Supraspinal, spinal, and motor unit adjustments to fatiguing isometric contractions of the knee extensors at low and high submaximal intensities in males.

Contraction intensity is a key factor determining the development of muscle fatigue and it has been shown to induce distinct changes along the motor pathway. The role of cortical and spinal inputs that regulate motor unit (MU) behaviour during fatiguing contractions is poorly understood. We studied the cortical, spinal, and neuromuscular response to sustained fatiguing isometric tasks performed at 20 and 70% of the maximum isometric voluntary contraction (MVC), together with MUs behaviour of knee extensors in healthy active males. Neuromuscular function was assessed before and after performing both tasks. Cortical and spinal responses during exercise were measured via stimulation of the motor cortex and spinal cord. High density electromyography was used to record individual MUs from the vastus lateralis (VL). Exercise at 70% MVC induced greater decline in MVC (p = 0.023), and potentiated twitch force compared to 20%MVC (p < .001), with no difference in voluntary activation (p = 0.514). Throughout exercise, corticospinal responses were greater during the 20%MVC task (p < 0.001), and spinal responses increased over time in both tasks (p ≤ 0.042). MU discharge rate increased similarly following both tasks (p ≤ 0.043) while recruitment and de-recruitment thresholds were unaffected (p ≥ 0.295). These results suggest that increased excitability of cortical and spinal inputs might be responsible for the increase in MU discharge rate. The increase in evoked responses together with the higher MUs discharge rate might be required to compensate for peripheral adjustments to sustain fatiguing contractions at different intensities.

Energy intake, hydration status, and sleep of world-class male archers during competition.

BACKGROUND: Nutritional intake and sleep, play an important role for recovery and performance in elite sport but little work has been undertaken in archery. The present study aimed to assess energy intake (EI), hydration status, and sleep parameters in world-class male archers over the course of a four-day competition. METHODS: Results, Conclusions Six male, elite-standard archers participated in the study and measurements of hydration status, EI, competition load, and sleep were recorded throughout each day of competition. RESULTS: Daily energy, carbohydrate, and protein intake ranged between 2,563 and 3,986 kcal, 4 and 7.1 g/kg BM, 2.2 and 3.6 g/kg BM per day, respectively. Thus, archers practiced elements of periodized nutrition such that energy and carbohydrate intake was greater on the high-volume competition days (i.e. days 1 and 3; more numbers of arrows, longer duration, and walking distance) in comparison to low-volume days (days 2 and 4) over the tournament (all p > 0.01). Additionally, urine specific gravity was higher after waking, compared to pre- and post-competition, and before bed (all p < 0.05). This indicates that archers were euhydrated pre- and post-competition and before bedtime, while they were slightly hypohydrated after waking up. Sleep data show that disturbances were kept to a minimum. CONCLUSIONS: Collectively, archers appear capable of periodizing their nutritional intake according to daily physical loading during a tournament whilst, staying euhydrated and maintaining sleep quality. In part, such data can help to explain why these archers experience a sustained level of success.

Influence of nitrate supplementation on motor unit activity during recovery following a sustained ischemic contraction in recreationally active young males.

PURPOSE: Dietary nitrate (NO3-) supplementation enhances muscle blood flow and metabolic efficiency in hypoxia, however, its efficacy on neuromuscular function and specifically, the effect on motor unit (MU) activity is less clear. We investigated whether NO3- supplementation affected MU activity following a 3 min sustained ischemic contraction and whether this is influenced by blood flow restriction (BFR) during the recovery period. METHOD: In a randomized, double-blinded, cross-over design, 14 males (mean ± SD, 25 ± 6 years) completed two trials following 5 days of supplementation with NO3--rich (NIT) or NO3--depleted (PLA) beetroot juice to modify plasma nitrite (NO2-) concentration (482 ± 92 vs. 198 ± 48 nmol·L-1, p < 0.001). Intramuscular electromyography was used to assess MU potential (MUP) size (duration and area) and mean firing rates (MUFR) during a 3 min submaximal (25% MVC) isometric contraction with BFR. These variables were also assessed during a 90 s recovery period with the first half completed with, and the second half completed without, BFR. RESULTS: The change in MUP area and MUFR, did not differ between conditions (all p > 0.05), but NIT elicited a reduction in MUP recovery time during brief isometric contractions (p < 0.001), and during recoveries with (p = 0.002) and without (p = 0.012) BFR. CONCLUSION: These novel observations improve understanding of the effects of NO3- on the recovery of neuromuscular function post-exercise and might have implications for recovery of muscle contractile function. TRIAL REGISTRATION: The study was registered on clinicaltrials.gov with ID of NCT05993715 on August 08, 2023.

Comparison of low-dose maximal-intent versus controlled-tempo resistance training on quality-of-life, functional capacity, and strength in untrained healthy adults: a comparative effectiveness study.

Lack of physical activity is a global issue for adults that can lead to sedentary behaviour and a higher prevalence of health complications and chronic diseases, resulting in reduced quality-of-life (QoL) and functional capacity (FC). A potential strategy to mitigate this inactivity is low-dose resistance training (RT); however, physiological, and psychological responses are limited in evidence. Twenty untrained participants aged 30-60 years old (mean ± SD age 42 ± 7 years, mass 77 ± 13 kg, stature 166 ± 8 cm; 18 females and two males) were recruited and randomly assigned to maximal velocity-intent (MI, n = 10) or controlled-tempo (CT, n = 10) RT according to CONsolidated Standards of Reporting Trials (CONSORT) guidelines. Participants attended one training session per week for 6 weeks, consisting of five sets of five repetitions at 60% of one-repetition maximum (1RM) leg press. The interventions differed only during the concentric phase, with MI group pushing with maximal intent, and CT group pushing in a time-controlled manner (3 s). Outcome measures assessed pre- and post-RT included body mass, body mass index (BMI), strength-to-mass ratio, bipedal balance, 6-minute walk test (6MWT), 30-second sit-to-stand (30s-STS), timed up and go (TUG), and leg press 1RM. Time effects were observed for all demographics and FC-related outcomes, such as identical reductions in mass and BMI (- 2%), improvements in strength-to-mass ratio (25%) leg press 1RM (22%), 6MWT (3%), and 30s-STS (14%), as well as a 9% improvement in both TUG-clockwise and anticlockwise. Results show low-dose once-weekly RT is effective in improving QoL, FC, and strength in untrained healthy adults, regardless of modality. Positive responses from participants suggest an increased likelihood of consistent participation for low-dose once-weekly RT over more intense modalities. Retrospective ClinicalTrials.gov ID (TRN): NCT06107855, 24/10/2023.

Provision of dietary education in UK-based cardiac rehabilitation: a cross-sectional survey conducted in conjunction with the British Association for Cardiovascular Prevention and Rehabilitation.

Dietary education is a core component of cardiac rehabilitation (CR). It is unknown how or what dietary education is delivered across the UK. We aimed to characterise practitioners who deliver dietary education in UK CR and determine the format and content of the education sessions. A fifty-four-item survey was approved by the British Association for Cardiovascular Prevention and Rehabilitation (BACPR) committee and circulated between July and October 2021 via two emails to the BACPR mailing list and on social media. Practitioners providing dietary education within CR programmes were eligible to respond. Survey questions encompassed: practitioner job title and qualifications, resources, and the format, content and individual tailoring of diet education. Forty-nine different centres responded. Nurses (65·1 %) and dietitians (55·3 %) frequently provided dietary education. Practitioners had no nutrition-related qualifications in 46·9 % of services. Most services used credible resources to support their education, and 24·5 % used BACPR core competencies. CR programmes were mostly community based (40·8 %), lasting 8 weeks (range: 2-25) and included two (range: 1-7) diet sessions. Dietary history was assessed at the start (79·6 %) and followed up (83·7 %) by most centres; barriers to completing assessment were insufficient time, staffing or other priorities. Services mainly focused on the Mediterranean diet while topics such as malnutrition and protein intake were lower priority topics. Service improvement should focus on increasing qualifications of practitioners, standardisation of dietary assessment and improvement in protein and malnutrition screening and assessment.

Physiological mechanisms associated with the use of a passive heat intervention: positive implications for soccer substitutes.

PURPOSE: Soccer substitutes are exposed to periods of limited activity before entering match-play, likely negating benefits of active warm-ups. This study aimed to determine the effects of using a passive heat intervention following a pre-match, and half-time warm-up, on muscle and core temperature in soccer players during ambient (18 °C) and cold (2 °C) conditions. METHODS: On four occasions, 8 male players, completed a pre-match warm-up, followed by 45 min of rest. Following this, participants completed a half-time re-warm-up followed by an additional 45 min of rest, simulating a full match for an unplaying substitute. During periods of rest, participants wore either standardised tracksuit bottoms (CON), or heated trousers (HEAT), over typical soccer attire. RESULTS: Vastus lateralis temperature declined less in HEAT compared to CON following the 1st half in 2 °C (Δ - 4.39 ± 0.81 vs. - 6.21 ± 1.32 °C, P = 0.002) and 18 °C (Δ - 2.48 ± 0.71 vs. - 3.54 ± 0.88 °C, P = 0.003). These findings were also observed in the 2nd half for the 2 °C (Δ - 4.36 ± 1.03 vs. - 6.26 ± 1.04 °C, P = 0.002) and 18 °C (Δ - 2.85 ± 0.57 vs. - 4.06 ± 1 °C, P = 0.018) conditions. In addition, core temperature declined less in HEAT compared to CON following the 1st (Δ - 0.41 ± 0.25 vs. - 0.84 ± 0.41 °C, P = 0.037) and 2nd (Δ - 0.25 ± 0.33 vs. - 0.64 ± 0.34 °C, P = 0.028) halves of passive rest in 2 °C, with no differences in the 18 °C condition. Perceptual data confirmed that participants were more comfortable in HEAT vs. CON in 2 °C (P < 0.01). CONCLUSIONS: Following active warm-ups, heated trousers attenuate the decline in muscle temperature in ambient and cold environments.

Serum transthyretin and aminotransferases are associated with lean mass in people with coronary heart disease: Further insights from the CARE-CR study.

Background: Low muscle mass disproportionately affects people with coronary heart disease compared to healthy controls but is under-researched and insufficiently treated. Inflammation, poor nutrition, and neural decline might contribute to low muscle mass. This study aimed to assess circulatory biomarkers related to these mechanisms [albumin, transthyretin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and C-terminal agrin fragment] and their relationship with muscle mass in people with coronary heart disease. Our findings could be beneficial to indicate mechanisms of sarcopenia, detect sarcopenia, and evaluate treatment. Methods: Serum blood samples from people with coronary heart disease were analysed for biomarker concentrations using enzyme-linked immunosorbent assays. Skeletal muscle mass was estimated using dual X-ray absorptiometry derived appendicular lean mass and reported as skeletal muscle index (SMI; kg m-2), and as a proportion of total body mass [appendicular skeletal mass (ASM%)]. Low muscle mass was defined as a SMI <7.0 and <6.0 kg m-2, or ASM% <25.72 and <19.43% for men and women, respectively. Associations between biomarkers and lean mass were adjusted for age and inflammation. Results: Sixty-four people were assessed; 14 (21.9%) had low muscle mass. People with low muscle mass had lower transthyretin (effect size 0.34, p = 0.007), ALT (effect size 0.34, p = 0.008), and AST (effect size 0.26, p = 0.037) concentrations, compared to those with normal muscle mass. SMI was associated with inflammation-corrected ALT (r = 0.261, p = 0.039) and with inflammation- and age-adjusted AST/ALT ratio (r = -0.257, p = 0.044). Albumin and C-terminal agrin fragment were not associated with muscle mass indices. Conclusion: Circulatory transthyretin, ALT and AST were associated with low muscle mass in people with coronary heart disease. Low concentrations of these biomarkers might indicate that low muscle mass is partially explained by poor nutrition and high inflammation in this cohort. Targeted treatments to address these factors could be considered for people with coronary heart disease.

The effectiveness of the Healthworks Staying Steady community-based falls prevention exercise programme to improve physical function in older adults: a 6-year service evaluation.

BACKGROUND: Falls prevention exercise programmes are evidence-based and recommended for improving physical function in older adults. However, few service evaluations exist to assess the effectiveness of community-delivered interventions in practice. METHODS: We conducted a six-year, retrospective evaluation of the community-delivered Staying Steady programme (Healthworks, United Kingdom). Staying Steady is a 27-week, tailored strength and balance programme delivered in a group setting (1-h, once/week) and at home (30-40 min, 2-3 times/week). Participants were referred by healthcare professionals, or self-referred, due to a history or risk of falling. Routinely collected outcome measures (30-s chair stand, Timed Up and Go, four-stage balance test, and patient reported outcomes; including 'fear of falling' and 'ability to manage health') were analysed. Factors associated with programme completion were reported. The intervention effect on physical function was analysed in subgroups: participants used arms to chair-stand or a walking-aid at both ('aided'), neither ('unaided'), or one assessment timepoint ('aided at baseline only' or 'aided at follow-up only'). RESULTS: There were 1,426 referrals; 835 (67.3%) participants enrolled on to the Staying Steady programme, 406 (32.7%) declined, 185 (13.0%) were inappropriately referred and excluded from analysis. After enrolling, 451 (54.0%) participants completed, and 384 (46.0%) dropped out. Chair stand performance improved in participants who were unaided (n = 264; median 2.0 [1.0, 4.0] repetitions; P < 0.001), or aided at baseline, follow-up or both (n = 170, P < 0.05). Timed Up and Go performance improved in the unaided (n = 387; median -3.1 [-5.4, -1.4] s, P < 0.001), and aided at baseline only (n = 32; median -4.9 [-10.8, -3.4] s, P < 0.001) groups. Four-stage balance performance improved (n = 295; median 1.0 [0.0, 1.0] points, P < 0.001). After programme completion, participants self-reported an improved ability to manage their health and daily activities, improved confidence, and a reduced fear of falling. Presence of chronic obstructive pulmonary disease, fear of falling, prescribed nutritional support, disability and social deprivation influenced non-completion of Staying Steady. CONCLUSIONS: Completing Staying Steady improved physical function in older adults. Methods to encourage retention of participants from groups associated with low uptake and adherence should be investigated.

The impact of passive heat maintenance strategies between an active warm-up and performance: a systematic review and meta-analysis.

BACKGROUND: Prior to exercise, a warm-up routine has been suggested to be an imperative factor in task readiness with the anticipation that it will enhance performance. One of the key benefits of a warm-up is the increase in muscle and core temperature, which can be achieved in a variety of ways. An effective way to achieve improvements in core and muscle temperature is by performing an active warm-up. However, lengthy transition periods between an active warm-up and exercise performance are known to cause a decline in core and muscle temperature, thereby reducing performance capability. As such, methods are needed to assist athletes during transition periods, to maintain the benefits of a warm-up with the aim of optimising performance. Accordingly, the purpose of this review is to systematically analyse the evidence base that has investigated the use of passive heating to aide sporting performance when a transition period is experienced. METHODS: A systematic review and meta-analysis were undertaken following relevant studies being identified using PubMed, Web of Science, and EBSCO. Studies investigating the effects of passive heating strategies during the transition period between an active warm-up and exercise performance were included. The quality of the included studies were assessed by two independent reviewers using a modified version of the Physiotherapy Evidence Database scale. RESULTS: Seven studies, all high quality (mean = 7.6), reported sufficient data (quality score > 5) on the effects of passive heating strategies on exercise performance, these studies consisted of 85 well-trained athletes (78 male and 7 female). Passive heating strategies used between an active warm-up and exercise, significantly increased peak power output in all studies (ES = 0.54 [95% CI 0.17 to 0.91]). However, only a favourable trend was evident for exercise performance (ES = 1.07 [95% CI - 0.64 to 0.09]). CONCLUSIONS: Based upon a limited number of well-conducted, randomised, controlled trials, it appears that passive heating strategies used between an active warm-up and exercise have a positive impact on peak power output. Although, additional research is necessary to determine the optimum procedure for passive warm-up strategies.

Does the reticulospinal tract mediate adaptation to resistance training in humans?

Resistance training increases volitional force-producing capacity, and it is widely accepted that such an increase is partly underpinned by adaptations in the central nervous system, particularly in the early phases of training. Despite this, the neural substrate(s) responsible for mediating adaptation remains largely unknown. Most studies have focused on the corticospinal tract, the main descending pathway controlling movement in humans, with equivocal findings. It is possible that neural adaptation to resistance training is mediated by other structures; one such candidate is the reticulospinal tract. The aim of this narrative mini-review is to articulate the potential of the reticulospinal tract to underpin adaptations in muscle strength. Specifically, we 1) discuss why the structure and function of the reticulospinal tract implicate it as a potential site for adaptation; 2) review the animal and human literature that supports the idea of the reticulospinal tract as an important neural substrate underpinning adaptation to resistance training; and 3) examine the potential methodological options to assess the reticulospinal tract in humans.

Effects of maximal-versus submaximal-intent resistance training on functional capacity and strength in community-dwelling older adults: a systematic review and meta-analysis.

The objective of this systematic review is to investigate the effects of different methods of resistance training (RT) on functional capacity in older adults. A systematic literature search was conducted using PubMed, SPORTDiscus, Web of Science, CINAHL, Cochrane CENTRAL, ClinicalTrials.gov databases, from inception to December 2021. Eligibility criteria consisted of randomised control trials (RCT's) involving maximal-intent resistance training (MIRT), where participants (aged 60+) had specific instruction to move 'as fast as possible' during the concentric phase of the exercise. Twelve studies were included within the meta-analysis. Divided into functional capacity and strength-related outcomes; Improvements were evident for timed-up-and-go (p = 0.001, SMD: - 1.74 [95% CI - 2.79, - 0.69]) and knee extension one-repetition maximum (1RM) (p = 0.01, SMD: - 1.21, [95% CI - 2.17, - 0.25]), both in favour of MIRT, as well as in 30 s sit-to-stand in favour of T-STR (p = 0.04, SMD: 3.10 [95% CI 0.07, 6.14]). No statistical significance was found for combined functional capacity outcomes (p = 0.17, SMD: - 0.84, [95% CI - 2.04, 0.37]), with near-significance observed in strength-related outcomes (p = 0.06. SMD: - 0.57, [95% CI - 1.16, 0.02]) favouring MIRT. Heterogeneity for FC-outcomes was observed as Tau2 = 4.83; Chi = 276.19, df = 14, I2 = 95%, and for strength-outcomes Tau2 = 1.290; Chi = 109.65, df = 115, I2 = 86%. Additionally, MIRT elicited substantial clinically meaningful improvements (CMI) in Short Physical Performance Battery (SPPB) scores but fell short of CMI in 400 m walk test by 0.6 s. In conclusion, this systematic review highlights the lack of sufficient and quality evidence for maximal- versus submaximal-intent resistance training on functional capacity and strength in community-dwelling older adults. Study limitations revolved around lack of research, low quality ("low" PEDro score), and largely due to the fact many comparison studies did not match their loads lifted (1500 kg vs. 500 kg), making comparisons not possible.

Etiology and Recovery of Neuromuscular Function Following Academy Soccer Training.

Aim: To profile the etiology and recovery time-course of neuromuscular function in response to a mixed-content, standard training week in professional academy soccer players. We concurrently examined physical performance, cognitive function, and perceptual measures of mood and wellness states to identify a range of simple tests applied practitioners could use in the field as surrogate measures of neuromuscular function. Methods: Sixteen professional academy soccer players completed a range of neuromuscular, physical, perceptual, mood, and cognitive function tests at baseline and after a strenuous training day (pitch and gym), with retest at 24, 48, and 72 h, and further pitch and gym sessions after 48 h post-baseline. Maximal voluntary contraction force (MVC) and twitch responses to electrical stimulation (femoral nerve) during isometric knee-extensor contractions and at rest were measured to assess central nervous system (voluntary activation, VA) and muscle contractile (potentiated twitch force, Qtw,pot) function. Results: Strenuous training elicited decrements in MVC force post-session (-11%, p = 0.001) that remained unresolved at 72 h (-6%, p = 0.03). Voluntary activation (motor nerve stimulation) was reduced immediately post-training only (-4%, p = 0.03). No change in muscle contractile function (Qtw,pot) was observed post-training, though was reduced at 24 h (-13%, p = 0.01), and had not fully recovered 72 h after (-9%, p = 0.03). Perceptions of wellness were impaired post-training, and recovered by 24 h (sleepiness, energy) and 48 h (fatigue, muscle soreness, readiness to train). Countermovement jump performance declined at 24 h, while RSI (Reactive Strength Index) decrements persisted at 48 h. No changes were evident in adductor squeeze, mood, or cognitive function. Conclusion: Elite youth soccer training elicits substantial decrements in neuromuscular function, which are still present 72 h post-strenuous exercise. Though central processes contribute to post-exercise neuromuscular alterations, the magnitude and prolonged presence of impairments in contractile function indicates it is the restitution of muscular function (peripheral mechanisms) that explains recovery from strenuous training in academy soccer players.

Corticospinal and peripheral responses to heat-induced hypo-hydration: potential physiological mechanisms and implications for neuromuscular function.

Heat-induced hypo-hydration (hyperosmotic hypovolemia) can reduce prolonged skeletal muscle performance; however, the mechanisms are less well understood and the reported effects on all aspects of neuromuscular function and brief maximal contractions are inconsistent. Historically, a 4-6% reduction of body mass has not been considered to impair muscle function in humans, as determined by muscle torque, membrane excitability and peak power production. With the development of magnetic resonance imaging and neurophysiological techniques, such as electromyography, peripheral nerve, and transcranial magnetic stimulation (TMS), the integrity of the brain-to-muscle pathway can be further investigated. The findings of this review demonstrate that heat-induced hypo-hydration impairs neuromuscular function, particularly during repeated and sustained contractions. Additionally, the mechanisms are separate to those of hyperthermia-induced fatigue and are likely a result of modulations to corticospinal inhibition, increased fibre conduction velocity, pain perception and impaired contractile function. This review also sheds light on the view that hypo-hydration has 'no effect' on neuromuscular function during brief maximal voluntary contractions. It is hypothesised that irrespective of unchanged force, compensatory reductions in cortical inhibition are likely to occur, in the attempt of achieving adequate force production. Studies using single-pulse TMS have shown that hypo-hydration can reduce maximal isometric and eccentric force, despite a reduction in cortical inhibition, but the cause of this is currently unclear. Future work should investigate the intracortical inhibitory and excitatory pathways within the brain, to elucidate the role of the central nervous system in force output, following heat-induced hypo-hydration.

Drop jumps versus sled towing and their effects on repeated sprint ability in young basketball players.

BACKGROUND: The aim of the investigation was to compare the occurrence of post-activation performance enhancement (PAPE) after drop jumps, or heavy sled towing, and the subsequent effect on repeated sprint ability (RSA). METHODS: Ten young basketball players (17 ± 1 yrs) performed, in randomized order, RSA test with changes of direction after a standardized warm up followed by drop jumps, heavy sled towing, or no exercise (control condition). Neuromuscular assessments composed of two maximal voluntary contractions of the knee extensors, peripheral nerve stimulation, and surface electromyography (EMG), responses were recorded before and immediately after the RSA. The EMG signal of leg muscles during sprinting were also recorded as well as the blood lactate concentration. RESULTS: The drop jumps improved the RSA mean time (P = 0.033), total time (P = 0.031), and slowest time (P = 0.029) compared to control condition, while heavy sled towing did not change RSA outcomes (P > 0.05). All conditions exhibited a decrease of doublet high frequency stimulation force (pre-post measurement) (P = 0.023) and voluntary activation (P = 0.041), evidencing the occurrence from peripheral and central components of fatigue after RSA, respectively, but no difference was evident between-conditions. There was a significantly greater EMG activity during sprints for the biceps femoris after drop jumps, only when compared to control condition (P = 0.013). CONCLUSION: Repeated drop jumps were effective to induce PAPE in the form of RSA, while heavy sled towing had no effect on RSA performance in young basketball players. Furthermore, both conditioning activities exhibited similar levels of fatigue following the RSA protocol. Thus, drop jumps may be used as an alternative to induce PAPE and thus improve performance during sprints in young male basketball players.

Neurostructural and Neurophysiological Correlates of Multiple Sclerosis Physical Fatigue: Systematic Review and Meta-Analysis of Cross-Sectional Studies.

Fatigue is one of the most debilitating symptoms for people with multiple sclerosis (PwMS). By consolidating a diverse and conflicting evidence-base, this systematic review and meta-analysis aimed to gain new insights into the neurobiology of MS fatigue. MEDLINE, ProQuest, CINAHL, Web of Science databases and grey literature were searched using Medical Subject Headings. Eligible studies compared neuroimaging and neurophysiological data between people experiencing high (MS-HF) versus low (MS-LF) levels of perceived MS fatigue, as defined by validated fatigue questionnaire cut-points. Data were available from 66 studies, with 46 used for meta-analyses. Neuroimaging studies revealed lower volumetric measures in MS-HF versus MS-LF for whole brain (-22.74 ml; 95% CI: -37.72 to -7.76 ml; p = 0.003), grey matter (-18.81 ml; 95% CI: -29.60 to -8.03 ml; p < 0.001), putamen (-0.40 ml; 95% CI: -0.69 to -0.10 ml; p = 0.008) and acumbens (-0.09 ml; 95% CI: -0.15 to -0.03 ml; p = 0.003) and a higher volume of T1-weighted hypointense lesions (1.10 ml; 95% CI: 0.47 to 1.73 ml; p < 0.001). Neurophysiological data showed reduced lower-limb maximum voluntary force production (-19.23 N; 95% CI: -35.93 to -2.53 N; p = 0.02) and an attenuation of upper-limb (-5.77%; 95% CI:-8.61 to -2.93%; p < 0.0001) and lower-limb (-2.16%; 95% CI:-4.24 to -0.07%; p = 0.04) skeletal muscle voluntary activation, accompanied by more pronounced upper-limb fatigability (-5.61%; 95% CI: -9.57 to -1.65%; p = 0.006) in MS-HF versus MS-LF. Results suggest that MS fatigue is characterised by greater cortico-subcortical grey matter atrophy and neural lesions, accompanied by neurophysiological decrements, which include reduced strength and voluntary activation. Prospero registration Prospero registration number: CRD42016017934.

The Relationship Between Neuromuscular Function and the W' in Elite Cyclists.

PURPOSE: To assess the association between the W' and measures of neuromuscular function relating to the capacity of skeletal muscle to produce force in a group of elite cyclists. METHODS: Twenty-two athletes specializing in a range of disciplines and competing internationally volunteered to participate. Athletes completed assessments of maximum voluntary torque (MVT), voluntary activation, and isometric maximum voluntary contraction to measure rate of torque development (RTD). This was followed by assessment of peak power output (PPO) and 3-, 5-, and 12-minute time trials to determine critical power. Pearson correlation was used to examine associations with critical power and W'. Goodness of fit was calculated, and significant relationships were included in a linear stepwise regression model. RESULTS: Significant positive relationships were evident between W' and MVT (r = .82), PPO (r = .70), and RTD at 200 milliseconds (r = .59) but not with RTD at 50 milliseconds and voluntary activation. Correlations were also observed between critical power and RTD at 200 milliseconds and MVT (r = .54 and r = .51, respectively) but not with PPO, voluntary activation, or RTD at 50 milliseconds. The regression analysis found that 87% of the variability in W' (F1,18 = 68.75; P < .001) was explained by 2 variables: MVT (81%) and PPO (6%). CONCLUSIONS: It is likely that muscle size and strength, as opposed to neural factors, contribute meaningfully to W'. These data can be used to establish training methods to enhance W' to improve cycling performance in well-trained athletes.

The influence of resistance training on neuromuscular function in middle-aged and older adults: A systematic review and meta-analysis of randomised controlled trials.

BACKGROUND: Deterioration of neuromuscular function is a major mechanism of age-related strength loss. Resistance training (RT) improves muscle strength and mass. However, the effects of RT on neuromuscular adaptations in middle-aged and older adults are unclear. METHODS: Randomised controlled RT interventions (≥2 weeks) involving adults aged ≥50 years were identified. Primary outcome measures were voluntary activation (VA), electromyographic (EMG) activity during maximal voluntary contraction (MVC), and antagonist coactivation. Data were pooled using a weighted random-effect model. Sub-analyses were conducted by muscle or muscle group and health status of participants. Sensitivity analysis was based on study quality. P < 0.05 indicated statistical significance. RESULTS: Twenty-seven studies were included. An effect was found for VA (standardised mean difference [SMD] 0.54, 0.01 to 1.07, P = 0.04), This result remained significant following sensitivity analysis involving only studies that were low risk of bias. Subgroup analyses showed an effect for plantar flexor VA (SMD 1.13, 0.20 to 2.06, P = 0.02) and VA in healthy participants (SMD 1.04, 0.32 to 1.76, P = 0.004). There was no effect for EMG activity or antagonist coactivation of any muscle group (P > 0.05). DISCUSSION: Resistance training did not alter EMG activity or antagonist coactivation in older adults. Sensitivity analysis resulted in the effect for VA remaining significant, indicating that this finding was not dependent on study quality. Studies predominantly involved healthy older adults (78%), limiting the generalisability of these findings to clinical cohorts. Future research should determine the effects of RT on neuromuscular function in people with sarcopenia and age-related syndromes.