Mechanical demands and pacing profile adopted by elite mountain bikers during different cross-country events / Demandas mecânicas e perfil de ritmo adotado por ciclistas de montanha de elite durante diferentes eventos do cross-country

ABSTRACT Different competitive environments appears to affect the physical demands during the sports competitions. Thus, the aim of this study was to report the mechanical demand and pacing behaviour of twelve male elite mountain bikers on cross-country short track (XCC) and cross-country Olympic (XCO). During both competition, total race time, speed, power output (PO) and cadence (CA) were recorded. As the race time in the XCC is shorter (21.0 ± 0.5 vs 84.0 ± 3.0 min; p<0.01), the average speed (26.6 ± 0.6 vs 17.8 ± 0.6 km/h; p<0.01), PO (365.0 ± 26.7 vs 301.0 ± 26.2 watts; p<0.01) and CA (81.2 ± 4.7 vs 77.4 ± 4.3 rev∙min−1; p=0.01) were higher than the XCO. While a variable pacing was adopted during XCC, a positive profile was adopted in XCO. In addition, athletes adopted a more conservative starting pace during XCC (below average race speed) but a faster start during XCO (above average race speed). These findings demonstrated that mechanical parameters and pacing profile adopted by cyclists are different between XCC and XCO. Therefore, mountain bikers and coaches must develop specific strategy and training methods in order to obtain success in each competition.

RESUMO Diferentes ambientes competitivos parecem afetar as demandas físicas durante as competições esportivas. Assim, o objetivo deste estudo foi reportar as demandas mecânicas e o comportamento do pacing de doze homens ciclistas de montanha da categoria elite durante o cross-country de pista curta (XCC) e o cross-country Olímpico (XCO). Durante ambas as competições, o tempo total de corrida, velocidade, potência (PO) e cadência (CA) foram gravados. Como o tempo de prova do XCC é menor (21,0±0,5 vs 84,0±3,0 min; p<0,01), a velocidade média (26,6±0,6 vs 17,8±0,6 km/h; p<0,01), PO (365,0±26,7 vs 301,0±26,2 watts; p<0,01) e CA (81,2±4,7 vs 77,4±4,3 rev∙min−1; p=0,01) foram maiores que no XCO. Enquanto um ritmo variável foi adotado no XCC, um perfil positivo foi adotado no XCO. Além disso, os atletas adotaram um ritmo inicial mais conservador durante o XCC (abaixo da velocidade média da prova), mas um início mais rápido durante o XCO (velocidade acima da média da prova). Esses achados demonstraram que os parâmetros mecânicos e o ritmo adotados pelos ciclistas são diferentes entre o XCC e XCO. Portanto, ciclistas e treinadores devem desenvolver estratégias e métodos de treinamento específicos para obter sucesso em cada competição.

Local muscle oxygenation during different cuff-pressures intervention: a punctual near-infrared spectroscopy measurement

Abstract Aim: To verify the response of tissue saturation index (TSI) during ischemia-reperfusion (IR) interventions with different cuff-pressures. Methods: Twenty-nine healthy men experienced in resistance training were recruited. Each one has undergone a control condition (no cuff) and one of the three IR interventions: 1) 190 mmHg (CP-190, 22.7 ± 3.0 years; 176.6 ± 3.9 cm; 77.3 ± 9.5 kg; 2) 100 mmHg (CP-100, 22.9 ± 6.3 years; 180.5 ± 4.0 cm; 85.2 ± 14.1 kg) and 3) 20 mmHg (CP-20, 20.3 ± 2.4 years; 171.8 ± 5.2 cm; 72.4 ± 6.0 kg). Cuffs were placed on the proximal region of the thighs. IR interventions consisted of three cycles of 2-min occlusion-reperfusion. TSI was measured using near-infrared spectroscopy (NIRS), positioned on the middle portion of the vastus lateralis of the dominant leg. The oxygenation was measured at the control conditions (no cuff) and during cuff interventions. Results: While TSI values of CP-20 did not change compared to control (p > 0.05), the TSI in CP-190 was lower in the ischemia (p < 0.05), and CP-100 was lower in the second and third ischemia (p < 0.05). However, the TSI value increased during reperfusion but did not return to control levels (p < 0.05). Conclusion: TSI of the CP-190 significantly decreased during ischemia. However, these values increased by about 16% in the reperfusion period. Thus, our results show that the RI intervention may have caused an increase in metabolic demand, as even with the release of blood flow, the TSI values were below those of the other interventions.

Cardiac autonomic alterations in different tactical profiles of brazilian jiu jitsu / Alterações autonômicas cardíacas em diferentes perfis táticos do jiu jitsu brasileiro / Alteraciones autonómicas cardíacas en diferentes perfiles tácticos del jiu jitsu brasileño

ABSTRACT Introduction Brazilian Jiu Jitsu (BJJ) is an individual sport, characterized by intermittent body movements aimed at the submission (defeat) of the opponent. The sport involves two tactical profiles of fighters: the guard (GG) and the passer (PG), which present potential differences in relation to anthropometric patterns and cardiac autonomic modulation. Objectives To evaluate the effects of different BJJ fighting styles on cardiac autonomic modulation. Methods Twelve PG-style athletes and 12 GG-style athletes, both male, with mean ages of 30.4 ± 1.9 and 30.6 ± 1.3 years, respectively, participated in the study. The following measurements were taken at rest: anthropometric profile, body composition and hemodynamic parameters (blood pressure [BP], basal heart rate [HR] and heart rate variability [HRV], the latter through linear and nonlinear analysis). Results The PG fighters had higher waist and hip circumference diameters compared to the GG fighters (p <0.05). There were no differences regarding baseline hemodynamic parameters of HR and BP. Total HRV as well as parasympathetic modulation indices in both the time and frequency domains were significantly lower in the GG fighters than in the PG fighters (p <0.05). In contrast, the sympathovagal modulation markers in the frequency domain, and the sympathovagal index, were higher in GG than in PG (p <0.05). The SD1 index of nonlinear analysis was lower in the GG fighters than in the PG (p <0.05). Conclusion In general, guardian style fighters have lower vagal modulation and cardiac sympathetic hyperactivity at rest, compared to passing fighters. Level of evidence IV; Case series.

RESUMO Introdução O jiu jitsu brasileiro (JJB) é um esporte individual, caracterizado por movimentos corporais intermitentes, cujo objetivo é a submissão (derrota) do oponente. Nessa modalidade, há dois perfis táticos dos lutadores, o guardeiro (GG) e o passador (GP), os quais apresentam potenciais diferenças em relação aos padrões antropométricos e à modulação autonômica cardíaca. Objetivos Avaliar os efeitos dos diferentes estilos de luta do JJB sobre a modulação autonômica cardíaca. Métodos Participaram do estudo 12 atletas com estilo de luta GP e 12 atletas com estilo de luta GG, ambos do sexo masculino e com idades médias de 30,4 ± 1,9 e 30,6 ± 1,3 anos, respectivamente. Foram avaliados, em repouso, o perfil antropométrico, a composição corporal e os parâmetros hemodinâmicos (pressão arterial [PA], frequência cardíaca [FC] basal e a variabilidade da frequência cardíaca [VFC], esta última através de análises lineares e não lineares). Resultados Os lutadores do GP apresentaram maiores diâmetros da circunferência da cintura e do quadril em comparação ao GG (p<0,05). Não houve diferenças em relação aos parâmetros hemodinâmicos basais da FC e da PA. A variabilidade total da FC, assim como os índices da modulação parassimpática tanto no domínio do tempo como no domínio da frequência, foram significativamente menores nos lutadores do GG quando comparados aos lutadores do GP (p<0,05). Em contrapartida, os marcadores da modulação simpática no domínio da frequência e o índice simpatovagal foram maiores no GG em relação ao GP (p<0,05). O índice SD1 da análise não linear foi menor nos lutadores do GG quando confrontados ao GP (p<0,05). Conclusão Lutadores com estilo predominantemente guardeiro apresentam menor modulação vagal e hiperatividade simpática cardíaca de repouso em comparação aos lutadores passadores. Nível de Evidência IV; Série de casos.

RESUMEN Introducción El Jiu Jitsu brasileño (JJB) es un deporte individual, caracterizado por movimientos corporales intermitentes, cuyo objetivo es la sumisión (derrota) del oponente. En esta modalidad, hay dos perfiles tácticos de luchadores, el guardiero (GG) y el pasador (GP), que presentan diferencias potenciales con relación a los patrones antropométricos y a la modulación autónoma cardíaca. Objetivos Evaluar los efectos de diferentes estilos de lucha de JJB sobre la modulación autónoma cardíaca. Métodos Participaron en el estudio 12 atletas con estilo de lucha GP y 12 atletas con estilo de lucha GG, ambos del sexo masculino y con edades promedio de 30,4 ± 1,9 y 30,6 ± 1,3 años, respectivamente. Fueron evaluados, en reposo, el perfil antropométrico, la composición corporal y los parámetros hemodinámicos (presión arterial [PA], frecuencia cardíaca [FC] basal y la variabilidad de la frecuencia cardíaca [VFC], ésta última a través de análisis lineales y no lineales). Resultados Los luchadores del GP presentaron mayores diámetros de circunferencia de cintura y cadera en comparación al GG (p <0,05). No hubo diferencias con relación a los parámetros hemodinámicos basales de FC y de la PA. La variabilidad total de la FC, así como los índices de modulación parasimpática tanto en el dominio del tiempo como en el dominio de la frecuencia, fueron significativamente menores en los luchadores del GG cuando comparados a los luchadores del GP (p <0,05). En contrapartida, los marcadores de la modulación simpática en el dominio de frecuencia y el índice simpatovagal fueron mayores en el GG con relación al GP (p <0,05). El índice SD1 de análisis no lineal fue menor en los luchadores del GG cuando comparados al GP (p <0,05). Conclusión Los luchadores con estilo predominantemente guardiero presentan menos modulación vagal e hiperactividad simpática cardíaca de reposo en comparación a los luchadores pasadores. Nivel de evidencia IV; Serie de casos .

The relative peak power output of amateur mountain bikers is inversely correlated with body fat but not with fat-free mass

Abstract Aims: To evaluate whether body mass (BM) and body composition may influence mountain bike cycling performance. Methods: Forty male amateur mountain bikers attended the laboratory on two non-consecutive days. At the first visit, anthropometric measures (height, BM, body fat [BF], fat-free mass [FFM] and body mass index [BMI]) and familiarization to incremental cycling test were performed. On the second visit, cyclists performed again the incremental cycling test to measure peak power output (PPO), peak power output relative to BM (PPO-BM), and time to exhaustion (TE), which were posteriorly correlated with BM and anthropometric measures. Results: A low and moderate significant correlation were observed between TE and BM (p<0.01; r=0.40) and FFM (p<0.01; r=0.56). Moderate significant correlation was found between PPO and BM (p<0.01; r=0.45), BMI (p=0.03; r=0.35) and strong with FFM (p<0.01; r=0.59). Also, PPO-BM significantly correlated with BM (p=0.04; r=-0.31), BMI (p=0.02; r=-0.35) and BF (p<0.01; r=-0.55). No other significant correlations were observed. Conclusion: Considering PPO-BM as mainly performance variable, BM and BF can be a determining factor in mountain biking performance but FFM did not.

Low levels of dehydroepiandrosterone sulfate are associated with the risk of developing cardiac autonomic dysfunction in elderly subjects

ABSTRACT Objective: To assess the relationships between serum dehydroepiandrosterone sulfate (DHEA-S) levels and heart rate variability (HRV) among different age groups. Subjects and methods: Forty-five healthy men were divided into 3 groups: young age (YA; 20-39 yrs; n = 15), middle age (MA; 40-59 yrs; n = 15) and old age (OA; ≥ 60 yrs; n = 15). Hemodynamic parameters, linear analyses of HRV and concentrations of cortisol and DHEA-S were measured at rest. Results: The OA group presented a higher resting heart rate (84.3 ± 4.6 bpm) than the YA group (72.0 ± 4.4 bpm; p < 0.05). The YA group showed an attenuated variance of HRV (2235.1 ± 417.9 ms2) compared to the MA (1014.3 ± 265.2 ms2; p < 0.05) and OA (896.3 ± 274.1 ms2; p < 0.05) groups, respectively. The parasympathetic modulation of HRV was lower in both the MA (244.2 ± 58.0 ms2) and OA (172.8 ± 37.9 ms2) groups in comparison with the YA group (996.0 ± 255.4 ms2; p < 0.05), while serum DHEA-S levels were significantly lower in both the MA (91.2 ± 19.6 mg/dL) and OA (54.2 ± 17.7 mg/dL) groups compared to the YA group (240.0 ± 50.8 mg/dL; p < 0.05). A positive correlation between lower serum concentrations of DHEA-S and attenuated variance of HRV (r = 0.47, p = 0.031), as well as lower serum concentrations of DHEA-S and decreased parasympathetic modulation of HRV (r = 0.54, p = 0.010), were found. Conclusion: The present study demonstrated that the decline of plasma DHEA-S is associated with reduced cardiac autonomic modulation during the aging process.

Ischemic preconditioning delays the time of exhaustion in cycling performance during the early but not in the late phase

Aims: To investigate the early and late ischemic preconditioning (IPC) effect on the trained cyclists' performance during incremental cycling test until exhaustion. Methods: Twenty-one male cyclists allocated to an IPC (2 x 5-min of blood flow occlusion at 50 mm Hg above systolic pressure followed + 5-min of deflation), SHAM (2 x 5-min at 20 mm Hg) or control (CON; no occlusion) interventions, performed three incremental cycling test (ICT) until exhaustion on separate days. The ICT were conducted pre interventions (baseline), 5-min and 24-h after interventions. The heart rate (HR) and power output (PO) were recorded during all ICT. Results: The IPC group increased ICT performance (4.4 ± 4.0 %; effect size (ES) = 0.27) 5-min post intervention, accompanied by HR mean reduction, compared to baseline (p < 0.05). However, there were no changes in SHAM (2.2 ± 4.2%; ES = 0.07) and CON (2.9 ± 5.0%; ES = 0.06) groups. In 24-h post intervention, SHAM (0.2 ± 4.7%; ES = 0.02) and CON (-1.0 ±1.6; ES = 0.03) maintained (p > 0.05) and IPC group decreased the performance (-4.6 ± 3.6 %; ES = 0.16) compared to 5-min post intervention (p < 0.05), but all groups were similar to baseline (p > 0.05). There were no difference (p > 0.05) among groups for PO peak, HR and ICT performance in all moments (baseline, 5-min and 24-h post intervention). Conclusion: The IPC increases early but not late incremental cycling test performance.(AU)

Exercise Training Attenuates Sympathetic Activity and Improves Morphometry of Splenic Arterioles in Spontaneously Hipertensive Rats / Treinamento Físico Atenua a Atividade Simpática e Melhora a Morfometria das Arteríolas Esplênicas em Ratos Espontaneamente Hipertensos

Abstract Background: Alterations in the structure of resistance vessels contribute to elevated systemic vascular resistance in hypertension and are linked to sympathetic hyperactivity and related lesions in target organs. Objective: To assess the effects of exercise training on hemodynamic and autonomic parameters, as well as splenic arteriolar damages in male Wistar Kyoto (WKY) and Spontaneously Hypertensive Rats (SHR). Methods: Normotensive sedentary (WKYS) and trained (WKYT) rats, and hypertensive sedentary (SHRS) and trained (SHRT) rats were included in this study. After 9 weeks of experimental protocol (swimming training or sedentary control), arterial pressure (AP) and heart rate (HR) were recorded in freely moving rats. We assessed the autonomic control of the heart by sympathetic and vagal autonomic blockade. Morphometric analyses of arterioles were performed in spleen tissues. The statistical significance level was set at p < 0.05. Results: Resting bradycardia was observed in both trained groups (WKYT: 328.0 ± 7.3 bpm; SHRT: 337.0 ± 5.2 bpm) compared with their respective sedentary groups (WKYS: 353.2 ± 8.5 bpm; SHRS: 412.1 ± 10.4 bpm; p < 0.001). Exercise training attenuated mean AP only in SHRT (125.9 ± 6.2 mmHg) vs. SHRS (182.5 ± 4.2 mmHg, p < 0.001). The WKYT showed a higher vagal effect (∆HR: 79.0 ± 2.3 bpm) compared with WKYS (∆HR: 67.4 ± 1.7 bpm; p < 0.05). Chronic exercise decreased sympathetic effects on SHRT (∆HR: -62.8 ± 2.8 bpm) in comparison with SHRS (∆HR: -99.8 ± 9.2 bpm; p = 0.005). The wall thickness of splenic arterioles in SHR was reduced by training (332.1 ± 16.0 µm2 in SHRT vs. 502.7 ± 36.3 µm2 in SHRS; p < 0.05). Conclusions: Exercise training attenuates sympathetic activity and AP in SHR, which may be contributing to the morphological improvement of the splenic arterioles.

Resumo Fundamento: Alterações na estrutura dos vasos de resistência contribuem para elevar a resistência vascular sistêmica na hipertensão, estando ligadas à hiperatividade simpática e lesões em órgãos-alvo. Objetivo: Avaliar os efeitos do treinamento físico nos parâmetros hemodinâmicos e autônomos, assim como as lesões arteriolares esplênica em ratos machos Wistar Kyoto (WKY) e espontaneamente hipertensos (SHR). Métodos: Ratos normotensos sedentários (WKYS) e treinados (WKYT), e ratos hipertensos sedentários (SHRS) e treinados (SHRT) foram incluídos neste estudo. Após nove semanas de aplicação do protocolo experimental (treinamento de natação ou controle sedentário), registraram-se a pressão arterial (PA) e a frequência cardíaca (FC) dos ratos em movimento livre. Avaliamos o controle autônomo do coração através de bloqueio autônomo simpático e vagal. Análises morfométricas das arteríolas esplênicas foram realizadas. Adotou-se o nível de significado estatístico de p < 0,05. Resultados: Observou-se bradicardia de repouso nos dois grupos treinados (WKYT: 328,0 ± 7,3 bpm; SHRT: 337,0 ± 5,2 bpm) em comparação aos seus respectivos grupos sedentários (WKYS: 353,2 ± 8,5 bpm; SHRS: 412,1 ± 10,4 bpm; p < 0,001). O treinamento físico atenuou a PA média apenas no grupo SHRT (125,9 ± 6,2 mmHg vs. 182,5 ± 4,2 mmHg no SHRS; p < 0,001). O grupo WKYT mostrou maior efeito vagal (∆FC: 79,0 ± 2,3 bpm) em comparação ao grupo WKYS (∆FC: 67,4 ± 1,7 bpm; p < 0,05). Exercício crônico diminuiu os efeitos simpáticos em SHRT (∆FC: -62.8 ± 2.8 bpm) em comparação a SHRS (∆FC: -99,8 ± 9,2 bpm; p = 0,005). A espessura da parede das arteríolas esplênicas nos SHR foi reduzida pelo treinamento (332,1 ± 16,0 µm2 nos SHRT vs. 502,7 ± 36,3 µm2 nos SHRS; p < 0,05). Conclusões: O treinamento físico atenua a atividade simpática e a PA em SHR, o que pode contribuir para melhorar a morfologia das arteríolas esplênicas.

Profile of the cardiac repolarization in cervical spinal cord injury subjects performing physical exercise / Perfil da repolarização cardíaca de sujeitos com lesão medular cervical submetidos a exercícios físicos

The aim of the study was to compare rest QT interval and QTcorrected intervals of electrocardiogram in trained men with and without cervical spinal cord injury (CSCI) and investigate cardiac electrocardiogram parameters in trained men with CSCI submitted to maximal effort test. Thirty men were separated into three groups: Control without CSCI (CON, 25.3 ± 4.1 yrs, strength training: 3 days week-1; aerobic training 1day week-1; n = 10), high volume exercise (30.5 ± 4.3 yrs, 3 day week-1 rugby specific exercises, 60min. day-1; n = 12) and moderate volume of exercise (33.7 ± 5.9 yrs, 2 days week- 1 specific rugby exercises, 60 min. day-1; n = 8) with incomplete CSCI (C5-C7 cervical vertrebae) more than 12 months. Electrocardiogram was recorded in rest, during and after effort test. QT interval was significantly reduced (p = 0.001) in the high volume exercise group compared to control. Corrected QT interval showed no difference between moderate vs. high volume exercise group (p > 0.05). No changes were observed in QT, corrected QT, PR and QRS intervals of electrocardiogram between rest and post effort (p > 0.05). Thus, effort test does not change electrocardiogram parameters in CSCI subjects. High volume of week exercise promotes abnormalities in cardiac repolarization compared to a moderate training program.

O objetivo do presente estudo foi comparar o perfil dos intervalos QT e QT corrigido (QTc) em homens treinados com e sem lesão medular cervical (LMC) e investigar o perfil eletrocardiográfico de homens treinados com LMC submetidos ao teste de esforço máximo. Trinta homens foram separados em três grupos: controle sem LMC (CON, indivíduos fisicamente ativos; n = 10), LMC praticantes de alto volume de exercícios (praticantes de rugby em cadeira de rodas 180 min. Semana-1; n = 12) e LMC praticantes de moderado volume de exercícios (praticantes de rugby em cadeira de rodas 120 min. Semana-1; n = 8). Todos os participantes do grupo LMC apresentavam lesões incompletas (C5-C7) mais do que 12 meses. Eletrocardiograma foi registrado em repouso, durante e após o teste de esforço. O intervalo QT apresentou redução significativa (p = 0,001) no grupo de alto volume de exercícios quando comparado ao controle. O QTc não mostrou diferença entre os distintos volumes de exercícios (p > 0,05). Ambos os grupos LMC não apresentaram mudanças significativas no intervalo QT, QTc, intervalos PR e QRS entre o repouso e pós-esforço (p > 0,05). Concluimos que o alto volume de exercícios semanais parece promover anormalidades na repolarização cardíaca.

Exercise training reverse autonomic dysfunction and hypertension in rats fed with high-fat diet

AIMS: We evaluated whether exercise training ameliorates cardiovascular autonomic dysfunction in obesity-induced by high-fat diet (HFD) in rats. METHODS Wistar male rats were assigned in normal diet, sedentary (ND-S) and trained (ND-T) and HFD, sedentary (HFD-S) and trained (HFD-T). Blood pressure (BP), heart rate (HR), HR variability (HRV), BP variability (BPV), cardiac baroreflex and cardiac autonomic tonus were assessed. HFD-S showed higher bodyweight increase (19.4%) compared to all other groups (HFD-T: 13.2%, ND-S: 14% and ND-T: 12.4%). Relative epididymal, retroperitoneal and visceral fat was also greater in HFD-S compared to all other groups. Resting bradycardia in ND-T (339.5±10.6 bpm) and HFD-T (341.0 ± 9.4 bpm) was more pronounced than ND-S (438.4 ± 6.3 bpm; p<0.05) and HFD-S (448.5 ± 18.7 bpm; p<0.05). The HFD-T group showed lower systolic (125.3 ( 1.9 mmHg), diastolic (88.5 ( 2.0 mmHg) and mean BP (100.3 ± 2.5 mmHg) in comparison with HFD-S (153.8 ( 3.7; 103.5 ( 2.6 and 120.5 ± 3.7 mmHg; p<0.05, respectively). Lower variance of HRV and higher variance of diastolic BPV was observed in HFD-S compared to other groups while sympathetic modulation of HRV and BPV was higher in HFD-S, as well as the LF/HF ratio. HFD-T showed a decrease in sympathetic tonus compared to HFD-S. ND-T and HFD-T showed higher cardiac vagal tonus than respective sedentary groups. Analysis showed an association between visceral fat, sympathetic activity and BP. CONCLUSIONS: HFD induces hypertension and is associated with autonomic imbalance in rats, while exercise training may reverse these harmful changes.(AU)

Profile of infrared thermography in elite soccer players

Abstract Aims The aim of this study was to establish thermographic profiles of lower limbs and to correlate them with creatine kinase level in professional players. Method Thirty healthy male professional soccer players (25.4 ± 4.7 years; 179.5 ± 6.7 cm; 78.3kg ± 7.5 kg; body fat 10.2 ± 4.2 %) from a club of Brazilian first division soccer league volunteered. Thermal images sequences of lower limbs (thighs and legs) were acquired in an anteroposterior manner (i.e., frontal and dorsal views) by a digital infrared thermo-camera. Blood creatine kinase (CK) concentration was assessed by reflectance photometry. All thermographic images and CK were performed between 8:00 and 9:00 am. Results No significant difference (p>0.05) was found between left and right sides from both anterior and posterior measurements of thighs and legs for mean or maximal skin temperature. Low values of correlation (range r=0.14 to r=0.38) was found between skin temperature and CK levels while contralateral thermal symmetry in the lower limbs (regions of interest < 0.2°C) was found. Conclusion It was observed contralateral thermal symmetry in the lower limbs and low correlation between CK and temperature values in elite soccer players.(AU)

Specific warm-up exercise is the best for vertical countermovement jump in young volleyball players

Abstract We evaluated the effect of performing various distinct warm-up exercises on vertical countermovement jump (VCMJ) performance. Eight volleyball players (age 15.4 ± 0.5 yrs) performed five different warm-up activities (in a counterbalanced, randomized crossover study) over five days, at 24-h intervals: stretching (4 × 30 s, 30 s between sets), cycloergometer (5 min at 50 W + 5 min at 100 W), resistance exercise (leg press 45°, 3 × 5 repetitions maximum, 3-min pause between sets), specific vertical jumping (4 × 10 VCMJ, 2-min pause between sets), and no warm-up at all (control condition). Beginning 3 min after their warm-up, the players performed 3 attempts (at intervals of 3 min) of VCMJ (on a contact carpet), and each player's best jump was considered in the analysis. All warm-up activities presented higher VCMJ performance (p< 0.05) than the control condition, with the exception of stretching. Vertical jumping revealed a large effect size(0.8) than other interventions. We conclude that in practical terms, vertical jumps are the best warm-up exercise (when applied by itself) to acutely improve VCMJ performance in volleyball players, but that other exercises can make a complementary contribution.

Análise da correlação entre o protocolo Polar Fitness Test® para predição de VO2máx e ergoespirometria / Analysis of the correlation between Polar Fitness Test® protocol and ergospirometry

INTRODUÇÃO: A importância da mensuração do consumo máximo de oxigênio (VO2máx)é justificada por sua aceitação internacional como o melhor parâmetro fisiológico para avaliar a capacidade funcional do sistema cardiorrespiratório tanto em atletas como em não atletas que treinam fisicamente com objetivo de obter melhor saúde. OBJETIVO: Verificar a concordância entre os protocolos Polar Fitness Test® para a estimativa do VO2máx e o teste de esforço máximo com medida direta de gases. MÉTODOS: Dezessete homens ativos (22,5 ± dois anos) participaram. Em repouso, aplicou-se o protocolo Polar Fitness Test® e, em seguida, a coleta direta de gases sob o esforço máximo, em esteira, seguindo o protocolo de Bruce. RESULTADOS: Houve diferença significativa entre os valores médios dos métodos para estimativa do VO2máx. O protocolo Polar Fitness Test® subestimou o VO2máx, em média 15% (IC95%: 24; -53%) comparado com a medida direta de gases. Os valores obtidos pelo Polar Fitness Test® não tiveram boa correlação com a medida direta em ergoespirômetro (r = 0,1). CONCLUSÃO: O protocolo Polar Fitness Test® não é válido para a estimativa do VO2máx em homens jovens ativos fisicamente.

INTRODUCTION: The importance of maximal oxygen consumption (VO2máx) measurement is justified by its international acceptance as the best physiological parameter to assess the functional capacity of the cardiorespiratory system in both athletes and non-athletes who physically train in order to achieve better health. OBJECTIVE: To determine the agreement between the Polar Fitness Test® protocols to estimate of VO2máx and the maximal exercise test with direct gas measurement. METHODS: Seventeen active males (22.5 ± 2 years) participated in the study. At rest, the Polar Fitness Test® protocol by direct gas collection under maximum effort on treadmill and the Bruce protocol were applied. RESULTS: Significant difference in the VO2máx estimation was observed between methods. The Polar Fitness Test® protocol underestimated VO2máx a mean of 15% (CI95%: 24;-53%) when compared to the direct protocol. The values obtained by the Polar Fitness Test® did not correlate well with direct measurement in ergospirometer (r = 0.1). CONCLUSION: The Polar Fitness Test® protocol is not valid to estimate VO2máx in physically active young men.

Estudo eletromiográfico dos músculos deltoide, peitoral maior e tríceps braquial de nadadores durante contrações bilaterais realizadas em exercício multiarticular com cargas variadas / Electromyographic study of the deltoid, pectoralis major and triceps brachial muscles in swimmers during bilateral contractions performed in multi-joint exercise with different loads

O objetivo deste trabalho foi comparar a atividade elétrica do músculo deltoide (porção média), peitoral maior (porção clavicular) e tríceps braquial (cabeça longa) durante contração bilateral realizada num aparelho multiarticular de desenvolvimento articulado convergente, com 40% e 80% da carga voluntária máxima (CVM), em 11 nadadores do gênero masculino (idades entre 15 e 23 anos, peso 70 ± 4kg, estatura 183 ± 6cm e tempo de prática do esporte de 10 ± 4 anos) treinados em exercícios resistidos. Os sinais eletromiográficos (EMG) foram captados através da colocação de eletrodos ativos de superfície diferenciais de ganho de 20 vezes, composto por duas barras retangulares paralelas da EMG System do Brasil, um eletrodo de referência (terra), e um módulo condicionador de sinais (eletromiógrafo), com aquisição simultânea de até oito canais diferenciais, filtro com faixa de passagem de 20Hz a 5Hz, estágio amplificador ajustável, possibilitando ganhos entre 100 e 4.960 vezes, impedância de entrada de canais de 10GΩ em módulos diferencial e CMRR de 93db a 60Hz, e um sistema de aquisição de dados (Alc-EMG) que forneceu dados numéricos em RMS (raiz quadrada da média) para análise dos resultados. Cada sinal coletado captou apenas a fase concêntrica do movimento e o mesmo teve duração de três segundos. Diante dos resultados (teste U de Mann-Whitney, Friedman e Wilcoxon) conclui-se que, em termos práticos de prescrição e periodização do treinamento neuromuscular, as contrações bilaterais realizadas no aparelho desenvolvimento articulado convergente são eficientes visando recrutamento (80% > 40%) dos músculos deltoide médio, peitoral maior (porção clavicular) e tríceps braquial (cabeça longa), sendo evidenciadas diferenças entre o membro dominante e o não dominante apenas para o tríceps braquial dominante com a carga de 80% da CVM nestes atletas nadadores com histórico de treinamento com pesos.

The objective of this study was to compare the electrical activity of the deltoid (middle portion), pectoralis major (clavicular portion) and triceps (long head) muscles during bilateral contraction performed in a multi-articulated joint shoulder-press convergent machine with 40% and 80% maximum voluntary load (MVL) in 11 male swimmers (15 to 23 years, 70 ± 4 kg, 183 ± 6 cm and 10 ± 4 years time practice in sport), trained in resistance exercise. Electromyographic signals (EMG) were obtained by placing surface active differential electrodes (20x gain), composed of two parallel rectangular bars (EMG System, Brazil®). A data acquisition system (EMG-Alc) which provided numerical data in RMS (Root Mean Square) to analyze the signals composed by a reference electrode (ground) and a signal conditioning module (EMG) with simultaneous acquisition of up to 8 differential channels (band-pass filter 5-20 Hz), adjustable amplifier stage, allowing gains between 100 and 4960 times, channel input impedance 10GΩ in differential modules and CMRR of 93 dB/60 Hz was used. Only the concentric phase (3 seconds duration) in each EMG signal collected was recorded. After the tests (Mann-Whitney U test, Friedman and Wilcoxon) were applied, it was concluded that for prescription and periodization of the neuromuscular training, bilateral contractions performed in the shoulder-press apparatus are efficient at aiming muscular recruitment (80%> 40% ) of middle portion of the deltoid, pectoralis major (clavicular portion), and triceps brachii (long head) muscles, evidencing differences between dominant and non-dominant limbs only for the dominant brachial triceps in 80% of MVL in swimmers trained in resistance exercises.

Noninvasive method for electrocardiogram recording in conscious rats: feasibility for heart rate variability analysis

Heart rate variability (HRV) analysis consists in a well-established tool for the assessment of cardiac autonomic control, both in humans and in animal models. Conventional methods for HRV analysis in rats rely on conscious state electrocardiogram (ECG) recording based on prior invasive surgical procedures for electrodes/transmitters implants. The aim of the present study was to test a noninvasive and inexpensive method for ECG recording in conscious rats, assessing its feasibility for HRV analysis. A custom-made elastic cotton jacket was developed to fit the rat's mean thoracic circumference, with two pieces of platinum electrodes attached on its inner surface, allowing ECG to be recorded noninvasively in conscious, restrained rats (n=6). Time- and frequency-domain HRV analyses were conducted, under basal and autonomic blockade conditions. High-quality ECG signals were obtained, being feasible for HRV analysis. As expected, mean RR interval was significantly decreased in the presence of atropine (p <0.05) and increased in the presence of propranolol (p<0.001). Also, reinforcing the reliability of the method, low- and high-frequency HRV spectral powers were significantly decreased in the presence of propranolol (p <0.05) and atropine (p< 0.001), respectively. In summary, the present work describes a novel, inexpensive and noninvasive method for surface ECG recording in conscious rats.

A análise da variabilidade da freqüência cardíaca (VFC) consiste em uma metodologia bem estabelecida para o estudo do controle autonômico cardíaco, tanto em humanos como em modelos animais. As metodologias convencionais para o estudo da VFC em ratos utilizam-se de procedimentos cirúrgicos para o implante de eletródios ou transmissores, o que possibilita a posterior aquisição do eletrocardiograma (ECG) no estado consciente. O objetivo do presente trabalho foi o de desenvolver e aplicar um método não-invasivo para o registro do ECG em ratos conscientes, verificando sua validade para a análise da VFC. Uma vestimenta de tecido elástico em algodão foi desenvolvida de acordo com as dimensões médias da circunferência torácica dos animais, e dois pequenos eletródios retangulares de platina foram aderidos à superfície interna da vestimenta, permitindo o registro do ECG de forma não-invasiva em ratos conscientes (n=6), sob contenção. Foram conduzidas análises de VFC nos domínios do tempo e da freqüência, tanto para a condição basal, como para as condições de bloqueio autonômico. Foram obtidos sinais de ECG de alta qualidade, viáveis para a análise de VFC. Conforme esperado, o intervalo RR médio foi significativamente reduzido na presença de atropina (p<0.05), e aumentado na presença de propranolol (p<0.001). Reforçando a validade do método, as potências espectrais de baixa e alta freqüência da VFC sofreram reduções significativas, respectivamente, na presença de propranolol (p<0.05) e atropina (p<0.05). Em resumo, o presente trabalho descreve um novo método, de baixo custo e natureza não-invasiva, para a realização do ECG de superfície em ratos conscientes.

Resposta aguda da pressão arterial, da frequência cardíaca e do duplo-produto após uma sessão de eletroestimulação em exercício de força / Acute response of blood pressure, heart rate and dual output after an electro-stimulation session with strength training exercises

Objetivo: Verificar as respostas cardiovasculares(frequência cardíaca, pressão arterial e duplo-produto)agudas após a utilização da eletroestimulação (EE) prévia aos exercícios de força. Métodos: Foram estudados 16 homens voluntários do sexo masculino (idade 25,7 mais ou menos 6 anos, massa 80 mais ou menos 10,5 kg, estatura 177,1 mais ou menos 7,41 cm) com previa experiência em exercício de força. Os indivíduos foram separados aleatoriamente em dois grupos: Grupo I: Grupo sem eletroestimulação )GSE n igual 8), Grupo 2: Grupo eletroestimulação (GEE n igual 8). Antes da coleta de dados, todos os indivíduos realizaram o teste de 10 repetições máximas (10-RM) no exercício extensão de joelhos simultâneos. Após 48 h do teste 10-RM, foi realizada a coleta de dados, com a execução de 3 séries de 10 repetições, a 80 por cento de 10-RM e intervalo de recuperação de 2 minutos fixos, para ambos os grupos, no exercício cadeira extensora. As mensurações da pressão arterial, da frequência cardíaca e do duplo-produto (PAS X FC) foram realizadas no repouso e ao final da 1, 2 e 3 séries de exercícios. No GEE foi adotada a aplicação da EE prévia à realização do exercício em uma frequência de 50 Hz...