Purpose: The objective of this study was to analyze the effects of a conditioning activity (CA) composed of continuous countermovement jumps on twitch torque production and 30-m sprint times. Methods: A total of 12 sprint athletes, 10 men (23.5 [7.7] y) and 2 women (23.0 [2.8] y), volunteered to participate in this study. The participants were evaluated in 2 sessions as follows: (1) to determine the effects of the CA (3 sets of 5 continuous vertical jumps with a 1-min interval between sets) on 30-m sprint performance over time (2, 4, 6, 8, and 10 min) and (2) to evaluate twitch peak torque to determine the magnitude and time course of the induced postactivation potentiation at the same recovery intervals. Results: Mixed-model analysis of variance with Bonferroni post hoc verified that there was a decrease on the 30-m sprint time at 2 minutes (P = .01; Δ = 2.78%; effect size [ES] = 0.43) and 4 minutes (P = .02; Δ = 2%, ES = 0.30) compared with pre when the CA preceded the sprints. The peak torque of quadriceps also showed significant increase from pretest to 2 minutes (P < .01; Δ = 17.0% [12.2%]; ES = 0.45) and 4 minutes (P = .02; Δ = 7.2% [8.8%]; ES = 0.20). Conclusion: The inclusion of CA composed of continuous countermovement jumps in the warm-up routine improved 30-m sprint performance at 2- and 4-minute time intervals after the CA (postactivation performance enhancement). Since postactivation potentiation was confirmed with electrical stimulation at the time when sprint performance increased, it was concluded that postactivation potentiation may have contributed to the observed performance increases.

Purpose. the objective of the study was to analyse the effects of post-activation potentiation induced by single-and multijoint maximal voluntary isometric contractions (MVIC) on squat jump performance. Methods. Overall, 13 resistance-training males volunteered to participate in the study. Isometric knee extension exercise was chosen to represent single-joint MVIC (MVIC_SJ) and isometric squat to represent multi-joint MVIC (MVIC_MJ). Four experimental protocols were implemented in a randomized order on different days as follows: P1: squat jump performed before and 3 minutes after MVIC_MJ; P2: squat jump performed before and 7 minutes after MVIC_MJ; P3: squat jump performed before and 3 minutes after MVIC_SJ; P4: squat jump performed before and 7 minutes after MVIC_SJ. Jump height, mean power output, peak power output, net impulse, and electromyographic activity of lower limbs were analysed in squat jump before and after the interventions. Results. ANOVA showed that peak power output increased in P1 (p = 0.04). No difference was found for electromyographic activity in any of the protocols. Conclusions. We concluded that MVIC_MJ performed 3 minutes before the main task (P1) was more effective than MVIC_SJ in optimizing squat jump performance and that the changes in performance were unrelated to muscle activation.

The objectives of this review were to (a) map the studies analyzing bilateral asymmetries in specific (in-water tests) and nonspecific (dry-land tests) swimming contexts and (b) investigate the effects of interlimb asymmetries on swimming performance. Searches were systematically conducted on 4 databases. Of 768 studies examined, 60 were eligible for the final selection (https://osf.io/46gya). Twenty-eight studies analyzed asymmetries during in-water tests, with asymmetry values ranging from 2.7 to 60.0%, and most studies (n = 18) reported significant between-limb differences (p < 0.05). Asymmetries were also analyzed during dry-land tests in 24 studies, with asymmetry values ranging from 1.1 to 16.6%. Interestingly, most of these studies (n = 12) did not verify any significant between-limb differences (p > 0.05). Eight studies measured asymmetries in both contexts and reported asymmetry values from −24.1–17.4%, with 4 studies finding significant differences between body sides (p < 0.05). Seven of the 60 studies selected investigated the relationship between asymmetries and swimming performance, with 5 reporting no meaningful associations. In conclusion, significant asymmetries in swimming are more evident during in-water than during dry-land tests. In addition, the few studies investigating asymmetries' influence on swimming performance reported that asymmetries rarely impact swimming performance.

ARTIGO ORIGINAL RESUMO | Introdução:A composição corporal é importante para o bombeiro militar no que diz respeito a sua saúde e ao seu desempenho no trabalho. Porém, o comportamento desse parâmetro não é elucidado nos diferentes grupos de trabalho do bombeiro militar. Objetivo: Comparar o perfil antropométrico de bombeiros militares entre os grupos de trabalho administrativo (ADM) e operacional. Métodos: A amostra foi composta por 121 (ADM = 50 e operacional = 71) bombeiros militares do sexo masculino. Foram aferidas massa corporal (MC), percentual de gordura (%G), massa gorda, massa magra, índice de massa corporal (IMC), circunferência da cintura (CC) e somatotipia. Resultados: Houve diferenças entre os grupos para as variáveis massa corporal (ADM = 78,5kg -operacional = 84,6kg), IMC (ADM = 25,8 -operacional = 27,2) e massa magra (ADM = 61,9kg -operacional = 66,2kg). Conclusão: Conclui-se que os grupos apresentam diferenças entre os perfis antropométricos e apresentam %G e IMC acima do recomendável. Palavras-chave | composição corporal; antropometria; saúde; bombeiros. ABSTRACT | Background:Body composition is relevant for the health and work performance of firefighters. However, the behavior of these parameters has not been elucidated for groups of firefighters performing different tasks. Objectives: To compare the anthropometric profile of military firefighters who perform administrative (ADM) or operational work . Methods: The sample comprised 121 (ADM = 50 and operational = 71) male military firefighters. Body mass (BM), body fat percentage (BFP), fat body mass, lean body mass, body mass index (BMI), waist circumference and somatotype were analyzed. Results: Intergroup difference was found for body mass (ADM = 78.5 kg -operational = 84.6 kg), BMI (ADM = 25.8 -operational = 27.2) and lean body mass (ADM = 61.9 kg -operational = 66.2 kg). Conclusion: The groups exhibited differences in their anthropometric profile and BFP and BMI above the recommended range.

Landing is a critical phase of movement for injury occurrence, in which lower limbs should be used equally to better absorb the shock. However, it has been suggested that fatigue can lead to the appearance of asymmetries. The aim of this study was to verify the acute and delayed effects of fatigue on the lower limb asymmetry indexes of peak ground reaction force, leg stiffness and intra-limb coordination during a landing task. Fifteen physically active men performed a fatigue protocol composed of 14 sets of 10 continuous vertical jumps, with a one-minute rest interval between the sets. A step-off landing task was performed before, immediately after, 24 h and 48 h after the fatigue protocol. Two force plates and a video analysis system were used. The symmetry index equation provided the asymmetry indexes. For statistical analysis, ANOVA and effect size analysis were utilized. Inferential statistics did not show the effect of fatigue in the asymmetry indexes for any variable or condition (p > .05). Moderate effect sizes were observed for peak ground reaction force (0.61) and leg stiffness (0.61) immediately after the application of the protocol. In conclusion, fatigue does not seem to significantly change the asymmetries of lower limbs, especially regarding intra-limb coordination. The moderate effects observed for peak ground reaction force and leg stiffness asymmetries suggest that these variables may be acutely affected by fatigue.