its role in the reduction of force. To date, the involvement of the reticulospinal tract during states of fatigue has not been explored. Fourteen participants (28 ± 6 years, nine males) visited the laboratory twice, first for a familiarisation, then for an experimental trial. Participants completed a 5‐min sustained elbow flexor contraction at an intensity eliciting 40% of the EMG recorded during a maximal isometric voluntary contraction (MVC). Before, during and after the contraction, transcranial magnetic stimulation and electrical cervicomedullary stimulation were used to elicit motor evoked potentials (MEPs) and cervicomedullary evoked potentials during the silent period (SP‐CMEPs), respectively, with CMEPs also being evoked in combination with a startling acoustic sound (CMEPcon). Electrical stimulation of the brachial plexus was used to evoke maximal compound action potentials of the elbow flexors ( M _max ). The 5‐min contraction induced a 53% loss of force ( P  < 0.001), with no change in background EMG (∼4% M _max , P  = 0.293). Neither MEP amplitude ( P  = 0.246) nor CMEPcon ratio ( P  = 0.489) was altered during the contraction, whereas CMEP and SP‐CMEP amplitudes were reduced by ∼20% and 50%, respectively ( P  < 0.001) and remained depressed post‐task. The results suggest that neither corticospinal nor reticulospinal tract excitability was altered during a 5‐min constant‐EMG task at 40% maximal EMG. Instead, the aetiology of the neural contribution to fatigability appeared to be primarily related to the loss of motoneuron excitability.

Unaccustomed eccentric exercise (EE) is protective against muscle damage following a subsequent bout of similar exercise. One hypothesis suggests the existence of an alteration in motor unit (MU) behaviour during the second bout, which might contribute to the adaptive response. Accordingly, the present study investigated MU changes during repeated bouts of EE. During two bouts of exercise where maximal lengthening dorsiflexion (10 repetitions × 10 sets) was performed 3 weeks apart, maximal voluntary isometric torque (MVIC) and MU behaviour (quantified using high‐density electromyography; HDsEMG) were measured at baseline, during (after set 5), and post‐EE. The HDsEMG signals were decomposed into individual MU discharge timings, and a subset were tracked across each time point. MVIC was reduced similarly in both bouts post‐EE (Δ27 vs. 23%, P = 0.144), with a comparable amount of total work performed (∼1,300 J; P = 0.905). In total, 1,754 MUs were identified and the decline in MVIC was accompanied by a stepwise increase in discharge rate (∼13%; P < 0.001). A decrease in relative recruitment was found immediately after EE in Bout 1 versus baseline (∼16%; P < 0.01), along with reductions in derecruitment thresholds immediately after EE in Bout 2. The coefficient of variation of inter‐spike intervals was lower in Bout 2 (∼15%; P < 0.001). Our data provide new information regarding a change in MU behaviour during the performance of a repeated bout of EE. Importantly, such changes in MU behaviour might contribute, at least in part, to the repeated bout phenomenon.

Tart cherry (TC) consumption has become a popular nutritional strategy for recovery, particularly for the attenuation of markers associated with muscle damage. However, there are relatively few studies that have examined an acute dosing strategy. The aim of this pilot study was to explore the feasibility of using powdered Vistula TC for recovery following a bout of muscle-damaging exercise. Twenty-two recreationally active participants (mean ± SD age, stature, and mass were 23 ± 3 years old, 173 ± 10 cm, and 74 ± 17 kg, respectively) performed 40 (5 sets of 8 repetitions) maximal lengthening contractions of the elbow flexors. The participants were randomised to receive either a spray-dried TC extract or a calorie-matched placebo (12 TC, 10 placebo) for 4 days in total, starting on the day of exercise. Dependent measures of maximal voluntary contraction (MVC), muscle soreness (assessed via visual analogue scales; VAS), pain pressure threshold (PPT), range of motion (ROM), and upper arm limb girth were taken at baseline (pre), 24, 48, and 72 h post damaging exercise. There were significant changes over time among all the variables (MVC, VAS, PPT, ROM, and girth, p ≤ 0.014). There were no significant differences between the conditions for any of the variables (MVC, VAS, PPT, ROM, and girth, p > 0.3). The TC group did not recover at an accelerated rate compared to the placebo. This study provides initial insights into the use of powdered Vistula TC and its effect following strenuous (damaging) exercise bouts. Vistula TC did not improve recovery when taken acutely following a bout of damaging exercise to the elbow flexors.

Purpose: This study aimed to verify whether the slowing of muscle contraction quickness, typically observed in states of fatigue, may worsen force control by decreasing the rate with which force fluctuations are modulated. Therefore, we investigated the relationship between rate of force development (RFD), and force fluctuations' magnitude (Coefficient of variation, CoV) and complexity (Approximate Entropy, ApEn; Detrended fluctuation analysis, DFAα). Methods: Fourteen participants performed intermittent ballistic isometric contractions of the plantar dorsiflexors at 70% of maximal voluntary force until task failure (under 60% twice). Results: Indices of RFD (RFD_peak, RFD₅₀, RFD₁₀₀, and RFD₁₅₀) decreased over time by approximately 46, 32, 44, and 39%, respectively (p all ≤ 0.007). DFAα increased by 10% (p < 0.001), and CoV increased by 15% (p < 0.001), indicating decreased force complexity along with increased force fluctuations, respectively. ApEn decreased by just over a quarter (28%, p < 0.001). The linear hierarchical models showed negative associations between RFD_peak and DFAα (β = − 3.6 10^–4, p < 0.001), CoV (β = − 1.8 10^–3, p < 0.001), while ApEn showed a positive association (β = 8.2 × 10^–5, p < 0.001). Conclusion: The results suggest that exercise-induced reductions in contraction speed, lead to smoother force complexity and diminished force control due to slower adjustments around the target force. The fatigued state resulted in worsened force producing capacity and overall force control.