Matthew R. Ely

Dose-dependent effect of caffeine on reducing leg muscle pain during cycling exercise is unrelated to systolic blood pressure

&NA; This double‐blind, within‐subjects experiment examined the effects of ingesting two doses of caffeine on perceptions of leg muscle pain and blood pressure during moderate intensity cycling exercise. Low caffeine consuming college‐aged males (N=12) ingested one of two doses of caffeine (5 or 10 mg·kg−1 body weight) or placebo and 1 h later completed 30 min of moderate intensity cycling exercise (60% Symbol). The order of drug administration was counter‐balanced. Resting blood pressure and heart rate were recorded immediately before and 1 h after drug administration. Perceptions of leg muscle pain as well as work rate, blood pressure, heart rate, and oxygen uptake Symbol were recorded during exercise. Caffeine increased resting systolic pressure in a dose‐dependent fashion but these blood pressure effects were not maintained during exercise. Caffeine had a significant linear effect on leg muscle pain ratings [F(2,22)=14.06; P<0.0001; &eegr;2=0.56]. The mean (±SD) pain intensity scores during exercise after ingesting 10 mg·kg−1 body weight caffeine, 5 mg·kg−1 body weight caffeine, and placebo were 2.1±1.4, 2.6±1.5, and 3.5±1.7, respectively. The results support the conclusion that caffeine ingestion has a dose–response effect on reducing leg muscle pain during exercise and that these effects do not depend on caffeine‐induced increases in systolic blood pressure during exercise. Symbol. No caption available. Symbol. No caption available.

Effect of Air Pollution on Marathon Running Performance

UNLABELLED Before the 2008 Olympic Games, there was concern that air pollution in Beijing would affect the performance of marathon runners. Air pollutant concentrations during marathon running and their effect on performance have not been reported. Evidence suggests that the lung function of females may be more susceptible than that of males to air pollution, but it is uncertain if this translates to decreased marathon performance. PURPOSE The purposes of this study were to 1) describe ambient air pollutant concentrations present during major US marathons, 2) quantify performance decrements associated with air pollutants, and 3) examine potential sex difference in performance related to air pollutants. METHODS Marathon race results, weather data, and air pollutant concentrations were obtained for seven marathons for 8-28 yr. The top three male and female finishing times were compared with the course record and contrasted with air pollutant levels and wet bulb globe temperature (WBGT). A WBGT-adjusted performance decrement was calculated, and regression analysis was used to quantify performance decrements associated with pollutants. RESULTS The air pollutant concentrations of carbon monoxide, ozone, particulate matter smaller than 10 microm (PM(10)), PM(2.5), nitrogen dioxide, and sulfur dioxide ranged from 0 to 5.9 ppm, from 0 to 0.07 ppm, from 4.5 to 41.0 microg x m(-3), from 2.8 to 42.0 microg x m(-3), from 0 to 0.06 ppm, and from 0 to 0.05 ppm, respectively. After adjusting for WBGT-associated performance decrements, only PM(10) was associated with decrements in performance of women. For every 10-microg x m(-3) increase in PM(10), performance can be expected to decrease by 1.4%. CONCLUSIONS The concentrations of air pollution present during marathons rarely exceed health-based national standards and levels known to affect lung function in laboratory situations. Regardless, PM(10) was significantly correlated with performance of women marathon runners.

Marathon Performance in Thermally Stressing Conditions

It is generally appreciated that warm weather negatively affects marathon running performance. This brief review summarises the historical literature on this topic and recent work that our laboratory has performed to quantify the impact of weather on marathon running performance. Using 140 race-years of data, we have demonstrated that marathon performance times slow progressively as weather warms above 5–10°C wet bulb globe temperature, that men and women are affected similarly, but slower runners suffer a greater performance penalty than elite runners. The recent generation of a nomogram that predicts changes in finishing time consequent to changes in weather conditions offers runners and coaches a tool for use in developing marathon race strategy.

Surface contamination artificially elevates initial sweat mineral concentrations

Several sweat mineral element concentrations decline with serial sampling. Possible causes include reduced dermal mineral concentrations or flushing of surface contamination. The purpose of this study was to simultaneously sample mineral concentrations in transdermal fluid (TDF), sweat, and serum during extended exercise-heat stress to determine if these compartments show the same serial changes during repeat sampling. Sixteen heat-acclimated individuals walked on a treadmill (1.56 m/s, 3.0% grade) in a 35°C, 20% relative humidity (RH), 1 m/s wind environment 50 min each hour for 3 h. Mineral concentrations of Ca, Cu, Fe, K, Mg, Na, and Zn were measured each hour from serum, sweat from upper back (sweat pouch) and arm (bag), and TDF from the upper back. Sites were meticulously cleaned to minimize surface contamination. Mineral concentrations were determined by spectrometry. TDF remained stable over time, with exception of a modest increase in TDF [Fe] (15%) and decrease in TDF [Zn] (-18%). Likewise, serum and pouch sweat samples were stable over time. In contrast, the initial arm bag sweat mineral concentrations were greater than those in the sweat pouch, and [Ca], [Cu], [Mg], and [Zn] declined 26-76% from initial to the subsequent samples, becoming similar to sweat pouch. Nominal TDF mineral shifts do not affect sweat mineral concentrations. Arm bag sweat mineral concentrations are initially elevated due to skin surface contaminants that are not removed despite meticulous cleaning (e.g., under fingernails, on arm hair), then decrease with extended sweating and approach those measured from the scapular region.

A retrospective cohort study on the influence of UV index and race/ethnicity on risk of stress and lower limb fractures

BackgroundLow vitamin D status increases the risk of stress fractures. As ultraviolet (UV) light is required for vitamin D synthesis, low UV light availability is thought to increase the risk of vitamin D insufficiency and poor bone health. The purpose of this investigation was to determine if individuals with low UV intensity at their home of record (HOR) or those with darker complexions are at increased risk of developing stress fractures and lower limb fractures during U.S. Army Basic Combat Training (BCT).MethodsThis was a retrospective cohort study using the Armed Forces Health Surveillance Center data repository. All Basic trainees were identified from January 1997 to January 2007. Cases were recruits diagnosed with stress fractures and lower limb fractures during BCT. The recruit’s home of record (HOR) was identified from the Defense Manpower Data Center database. The average annual UV intensity at the recruits’ HOR was determined using a U.S National Weather Service database and recruits were stratified into low (≤3.9); moderate (4.0-5.4), and high (≥5.5) UV index regions. Race was determined from self-reports.ResultsThe dataset had 421,461 men and 90,141women. Compared to men, women had greater risk of developing stress fractures (odds ratio (OR) = 4.5, 95% confidence interval (95%CI) = 4.4-4.7, p < 0.01). Contrary to the hypothesized effect, male and female recruits from low UV index areas had a slightly lower risk of stress fractures (male OR (low UV/high UV) = 0.92, 95%CI = 0.87-0.97; females OR = 0.89, 95%CI = 0.84-0.95, p < 0.01) and were at similar risk for lower limb fractures (male OR = 0.98, 95%CI = 0.89-1.07; female OR = 0.93, 95%CI = 0.80-1.09) than recruits from high UV index areas. Blacks had lower risk of stress and lower limb fractures than non-blacks, and there was no indication that Blacks from low UV areas were at increased risk for bone injuries.ConclusionsThe UV index at home of record is not associated with stress or lower limb fractures in BCT. These data suggest that UV intensity is not a risk factor for poor bone health in younger American adults.