Prior Exercise Reduces Fast-Start Duration and End-Spurt Magnitude during Cycling Time-Trial

We examined the pacing strategy and the magnitude of the end spurt during a 200-kJ cycling time trial performed 12–14 h after an exercise protocol designed to reduce muscle glycogen content. 9 physically-active men performed 5 familiarization sessions and 2 experimental 200-kJ time trials in either a control condition (CON) or after an exercise protocol performed the previous evening that was designed to induce muscle glycogen depletion (EP). Mean total time was faster and power output was higher in the CON than in the EP (P<0.01). A fast-start was maintained until the 50-kJ section in CON, but only the 25-kJ section for EP (P<0.05). The power outputs during the 50-, 150- and 200-kJ sections, and the magnitude of the end-spurt, were significantly higher for the CON than for the EP condition (P<0.05). There was no significant difference in the rating of perceived exertion (overall feeling and feeling in legs) between conditions. In conclusion, a protocol designed to decrease muscle glycogen stores reduced the duration of the fast-start and the magnitude of the end spurt during a 200-kJ cycling time trial, impairing the overall performance

Effect of Time of Day on Performance, Hormonal and Metabolic Response during a 1000-M Cycling Time Trial

The aim of this study was to determine the effect of time of day on performance, pacing, and hormonal and metabolic responses during a 1000-m cycling time-trial. Nine male, recreational cyclists visited the laboratory four times. During the 1st visit the participants performed an incremental test and during the 2nd visit they performed a 1000-m cycling familiarization trial. On the 3rd and 4th visits, the participants performed a 1000-m TT at either 8 am or 6 pm, in randomized, repeated-measures, crossover design. the time to complete the time trial was lower in the evening than in the morning (88.2 +/- 8.7 versus 94.7 +/- 10.9 s, respectively, p<0.05), but there was no significant different in pacing. However, oxygen uptake and aerobic mechanical power output at 600 and 1000 m tended to be higher in the evening (p<0.07 and 0.09, respectively). There was also a main effect of time of day for insulin, cortisol, and total and free testosterone concentration, which were all higher in the morning (+60%, +26%, +31% and +22%, respectively, p<0.05). the growth hormone, was twofold higher in the evening (p<0.05). the plasma glucose was similar to 11% lower in the morning (p<0.05). Glucagon, norepinephrine, epinephrine and lactate were similar for the morning and evening trials (p<0.05), but the norepinephrine response to the exercise was increased in the morning (+46%, p<0.05), and it was accompanied by a 5-fold increase in the response of glucose. Muscle recruitment, as measured by electromyography, was similar between morning and evening trials (p<0.05). Our findings suggest that performance was improved in the evening, and it was accompanied by an improved hormonal and metabolic milieu.Alagoas Research Foundation (FAPEAL)Univ Fed Alagoas, Sports Sci Res Grp, Maceio, Alagoas, BrazilUniv Fed Pernambuco, CAV, Dept Phys Educ & Sports Sci, Vitoria de Santo Anta, PE, BrazilUniv São Paulo, Sch Phys Educ & Sport, Endurance Performance Res Grp, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilVictoria Univ, Inst Sport Exercise & Act Living, Melbourne, Vic 8001, AustraliaUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilAlagoas Research Foundation (FAPEAL): 20110825-011-0025-0004Web of Scienc

Prior Low- or High-Intensity Exercise Alters Pacing Strategy, Energy System Contribution and Performance during a 4-km Cycling Time Trial

We analyzed the influence of prior exercise designed to reduce predominantly muscle glycogen in either type I or II fibers on pacing and performance during a 4-km cycling time trial (TT). After preliminary and familiarization trials, in a randomized, repeated-measures crossover design, ten amateur cyclists performed: 1) an exercise designed to reduce glycogen of type I muscle fibers, followed by a 4-km TT (EX-FIB I); 2) an exercise designed to reduce glycogen of type II muscle fibers, followed by a 4-km TT (EX-FIB II) and; 3) a 4-km TT, without the prior exercise (CONT). the muscle-glycogen-reducing exercise in both EX-FIB I and EX-FIB II was performed in the evening, similar to 12 h before the 4-km TT. Performance time was increased and power output (PO) was reduced in EX-FIB I (432.8 +/- 8.3 s and 204.9 +/- 10.9 W) and EX-FIB II (428.7 +/- 6.7 s and 207.5 +/- 9.1 W) compared to CONT (420.8 +/- 6.4 s and 218.4 +/- 9.3 W; P0.05). the PO was lower in EX-FIB I than in CONT at the beginning and middle of the trial (P0.05). the integrated electromyography was unchanged between conditions (P>0.05). Performance may have been impaired in EX-FIB I due a more conservative pacing at the beginning and middle, which was associated with a reduced aerobic contribution. in turn, the PO profile adopted in EX-FIB II was also reduced throughout the trial, but the impairment in performance may be attributed to a reduced glycolytic contribution (i.e. reduced lactate accumulation).Foundation of Aids to Scientific Research of the State of Alagoas (FAPEAL)Univ Fed Pernambuco, CAV, Dept Phys Educ & Sports Sci, Sports Sci Res Grp, Vitoria de Santo Antao, Pernambuco, BrazilUniv São Paulo, Sch Phys Educ & Sport, Endurance Performance Res Grp, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilVictoria Univ, Coll Sport & Exercise Sci, Inst Sport Exercise & Active Living, Melbourne, Vic 8001, AustraliaUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilWeb of Scienc

Strength-Training with Whole-Body Vibration in Long-Distance Runners: A Randomized Trial

A parallel group randomized trial was designed to analyze the impact of 6 weeks of strength training programs performed with or without whole-body vibration on muscular and endurance performance parameters in long-distance runners. 22 endurance runners were allocated into strength with whole-body vibration (n=8), without (n=8), and control (n=6) groups. Before and after the experimental period the subjects performed the following tests: a) maximum dynamic strength test, b) maximal incremental treadmill test, and c) time to exhaustion at velocity corresponding to maximal oxygen uptake. The fractions of the aerobic and anaerobic contribution in time to exhaustion test were also calculated. Both strength trained groups showed a similar increase in maximum dynamic strength (~18%). The aerobic contribution was enhanced for strength training group without whole-body vibration (~25%) after experimental period. No statistical differences were observed in any other variable. These results suggest that 6 weeks of strength training performed with or without whole-body vibration improve similarly the maximum dynamic strength in long-distance runners. In addition, both training modes studied had no deleterious effects on the traditional parameters of endurance performance, traditional strength training program results in increased aerobic contribution during high-intensity aerobic exercise

Psychological and psychophysiological mechanisms underlying the effects of meditation during moderate-intensity exercise

The present experiment sought to further understanding of the psychological and psychophysiological mechanisms underlying the effects of a single session of audio-guided meditation during moderate-intensity cycling exercise. Twenty-four healthy participants were recruited. A portable EEG device was employed to investigate the cerebral responses associated with the effects of meditation on exercise. Psychological measures were administered at three timepoints during the exercise bout. Two experimental conditions (endurance meditation [EM] and catastrophic meditation [CM]) and a control condition (CO) were administered. Participants were asked to exercise for 8 min (2 min of warm-up performed at 20% below the first ventilatory threshold + 6 min of exercise performed at the first ventilatory threshold) at 60 rpm. The EEG signal from frontal electrode sites was decomposed using Morlet Complex Wavelets, and event-related perturbation was calculated to investigate changes in beta frequency associated with the cycling phase. The results indicate that EM was sufficiently potent to ameliorate exertion and enhance affect to a greater degree than CO and CM. The neural mechanisms underlying the effects of EM appear to be associated with increased beta activity in the right frontal regions. The results of this study also indicate that exertional fatigue can be modulated through an alternative route that is not reliant upon the use of dissociative thoughts and does not require motivation to be up-regulated

Energy systems contributions in 2,000 m race simulation: a comparison among rowing ergometers and water

This study investigated the energy system contributions of rowers in three different conditions: rowing on an ergometer without and with the slide and rowing in the water. For this purpose, eight rowers were submitted to 2,000 m race simulations in each of the situations defined above. The fractions of the aerobic (W(AER)), anaerobic alactic (W(PCR)) and anaerobic lactic (W([La-])) systems were calculated based on the oxygen uptake, the fast component of excess post-exercise oxygen uptake and changes in net blood lactate, respectively. In the water, the metabolic work was significantly higher [(851 (82) kJ] than during both ergometer [674 (60) kJ] and ergometer with slide [663 (65) kJ] (P <= 0.05). The time in the water [515 (11) s] was higher (P < 0.001) than in the ergometers with [398 (10) s] and without the slide [402 (15) s], resulting in no difference when relative energy expenditure was considered: in the water [99 (9) kJ min(-1)], ergometer without the slide [99.6 (9) kJ min(-1)] and ergometer with the slide [100.2 (9.6) kJ min(-1)]. The respective contributions of the WAER, WPCR and W[La-] systems were water = 87 (2), 7 (2) and 6 (2)%, ergometer = 84 (2), 7 (2) and 9 (2)%, and ergometer with the slide = 84 (2), 7 (2) and 9 (1)%. (V) over dotO(2), HR and lactate were not different among conditions. These results seem to indicate that the ergometer braking system simulates conditions of a bigger and faster boat and not a single scull. Probably, a 2,500 m test should be used to properly simulate in the water single-scull race.CNPq[470572/2007-8

Metabolismo do lactato: uma revisão sobre a bioenergética e a fadiga muscular

O objetivo desse trabalho foi apresentar os principais eventos que envolvem o metabolismo do lactato muscular, de modo a favorecer a compreensão acerca da utilização das concentrações sangüíneas de lactato ([La-]) na estimativa do metabolismo anaeróbio lático e a sua possível relação com a fadiga muscular aguda. Tradicionalmente, o aumento das [La-] esteve associado à redução do oxigênio mitocondrial. Porém, outros estudos demonstraram que demais substâncias, tais como a epinefrina e o fosfato inorgânico, são capazes de elevarem as [La-]. A associação entre o lactato e o processo de fadiga muscular esteve baseada no aumento da acidose celular. No entanto, investigações recentes demonstraram que a acidose é capaz de restabelecer parcialmente a contração de músculos isolados e estimulados eletricamente. Nesse sentido, talvez a utilização das [La-] na estimativa da contribuição do metabolismo anaeróbio lático seja limitada, bem como a relação deste metabólito com a fadiga muscular possa ser casual

Caffeine during High-Intensity Whole-Body Exercise: An Integrative Approach beyond the Central Nervous System

Caffeine is one of the most consumed ergogenic aids around the world. Many studies support the ergogenic effect of caffeine over a large spectrum of exercise types. While the stimulatory effect of caffeine on the central nervous system is the well-accepted mechanism explaining improvements in exercise performance during high-intensity whole-body exercise, in which other physiological systems such as pulmonary, cardiovascular, and muscular systems are maximally activated, a direct effect of caffeine on such systems cannot be ignored. A better understanding of the effects of caffeine on multiple physiological systems during high-intensity whole-body exercise might help to expand its use in different sporting contexts (e.g., competitions in different environments, such as altitude) or even assist the treatment of some diseases (e.g., chronic obstructive pulmonary disease). In the present narrative review, we explore the potential effects of caffeine on the pulmonary, cardiovascular, and muscular systems, and describe how such alterations may interact and thus contribute to the ergogenic effects of caffeine during high-intensity whole-body exercise. This integrative approach provides insights regarding how caffeine influences endurance performance and may drive further studies exploring its mechanisms of action in a broader perspective