Evaluation of multi-directional speed qualities throughout adolescence in youth soccer: The non-linear nature of transfer.

Training and assessment of agility is often prioritised by soccer coaches and practitioners aiming to develop multi-directional speed. Although the importance of agility is advocated throughout childhood and adolescence, limited data evidence agility performance at different stages of adolescence. The purpose of this study was to examine differences in multi-directional speed performance in youth soccer players spanning an entire soccer academy. A total of 86 male junior-elite soccer players volunteered to participate. Anthropometric data were collected, alongside performance data from a battery of physical tests including sprinting, jumping, change of direction, reaction time, and agility. Bayesian models using log-likelihoods from posterior simulations of parameter values displayed linear or curvilinear relationships between both chronological and biological age and performance in all tests other than agility and reaction time. For agility and reaction time tests, performance improved until ~14 years of age or the estimated age of peak height velocity whereby arrested development in performance was observed. Our results demonstrate that while most performance skills improve as chronological or biological age increases, measures of agility and reaction time may not. These findings support the notion that agility performance is complex and multifaceted, eliciting unique, challenging physical demands and non-linear development.

Enhanced skeletal muscle contractile function and corticospinal excitability precede strength and architectural adaptations during lower-limb resistance training.

PURPOSE: Evolving investigative techniques are providing greater understanding about the early neuromuscular responses to resistance training among novice exercisers. The aim of this study was to investigate the time-course of changes in muscle contractile mechanics, architecture, neuromuscular, and strength adaptation during the first 6-weeks of lower-limb resistance training. METHODS: Forty participants: 22 intervention (10 males/12 females; 173.48 ± 5.20 cm; 74.01 ± 13.13 kg) completed 6-week resistance training, and 18 control (10 males/8 females; 175.52 ± 7.64 cm; 70.92 ± 12.73 kg) performed no resistance training and maintained their habitual activity. Radial muscle displacement (Dm) assessed via tensiomyography, knee extension maximal voluntary contraction (MVC), voluntary activation (VA), corticospinal excitability and inhibition via transcranial magnetic stimulation, motor unit (MU) firing rate, and muscle thickness and pennation angle via ultrasonography were assessed before and after 2, 4, and 6-weeks of dynamic lower-limb resistance training or control. RESULTS: After 2-weeks training, Dm reduced by 19-25% in the intervention group; this was before any changes in neural or morphological measures. After 4-weeks training, MVC increased by 15% along with corticospinal excitability by 16%; however, there was no change in VA, corticospinal inhibition, or MU firing rate. After 6-weeks training there was further MVC increase by 6% along with muscle thickness by 13-16% and pennation angle by 13-14%. CONCLUSION: Enhanced contractile properties and corticospinal excitability occurred before any muscle architecture, neural, and strength adaptation. Later increases in muscular strength can be accounted for by architectural adaptation.

Bayesian analysis of changes in standing horizontal and vertical jump after different modes of resistance training.

Training interventions often have small effects and are tested in small samples. We used a Bayesian approach to examine the change in jump distance after different resistance training programmes. Thirty-three 18- to 45-year-old males completed one of three lower limb resistance training programmes: deadlift (DL), hip thrust (HT) or back squat (BS). Horizontal and vertical jump performance was assessed over the training intervention. Examination of Bayesian posterior distributions for jump distance estimated that the probability of a change above a horizontal jump smallest worthwhile change (SWC) of 4.7 cm for the DL group was ~12%. For the HT and BS groups, the probability of a change above the SWC was ~87%. The probability of a change above a vertical jump SWC of 1.3 cm for the DL group was ~31%. For the HT and BS groups, the probability of a change above the vertical jump SWC was ~62% and ~67%, respectively. Our study illustrates that a Bayesian approach provides a rich inferential interpretation for small sample training studies with small effects. The extra information from such a Bayesian approach is useful to practitioners in Sport and Exercise Science where small effects are expected and sample size is often constrained.

Progression from youth to professional soccer: A longitudinal study of successful and unsuccessful academy graduates.

To optimize use of available resources, professional academies develop strategies to assess, monitor, and evaluate players as they progress through adolescence toward adulthood. However, few published reports exist using longitudinal study designs to examine performance throughout adolescence and the transition from youth to professional soccer. We examined differences in the age of player recruitment alongside longitudinal performance differences on field-based fitness tests of successful vs. unsuccessful graduates across the entire age spectrum recruited by a professional soccer academy. Altogether, 537 youth soccer players volunteered to participate. We recorded the age of recruitment, biannual fitness test performance, and subsequent success in attaining a senior professional contract at the club across a period of 12 years. Only 53 (10%) of players were successful in obtaining a professional contract, with 68% of players who became professional being recruited at 12 years of age or older. Individuals recruited at an earlier age did not display a higher probability of success in attaining a professional contract. Bayesian regression models reported a consistent interaction between age and group for data on all performance measures. Moreover, "successful" academy graduates only physically outperformed their "unsuccessful" counterparts from age ~13-14 years onward, with either no differences in performance, or performance on physical fitness tests favoring "unsuccessful" players prior to this age. Findings suggest that high achievers during childhood and early adolescence may not develop into successful senior professionals, raising concerns about the predictive utility of talent identification models.

Understanding factors associated with sarcopenic obesity in older African women from a low-income setting: a cross-sectional analysis.

BACKGROUND: High rates of food insecurity, obesity and obesity-related comorbidities in ageing South African (SA) women may amplify the risk of developing sarcopenic obesity. This study aimed to investigate the prevalence and correlates of sarcopenic obesity and its diagnostic components [grip strength, appendicular skeletal muscle mass (ASM) and body mass index (BMI)] in older SA women from a low-income setting. METHODS: This cross-sectional study recruited black SA women between the ages of 60-85 years (n = 122) from a low-income community. Testing included a fasting blood sample (markers of cardiometabolic risk, HIV), whole body and regional muscle and fat mass (dual-energy absorptiometry x-ray), anthropometry, blood pressure, functional movement tests, current medication use, demographic and health questionnaires, physical activity (PA; accelerometery), household food insecurity access scale, and a one-week quantified food frequency questionnaire. Foundation for the National Institutes of Health (FNIH) criteria (grip strength and ASM, adjusted for BMI) were used to classify sarcopenia. Participants with sarcopenia alongside a BMI of > 30.0 kg/m2 were classified as having sarcopenic obesity. Prevalence using other criteria (European Working Group on Sarcopenia in Older People, Asian Working Group for Sarcopenia and the International Working Group for Sarcopenia) were also explored. RESULTS: The prevalence of sarcopenia was 27.9%, which comprised of sarcopenia without obesity (3.3%) and sarcopenic obesity (24.6%). Other classification criteria showed that sarcopenia ranged from 0.8-14.7%, including 0.8-9.8% without obesity and 0-4.9% with sarcopenic obesity. Using multivariate-discriminant analysis (OPLS-DA) those with sarcopenic obesity presented with a descriptive profile of higher C-reactive protein, waist circumference, food security and sedentary time than women without sarcopenic obesity (p = 0.046). A similar profile described women with low BMI-adjusted grip strength (p < 0.001). CONCLUSIONS: The majority of women with sarcopenia were also obese (88%). We show a large discrepancy in the diagnostic criteria and the potential for significantly underestimating the prevalence of sarcopenia if BMI is not adjusted for. The main variables common to women with sarcopenic obesity were higher food security, lower PA and chronic inflammation. Our data highlights the importance of addressing obesity within these low-income communities to ensure the prevention of sarcopenic obesity and that quality of life is maintained with ageing.

The match between what is prescribed and reasons for prescribing in exercise referral schemes: a mixed method study.

BACKGROUND: Exercise referral schemes (ERS) aim to tackle non-communicable disease (NCD) by increasing physical activity levels through prescribed exercise. However, there is a sparsity of knowledge upon what exercises are prescribed and if they are targeted towards tackling NCD. METHOD: Mixed methods were employed. Quantitative data was extracted from exercise prescription cards of 50 participants and were assessed for frequency, intensity, type and time of prescribed exercise. Descriptive measures of aggregate data are expressed as median (range: minimum-maximum). Thematic analysis of semi-structured interviews generated qualitative data on exercise referral instructors' experiences of prescribing exercise. RESULTS: Thirty-eight different types of exercise were prescribed. Median prescription was 4 (1-11) exercises per session, at a moderate intensity. Participants were prescribed a median of 35 (5-70) minutes of aerobic exercise per referral session. Exercise referral instructors prescribed exercise to improve activities of daily living, promote independence and autonomy of participants, rather than explicitly targeting the referral condition. CONCLUSIONS: Knowledge that prescribed exercises are not explicitly targeted to the referral condition provides critical information in understanding the purpose of exercise prescription. Future evaluations of ERS should be mindful of this, that is, perceived outcomes might not match up to what is being prescribed within ERS.

Impact of resistance training status on trunk muscle activation in a fatiguing set of heavy back squats.

PURPOSE: In this study we measured neural activation (EMG) in four trunk stabilizer muscles and vastus lateralis (VL) in trained and novice participants during a set of squat repetitions to volitional fatigue at 85% 1RM. METHODS: Forty males were recruited into two groups, novice (NG: n = 21) and experienced (EG: n = 19), according to relative squat 1RM. Participants were tested twice to: (1) determine squat 1RM, and (2) complete a single set of repetitions to volitional fatigue at 85% 1RM. Relative squat 1RM; NG < 140% body mass, EG > 160% body mass. Neuromuscular activation was measured by EMG for the following: rectus abdominus (RA), external oblique (EO), lumbar sacral erector spinae (LSES), upper lumbar erector spinae (ULES) and VL in eccentric and concentric phase. Completed repetitions, RPE and EMG in repetition 1 and at 20, 40, 60, 80 and 100% of completed repetitions were analysed. RESULTS: No group differences were found between number repetitions completed and RPE in repetitions to volitional fatigue at 85% 1RM. Neuromuscular activation increased significantly in all muscle groups in eccentric and concentric phase apart from RA in the eccentric phase. Trunk neuromuscular activation was higher in NG compared to EG and this was significant in EO, LSES and ULES in eccentric phase and LSES in the concentric phase. VL activation increased in both phases with no group differences. CONCLUSION: Trunk neuromuscular activation increases in a fatiguing set of heavy squats regardless of training status. Increased back squat strength through training results in lower neuromuscular activation despite greater absolute external squat loads.

A case study comparison of objective and subjective evaluation methods of physical qualities in youth soccer players.

Subjective and objective assessments may be used congruently when making decisions regarding player recruitment in soccer, yet there have been few attempts to examine the level of agreement between these methods. Therefore, we compare levels of agreement between subjective and objective assessments of physical qualities associated with youth soccer performance. In total, 80 male youth soccer players (13.2 ± 1.9 years), and 12 professional coaches volunteered to participate. Players were objectively assessed using five fitness measures: Yo-Yo Intermittent Recovery Test Level 1; Countermovement vertical jump; Functional Movement Screen™; 5/20 m sprint; alongside anthropometric measures. Additionally, coaches subjectively rated each player on the same five physical qualities using 5-point Likert scales. Inter-rater agreement between ratings from lead and assistant coaches was established for each age group. Moreover, Bayesian regression models were fitted to determine how well coach ratings were able to predict fitness test performance. Although inter-rater agreement between lead and assistant coaches was moderate-to-substantial (ω = 0.48-0.68), relationships between coaches subjective rating's and corresponding fitness test performance were only highly related for the highest and lowest performing players. We suggest that while ratings derived from objective and subjective assessment methods may be related when attempting to differentiate between distinct populations, concerns exist when evaluating homogeneous samples using these methods. Our data highlight the benefits of using both types of measures in the talent identification process.

Trunk Muscle Activation in the Back and Hack Squat at the Same Relative Loads.

Clark, DR, Lambert, MI, and Hunter, AM. Trunk muscle activation in the back and hack squat at the same relative loads. J Strength Cond Res 33(7S): S60-S69, 2019-The hack squat (HS) is likely to produce a greater 1 repetition maximum (1RM) compared with the back squat (BS). This can be attributed to the support of the trunk during the HS compared with no support during BS. This support, however, may compromise trunk muscle activation (TMA), therefore producing different training adaptations. Accordingly, the purpose of this study was to compare 1RM in BS and HS and TMA at 4 relative loads, 65, 75, 85, and 95% of maximal system mass. Ten males completed 3 test sessions: (a) BS and HS 1RM, (b) HS and BS neuromuscular test familiarization, and (c) neuromuscular test for 3 reps at 4 loads for BS and HS. Back squat TMA was significantly greater (p ≤ 0.05) than HS for all muscles and phases except rectus abdominus in concentric phase. Trunk muscle activation increased (p ≤ 0.05) with load in all muscles for both exercises and phases apart from lumbar sacral erector spinae in HS eccentric phase. Mean HS 1RM and submaximal loads were significantly (p < 0.0001) higher than the equivalent BS loads. Duration of the eccentric phase was higher (p < 0.01) in HS than BS but not different in concentric phase. Duration increased significantly (p < 0.01) with load in both exercises and both phases. Despite higher absolute tests loads in HS, TMA was higher in BS. Trunk muscle activation is sensitive to load in both exercises. Back squat is more effective than HS in activating the muscles of the trunk and therefore, arguably more effective in developing trunk strength and stability for dynamic athletic performance.

Influence of the "Slingshot" Bench Press Training Aid on Bench Press Kinematics and Neuromuscular Activity in Competitive Powerlifters.

Dugdale, JH, Hunter, AM, Di Virgilio, TG, Macgregor, LJ, and Hamilton, DL. Influence of the "Slingshot" bench press training aid on bench press kinematics and neuromuscular activity in competitive powerlifters. J Strength Cond Res 33(2): 327-336, 2019-This study examined the acute effects of the "Slingshot" (SS) on bench press performance, prime mover surface electromyographic (sEMG) amplitude, and barbell velocity during maximal and submaximal bench pressing in competitive male powerlifters. Fifteen male powerlifters (mean ± SD; age: 27.05 ± 5.94 years; mass: 94.15 ± 13.43 kg; 1 repetition maximum [1RM] bench press: 139.7 ± 16.79 kg) participated in the study. Bench press strength, average barbell velocity, and sEMG amplitude of the prime mover muscles (triceps brachii, pectoralis major, and anterior deltoid) were measured during 2 conditions; "Raw" (without use of any assistance) and "SS" (using the "Slingshot" to perform both the weight achieved during "Raw" 1RM testing [Raw max/SS], and absolute 1RM using the "SS"). The results showed that the "SS" significantly increased bench press 1RM performance by a mean ± SD of 20.67 ± 3.4 kg. Barbell velocity and stick point analysis indicate that this improvement is likely driven by an increase in peak and prestick barbell velocity as triceps root mean square (RMS) was lower throughout all rep max phases with the "SS." The "SS" also caused reductions in RMS, specifically of the triceps at all rep ranges but barbell velocity was better maintained in the last reps of all sets. These data indicate that the "SS" specifically deloaded the triceps muscle throughout all rep ranges and provide assistance to maintaining barbell velocity under fatigue during later repetitions of multiple repetition sets. The "SS" training aid could therefore be used in deload phases of bench press training or as an overreaching and velocity training aid.

Reliability and Measurement Error of Tensiomyography to Assess Mechanical Muscle Function: A Systematic Review.

Martín-Rodríguez, S, Loturco, I, Hunter, AM, Rodríguez-Ruiz, D, and Munguia-Izquierdo, D. Reliability and measurement error of tensiomyography to assess mechanical muscle function: A systematic review. J Strength Cond Res 31(12): 3524-3536, 2017-Interest in studying mechanical skeletal muscle function through tensiomyography (TMG) has increased in recent years. This systematic review aimed to (a) report the reliability and measurement error of all TMG parameters (i.e., maximum radial displacement of the muscle belly [Dm], contraction time [Tc], delay time [Td], half-relaxation time [½ Tr], and sustained contraction time [Ts]) and (b) to provide critical reflection on how to perform accurate and appropriate measurements for informing clinicians, exercise professionals, and researchers. A comprehensive literature search was performed of the Pubmed, Scopus, Science Direct, and Cochrane databases up to July 2017. Eight studies were included in this systematic review. Meta-analysis could not be performed because of the low quality of the evidence of some studies evaluated. Overall, the review of the 9 studies involving 158 participants revealed high relative reliability (intraclass correlation coefficient [ICC]) for Dm (0.91-0.99); moderate-to-high ICC for Ts (0.80-0.96), Tc (0.70-0.98), and ½ Tr (0.77-0.93); and low-to-high ICC for Td (0.60-0.98), independently of the evaluated muscles. In addition, absolute reliability (coefficient of variation [CV]) was low for all TMG parameters except for ½ Tr (CV = >20%), whereas measurement error indexes were high for this parameter. In conclusion, this study indicates that 3 of the TMG parameters (Dm, Td, and Tc) are highly reliable, whereas ½ Tr demonstrate insufficient reliability, and thus should not be used in future studies.

Reduced Radial Displacement of the Gastrocnemius Medialis Muscle After Electrically Elicited Fatigue.

CONTEXT: Assessments of skeletal-muscle functional capacity often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated as a means to assess muscle contractile function after fatigue; however, observations have not been contextualized by concurrent physiological measures. OBJECTIVE: To measure peripheral-fatigue-induced alterations in mechanical and contractile properties of the plantar-flexor muscles through noninvasive TMG concurrently with maximal voluntary contraction (MVC) and passive muscle tension (PMT) to validate TMG as a gauge of peripheral fatigue. DESIGN: Pre- and posttest intervention with control. SETTING: University laboratory. PARTICIPANTS: 21 healthy male volunteers. INTERVENTIONS: Subjects' plantar flexors were tested for TMG parameters, along with MVC and PMT, before and after either a 5-min rest period (control) or a 5-min electrical-stimulation intervention (fatigue). MAIN OUTCOME MEASURES: Temporal (contraction velocity) and spatial (radial displacement) contractile parameters of the gastrocnemius medialis were recorded through TMG. MVC was measured as an indicator of muscle fatigue, and PMT was measured to assess muscle stiffness. RESULTS: Radial displacement demonstrated a fatigue-associated reduction (3.3 ± 1.2 vs 4.0 ± 1.4 mm, P = .031), while contraction velocity remained unaltered. In addition, MVC significantly declined by 122.6 ± 104 N (P < .001) after stimulation (fatigue). PMT was significantly increased after fatigue (139.8 ± 54.3 vs 111.3 ± 44.6 N, P = .007). CONCLUSION: TMG successfully detected fatigue, evident from reduced MVC, by displaying impaired muscle displacement accompanied by elevated PMT. TMG could be useful in establishing skeletal-muscle fatigue status without exacerbating the functional decrement of the muscle.

The Ingestion of 39 or 64 g·h(-1) of Carbohydrate is Equally Effective at Improving Endurance Exercise Performance in Cyclists.

In an investigator-blind, randomized cross-over design, male cyclists (mean± SD) age 34.0 (± 10.2) years, body mass 74.6 (±7.9) kg, stature 178.3 (±8.0) cm, peak power output (PPO) 393 (±36) W, and VO2max 62 (±9) ml·kg-1·min(-1) training for more than 6 hr/wk for more than 3y (n = 20) completed four experimental trials. Each trial consisted of a 2-hr constant load ride at 95% of lactate threshold (185 ± 25 W) then a work-matched time trial task (~30 min at 70% of PPO). Three commercially available carbohydrate (CHO) beverages, plus a control (water), were administered during the 2-hr ride providing 0, 20, 39, or 64 g·hr-1 of CHO at a fluid intake rate of 1L·hr(-1). Performance was assessed by time to complete the time trial task, mean power output sustained, and pacing strategy used. Mean task completion time (min:sec ± SD) for 39 g·hr(-1) (34:19.5 ± 03:07.1, p = .006) and 64 g·hr(-1) (34:11.3 ± 03:08.5 p = .004) of CHO were significantly faster than control (37:01.9 ± 05:35.0). The mean percentage improvement from control was -6.1% (95% CI: -11.3 to -1.0) and -6.5% (95% CI: -11.7 to -1.4) in the 39 and 64 g·hr(-1) trials respectively. The 20 g·hr(-1) (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared with control (p = .126) despite a mean improvement of -3.7% (95% CI -8.8-1.5%). No further differences between CHO trials were reported. No interaction between CHO dose and pacing strategy occurred. 39 and 64 g·hr-1 of CHO were similarly effective at improving endurance cycling performance compared with a 0 g·hr(-1) control in our trained cyclists.

Dryland Performance Tests Are Not Good Predictors of World Aquatics Points in Elite Male and Female Swimmers.

Background: Swim performance can be reliant on strength and power. Standardisation of swim performance in different events, distances, and sexes can be completed using World Aquatics points, allowing for ranking of swimmers. The aim of this retrospective cross-sectional study was to assess whether relationships between World Aquatics points and dryland markers of performance existed in male and female elite swimmers separately and combined. Methods: Dryland tests included Optojump® photoelectric cell countermovement jump, countermovement jump reach with a Vertec® system, standing broad jump using a tape measure, repetition maximum testing in the barbell back squat, barbell deadlift, and barbell bench press. Swim performance data and dryland test data on elite male (n = 38) and female (n = 20) Scottish swimmers from 2009-2017 were collected. Swim performance data were converted to World Aquatics federation points, and Bayesian linear regression analyses examined relationships between World Aquatics points and dryland performance tests: countermovement jump height (cm) using an Optojump® photoelectric cells system, countermovement jump height (cm) using a Vertec® device, standing broad jump distance (cm), relative strength (load lifted (kg) per kg of body mass) in the barbell bench press (kg/kg), barbell back squat (kg/kg), barbell deadlift (kg/kg). Results: The Bayesian estimates of change of World Aquatics points for a unit change in jump-based measures were: Optojump®-men = 0.6, women = 0.6, combined = 0.4; Vertec®-men = 4.3, women = -1.6, combined = 2.4; standing broad jump-men = 0, women = 0, combined = 0.4. Strength-based measures were: barbell back squat-men = 2.3, women = 22, combined = -2.5; barbell deadlift-men = -5; barbell bench press-men = 41.8. Conclusions: Dryland performance tests are not good predictors of World Aquatics points and should rather be used for assessing training quality and monitoring injury risks.

Contrasting Characteristics and Outcomes of Sports-Related and Non-Sports-Related Traumatic Brain Injury.

Importance: Exposure to traumatic brain injury (TBI) has raised widespread concern over participation in sports, particularly over possible long-term consequences. However, little is known about the outcomes of individuals presenting to hospitals with sports-related TBI. Objective: To compare the characteristics and outcomes of individuals presenting to hospitals with sports-related and non-sports-related TBI. Design, Setting, and Participants: The CENTER-TBI (Collaborative European NeuroTrauma Effectiveness Research in TBI) observational cohort study was conducted at hospitals in 18 countries. The study enrolled 4509 patients who had TBI and had an indication for computed tomography (CT), of whom 4360 were 16 years or older. Outcomes were assessed at 3 and 6 months, and groups were compared using regression analyses adjusting for clinical and demographic differences. Data were collected between December 9, 2014, and December 17, 2017, and analyzed from August 2022 to March 2023. Exposure: Sports-related and non-sports-related TBI with subgroups selected by severity of injury. Main Outcomes and Measures: The main outcome was the Glasgow Outcome Scale-Extended (GOSE) at 6 months, with secondary outcomes covering postconcussion symptoms, health-related quality of life, and mental health. Results: A total of 4360 patients were studied, including 256 (6%) with sports-related TBI (mean [SD] age, 38.9 [18.1] years; 161 [63%] male) and 4104 with non-sports-related TBI (mean [SD] age, 51.0 [20.2] years; 2773 [68%] male). Compared with patients with non-sports-related TBI, patients with sports-related TBI were younger, more likely to have tertiary education, more likely to be previously healthy, and less likely to have a major extracranial injury. After adjustment, the groups did not differ in incomplete recovery (GOSE scores <8) at 6 months (odds ratio [OR], 1.27; 95% CI, 0.90-1.78; P = .22 for all patients; OR, 1.20; 95% CI, 0.83-1.73; P = .34 for those with mild TBI; and OR, 1.19; 95% CI, 0.74-1.92; P = .65 for those with mild TBI and negative CT findings). At 6 months, there was incomplete recovery in 103 of 223 patients (46%) with outcomes in the sports-related TBI group, 65 of 168 (39%) in those with mild sports-related TBI, and 30 of 98 (31%) in those with mild sports-related TBI and negative CT findings. In contrast, at 6 months, the sports-related TBI group had lower prevalence of anxiety, depression, posttraumatic stress disorder, and postconcussion symptoms than the non-sports-related group. Conclusions and Relevance: In this cohort study of 4360 patients with TBI, functional limitations 6 months after injury were common after sports-related TBI, even mild sports-related TBI. Persisting impairment was evident in the sports-related TBI group despite better recovery compared with non-sports-related TBI on measures of mental health and postconcussion symptoms. These findings caution against taking an overoptimistic view of outcomes after sports-related TBI, even if the initial injury appears mild.

The Use of Biofluid Markers to Evaluate the Consequences of Sport-Related Subconcussive Head Impact Exposure: A Scoping Review.

BACKGROUND: Amidst growing concern about the safety of sport-related repetitive subconcussive head impacts (RSHI), biofluid markers may provide sensitive, informative, and practical assessment of the effects of RSHI exposure. OBJECTIVE: This scoping review aimed to systematically examine the extent, nature, and quality of available evidence from studies investigating the effects of RSHI on biofluid markers, to identify gaps and to formulate guidelines to inform future research. METHODS: PRISMA extension for Scoping Reviews guidelines were adhered to. The protocol was pre-registered through publication. MEDLINE, Scopus, SPORTDiscus, CINAHL, PsycINFO, Cochrane Library, OpenGrey, and two clinical trial registries were searched (until March 30, 2022) using descriptors for subconcussive head impacts, biomarkers, and contact sports. Included studies were assessed for risk of bias and quality. RESULTS: Seventy-nine research publications were included in the review. Forty-nine studies assessed the acute effects, 23 semi-acute and 26 long-term effects of RSHI exposure. The most studied sports were American football, boxing, and soccer, and the most investigated markers were (in descending order): S100 calcium-binding protein beta (S100B), tau, neurofilament light (NfL), glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), brain-derived neurotrophic factor (BDNF), phosphorylated tau (p-tau), ubiquitin C-terminal hydrolase L1 (UCH-L1), and hormones. High or moderate bias was found in most studies, and marker-specific conclusions were subject to heterogeneous and limited evidence. Although the evidence is weak, some biofluid markers-such as NfL-appeared to show promise. More markedly, S100B was found to be problematic when evaluating the effects of RSHI in sport. CONCLUSION: Considering the limitations of the evidence base revealed by this first review dedicated to systematically scoping the evidence of biofluid marker levels following RSHI exposure, the field is evidently still in its infancy. As a result, any recommendation and application is premature. Although some markers show promise for the assessment of brain health following RSHI exposure, future large standardized and better-controlled studies are needed to determine biofluid markers' utility.

The impact of 6-month training preparation for an Ironman triathlon on the proportions of naïve, memory and senescent T cells in resting blood.

Athletes appear to be at a greater risk of illness while undertaking arduous training regimens in preparation for endurance events. As infection susceptibility has been linked with increased proportions of differentiated and senescent T cells in the periphery, changes in the proportions of these cell types due to long-term high-volume exercise training could have important implications for athlete infection risk. This study examined the effects of 6-month training preparation for an Ironman triathlon on the proportions of naïve, memory and senescent T cells in resting blood. Ten club-level triathletes (9 males; 1 female: 43 ± 3 years) were sampled at 27 (December), 21 (January), 15 (March), 9 (May) and 3 (June) weeks before an Ironman Triathlon. An additional sample was collected 2-week post-competition (August). Four-colour flow cytometry was used for the phenotypic analysis of CD4+ and CD8+ blood T cells. Proportions of differentiated (KLRG1+/CD57-) CD8+ T cells and "transitional" (CD45RA+/CD45RO+) CD4+ and CD8+ T cells increased with training, as the values in June were elevated 37, 142 and 116%, respectively, from those observed in December. Proportions of senescent (KLRG1+/CD57+) CD4+ or CD8+ T cells did not change during the training phase. Two weeks post-race, proportions of differentiated CD8+ T cells had returned to baseline values, while the proportions of senescent CD4+ T cells increased 192% alongside a 31% reduction in naïve (CD45RA+/CD45RO-) cells. In conclusion, increases in differentiated and "transitional" T cells due to arduous exercise training could compromise host protection to novel pathogens and increase athlete infection risk, although whether or not the composition of naïve and differentiated T cells in blood can serve as prognostic biomarkers in athletes remains to be established.

Muscle activation in the loaded free barbell squat: a brief review.

The purpose of this article was to review a series of studies (n = 18) where muscle activation in the free barbell back squat was measured and discussed. The loaded barbell squat is widely used and central to many strength training programs. It is a functional and safe exercise that is obviously transferable to many movements in sports and life. Hence, a large and growing body of research has been published on various aspects of the squat. Training studies have measured the impact of barbell squat loading schemes on selected training adaptations including maximal strength and power changes in the squat. Squat exercise training adaptations and their impact on a variety of performance parameters, in particular countermovement jump, acceleration, and running speed, have also been reported. Furthermore, studies have reported on the muscle activation of the lower limb resulting from variations of squat depth, foot placement, training status, and training intensity. There have also been studies on the impact of squatting with or without a weight belt on trunk muscle activation (TMA). More recently, studies have reported on the effect of instability on TMA and squat performance. Research has also shown that muscle activation of the prime movers in the squat exercise increases with an increase in the external load. Also common variations such as stance width, hip rotation, and front squat do not significantly affect muscle activation. However, despite many studies, this information has not been consolidated, resulting in a lack of consensus about how the information can be applied. Therefore, the purpose of this review was to examine studies that reported muscle activation measured by electromyography in the free barbell back squat with the goal of clarifying the understanding of how the exercise can be applied.

The Reliability of Transcranial Magnetic Stimulation-Derived Corticomotor Inhibition as a Brain Health Evaluation Tool in Soccer Players.

BACKGROUND: The suitability of corticomotor inhibition and corticospinal excitability to measure brain health outcomes and recovery of sport-related head impact (concussion and subconcussion) depends on good inter-day reliability, which is evaluated in this study. Transcranial magnetic stimulation (TMS) reliability in soccer players is assessed by comparing soccer players, for whom reliability on this measure may be reduced due to exposure to head impacts, to generally active individuals not engaged in contact sport. METHODS: TMS-derived corticomotor inhibition and corticospinal excitability were recorded from the rectus femoris muscle during two testing sessions, spaced 1-2 weeks apart in 19 soccer players (SOC-age 22 ± 3 years) and 20 generally active (CON-age 24 ± 4 years) healthy volunteers. Inter-day reliability between the two time points was quantified by using intra-class correlation coefficients (ICC). Intra-group reliability and group differences on actual measurement values were also explored. RESULTS: Good inter-day reliability was evident for corticomotor inhibition (ICCSOC = 0.61; ICCCON = 0.70) and corticospinal excitability (ICCSOC = 0.59; ICCCON = 0.70) in both generally active individuals and soccer players routinely exposed to sport-related head impacts. Corticomotor inhibition showed lower coefficients of variation than excitability for both groups (InhibSOC = 15.2%; InhibCON = 9.7%; ExcitabSOC = 41.6%; ExcitabCON = 39.5%). No group differences between soccer players and generally active individuals were found on the corticomotor inhibition value (p > 0.05), but levels of corticospinal excitability were significantly lower in soccer players (45.1 ± 20.8 vs 85.4 ± 6.2%Mmax, p < 0.0001). Corticomotor inhibition also showed excellent inter-rater reliability (ICC = 0.87). CONCLUSIONS: Corticomotor inhibition and corticospinal excitability are stable and maintain good degrees of reliability when assessed over different days in soccer players, despite their routine exposure to head impacts. However, based on intra-group reliability and group differences of the levels of excitability, we conclude that corticomotor inhibition is best suited for the evaluation of neuromuscular alterations associated with head impacts in contact sports.

Protocol for a randomised controlled trial to investigate the effects of vitamin K2 on recovery from muscle-damaging resistance exercise in young and older adults-the TAKEOVER study.

BACKGROUND: Regular participation in resistance exercise is known to have broad-ranging health benefits and for this reason is prominent in the current physical activity guidelines. Recovery after such exercise is important for several populations across the age range and nutritional strategies to enhance recovery and modulate post-exercise physiological processes are widely studied, yet effective strategies remain elusive. Vitamin K2 supplementation has emerged as a potential candidate, and the aim of the current study, therefore, is to test the hypothesis that vitamin K2 supplementation can accelerate recovery, via modulation of the underlying physiological processes, following a bout of resistance exercise in young and older adults. METHODS: The current study is a two-arm randomised controlled trial which will be conducted in 80 (40 young (≤40 years) and 40 older (≥65 years)) adults to compare post-exercise recovery in those supplemented with vitamin K2 or placebo for a 12-week period. The primary outcome is muscle strength with secondary outcomes including pain-free range of motion, functional abilities, surface electromyography (sEMG) and markers of inflammation and oxidative stress. DISCUSSION: Ethical approval has been granted by the College of Medical Veterinary and Life Sciences Ethical Committee at the University of Glasgow (Project No 200190189) and recruitment is ongoing. Study findings will be disseminated through a presentation at scientific conferences and in scientific journals. TRIAL REGISTRATION: ClinicialTrials.gov NCT04676958. Prospectively registered on 21 December 2020.