Validity of the relative fat mass pediatric index (RFMp) for the analysis of body composition in physically active youths at different stages of biological maturation.

BACKGROUND: The paediatric relative fat mass (RFMp) index was valid for analysis of percent body fat (BF%). However, the validation did not consider biological maturation (BM) stages. The present study aimed to verify the validity of the RFMp index in the estimation of BF% in children and adolescents of both sexes at different stages of BM. METHODS: A cross-sectional study was conducted with a sample of 146 young (males: 64.5%. females: 35.5%. age: 13.0 ± 2.2 years) practising sports modalities. We tested the validity of four RFMp equations (1: for boys aged 8-14 years; 2: for girls aged 8-14 years; 3: for both sexes aged 8-14 years; and 4: for both sexes aged 15-19 years) to analyse BF% using dual-energy X-ray absorptiometry as a reference method. BM was analysed by peak height velocity (PHV). Thus, we created subgroups by BM stage (pre-PHV, circum-PHV and post-PHV). RESULTS: Analyses of agreement between methods showed that only the RFMp-3 equation was reliable to analyse BF% in subjects of both sexes aged 8-14 years at the circum-PHV BM stage (proportion bias 95% confidence interval = -0.3 to 0.5, p = 0.7. concordance correlation coefficient = 0.3; validity = 0.9). CONCLUSIONS: The RFMp equation developed for the paediatric population of both sexes aged 8-14 years was valid for predicting BF% in children and adolescents of both sexes at the Circum-PHV stage of the BM.

Acute Responses in Blood Flow Restriction Low-intensity Aerobic Training: A Meta-analysis.

The purpose was to determine the effect low-intensity training with blood flow restriction (LI-BFR) versus high-intensity aerobic training (HIT) on acute physiological and perceptual responses. The Cumulative Index to Nursing and Allied Health Literature, National Library of Medicine, Scopus, SPORTDiscus and Web of Science databases and the reference list of eligible studies were consulted to identify randomized experimental studies, published until July 4, 2022, that analyzed physiological or perceptual responses between LI-BFR versus HIT in healthy young individuals. Mean difference (MD) and standardized mean difference (SMD) were used as effect estimates and random effects models were applied in all analyses. Twelve studies were included in this review. During exercise sessions, HIT promoted higher values of heart rate (MD=28.9 bpm; p<0.00001; I 2 =79%), oxygen consumption (SMD=4.01; p<0.00001; I 2 =83%), ventilation (MD=48.03 l/min; p=0.0001; I 2 =97%), effort (SMD=1.54; p=0.003; I 2 =90%) and blood lactate (MD=3.85 mmol/L; p=0.002; I 2 =97%). Perception of pain/discomfort was lower in HIT (SMD=-1.71; p=0.04; I 2 =77.5%). In conclusion, LI-BFR promotes less pronounced physiological responses than HIT but with greater perception of pain.

Retrospective Study of Risk Factors and the Prevalence of Injuries in HIFT.

The aim of this study was to investigate the risk factors and the incidence of injuries in high-intensity functional training (HIFT) practitioners. A survey was administered to 213 HIFT practitioners. Participants reported the number of injuries, the location of the injuries, and training exposure during the preceding six months and answered questions regarding potential risk factors for injury. We found there were 7.1 injuries for every 1000 hours of training. In addition, we found that individuals with experience in the modality (>2 years) were 3.77 times more likely to be affected by injury when compared with beginner individuals (<6 months) (CI95%=1.59-8.92; p=0.003). When the analysis was performed only for the competitive level, we found that practitioners competing at the national level were 5.69 times more likely to experience an injury than competitors who do not compete (CI95%=1.10-29.54; p=0.038). We also found that the injuries mainly affect the shoulder and lumbar regions. It was possible to conclude that subjects with a higher level of experience in the modality are more likely to be affected by injuries and that the shoulder and lumbar areas are most likely to be injured during HIFT.

The Influence of Warm-Up on Body Temperature and Strength Performance in Brazilian National-Level Paralympic Powerlifting Athletes.

Background and Objectives: The effects of warm-up in athletic success have gained strong attention in recent studies. There is, however, a wide gap in awareness of the warm-up process to be followed, especially in Paralympic powerlifting (PP) athletes. This study aimed to analyze different types of warm-up on the physical performance of PP athletes. Materials and Methods: The sample consisted of 12 elite Brazilian PP male athletes (age, 24.14 ± 6.21 years; bodyweight, 81.67 ± 17.36 kg). The athletes performed maximum isometric force (MIF), rate of force development (RFD), and speed test (Vmax) in three different methods of warm-up. Tympanic temperature was used to estimate the central body temperature. Results: A significant difference was observed for MIF in the without warm-up (WW) condition in relation to the traditional warm-up (TW) and stretching warm-up (SW) (p = 0.005, η2p = 0.454, high effect). On the contrary, no significant differences were observed in RFD, fatigue index (FI) and time in the different types of warm up (p > 0.05). Furthermore, no significant differences were observed in relation to the maximum repetition (p = 0.121, η2p = 0.275, medium effect) or the maximum speed (p = 0.712, η2p = 0.033, low effect) between the different types of warm up. In relation to temperature, significant differences were found for the TW in relation to the "before" and "after" conditions. In addition, differences were found between WW in the "after" condition and SW. In addition, WW demonstrated a significant difference in relation to TW in the "10 min later" condition (F = 26.87, p = 0.05, η2p = 0.710, high effect). Conclusions: The different types of warm-up methods did not seem to provide significant differences in the force indicators in elite PP athletes.

Comparison of Neuromuscular Fatigue in Powerlifting Paralympics in Different Training Methods.

Mean propulsive velocity (MPV) has been associated with neuromuscular fatigue; however, its suitability for strength training in Paralympic powerlifting (PP) remains uncertain. The objective of this work was to evaluate the MPV in two training methods (traditional-TRAD and eccentric-ECC). Eleven PP athletes were evaluated pre, during the intervention and post intervention at a load of 80% of the 1RM for TRAD and 110%-80% of 1 RM for ECC. The results demonstrated that there was no significant neuromuscular fatigue for the TRAD (~5% performance loss), as well as no significant decline in MPV during the intervention. For the ECC, there is a significant reduction in MPV before and after training (~12% loss of performance). A difference between TRAD and ECC after the intervention was also identified (0.87 m/s±0.22, 95% CI 0.72-1.02 vs. 0.72±0.20, 95% CI 0.59-0.86 p=0.042, F(3.30)=10.190, η2p=0.505 - very high effect). During the intervention for ECC, no significant decline in MPV was observed. The results of this study suggest that the mechanical indices of MPV do not seem to be effective indicators of neuromuscular fatigue in the sample studied or in the context of this specific training regime, being more indicated as a control of training volume.

Home-Based Indoor Physical Activity Programs for Community-Dwelling Older Adults: A Systematic Review.

CONTEXT: Home-based exercise programs are a good strategy to promote benefits to health for people who cannot visit gyms, clinics, or have limited time for physical activity outside. OBJECTIVE: To synthesize the effect of home-based indoor physical activity on psychosocial outcomes and mobility in community-dwelling older adults. DATA SOURCES: A comprehensive search was conducted in the MEDLINE, PubMed, Embase, SPORTDiscus, Cochrane Library, Scopus, and Google Scholar databases. STUDY SELECTION: A total of 11 studies (13 publications) were included involving a total of 1004 older adults. STUDY DESIGN: A systematic review of randomized controlled trials was conducted using the aforementioned 7 databases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. LEVEL OF EVIDENCE: Level 2. DATA EXTRACTION: Two authors independently selected studies, extracted data, and determined the risk of bias and evidence level using the Grading quality of evidence and strength of recommendations (GRADE) guidelines. We conducted a synthesis without meta-analysis (SWiM) to assess the outcome. RESULTS: There is moderately certain evidence that home-based exercise programs reduced the fear of falling. Psychosocial (mental health and quality of life) and mobility outcomes may improve after participating in the intervention inside the home. CONCLUSION: The review found very low to certain evidence that home-based exercises programs improved psychosocial outcomes (mental health and quality of life) and walking speed (mobility). Moderately certain evidence suggests that home-based exercises improved fear of falling. PROTOCOL REGISTER NUMBER: CRD42020182008.

Are there differences in anaerobic relative muscle power between upper and lower limbs in adolescent swimmers: A blinded study.

Success in speed swimming depends on the efficiency of the anaerobic system for the production of cellular energy, especially during muscle power production. In the adolescent athletes much is unknown with regards to the relationships between relative power of upper and lower limbs with speed swimming performance. The aim the present study was to identify differences in relative muscle power of upper and lower limbs in adolescent swimmers and relate these to speed swimming performances. Sixty adolescents, of both sexes (50% female, 50% male, 30 swimmers and 30 controls), were recruited. The relative upper limb power (ULP[W/kg]) was assessed by a medicine ball test and the relative lower limbs power (LLP[W/kg]) by a jump test on a jumping platform. Lean mass of the upper and lower limbs was assessed by dual-energy X-ray absorptiometry (DXA) (g). Sport performance was assessed during national level competition (50-m swimming time [in seconds]). Biological maturation (BM) was indexed by years from attainment of peak height velocity. ULP(W/kg) was higher than LLP(W/kg) in both groups (p â€‹< â€‹0.05). Upper and lower limb lean mass (g) correlated significantly with ULP(W/kg) and LLP(W/kg) in both groups (p â€‹< â€‹0.05). ULP(W/kg) and LLP(W/kg) correlated with 50-m swimming performance (s), in both sexes (p â€‹< â€‹0.05). Advanced BM was associated with ULP(W/kg) and LLP(W/kg) in both groups (p â€‹< â€‹0.05), and with 50-m swimming performance (s) in both sexes (p â€‹< â€‹0.05). We concluded that ULP(W/kg) is higher than LLP (W/kg) in adolescent swimmers. Upper and lower limb lean mass and BM were both positively associated with increased ULP (W/kg) and LLP (W/kg).

Physiological mechanisms of muscle strength and power are dependent on the years post obtaining peak height velocity in elite juniors rowers: A cross-sectional study.

BACKGROUND: It is not yet known whether the years after peak height velocity (PHV) are associated with the physiological mechanisms of muscle strength and power in Juniors rowers. OBJECTIVE: To identify the association between years post PHV (YPPHV) with muscle power and strength in Juniors rowers. METHODS: We tested 235 Brazilian rowing athletes (male: 171, female: 64, Juniors category). We measured: power (indoor rowing over 100-m, 500-m, 2,000-m and 6,000-m) and muscle strength (one repetition maximum (1RM) test in squat, deadlift, bench press and bent row on the bench). Biological maturation was index by age of PHV. The sample was divided into groups considering YPPHV recent (2.5 to 3.9), median (2.51 to 4.9) and veteran (>4.9). We use a Baysian approach to data handling. RESULTS: When compared to their peers in the recent and median post PHV groups, the male veteran group were superior in muscle power (Absolute: 100-m (BF10: 2893.85), 500-m (BF10: 553.77) and 6,000-m (BF10: 22.31). Relative: (100-m (BF10: 49.9)) and strength (BF10≥10.0 in squat, bench press and deadlift), and in the female the veteran group were superior in test time (500-m, BF10: 88.4). CONCLUSION: In elite Juniors rowers the increasing YPPHV are associated with muscle power performance in both sexes and muscle strength performance in males.

Influence of age and fitness level on immune responses of T and NK cells in healthy physically active subjects after strenuous aerobic exercise: a cross-sectional study.

Aim: The aim of this study is to analyze whether immune responses after strenuous exercise are influenced by chronological age and fitness level in physically active healthy men. Methods: Cross-sectional study with a sample of 32 physically active men. Participants were divided into two groups based on chronological age (younger: age 21.8 ± 1.8 vs. older: age 34.6 ± 8.3) and subsequently regrouped and divided based on fitness level (More conditioned: excellent and superior VO2max vs. Less conditioned: VO2max: weak, regular and good). Fitness was classified according to VO2max levels obtained by a treadmill test using a gas analyzer. Before and immediately after the ergospirometry test, blood samples were collected for evaluation of immunological markers: leukocytes, neutrophils, lymphocytes and subpopulations. Results: Chronological age had a moderate effect on CD3+CD4+ lymphocyte count (effect size: 0.204) and CD4/CD8 ratio (effect size: 0.278), favoring older subjects. The level of physical fitness had no significant effect on the analyzed immunological markers. Conclusions: Immune responses observed immediately after strenuous exercise may be more dependent on chronological age than on fitness level in healthy, physically active men.

Exercise Immunology Applied to Pediatric Sport and the Importance of Monitoring Stages of Puberty and Biological Maturation.

CONTEXT: Exercise immunology is aimed at understanding how exercise sessions can affect the immune system in athletic subjects of different age groups. The objective of the current study was to discuss in which stage of biological maturation (BM) young athletes may be more vulnerable in relation to the immune system, and whether there is a BM range in which it is safer to perform sports training with strenuous exercise loads. EVIDENCE ACQUISITION: Evidence from scientific research from several scientific disciplines (eg, immunology, sport immunology, pediatrics, sports medicine, human development) was gathered to holistically examine the main particularities of exercise immunology as applied to pediatric sport. STUDY DESIGN: Narrative review. LEVEL OF EVIDENCE: Level 5. RESULTS: In pediatric patients, lymphoid tissue expands during puberty and involutes after puberty until it returns to pre-expansion values. This suggests that there is a specific period in which the immune system may be stronger, which may provide opportunities for strenuous exercise in pediatric athletes. However, the chronological period when puberty occurs will be determined by BM, which is the rate at which the biological systems of the human body improves. This may affect the period of lymphoid tissue expansion and, consequently, the behavior of the immune system in pediatric subjects of the same age category. CONCLUSION: During puberty, there is a significant increase in the proinflammatory profile; to compensate for this, there is an expansion of lymphoid tissue that may favor the efficiency of the immune system. The period in which puberty is reached may vary according to the stages of BM. Therefore, in exercise immunology applied to pediatric sports, in addition to external and internal training loads, it is necessary to consider BM and puberty, which have been shown to be safer biomarkers than chronological age for determining immune system behavior in pediatric athletes. STRENGTH-OF-RECOMMENDATION TAXONOMY (SORT): Evidence B level 3.

Evaluating the Asymmetry of Muscle Activation and Strength in Paralympic Powerlifting Athletes.

BACKGROUND: Strength training is a complex task, as it requires a combination of many variables. In paralympic powerlifting (PP) asymmetries for the evaluation of activation, and static force indicators have been increasingly studied. OBJECTIVE: To investigate the asymmetries in the strength and muscle activation indicators, before and after a training session of PP athletes. METHODOLOGY: Twelve elite athletes from the PP participated in the study, and asymmetry was evaluated through surface electromyography (sEMG) and static strength indicators. Evaluations were made before and after a protocol of five series of five repetitions (5 × 5), with 80% of 1-Maximum Repetition (1RM). RESULTS: In the pectoral muscles, there were differences in the non-dominant limbs between the before and after in the sEMG. There were differences in the pectoralis muscle in the non-dominant limb between moments before (110.75 ± 59.52%) and after (130.53 ± 98.48%, p < 0.001), and there was no difference in triceps activation. In the Maximum Isometric Strength (MIF), there was a difference in the non-dominant limb between before (710.36 ± 129.36) and after (620.27 ± 69.73; p < 0.030). There was a difference before in the dominant (626.89 ± 120.16; 95% CI 550.55-703.24) and non-dominant (710.36 ± 129.36; p = 0.011) limbs. There was no difference in time to MIF. CONCLUSION: PP athletes showed small levels of asymmetry before and after training, and adaptation to training tends to promote fewer asymmetries.

Physiological adaptations and myocellular stress in short-term, high-frequency blood flow restriction training: A scoping review.

BACKGROUND: High frequency (1-2 times per day) low-intensity blood flow restriction (BFR) training has been recommended as a prescription approach for short durations of time to maximize relevant physiological adaptations. However, some studies demonstrate negative physiological changes after short periods of high-frequency BFR training, including prolonged strength decline and muscle fiber atrophy. OBJECTIVES: To provide a comprehensive overview of short-term, high-frequency blood flow restriction training, including main adaptations, myocellular stress, limitations in the literature, and future perspectives. METHODS: A systematic search of electronic databases (Scopus, PubMed®, and Web of Science) was performed from the earliest record to April 23, 2022. Two independent reviewers selected experimental studies that analyzed physical training protocols (aerobic or resistance) of high weekly frequency (>4 days/week) and short durations (≤3 weeks). RESULTS: In total, 22 studies were included in this review. The samples were composed exclusively of young predominantly male individuals. Muscle strength and hypertrophy were the main outcomes analyzed in the studies. In general, studies have demonstrated increases in strength and muscle size after short term (1-3 weeks), high-frequency low-intensity BFR training, non-failure, but not after control conditions (non-BFR; equalized training volume). Under failure conditions, some studies have demonstrated strength decline and muscle fiber atrophy after BFR conditions, accompanying increases in muscle damage markers. Significant limitations exist in the current HF-BFR literature due to large heterogeneities in methodologies. CONCLUSION: The synthesis presented indicates that short-term, high-frequency BFR training programs can generate significant neuromuscular adaptations. However, in resistance training to failure, strength declines and muscle fiber atrophy were reported. Currently, there are no studies analyzing low-frequency vs. high-frequency in short-term BFR training. Comparisons between resistance exercises of similar intensities (e.g., combined effort) are lacking, limiting conclusions on whether the effect is a product of proximity to failure or a specific effect of BFR.

Development and cross-validation of predictive equations for fat-free mass and lean soft tissue mass by bioelectrical impedance in Brazilian women.

BACKGROUND/OBJECTIVES: Bioelectrical impedance is one of the most used clinical techniques to assess body composition; however, it is necessary that the available predictive equations are valid for the evaluated subjects. This study aimed to develop and cross-validate equations for fat-free mass (FFM) and lean soft tissue mass (LSTM) by bioelectrical impedance for Brazilian women, in addition to test the validity of other available equations. SUBJECTS/METHODS: Cross-sectional study with 222 women aged 20-59 years, randomly divided into two groups: development and cross-validation. The standard technique for assessing fat mass, FFM and LSTM was dual energy X-ray absorptiometry. Paired t test, multiple regression, and Bland-Altman plots were used to test the validity of the proposed models, as well as to perform cross-validation of the models. RESULTS: The equations derived in this study were: FFM = 16.284 + 0.442 × (Height2/Resistance) - 0.13 × age + 0.302 × Weight - 0.121 × Waist Circumference; r2 = 0.86; SEE = 2.32 kg; and LSTM = 14.732 + 0.427 × (Height2/Resistance) - 0.125 × age + 0.291 × Weight - 0.115 × Waist Circumference; r2 = 0.92; SEE = 2.29 kg. In addition, the new equation for FFM showed better agreement when compared to another equation developed for a Brazilian population. CONCLUSIONS: The newly developed equations provide a valid FFM and LSTM estimation and are recommended for Brazilian women with similar characteristics.

Development and Cross-Validation of a Predictive Equation for Fat-Free Mass in Brazilian Adolescents by Bioelectrical Impedance.

The bioelectrical impedance analysis (BIA) is one of the most commonly used techniques for assessing body composition in a clinical setting and in field approaches, as it has the advantages of easy application, fast, and non-invasive, in addition to its relatively low cost. However, the available predictive equations need to be valid for the evaluated subjects. The aim of this study was to verify the validity of several published BIA equations in estimating fat-free mass (FFM) among Brazilian adolescents, in addition to developing and cross-validating a BIA equation to estimate FFM appropriate for Brazilian adolescents. This is a cross-sectional study with 257 adolescents (128 girls) aged 10-19 years, randomly divided into two groups, namely, development (n = 172) and cross-validation (n = 85). The standard technique for assessing FFM was dual X-ray absorptiometry (DXA). The paired t-test, multiple regression, and the Bland-Altman plots were used to test the validity of the proposed models and to perform cross-validation of the model. The equation derived in this study was as follows: FFM = -17.189 + 0.498 (Height2/Resistance) + 0.226 Weight + 0.071 Reactance - 2.378 Sex + 0.097 Height + 0.222 Age; r 2 = 0.92; standard error of the estimate = 2.49 kg; the new equation for FFM showed better agreement when compared with that of the equations developed in other countries. In conclusion, the newly developed equations provide a valid FFM estimation and are recommended for Brazilian adolescents with similar characteristics.

Corrigendum: Development and cross-validation of a predictive equation for fat-free mass in Brazilian adolescents by bioelectrical impedance.

[This corrects the article DOI: 10.3389/fnut.2022.820736.].

Influence of Advancing Biological Maturation on Aerobic and Anaerobic Power and on Sport Performance of Junior Rowers: A Longitudinal Study.

Background: Researches are linking Biological Maturation (BM) with the performance of adolescent rowers from both genders. Despite this, there is still not enough information about the influence of BM advancement correlating to sports, aerobic and anaerobic performance in adolescent athletes at the sport modality rowing. Objective: Investigate the influence of Biological Maturation on sports performance and aerobic and anaerobic power in adolescent rowing athletes. Methods: A longitudinal observational study, developed over 3 years, with a sample of 52 adolescents, rowing athletes, of both genders (61% male and 39% female) mean age of 16.0 ± 0.5 years old at the start and 18.4 ± 0.5 years old at the end of the study. Analysis was performed once a year. BM was evaluated through maturational groups generated from Age Peak Height Velocity; maximum aerobic power [VO2Max (ml/kg/min)] and mean anaerobic power (Watts) through the ergometer test (indoor rowing); peak anaerobic power (Watts) through a mathematical model derived from competition time, to determine sports performance analyzed the race time during world championship tryouts. Results: The advancement of BM influenced the reduction of the test time and increase of the mean anaerobic power (Watts) in indoor rowing (η2p > 0.36, p < 0.05), as well as an improvement in performance in sports competition (η2p > 0.35, p < 0.05). However, the advancement of BM did not affect VO2Max (ml/kg/min) in young elite rowing athletes of both sexes (p > 0.05). Conclusion: Advances in biological maturation have been shown to influence the anaerobic and sports performance (reduction of the execution time in 2,000-m) of adolescent rowing athletes of both genders.

Performance of postural balance in children and adolescents living with and without HIV.

RESEARCH QUESTION: The present study aimed to compare the postural control of children and adolescents with and without Human Immunodeficiency Virus (HIV). METHODS: A total of 32 children and adolescents (18 with HIV and 14 without) of both sexes, aged 6-18 years, were included in the present study. Participants in the HIV + group were infected through vertical transmission and received antiretroviral therapy. Participants maintained an erect, bipedal posture in the following conditions: with vision, without vision, and on a foam base. RESULTS: Concerning the evaluation of time variables, higher values ​​were observed in the HIV + group for mean anterior-posterior (AP) velocity, mean medial-lateral (ML) velocity, AP perimeter (p = 0.001), and ML perimeter (p = 0.001). Concerning the evaluation of conditions, a difference was observed in the mean AP mean sway amplitude (MSA) (p = 0.039), as the AP MSA was lower with vision than without vision or with foam. Concerning the evaluation of spectral domain variables, higher values ​​were observed in the HIV+ group for the predominant ML frequency (p = 0.04) and mean AP (p = 0.001) and ML frequencies (p = 0.001). Regarding the evaluation of conditions, a difference was found only in the predominant AP frequency (p = 0.001). Higher values ​​were found in the closed eye condition than in with foam (Δ = +103 %). CONCLUSION: The results of the present study indicated that children and adolescents living with HIV have poorer postural control performance than those without HIV.

The Body Adiposity Index is not applicable to the Brazilian adult population.

Background: Obesity is a serious disease that burdens public health systems around the world. It is a risk factor for the development of several non-communicable chronic diseases that are related to the amount and distribution of body fat. Body composition assessment using simple and low-cost techniques can help in the early detection of excess fat, allowing for the prevention and treatment of both obesity and associated diseases. Thus, identifying and proposing valid anthropometric indices for this purpose can be a great ally of health programs. Objective: To verify the validity of the Body Adiposity Index (BAI) in relation to Dual Energy X-Ray Absorptiometry (DXA) for estimating body fat percentage in Brazilian adults, as well as to propose a new mathematical model to estimate the fat-free mass of this population. Methods: In a cross-sectional study, 424 subjects (of which 220 were women), aged between 20 and 59 years, were evaluated by BAI and DXA, then randomly divided into two groups stratified by sex: the development group (n = 283) and the cross-validation group (n = 141). Statistical analyses to test the validity of BAI as a predictor of fat mass, in addition to proposing a new mathematical model for estimating fat-free mass, using DXA as a reference method. The analysis included paired t-test, stepwise multiple regression, coefficient of concordance correlation, and Bland-Altman plots. Results: The BAI validity analysis showed a low correlation coefficient of agreement [CCC = 0.626; ρ (precision) = 0.795; Cb(accuracy) = 0.787]; in addition, the mean difference in the Bland-Altman plot was different from zero in the cross-validation group (p < 0.01) and limits of agreement (LOA) ranged between-8.0 and 14.4 kg, indicating a poor agreement between the BAI and the reference method. The new mathematical model for estimating FFM showed a high correlation coefficient of agreement (CCC = 0.952; ρ = 0.953; Cb = 0.999), in addition to acceptable LOA in the Bland-Altman plot (-6.7 and 6.7). Conclusion: In the studied sample, the BAI showed low validity for estimating body fat, while the new proposed model was found to be a good option to assess the body composition of Brazilian adults.

Mental Fatigue Reduces Training Volume in Resistance Exercise: A Cross-Over and Randomized Study.

The present study aimed to determine the effect of mental fatigue (MF) on total training volume (TTV; number of repetitions x number of sets x load) and on ratings of perceived exertion (RPE; Borg, 1982) in the half-back squat exercise (HBSE). Nine male subjects (M age = 22.6 years, SD = 2.3; M height = 172.3 cm, SD = 6.8; M weight = 76.2 kg, SD = 9.8; M years of resistance training experience = 4.1, SD = 2.3 years) recruited from a university population were study participants in this participant-blind cross-over and randomized study. Participants underwent either the Stroop task - a highly demanding cognitive task (CT) - or a control condition (CON) in which they viewed a documentary exhibition for 30 minutes. Perception of MF and motivation were assessed after treatments using a visual analog scale of 100 mm. Participants then engaged in a countermovement jump (CMJ) test and three sets of HBSE until they reached momentary concentric failure, reporting RPE at the end of each exercise set. Following the CT, participants showed a significantly increased self-perception of MF in relation to the CON condition (p = 0.01; d = 1.2), but this did not affect their motivation to engage in subsequent tests (p = 0.99; d = 0.006). Neither the CMJ performances nor the RPE were statistically different between CT and CON conditions (p = 0.33; d = 0.09 and p = 0.20; η2 = 0.20, respectively). TTV was significantly lower in the CT relative to the CON experimental condition (Δ = -15.8%; p = 0.04; η2 = 0.48). Prolonged involvement in a CT was associated with reduced volume on a resistance exercise, though this effect was not associated with changes in CMJ performance or motivation to exercise.