Eduardo Kokubun

MAXIMAL LACTATE STEADY STATE IN RUNNING MICE: EFFECT OF EXERCISE TRAINING

1 Maximal lactate steady state (MLSS) corresponds to the highest blood lactate concentration (MLSSc) and workload (MLSSw) that can be maintained over time without continual blood lactate accumulation and is considered an important marker of endurance exercise capacity. The present study was undertaken to determine MLSSw and MLSSc in running mice. In addition, we provide an exercise training protocol for mice based on MLSSw. 2 Maximal lactate steady state was determined by blood sampling during multiple sessions of constant‐load exercise varying from 9 to 21 m/min in adult male C57BL/6J mice. The constant‐load test lasted at least 21 min. The blood lactate concentration was analysed at rest and then at 7 min intervals during exercise. 3 The MLSSw was found to be 15.1 ± 0.7 m/min and corresponded to 60 ± 2% of maximal speed achieved during the incremental exercise testing. Intra‐ and interobserver variability of MLSSc showed reproducible findings. Exercise training was performed at MLSSw over a period of 8 weeks for 1 h/day and 5 days/week. Exercise training led to resting bradycardia (21%) and increased running performance (28%). Of interest, the MLSSw of trained mice was significantly higher than that in sedentary littermates (19.0 ± 0.5 vs 14.2 ± 0.5 m/min; P = 0.05), whereas MLSSc remained unchanged (3.0 mmol/L). 4 Altogether, we provide a valid and reliable protocol to improve endurance exercise capacity in mice performed at highest workload with predominant aerobic metabolism based on MLSS assessment.

Blood glucose responses in humans mirror lactate responses for individual anaerobic threshold and for lactate minimum in track tests

Abstract The equilibrium point between blood lactate production and removal (La−min) and the individual anaerobic threshold (IAT) protocols have been used to evaluate exercise. During progressive exercise, blood lactate [La−]b, catecholamine and cortisol concentrations, show exponential increases at upper anaerobic threshold intensities. Since these hormones enhance blood glucose concentrations [Glc]b, this study investigated the [Glc] and [La−]b responses during incremental tests and the possibility of considering the individual glucose threshold (IGT) and glucose minimum (Glcmin) in addition to IAT and La−min in evaluating exercise. A group of 15 male endurance runners ran in four tests on the track 3000 m run (v3km); IAT and IGT – 8 × 800 m runs at velocities between 84% and 102% of v3km; La−min and Glcmin– after lactic acidosis induced by a 500-m sprint, the subjects ran 6 × 800 m at intensities between 87% and 97% of v3km; endurance test (ET) – 30 min at the velocity of IAT. Capillary blood (25 μl) was collected for [La−]b and [Glc]b measurements. The IAT and IGT were determined by [La−]b and [Glc]b kinetics during the second test. The La−min and Glcmin were determined considering the lowest [La−] and [Glc]b during the third test. No differences were observed (P < 0.05) and high correlations were obtained between the velocities at IAT [283 (SD 19) and IGT 281 (SD 21) m. · min−1; r = 0.096; P < 0.001] and between La−min [285 (SD 21)] and Glcmin [287 (SD 20) m. · min−1r = 0.77; P < 0.05]. During ET, the [La−]b reached 5.0  (SD 1.1) and 5.3 (SD 1.0) mmol · l−1 at 20 and 30 min, respectively (P > 0.05). We concluded that for these subjects it was possible to evaluate the aerobic capacity by IGT and Glcmin as well as by IAT and La−min.

Predicting MAOD Using Only a Supramaximal Exhaustive Test

The objective of this study was to propose an alternative method (MAOD(ALT)) to estimate the maximal accumulated oxygen deficit (MAOD) using only one supramaximal exhaustive test. Nine participants performed the following tests: (a) a maximal incremental exercise test, (b) six submaximal constant workload tests, and (c) a supramaximal constant workload test. Traditional MAOD was determined by calculating the difference between predicted O(2) demand and accumulated O(2) uptake during the supramaximal test. MAOD(ALT) was established by summing the fast component of excess post-exercise oxygen consumption and the O(2) equivalent for energy provided by blood lactate accumulation, both of which were measured during the supramaximal test. There was no significant difference between MAOD (2.82+/-0.45 L) and MAOD(ALT) (2.77+/-0.37 L) (P=0.60). The correlation between MAOD and MAOD(ALT) was also high (r=0.78; P=0.014). These data indicate that the MAOD(ALT) can be used to estimate the MAOD.

Effects of preferred and nonpreferred music on continuous cycling exercise performance.

The aim of this study was to investigate the effects of preferred and nonpreferred music on exercise distance, Heart Rate (HR), and Rating of Perceived Exertion (RPE) during continuous cycling exercise performed at high intensity. Fifteen participants performed five test sessions. During two sessions, they cycled with fixed workload on ergometer to determine the Critical Power (CP) intensity. Then, they performed three more sessions cycling at CP intensity: listening to Preferred Music, listening to Nonpreferred Music, and No Music. The HR responses in the exercise sessions did not differ among all conditions. However, the RPE was higher for Nonpreferred Music than in the other conditions. The performance under Preferred Music (9.8 ± 4.6km) was greater than under Nonpreferred Music (7.1 ± 3.5km) conditions. Therefore, listening to Preferred Music during continuous cycling exercise at high intensity can increase the exercise distance, and individuals listening to Nonpreferred Music can perceive more discomfort caused by the exercise.

Changes of glycogen content in liver, skeletal muscle, and heart from fasted rats.

Glycogen content of white and red skeletal muscles, cardiac muscle, and liver was investigated in conditions where changes in plasma levels of non‐esterified fatty acids (NEFA) occur. The experiments were performed in fed and 12 and 48 h‐fasted rats. The animals were also submitted to swimming for 10 and 30 min. Glycogen content was also investigated in both pharmacologically induced low plasma NEFA levels fasted rats and pharmacologically induced high plasma NEFA levels fed rats. The participation of Akt and glycogen synthase kinase‐3 (GSK‐3) in the changes observed was investigated. Plasma levels of NEFA, glucose, and insulin were determined in all conditions. Fasting increased plasma NEFA levels and reduced glycogen content in the liver and skeletal muscles. However, an increase of glycogen content was observed in the heart under this condition. Akt and GSK‐3 phosphorylation was reduced during fasting in the liver and skeletal muscles but it remained unchanged in the heart. Our results suggest that in conditions of increased plasma NEFA levels, changes in insulin‐stimulated phosphorylation of Akt and GSK‐3 and glycogen content vary differently in liver, skeletal muscles, and heart. Akt and GSK‐3 phosphorylation and glycogen content are decreased in liver and skeletal muscles, but in the heart it remain unchanged (Akt and GSK‐3 phosphorylation) or increased (glycogen content) due to consistent increase of plasma NEFA levels. Copyright

The International Physical Activity Questionnaire-long form overestimates self-reported physical activity of Brazilian adults.

OBJECTIVE To explore issues associated with measuring physical activity using the International Physical Activity Questionnaire (IPAQ)-long form in adults living in a mid-sized Brazilian city. METHODS A stratified random sampling procedure was used to select a representative sample of adults living in Rio Claro. This yielded 1572 participants who were interviewed using the IPAQ-long form. The data were analysed using standard statistical procedures. RESULTS Overall, 83% of men and 89% of women reported at least 150 min of combined moderate and/or vigorous physical activity per week. Reliable values of leisure and transportation-related physical activity were observed for both males and females. With regard to the household and work-related physical activity domains, both males and females reported unusually high levels of participation. CONCLUSION The IPAQ-long form appears to overestimate levels of physical activity for both males and females, suggesting that the instrument has problems in measuring levels of physical activity in Brazilian adults. Accordingly, caution is warranted before using IPAQ data to support public policy decisions related to physical activity.

Physical Inactivity and Related Barriers: A Study in a Community Dwelling of Older Brazilians

This study sought to investigate the prevalence of physical inactivity and related barriers in older Brazilian adults. A cross-sectional, population-based study was conducted, and a stratified random sampling procedure was used. A total of 359 older adults were interviewed. The long version of the International Physical Activity Questionnaire (IPAQ) and the Questionnaire of Barriers to Physical Activity Practice were used to assess physical activity level and barriers, respectively. No statistically significant difference was observed on the prevalence of physical inactivity in either gender or age groups. Regarding barriers, the proportion of 9 out of 22 barriers was statistically significant between men and women. Self-reported physical inactivity/activity in older Brazilian adults continues to be a concern. Uncommonly, older males reported a higher prevalence of physical inactivity compared to their counterparts. Additionally, physical inactivity prevalence continued to increase with the aging process. Yet, personal barriers such as lack of time and poor health were strongly associated with physical inactivity. The results of this study may help health professionals and public policy makers to better address the issues related to a healthy lifestyle among older adults and promote physical activity among Brazilian older adults and in other countries with similar characteristics.

Utilização do esforço percebido na determinação da velocidade crítica em corrida aquática

La relacion lineal entre la intensidad del ejercicio y la tasa de aumento de la actividad neuromuscular estimada por la electromiografia permite estimar el limite de fatiga que seria la intensidad que podria estar mantenida indefinidamente sin aumento de senales electromiograficos a largo plazo. Se planteo la hipotesis de que la percepcion subjetiva del esfuerzo tendria un comportamiento semejante a la activacion neuromuscular, y que el umbral del esfuerzo percibido (LEP), identificado de forma semejante al umbral de fatiga electromiografica, podria coincidir con la velocidad critica (VCrit). Trece individuos de ambos sexos (23 ± 2.5 anos) en una piscina de 15 ms de extension y 2.5 ms de profundidad, realizaron 3 tests exhaustivos de maraton acuatica para la determinacion de los parametros de velocidad critica, reportando el esfuerzo percibido (escala de Borg de 6 a 20 puntos) cada 15 min. Para identificacion del LEP, los coeficientes de inclinacion de las rectas de aumento del esfuerzo percibido en el tiempo (ordenada) y las velocidades utilizadas (abcisa) fueron ajustados a una funcion lineal que marcaba un punto de crecimiento de velocidad donde teoricamente el esfuerzo percibido estaria establecido indefinidamente. La VCrit fue estimada por las ecuasiones usadas en el modelo de la velocidad critica. Para comparacion de las estimativas de Vcrit, del LEP y de sus asociaciones, fue hecha ANOVA para medidas repetidas (p < 0.05) y calculada la correlacion de Pearson. Los datos obtenidos para la determinacion de VCrit se ajustaran a los criterios adoptados para la validacion del modelo, y la VCrit y LEP no presentaron diferencias estadisticas (0.23 ± 0.02 m/s x 0.24 +/- 0.03 m/s) y fueron significativamente correlacionados (r = 0.85). Estos resultados sugieren que el LEP parece representar la intensidad maxima de ejercicio en que las variables fisiologicas y sicofisicas encontrarian estabilidad, y que este indice puede ser utilizado para la determinacion de la VCrit.

The influence of resting period length on jumping performance.

Pereira, G, Almeida, AG, Rodacki, ALF, Ugrinowitsch, C, Fowler, NE, Kokubun, E. The influence of resting period length on jumping performance. J Strength Cond Res 22: 1259-1264, 2008-The purpose of this study was to determine a resting interval between countermovement jumps (i.e., volleyball spikes) that allows the maintenance of maximal jumping performance. Ten male volleyball players (1.85 ± 0.05 m, 77.2 ± 10.6 kg, 21.6 ± 5.3 years) performed 6 experimental jumping sessions. In the first and sixth sessions, maximal countermovement jump height was measured, followed by submaximal countermovement jumps to the point of volitional fatigue. The number of countermovement jumps was used as a reference to test the effect of rest period between volleyball spikes. From the second to fifth experimental sessions, 30 maximal volleyball spikes were performed with different resting periods (i.e., 8, 14, 17, and 20 seconds) followed by countermovement jumps. Between the 15th and 30th spikes, the blood lactate concentration and heart rate were measured. Because the performance on the first and sixth sessions was the same, no training effects were noticed. During the 8-second resting interval set, the lactate concentration increased significantly between the 15th and 30th spikes (i.e., from 3.37 ± 1.16 mmol to 4.94 ± 1.49 mmol); the number of countermovement jumps decreased significantly after spikes compared to those performed without a previous effort (i.e., from 23 ± 7 jumps to 17 ± 9 jumps); and these variables were significantly correlated (r = -0.7). On the other hand, the lactate concentration and number of countermovement jumps were stable across the other resting intervals, without a heart rate steady state. The results indicate that an adequate resting period between spikes allowed participants to achieve a lactate steady state in which the performance was maintained during the exercise. These findings show that resting intervals between 14 and 17 seconds, typical during volleyball matches, are indicated to use in volleyball spike drills due to their capacity to maintain maximal jumping performance.

Characteristics of physical activity programs in the Brazilian primary health care system

O objetivo foi descrever as caracteristicas dos programas de atividade fisica na atencao basica de saude de acordo com a presenca de Nucleo de Apoio a Saude da Familia (NASF) no municipio e por regioes do Brasil. Foi realizado um estudo transversal por inquerito telefonico com 1.251 coordenadores de unidades de saude. Foi aplicado um questionario sobre presenca de intervencoes com atividade fisica e suas caracteristicas de funcionamento. Quatro em cada dez unidades de saude relataram ter uma intervencao com atividade fisica, especialmente grupos de caminhada. A maior parte da atividade e realizada na manha uma vez ou duas vezes por semana, com sessoes de 30 minutos ou mais. Profissionais de educacao fisica sao os principais responsaveis por supervisionar as atividades. Os programas ocorrem na unidade de saude ou outros espacos comunitarios. Estas caracteristicas, de modo geral, foram semelhantes entre unidades com ou sem NASF no municipio e apresentaram variacao entre as regioes. Os resultados desse estudo irao permitir melhor direcionamento das proximas acoes de promocao de atividade fisica na atencao basica de saude.The aim of this study was to describe the characteristics of programs that promote physical activity in the public primary care system by region of Brazil, subject to the presence or absence of multidisciplinary primary care teams (NASF). We conducted a cross sectional and population-based telephone survey of the health unit coordinators from 1,251 health care units. Coordinators were asked about the presence and characteristics of physical activity programs. Four out of ten health units reported having a physical activity intervention program, the most common involving walking groups. Most of the activities were performed in the morning, once or twice a week, and in sessions of 30 minutes or more. Physical education professionals were primarily responsible for directing the activities. Interventions occurred in the health unit itself or in adjacent community spaces. In general, these characteristics were similar between units with or without NASF, but varied substantially across regions. These findings will guide future physical activity policies and programs within primary care in Brazil.