Exercising in the urban center: Inflammatory and cardiovascular effects of prolonged exercise under air pollution.

The aim of this study was to investigate, in a well-controlled experimental environment, whether air pollution from an urban center would affect inflammatory and cardiorespiratory responses during prolonged moderate exercise (i.e., 90 min). Ten healthy men performed two experimental trials under filtered and polluted air, inside an environmental chamber located in Sao Paulo downtown, Brazil. Blood samples were obtained at rest, 30, 60, and 90 min of the exercise to determine the serum cytokines concentration, while arterial pressure was recorded immediately after the exercise. The serum cytokines were not altered until 60 min of exercise for both conditions (P > 0.05). Otherwise, at 90 min of exercise, the IL-6 (P = 0.047) and vascular endothelial growth factor (VEGF) (P = 0.026) were significantly higher and IL-10 tended to decrease (P = 0.061) in polluted air condition compared to filtered air condition. In addition, both systolic (P = 0.031) and diastolic (P = 0.009) arterial pressure were higher in polluted air condition than filtered air condition. These findings demonstrate that the exercise of longer duration (i.e., 90 min), but not of shorter duration (i.e., <60 min), performed in vehicular air pollution condition results in pronounced pro-inflammatory and increased arterial pressure responses.

Determinant factors of peak treadmill speed in physically active men.

BACKGROUND: The aim of the present study was to determine whether physiological factors and maximal dynamic strength are able to determine the peak treadmill speed (PTS) in physically active individuals. METHODS: One hundred and fifty physically active healthy males voluntarily visit the laboratory on three separate occasions and underwent the following activities: first visit - IPAQ (short version), anthropometric measurements, and a maximal incremental test performed for physiological variables (maximal oxygen uptake [V̇O2] and respiratory compensation point [RCP]); second visit - constant speed test for running economy (RE) measurement, and familiarization with the Maximum Dynamic Strength (1RM) Test in the leg press exercise; third visit - 1RM test. RESULTS: The stepwise multiple regression model selected four independent variables to predict PTS (RCP, V̇O2, RE, and 1RM). RCP explained 59% (P<0.001) of variance in PTS, whereas V̇O2, RE and 1RM accounted for additional 8% (P<0.001), 4% (P<0.001), and 1.4% (P=0.038), respectively. CONCLUSIONS: In conclusion, the results of the present study demonstrate that PTS, an important predictor of endurance performance, is determined by both physiological (i.e., RCP, V̇O2, and RE) and muscular (1RM) parameters in healthy active individuals. These results demonstrate that, during a physical evaluation, PTS is able to represent physiological and muscular parameters of physically active individuals. This has the advantage during aerobic fitness evaluations of not requiring expensive equipment and specialized software.

Head-to-head running race simulation alters pacing strategy, performance, and mood state.

The objective of this study was to analyze the influence of the presence and absence of competitors on pacing, overall running performance, and mood state during a self-paced 3-km run. Nine recreational runners participated in this study. They performed the following tests: a) an incremental test to exhaustion to measure the respiratory compensation point (RCP), maximal oxygen uptake, and peak treadmill speed; b) a submaximal speed constant test to measure running economy; and c) two 3-km running time trials performed collectively (COL, head-to-head competition) or individually (IND, performed alone) to establish pacing and running performance. The COL condition was formed of a group of four runners or five runners. Runners were grouped by matched performance times and to retain head-to-head characteristics.A mood state profile questionnaire was completed before and after the 3-km running time trial. The overall performance was better in the COL than in the IND (11.75 ± 0.05 min vs. 12.25 ± 0.06 min, respectively; p = 0.04). The running speeds during the first 500 m were significantly greater in COL (16.8 ± 2.16 km·h−1) than in IND (15.3 ± 2.45 km·h−1) (p = 0.03).The gain in running speed from IND to COL during the first 400 m (i.e. running speed in COL less running speed in IND) was significantly correlated with the RCP (r = 0.88; p = 0.05). The vigor score significantly decreased from pre- to post-running in COL (p=0.05), but not in IND (p=0.20). Additionally, the post running vigor was significantly higher in IND compared to COL (p = 0.03).These findings suggested that the presence of competitors induces a fast start, which results in an improved overall performance and reduced post-exercise vigor scores, compared to an individual run.

Effects of resistance training on neuromuscular characteristics and pacing during 10-km running time trial.

PURPOSE: The purpose of this study was to analyze the impact of an 8-week strength training program on the neuromuscular characteristics and pacing adopted by runners during a self-paced endurance running. METHODS: Eighteen endurance runners were allocated into either strength training group (STG, n = 9) or control group (CG, n = 9) and performed the following tests before and after the training period: (a) incremental test, (b) running speed-constant test, (c) 10-km running time trial, (d) drop jump test, (e) 30-s Wingate anaerobic test, (f) maximum dynamic strength test (1RM). During 1RM, the electromyographic activity was measured. RESULTS: In the STG, the magnitude of improvement for 1RM (23.0 ± 4.2 %, P = 0.001), drop jump (12.7 ± 4.6 %, P = 0.039), and peak treadmill speed (2.9 ± 0.8 %, P = 0.013) was significantly higher compared to CG. This increase in the 1RM for STG was accompanied by a tendency to a higher electromyographic activity (P = 0.080). The magnitude of improvement for 10-km running performance was higher (2.5 %) for STG than for CG (-0.7 %, P = 0.039). Performance was improved mainly due to higher speeds during the last seven laps (last 2800 m) of the 10-km running trial. There were no significant differences between before and after training period for maximal oxygen uptake, respiratory compensation point, running economy, and anaerobic performance for both groups (P > 0.05). CONCLUSIONS: These findings suggest that a strength training program offers a potent stimulus to counteract fatigue during the last parts of a 10-km running race, resulting in an improved overall running performance.

Static stretching alters neuromuscular function and pacing strategy, but not performance during a 3-km running time-trial.

PURPOSE: Previous studies report that static stretching (SS) impairs running economy. Assuming that pacing strategy relies on rate of energy use, this study aimed to determine whether SS would modify pacing strategy and performance in a 3-km running time-trial. METHODS: Eleven recreational distance runners performed a) a constant-speed running test without previous SS and a maximal incremental treadmill test; b) an anthropometric assessment and a constant-speed running test with previous SS; c) a 3-km time-trial familiarization on an outdoor 400-m track; d and e) two 3-km time-trials, one with SS (experimental situation) and another without (control situation) previous static stretching. The order of the sessions d and e were randomized in a counterbalanced fashion. Sit-and-reach and drop jump tests were performed before the 3-km running time-trial in the control situation and before and after stretching exercises in the SS. Running economy, stride parameters, and electromyographic activity (EMG) of vastus medialis (VM), biceps femoris (BF) and gastrocnemius medialis (GA) were measured during the constant-speed tests. RESULTS: The overall running time did not change with condition (SS 11:35±00:31 s; control 11:28±00:41 s, p = 0.304), but the first 100 m was completed at a significantly lower velocity after SS. Surprisingly, SS did not modify the running economy, but the iEMG for the BF (+22.6%, p = 0.031), stride duration (+2.1%, p = 0.053) and range of motion (+11.1%, p = 0.0001) were significantly modified. Drop jump height decreased following SS (-9.2%, p = 0.001). CONCLUSION: Static stretch impaired neuromuscular function, resulting in a slow start during a 3-km running time-trial, thus demonstrating the fundamental role of the neuromuscular system in the self-selected speed during the initial phase of the race.

Impact of acute static-stretching on the optimal height in drop jumps / Impacto agudo do alongamento estático sobre a altura ideal de queda no salto em profundidade / Impacto agudo del estiramiento estático sobre la altura óptima de caída en el salto en profundidad

This study analyzed the effect of static stretching on performance during drop jumps. Furthermore, we investigated if a reduction in drop height would compensate the stretching-caused alterations. Ten physically active male subjects performed drop jumps at four different drop heights without static stretching for the optimal drop height determination. After, they performed drop jumps on two drop heights with static stretching previously. The jump height, contact time and reactive strength index were significantly affected by static stretching. However, only the contact time was significantly improved by the reduction in drop height with previous static stretching. Our results suggest that the decrement in performance after static stretching could be partially compensated by a reduction in drop height, which decreases the contact time near a non-stretching jump condition. This can be explained by the lower landing velocity and, possibly, the smaller reduction in the activation of the plantar flexors muscles. In conclusion, the reduction in drop height seems to be interesting after a static stretching session, aiming to expose the athletes to lower impact forces to maintain jump performance.

O presente estudo analisou o efeito do alongamento estático sobre o desempenho no salto em profundidade. Adicionalmente, foi investigada a redução na altura de queda poderia compensar as alterações causadas pelo alongamento prévio. Dez homens fisicamente ativos realizaram o salto em profundidade em quatro alturas de queda diferentes sem alongamento estático prévio, para determinação da altura de queda ideal, em duas alturas com o alongamento prévio. A altura de salto, o tempo de contato e o índice de força reativa foram significativamente afetados pelo alongamento estático. Contudo, apenas o tempo de contato foi significativamente melhorado com a redução na altura de queda do salto após o alongamento. Nossos resultados sugerem que a diminuição no desempenho após o alongamento pode ser parcialmente compensada com uma redução na altura de queda, diminuindo o tempo de contato para valores próximos ao salto sem alongamento prévio. Isso pode ser explicado pelo menor velocidade de aterrissagem e, possivelmente, pela menor redução na ativação dos músculos flexores plantares. Assim, a diminuição na altura de queda parece ser interessante após a realização do alongamento estático, visando submeter os atletas a menores forças de impacto e manter o desempenho do salto.

En este estudio se analizó el efecto del estiramiento estático sobre el rendimiento en saltos en profundidad. Además, se investigó si una reducción de la altura de caída compensaría las alteraciones causadas por el estiramiento previo. Diez hombres físicamente activos realizaron el salto en profundidad en cuatro alturas diferentes de caída sin estiramiento estático, para la determinación de la altura de caída óptima y en dos alturas con el estiramiento estático previo. La altura del salto, el tiempo de contacto y el índice de fuerza reactiva fueron afectados significativamente por el estiramiento estático. Sin embargo, sólo el tiempo de contacto mejoró significativamente por la reducción de la altura de caída del salto, después del estiramiento. Nuestros resultados sugieren quela disminución en el rendimiento después del estiramiento estático, podría ser parcialmente compensada con una reducción en la altura de caída, disminuyendo el tiempo de contacto para valores próximos al del salto sin estiramiento previo. Esto se puede explicar por la menor velocidad de aterrizaje y, posiblemente, por la menor reducción en la activación de los músculos flexores plantares. En conclusión, la reducción de la altura de caída parece ser interesante después de realizar una sesión de estiramientos estáticos, con el objetivo de someter a los atletas a menores fuerzas de impacto y mantener el rendimiento en el salto.

Pacing strategy determinants during a 10-km running time trial: contributions of perceived effort, physiological, and muscular parameters.

The purpose of this study was to identify the main determinants of the self-selected pacing strategy during a 10-km running time trial. Twenty eight male long-distance runners performed the following tests: (a) maximal incremental treadmill test, (b) economy running test, (c) maximum dynamic strength test, and (d) 10-km running time trial on an outdoor track. A stepwise multiple regression model was used to identify the contribution of rating of perceived exertion (RPE), physiological, and muscular parameters on the pacing strategy adopted by athletes. In the start phase (first 400 m), RPE accounted for 72% (p = 0.001) of the pacing variance. Peak treadmill speed (PTS) measured during a maximal incremental test explained 52% (p = 0.001) of the pacing variance during the middle phase (400-9,600 m), whereas maximal oxygen uptake and maximum dynamic strength accounted for additional 23% (p = 0.002) and 5% (p = 0.003), respectively. In the end phase (last 400 m), PTS accounted alone for 66% (p = 0.003) of the pacing variance. These data suggest that predictors of the pacing strategy during a 10-km running time trial have a transitional behavior from perceptive (start phase) to muscular and physiological factors (middle and end phases).