Abstract--This study analyzed the effect of different repetition durations on electromyographic and blood lactate responses of the bench press exercise. Fifteen recreationally trained male volunteers completed two training protocols, matched for intensity (% one-repetition maximum; 1RM), number of sets, number of repetitions, and rest intervals. One of the protocols was performed with a repetition duration of 4 s (2 s concentric: 2 s eccentric; 2:2 protocol), whereas the second protocol had a repetition duration of 6 s (2 s concentric: 4 s eccentric; 2:4 protocol). The results showed higher normalized integrated electromyography (pectoralis major and triceps brachii) for the 2:4 protocol. Blood lactate concentration was also higher in the 2:4 protocol across all sets. These results show that adding 2 s to the eccentric action in matched training protocols increases muscle activation and blood lactate response, which reinforces the notion that increasing repetition duration is an alternative load progression in resistance training.

Deep hypothermic circulatory arrest (DHCA) is a technique of extracorporeal circulation commonly used in children with complex congenital heart defects undergoing surgical repairs. The use of profound cooling (20 degrees C) and complete cessation of circulation allow adequate exposure and correction of these complex lesions, with enhanced cerebral protection. However, the profound physiologic state of DHCA results in significant derangement of the coagulation system and a high incidence of postoperative bleeding. This review examines the impact of DHCA on bleeding and transfusion requirements in children and the pathophysiology of DHCA-induced platelet dysfunction. It also focuses on possible pharmacologic interventions to decrease bleeding following DHCA in children.

This study investigated the effect of different repetition durations on ratings of perceived exertion (RPE) in active muscles (RPE-AM) and the overall body (RPE-O). 19 male volunteers (M age = 25.4 yr., SD = 3.5) performed strength training protocols with multiple sets matched by the number of sets and repetitions, intensity and rest interval but different repetition durations: 4 sec., 6 sec., or self-paced. Participants were asked to estimate their RPE-AM and RPE-O after each set. Training protocols with a 6-sec. repetition duration produced distinct responses on RPE during and after performance compared to 4-sec. and self-paced durations. However, there were no significant differences between 4-sec. and self-paced durations.

We investigated brain mechanisms modulating fatigue during prolonged physical exercise in cold environments. In a first set of studies, each rat was subjected to three running trials in different ambient temperatures (T(a)). At 8 °C and 15 °C, core body temperature (T(core)) decreased and increased, respectively, whereas at 12 °C, the T(core) did not change throughout the exercise. In another set of experiments, rats were randomly assigned to receive bilateral 0.2 μL injections of 2.5 × 10(-2) M methylatropine or 0.15 M NaCl solution into the ventromedial hypothalamic nuclei (VMH). Immediately after the injections, treadmill exercise was started. Each animal was subjected to two experimental trials at one of the following T(a) : 5 °C, 12 °C or 15 °C. Muscarinic blockade of the VMH reduced the time to fatigue (TF) in cold environments by 35-37%. In all T(a) studied, methylatropine-treated rats did not present alterations in T(core) and tail skin temperature compared with controls. These results indicate that, below the zone of thermoneutrality, muscarinic blockade of the VMH decreases the TF, independent of changes in T(core). In conclusion, our data suggest that VMH muscarinic transmission modulates physical performance, even when the effects of thermoregulatory adjustments on fatigue are minimal.

ArticlesClinical Investigation nature publishing group INTRODUCTION: Magnetic resonance imaging (MRI) and spectroscopy (MRs) have proven valuable in evaluating neonatal hypoxic-ischemic injury (hII). RESULTS: MRI scores in the basal ganglia of hII/hT + neonates were significantly lower than hII/hT − neonates, indicating less severe injury and were associated with lower discharge encephalopathy severity scores in the hII/hT + group (P = 0.01). Lactate (Lac) was detected in the occipital gray matter (OGM) and thalamus (Th) of significantly more hII/hT − neonates (31.6 and 35.3%) as compared to the hII/hT + group (10.5 and 15.8%). In contrast, the N-acetylaspartate (Naa)-based ratios in the OGM and Th did not differ between the hII groups. DISCUSSION: Our data show that the hT was associated with a decrease in the number of hII neonates with detectable cortical and subcortical Lac as well as a decrease in the number of MRI-detectable subcortical lesions. METHODS:We retrospectively compared the medical and neuroimaging data of 19 hII neonates who received 72 h of wholebody cooling (hII/hT + ) with those of 19 noncooled hII neonates (hII/hT − ) to determine whether hypothermia was associated with improved recovery from the injury as measured by MRI and MRs within the first 14 days of life. MRI scores and metabolite ratios of hII/hT + and hII/hT − neonates were also compared with nine healthy, nonasphyxiated "control" neonates.