Comparative effects of caffeine and albuterol on the bronchoconstrictor response to exercise in asthmatic athletes

The main aim of this study was to evaluate the comparative and additive effects of caffeine and albuterol (short-acting beta (2)-agonist) on the severity of EIB. Ten asthmatic subjects with EIB (exercise-induced bronchoconstriction) participated in a randomized, double-blind, double-dummy crossover study. One hour before an exercise challenge, each subject was given 0, 3, 6, or 9 mg/kg of caffeine or placebo mixed in a flavored sugar drink. Fifteen minutes before the exercise bout, an inhaler containing either albuterol (180 microg) or placebo was administered to each subject. Pulmonary function tests were conducted pre- and post-exercise. Caffeine at a dose of 6 and 9 mg/kg significantly reduced (p0.05) in the post-exercise % fall in FEV (1) between albuterol ( PLUS CAFFEINE PLACEBO) (-4.0+/-5.2%) and the 9 mg/kg dose of caffeine (-6.8+/-6.5%). Interestingly, there was no significant difference (p>0.05) in the post-exercise % fall in FEV (1) between albuterol ( PLUS CAFFEINE PLACEBO) (-4.0+/-5.2%) and albuterol with 3, 6 or 9 mg/kg of caffeine (-4.4+/-3.8, -6.8+/-5.6, -4.4+/-6.0% respectively). Similar changes were observed for the post-exercise % fall in FVC, FEF (25-75%) and PEF. These data indicate that moderate (6 mg/kg) to high doses (9 mg/kg) of caffeine provide a significant protective effect against EIB. It is feasible that the negative effects of daily use of short-acting beta (2)-agonists by asthmatic athletes could be reduced simply by increasing caffeine consumption prior to exercise

Temperature dependence of soleus H-reflex and M wave in young and older women

The purpose of this study was to investigate the effect of altered local temperature on soleus H-reflex and compound muscle action potential (M wave) in young and older women. H-reflex and M wave responses were elicited in 10 young (22.3±3.3 years) and 10 older (72.5±3.2 years) women at three muscle temperatures: control (34.2±0.3°C), cold (31.3±0.5°C) and warm (37.1±0.2°C). H-reflex output, expressed as the ratio between maximal H-reflex and maximal M wave (Hmax/Mmax), was lower in the older, compared with the younger, group, regardless of temperature. In control temperature conditions, for example, the Hmax/Mmax ratio was 36.8±24% in the young and 25.4±20% in the older (P<0.05). Warming had no effect on the H-reflex output in either group, whilst cooling increased H-reflex output only in the younger group (+28%). In both groups, cooling increased (+5.3%), and warming decreased (-5.5%) the H-reflex latency. This study confirms that older individuals experience a reduced ability to modulate the reflex output in response to a perturbation. In a cold environment, for example, the lack of facilitation in the reflex output, along with a delayed reflex response could be critical to an older individual in responding to postural perturbations thus potentially compromising both static and dynamic balance