Decreased neural drive affects the early rate of force development after repeated burst-like isometric contractions.

The neural drive to the muscle is the primary determinant of the rate of force development (RFD) in the first 50 ms of a rapid contraction. It is still unproven if repetitive rapid contractions specifically impair the net neural drive to the muscles. To isolate the fatiguing effect of contraction rapidity, 17 male adult volunteers performed 100 burst-like (i.e., brief force pulses) isometric contractions of the knee extensors. The response to electrically-evoked single and octet femoral nerve stimulation was measured with high-density surface electromyography (HD-sEMG) from the vastus lateralis and medialis muscles. Root mean square (RMS) of each channel of HD-sEMG was normalized to the corresponding M-wave peak-to-peak amplitude, while muscle fiber conduction velocity (MFCV) was normalized to M-wave conduction velocity to compensate for changes in sarcolemma properties. Voluntary RFD 0-50 ms decreased (d = -0.56, p < 0.001) while time to peak force (d = 0.90, p < 0.001) and time to RFDpeak increased (d = 0.56, p = 0.034). Relative RMS (d = -1.10, p = 0.006) and MFCV (d = -0.53, p = 0.007) also decreased in the first 50 ms of voluntary contractions. Evoked octet RFD 0-50 ms (d = 0.60, p = 0.020), M-wave amplitude (d = 0.77, p = 0.009) and conduction velocity (d = 1.75, p < 0.001) all increased. Neural efficacy, i.e., voluntary/octet force ratio, largely decreased (d = -1.50, p < 0.001). We isolated the fatiguing impact of contraction rapidity and found that the decrement in RFD, particularly when calculated in the first 50 ms of muscle contraction, can mainly be explained by a decrease in the net neural drive.

Neural and contractile determinants of burst-like explosive isometric contractions of the knee extensors.

Walking and running are based on rapid burst-like muscle contractions. Burst-like contractions generate a Gaussian-shaped force profile, in which neuromuscular determinants have never been assessed. We investigated the neural and contractile determinants of the rate of force development (RFD) in burst-like isometric knee extensions. Together with maximal voluntary force (MVF), voluntary and electrically evoked (8 stimuli at 300 Hz, octets) forces were measured in the first 50, 100, and 150 ms of burst-like quadriceps contractions in 24 adults. High-density surface electromyography (HDsEMG) was adopted to measure the root mean square (RMS) and muscle fiber conduction velocity (MFCV) from the vastus lateralis and medialis. The determinants of voluntary force at 50, 100, and 150 ms were assessed by stepwise multiple regression analysis. Force at 50 ms was explained by RMS (R2  = 0.361); force at 100 ms was explained by octet (R2  = 0.646); force at 150 ms was explained by MVF (R2  = 0.711) and octet (R2  = 0.061). Peak RFD (which occurred at 60 ± 10 ms from contraction onset) was explained by MVF (R2  = 0.518) and by RMS50 (R2  = 0.074). MFCV did not emerge as a determinant of RFD. Muscle excitation was the sole determinant of early RFD (50 ms), while contractile characteristics were more relevant for late RFD (≥100 ms). As peak RFD is mostly determined by MVF, it may not be more informative than MVF itself. Therefore, a time-locked analysis of RFD provides more insights into the neuromuscular characteristics of explosive contractions.

Motor neuron degeneration, severe myopathy and TDP-43 increase in a transgenic pig model of SOD1-linked familiar ALS.

Amyotrophic Lateral Sclerosis (ALS) is a neural disorder gradually leading to paralysis of the whole body. Alterations in superoxide dismutase SOD1 gene have been linked with several variants of familial ALS. Here, we investigated a transgenic (Tg) cloned swine model expressing the human pathological hSOD1G93A allele. As in patients, these Tg pigs transmitted the disease to the progeny with an autosomal dominant trait and showed ALS onset from about 27 months of age. Post mortem analysis revealed motor neuron (MN) degeneration, gliosis and hSOD1 protein aggregates in brainstem and spinal cord. Severe skeletal muscle pathology including necrosis and inflammation was observed at the end stage, as well. Remarkably, as in human patients, these Tg pigs showed a quite long presymptomatic phase in which gradually increasing amounts of TDP-43 were detected in peripheral blood mononuclear cells. Thus, this transgenic swine model opens the unique opportunity to investigate ALS biomarkers even before disease onset other than testing novel drugs and possible medical devices.

Neuromuscular efficiency in fibromyalgia is improved by hyperbaric oxygen therapy: looking inside muscles by means of surface electromyography.

OBJECTIVES: Neuromuscular efficiency (NME) is impaired in fibromyalgia (FM). Hyperbaric oxygen therapy (HBOT) is a medical treatment using 100% of oxygen through an oxygen mask. HBOT in FM induces changes in cortical excitability and a secondary reduction in pain and muscle fatigue. However, there are still no direct data indicating changes in muscle fatigue. The aim of this study was to assess whether the reduction in muscle fatigue so far attributed to a central effect of HBOT can be directly detected by means of non-invasive sEMG as a change in NME. METHODS: The study was an observational longitudinal study on changes in NME induced by 20 sessions of HBOT at 2.4 atmosphere, in 22 patients with FM (3M; 19F) (age 49.8±9.5; height 164.7±7.5; weight 63.8±12.7). sEMG was recorded in single differential configuration from the biceps brachii muscle during the 30-second fatiguing contractions using linear arrays of eight adhesive electrodes. RESULTS: Evaluations made before and immediately after the first session showed that maximal strength did not change (T0 49±20 N, T1 49±19 N, p=0.792), thus suggesting that HBOT did not induce muscle fatigue or potentiation. After 20 sessions of HBOT, NME increased from 1.6±1.1 to 2.1±0.8 (p=0.050), whereas maximal strength, EMG amplitude and muscle fibre CV did not change. CONCLUSIONS: HBOT did not improve muscle strength or change muscle fibre content, but improved the ability of the central motor command to generate the same effort (MVC) with fewer recruited fibres. Our sEMG findings underlined a modified central mechanism related to fibre type recruitment order, thus suggesting that muscle fatigue is not primarily a muscular problem, as also demonstrated by other authors with different methods.

A comparison between an ICT tool and a traditional physical measure for frailty evaluation in older adults.

BACKGROUND: Frailty is a clinical condition among older adults defined as the loss of resources in one or more domains (i.e., physical, psychological and social domains) of individual functioning. In frail subjects emergency situations and mobility levels need to be carefully monitored. This study aimed to: i) evaluate differences in the mobility index (MI) provided by ADAMO system, an innovative remote monitoring device for older adults; ii) compare the association of the MI and a traditional physical measure with frailty. METHODS: Twenty-five community-dwelling older adults (71 ± 6 years; 60% women) wore ADAMO continuously for a week. The time percentage spent in Low, Moderate and Vigorous Activities was assessed using ADAMO system. Walking ability and frailty were measured using the 400 m walk test and the Tilburg Frailty Indicator, respectively. RESULTS: Controlling for age and gender, the ANCOVA showed that frail and robust participants were different for Low (frail = 58.8%, robust = 42.0%, p < 0.001), Moderate (frail = 25.5%, robust = 33.8%, p = 0.008), and Vigorous Activity (frail = 15.7%, robust = 24.2%, p = 0.035). Using cluster analysis, participants were divided into two groups, one with higher and one with lower mobility. Controlling for age and gender, linear regression showed that the MI clusters were associated with total (ß = 0.571, p = 0.002), physical (ß = 0.381, p = 0.031) and social (ß = 0.652, p < 0.001) frailty; and the 400 m walk test was just associated with total (ß = 0.404, p = 0.043) and physical frailty (ß = 0.668, p = 0.002). CONCLUSION: ADAMO system seems to be a suitable time tracking that allows to measure mobility levels in a non-intrusive way providing wider information on individual health status and specifically on frailty. For the frail individuals with an important loss of resources in physical domain, this innovative device may represent a considerable help in preventing physical consequences and in monitoring functional status.

Severe COPD Alters Muscle Fiber Conduction Velocity During Knee Extensors Fatiguing Contraction.

The aim of this study was to assess the changes in muscle fiber conduction velocity (CV), as a sign of fatigue during knee extensor contraction in patients with chronic obstructive pulmonary disease (COPD) as compared with healthy controls. Eleven male patients (5 with severe and 6 with moderate COPD; age 67 ± 5 years) and 11 age-matched healthy male controls (age 65 ± 4 years) volunteered for the study. CV was obtained by multichannel surface electromyography (EMG) from the vastus lateralis (VL) and medialis (VM) of the quadriceps muscle during isometric, 30-second duration knee extension at 70% of maximal voluntary contraction. The decline in CV in both the VL and VM was steeper in the severe COPD patients than in healthy controls (for VL: severe COPD vs. controls -0.45 ± 0.07%/s; p < 0.001, and for VM: severe COPD vs. controls -0.54 ± 0.09%/s, p < 0.001). No difference in CV decline was found between the moderate COPD patients and the healthy controls. These findings suggest that severe COPD may impair muscle functions, leading to greater muscular fatigue, as expressed by CV changes. The results may be due to a greater involvement of anaerobic metabolism and a shift towards fatigable type II fibers in the muscle composition of the severe COPD patients.

The Application of sEMG in Aging: A Mini Review.

The aim of this mini-review is to describe the potential application of surface electromyography (sEMG) techniques in aging studies. Aging is characterized by multiple changes of the musculoskeletal system physiology and function. This paper will examine some of the innovative methods used to monitor age-related alterations of the neuromuscular system from sEMG signals. A description of critical assumptions which underlie some of these approaches is emphasized. The first part focuses on the evolution of the recording techniques and describes some methodological issues. The second part focuses on how to use the following techniques to characterize aging: amplitude and spectral sEMG signal analysis, muscle fiber conduction velocity estimation, and myoelectric fatigue assessment. The last part describes a number of advanced sEMG approaches which seem promising in the geriatric population to estimate motor unit number, size, recruitment thresholds, and firing rates.

University courses, eating problems and muscle dysmorphia: are there any associations?

BACKGROUND: Orthorexia and muscle dysmorphia are disorders affecting above all young adults whose prevalence and social impact are still unclear. We aimed to evaluate the prevalence of the traits of orthorexia and muscle dysmorphia among freshmen attending university courses focused on nutrition (Dietetics) and body care (Exercise and Sport Sciences). Students of Biology were considered as a control group. The prevalence of eating disorder (ED) traits were also evaluated. METHODS: All participants (n = 440; n = 53 Dietetics school, n = 200 Exercise and Sport Sciences school, n = 187 the Biology school) completed the following questionnaires: ORTO-15, Muscle-Dysmorphic-Disorder-Inventory, and Eating Attitudes Test-26. RESULTS: The prevalence of the traits of EDs, orthorexia, and muscle dysmorphia was 9.1%, 25.9%, and 5.9%, respectively. When compared to other students, those attending the Dietetics school showed a 2-fold higher risk of EDs and those from the Exercise and Sport Sciences school a 10-fold higher risk of muscle dysmorphia. The prevalence of orthorexia traits was high in all schools (35.9%, 22.5%, 26.5% in Dietetics, Biology, and Exercise and Sport Sciences schools, respectively). Overall, individuals with traits of any of these disorders were more frequently on diet or on supplement use. In a logistic regression model, attending the Dietetics school (OR = 2.71; 95% CI 1.14-6.48) was significantly associated with the ED traits, but not with the orthorexia traits (OR = 1.75; 95% CI 0.93-3.29), while attending the Exercise and Sport Sciences school was significantly associated with the muscle dysmorphia traits (OR = 5.15; 95% CI 1.44-18.4). Finally, when evaluating the relationships among the types of study programs as dependent variables and traits of these disturbances, the associations between the traits of ED (OR = 3.35; 95% CI 1.38-8.13) and matriculation at the school of Dietetics, and between the traits of muscle dysmorphia (OR = 4.32; 95% CI 1.16-16.1) and the choice of the Exercise and Sport Sciences school were confirmed. CONCLUSIONS: The choice of the university courses might be influenced by pre-existing disorders in eating behaviors, which were relatively frequent in the considered sample.

Innervation zone locations in 43 superficial muscles: toward a standardization of electrode positioning.

INTRODUCTION: We describe the innervation zone (IZ) location in 43 muscles to provide information for appropriate positioning of bipolar electrodes for clinical and research applications. METHODS: The IZ was studied in 40 subjects (20 men and 20 women) using multichannel surface electromyography (sEMG). Signal quality was checked visually to identify motor unit action potentials and estimate muscle fiber conduction velocity. RESULTS: Results in 33 muscles were classified as excellent or good, because it was possible to identify an area which is favorable for appropriate positioning of an electrode pair without the need to previously determine the IZ location. CONCLUSIONS: Knowledge of IZ location will increase standardization and repeatability of sEMG measures.

Performance pathways in elite middle- and long-distance track and field athletes: The influence of a successful youth.

OBJECTIVES: There is limited information on the performance progression of athletics endurance athletes from junior-to-senior status and the determinants of success in adulthood. This study aimed to quantify the youth-to-senior transition rate, the likelihood of success and the relationship between youth and senior performance amongst world-class athletes competing in middle- and long-distance disciplines. DESIGN: Retrospective design examining public data between 2000 and 2019. METHODS: The performances of 4678 international athletes (45.3 % female) were analysed. World's all-time top 50 athletes were identified for U18 and Senior categories (age ≥ 20 years). Youth-to-senior transition rate and transition probabilities were calculated. Correlations between best U18 and Senior performances were determined to assess the stability of the performance. RESULTS: The youth-to-senior transition rate for top U18 athletes was low for males and females (~19 % and 21 %). Nevertheless, the probability of transition to a top senior was ~7 times higher for top U18 athletes than for non-top U18 athletes. The correlations between youth and senior best performances were low-to-high. CONCLUSIONS: Few top U18 athletes maintained top world ranking status during their senior careers. Still, they are more likely to become top senior athletes than those who did not perform at the top level in U18. The association between youth and senior performance is stronger when comparing the same discipline or when athletes competed over longer distances in their senior compared to U18 career. Being a successful youth athlete may represent a small advantage for future success, however, it does not guarantee advancement to the senior top level.

Mitigating against relative age effects in youth Track & Field: Validating corrective adjustment procedures across multiple events.

OBJECTIVES: With the aim to better identify talented Track & Field performance development, this study estimated the relationships between chronological (decimal) age with 60-m sprint, high jump, triple jump, and pole vault performance. Then, to mitigate against expected Relative Age Effects (RAEs), Corrective Adjustment Procedures (CAPs) were applied to an independent sample. DESIGN: Mixed-longitudinal design examining public data between 2005 and 2019. METHODS: The performances of 5339 Italian sprinters and jumpers (53.1 %) spanning 11.01-17.99 years of age were examined, with trendlines between chronological age and performance established. Related to an independent sample (N = 40,306; female 45.5 %), trendlines were then utilised to apply CAPs and adjust individual performance. Considering raw and adjusted performance data, RAE distributions were examined for the top 25 % and 10 % performers. RESULTS: For all male and female events, quadratic models best summarised the relationships between chronological age and performance (R2 = 0.74-0.89). When examining independent athletes in similar event, RAEs were more pronounced in males (Cramer's V = 0.35-0.14) than females (Cramer's V = 0.29-0.07). For both sexes, RAE magnitude decreased with age and increased according to performance level (i.e., Top25%-Top10%). However, following CAP applications, RAEs were reduced or removed within annual age groups and performance levels. CONCLUSIONS: With RAEs prevalent across Italian youth Track & Field events, findings validate CAPs as a strategy to account for the influence of relative age differences on athletic performance. CAPs help establish a more equitable strategy for performance evaluation and could help improve the efficacy of long-term athlete development programming.

Upper-Limb Muscle Fatigability in Para-Athletes Quantified as the Rate of Force Development in Rapid Contractions of Submaximal Amplitude.

This study aimed to compare neuromuscular fatigability of the elbow flexors and extensors between athletes with amputation (AMP) and athletes with spinal cord injury (SCI) for maximum voluntary force (MVF) and rate of force development (RFD). We recruited 20 para-athletes among those participating at two training camps (2022) for Italian Paralympic veterans. Ten athletes with SCI (two with tetraplegia and eight with paraplegia) were compared to 10 athletes with amputation (above the knee, N = 3; below the knee, N = 6; forearm, N = 1). We quantified MVF, RFD at 50, 100, and 150 ms, and maximal RFD (RFDpeak) of elbow flexors and extensors before and after an incremental arm cranking to voluntary fatigue. We also measured the RFD scaling factor (RFD-SF), which is the linear relationship between peak force and peak RFD quantified in a series of ballistic contractions of submaximal amplitude. SCI showed lower levels of MVF and RFD in both muscle groups (all p values ≤ 0.045). Despite this, the decrease in MVF (Cohen's d = 0.425, p < 0.001) and RFDpeak (d = 0.424, p = 0.003) after the incremental test did not show any difference between pathological conditions. Overall, RFD at 50 ms showed the greatest decrease (d = 0.741, p < 0.001), RFD at 100 ms showed a small decrease (d = 0.382, p = 0.020), and RFD at 150 ms did not decrease (p = 0.272). The RFD-SF decreased more in SCI than AMP (p < 0.0001). Muscle fatigability impacted not only maximal force expressions but also the quickness of ballistic contractions of submaximal amplitude, particularly in SCI. This may affect various sports and daily living activities of wheelchair users. Early RFD (i.e., ≤50 ms) was notably affected by muscle fatigability.

Studying the Changes in Physical Functioning and Oxidative Stress-Related Molecules in People Living with HIV after Switching from Triple to Dual Therapy.

BACKGROUND: Physical activity could increase the production of oxidative stress biomarkers, affecting the metabolism and excretion of antiretroviral drugs and, consequently, the clinical outcome. Nowadays, people living with HIV (PLWH) are mostly switching from triple to dual therapy, but no data are available in terms of physical functioning and oxidative stress. The aim of this study was to evaluate if some antioxidant biomarkers and physical functioning tests could be different according to triple or dual antiretroviral therapy. METHODS: PLWH were evaluated at baseline (BL), while treated with three drugs, and six months after the switch to dual therapy. Physical functioning was quantified using validated tools. Mitochondrial and cytosol antioxidant molecules were evaluated through liquid chromatography. RESULTS: Twenty-five patients were analyzed. A statistically significant difference between triple and dual therapy was found for mitochondrial glutathione, but not for physical tests. Evaluating differences between physically active and inactive individuals, the following statistically significant differences were suggested, considering triple therapy (mitochondrial n-formyl-methionine p = 0.022, triglycerides p = 0.023) and double therapy (mitochondrial glycine p = 0.035, cytosol glutamic acid p = 0.007, cytosol s-adenosylmethionine p = 0.021). CONCLUSIONS: For the first time, this study suggests possible differences in terms of antioxidant molecules and physical functioning in PLWH switching from triple to dual therapy.

Two Is Better than One: Successful World-Class Sprinters Compete in Two Disciplines.

We aimed to quantify the prevalence of track and field sprinters competing at a world-class level in more than one discipline, and we describe the career characteristics of single- and double-discipline athletes in terms of peak performance and the age of peak performance. The career performance of athletes ranked in the top 200 positions of the World Athletics database in the 100 m, 200 m, and 400 m were analyzed, i.e., 5514 career profiles (49.9% female). Using binomial proportion, we calculated how many competed in only one or more than one discipline. We also compared the peak performance and the age of peak performance of athletes who competed in one vs. more than one discipline. Independent of gender, about 50% of the athletes competing in the 100 m and 200 m also competed in the other discipline (i.e., 200 m and 100 m, respectively). Differently, only 20% of the athletes competing in the 400 m also competed in the 200 m. Sprinters competing in the 100-200 m and 200-400 m couples showed better peak performance than the sprinters competing in only one discipline. Many world-class sprinters compete in two disciplines, and the 100-200 m was the most prevalent couple. Our results also suggest that sprinters who compete in two disciplines may be advantaged compared to sprinters who compete in only one event.

"Stay at Home" during the COVID-19 Pandemic: Effects on Physical Activity and Sedentary Behavior in an Italian Academic Community.

This study investigates changes in physical activity (PA) and sedentary behavior in an Italian university community during Phase 1 of SARS-CoV-2 lockdown ("stay at home" government decree, from March 8th to May 4th, 2020) compared to their habits prior to the COVID-19 pandemic. We also examine differences according to gender, university position, BMI categories, and sport participation. A total of 2596 people (median age 24, IQR 11 years; 70.8% women) filled out a survey after eight weeks of statutory confinement at home. The International Physical Activity Questionnaire measured PA and sedentary behavior in a typical week before and during lockdown. Physically inactive people passed from 10.9% to 35.0% before−during the lockdown. The total amount of PA decreased (median 2307 vs. 1367 MET-min/week; p < 0.001), while sedentary behavior increased (median 349 vs. 440 min/day; p < 0.001) between before and during the lockdown. The following categories showed a higher reduction in the total amount of PA: men when compared to women; people with normal weight when compared to pre-obese/obese people; and people who played sports when compared to those who did not play sports. There is a need to propose PA/exercise programs to counteract physical inactivity and sedentarism during a social emergency, with special attention to people who showed higher PA reduction.

Impact of active lifestyle on the primary school children saliva microbiota composition.

The aim of the study was to evaluate the effects of Active or Sedentary lifestyle on saliva microbiota composition in Italian schoolchildren. Methods: Male (114) and female children (8-10 years) belonging to five primary schools in the neighborhoods of Turin were classified as active (A) or sedentary (S) based on PAQ-C-It questionnaire. PCR amplification of salivary DNA targeted the hypervariable V3-V4 regions of the 16S rRNA bacterial genes. DADA2 workflow was used to infer the Amplicon Sequence Variants and the taxonomic assignments; the beta-diversity was obtained by PCoA with the UniFrac method; LEfSe algorithm, threshold at 5%, and Log LDA cutoff at ±0.5 were used to identify differently abundant species in A compared to S saliva sample. Daily food intake was assessed by 3-Days food record. The metabolic potential of microbial communities was assessed by PICRUSt. Results: No significant differences were found in individual's gender distribution (p = 0.411), anthropometry, BMI (p > 0.05), and all diet composition between A and S groups (p > 0.05). Eight species were differently abundant: Prevotella nigrescens (LDA score = -3.76; FDR = 1.5×10-03), Collinsella aerofaciens (LDA score = -3.17; FDR = 7.45×10-03), Simonsiella muelleri (LDA score = -2.96; FDR = 2.76×10-05), Parabacteroides merdae (LDA score = -2.43; FDR = 1.3×10-02) are enriched in the A group; Gemella parahaemolysans, Prevotella aurantiaca (LDA score = -3.9; FDR = 5.27×10-04), Prevotella pallens (LDA score = 4.23; FDR = 1.93×10-02), Neisseria mucosa (LDA score = 4.43; FDR = 1.31×10-02; LDA score = 2.94; FDR = 7.45×10-03) are enriched in the S group. A prevalence of superpathway of fatty acid biosynthesis initiation (E. coli) and catechol degradation II (meta-cleavage pathway) was found in saliva from A compared to S children. Conclusion: Our results showed that active children had an enrichment of species and genera mainly associated with a healthier profile. By contrast, the genera and the species enriched in the sedentary group could be linked to human diseases.

Effects of a Multicomponent Exercise Program on Prevalence and Severity of the Frailty Syndrome in a Sample of Italian Community-Dwelling Older Adults.

Background: Frailty is a well-known condition that leads to a lack of resilience, with a reduced homeostatic capacity and a consequent higher risk of suffering adverse health outcomes. This study investigated the effectiveness of an exercise program to improve and reverse physical frailty amongst Italian older adults. Methods: One hundred and twenty-three community dwelling older adults (mean age 74 years, SD = 6; 64% women) were involved in an experimental (EG; n = 62) and a control (CG; n = 61) group. Frailty was assessed at baseline and after the intervention using an adapted version of the frailty phenotype. The EG took part in a 16-week exercise program, consisting of endurance, strength, balance and flexibility exercises, while the CG maintained the same routine. Results: After the exercise program, the EG was more robust than the CG (F = 43.51, p < 0.001). Within the EG, 46% of pre-frail and 50% of frail people reached the robust and pre-frail levels, respectively. Effects of training were higher in frail and pre-frail people (reduction of frailty of 0.67 and 0.76 points, respectively) compared to robust ones (who frailty levels increased by 0.23 points; F = 11.32, p < 0.001). Conclusions: A multicomponent exercise program may be effective at improving and reverting frailty, specifically for frail and pre-frail people.

Corrective Adjustment Procedures as a strategy to remove Relative Age Effects: Validation across male and female age-group long jumping.

OBJECTIVES: To validate the application of Corrective Adjustment Procedures for removing Relative Age Effects in youth athletic contexts, this study estimated the longitudinal relationships between decimal age (chronological and relative) and performance in male and female long jumpers. Using trendlines, Corrective Adjustment Procedures were applied, and Relative Age Effect distributions associated with performance attainment were re-examined. DESIGN: Retrospective longitudinal design examining competitive long-jump data between 2005 and 2019. METHODS: In Part I, participants were 689 junior Italian long jumpers (age range = 11.01-17.99 years; 56.6% females) who participated in ≥three events. Longitudinal modelling and regression equations quantified the sex-specific relationships between decimal age and long jump performance. In Part II, equations were utilised to adjust individual performance within an independent sample (N = 13,639; 50.1% females) of age-matched jumpers. Relative Age Effect distributions within attainment levels (i.e., Top 25-10%) were examined based on raw and correctively adjusted performance. RESULTS: Irrespective of sex, Relative Age Effects were prevalent across all age-groups with medium-large effect sizes at 12-17 (males and females) and 12-17 years (females) of age (Cramer's V range = 0.07-0.28). Relative Age Effect bias magnitude also increased with attainment level (i.e., Top 25-10%). Following Corrective Adjustment Procedure application, typical Relative Age Effects were removed with non-significant deviations in relative age distributions regardless of sex or age-group or attainment level (Top 25 or 10%). CONCLUSIONS: Findings provide efficacy for Corrective Adjustment Procedure application to remove Relative Age Effects across youth long jumping events. Corrective Adjustment Procedures suggest potential in improving performance evaluation, identification of technically skilled performers, and sporting experiences.

The Cut-Off Value for Classifying Active Italian Children Using the Corresponding National Version of the Physical Activity Questionnaire.

The present study aimed to determine a cut-off value following the filling in of a questionnaire (PAQ-C-It) to identify active Italian children. One-hundred-twenty-nine primary school children (5 Piedmont schools; 47.3% female; mean age = 10 ± 1 years) wore an accelerometer (Actigraph wGT3X-BT) to objectively quantify individual moderate-to-vigorous physical activity during one week. Afterwards, the PAQ-C-It was filled in by participants. A ROC curve procedure was applied to obtain an active/non-active cut-off point. Spearman's correlation coefficient was also applied to establish the relationship between the two parameters. According to the ROC analysis, the PAQ-C-It cut-off point value is identifiable at >2.75 to indicate active children (area under the curve = 0.62; standard error = 0.05; p = 0.025; coefficient intervals = 0.518−0.716; sensitivity = 0.592, specificity = 0.382), determining that 65 participants (55%) were non-active (mean PAQ-C-It value = 2.3 ± 0.4; active mean PAQ-C-It value = 3.3 ± 0.4). Spearman's correlation coefficient results were significant but with a small effect size (rho = 0.214; p = 0.008). In conclusion, the present results suggest that the PAQ-C-It can be cautiously used as tool to practically classify active Italian children because of a non-solid relationship between respective accelerometer data and MVPA daily data.

Strength Asymmetries Are Muscle-Specific and Metric-Dependent.

We investigated if dominance affected upper limbs muscle function, and we calculated the level of agreement in asymmetry direction across various muscle-function metrics of two heterologous muscle groups. We recorded elbow flexors and extensors isometric strength of the dominant and non-dominant limb of 55 healthy adults. Participants performed a series of explosive contractions of maximal and submaximal amplitudes to record three metrics of muscle performance: maximal voluntary force (MVF), rate of force development (RFDpeak), and RFD-Scaling Factor (RFD-SF). At the population level, the MVF was the only muscle function that showed a difference between the dominant and non-dominant sides, being on average slightly (3-6%) higher on the non-dominant side. At the individual level, the direction agreement among heterologous muscles was poor for all metrics (Kappa values ≤ 0.15). When considering the homologous muscles, the direction agreement was moderate between MVF and RFDpeak (Kappa = 0.37) and low between MVF and RFD-SF (Kappa = 0.01). The asymmetries are muscle-specific and rarely favour the same side across different muscle-performance metrics. At the individual level, no one side is more performative than the other: each limb is favoured depending on muscle group and performance metric. The present findings can be used by practitioners that want to decrease the asymmetry levels as they should prescribe specific exercise training for each muscle.