What can you do to keep cool during exercise in hot weather? Drink Accelerade and, in races, throw cold water on your body and put ice under your hat. But there may be something else: spraying yourself with menthol. That’s right, there is some research evidence that spraying a menthol solution either on the tongue or on the body induces cooling sensations that reduce perceived effort and elevate exercise performance in the heat. Researchers from the University of Portsmouth, England, recently tested two menthol sprays designed for this use. Surprisingly, the researchers found that use of the spray during 45 minutes of moderate-intensity exercise in warm conditions actually increased core body temperature while reducing the perceived body temperature. This leaves open the question whether using menthol sprays during exercise is helpful or not.

That’s an intriguing headline. What the heck does it mean? I’ll tell you. It is a well-established fact that women rely more on fat and less on muscle glycogen than men do to provide energy for moderate-intensity exercise. But a new study in Medicine & Science in Sports & Exercise reports that this gender difference in fuel selection disappears when carbohydrate is consumed during exercise. During moderate-intensity exercise without carbohydrate intake, men were found to get 62 percent of their energy from carbohydrate, women 53 percent. But when they drank a sports drink during exercise, carbohydrate burning increased to 74 percent in men and 77 percent in women. The much larger jump in women was due to the fact that consuming carbs during exercise caused a much smaller decrease in the use of muscle glycogen in women than in men.

You may have heard the recommendation that athletes consume 30 to 60 grams of carbohydrate per hour during exercise. This recommendation is based on laboratory studies on the rate of ingested carbohydrate burning during exercise. But most such studies have involved cycling, and it’s not safe to assume that the body burns ingested carbs at the same rate in all forms of exercise. So researchers from the University of Birmingham, England, recently compared the rates of ingested carbohydrate burning in athletes during two hours of cycling and two hours of running at 60 percent VO2max. They found that the athletes burned the carbs supplied by a sports drink at the same rate in the two different exercise modalities. So it appears that you can apply the 30-60 g CHO/hr rule to running as well as cycling.

Science has firmly established as fact that consuming carbohydrates during strenuous endurance exercise enhances performance. Recently some scientists have explored the idea that habitually withholding carbohydrate during training might enhance certain physiological adaptations to training and thereby ultimately improve race performance. Research on this question has so far provided little support for it. Some scientists think it more likely that habitually consuming carbohydrate during training might ultimately result in better race performance by allowing athletes to perform at a higher level in each session. Researchers from the Australian Institute of Sport recently put this conjecture to the test. The divided a pool of trained cyclists and triathletes into separate groups and had each of them go through a 28-day block of training, with one group consuming carbs during every workout and the other group abstaining from carbohydrate intake during workouts. Performance was measured before and at the end of the training block in a cycling time trial. The researchers found that performance improved equally–7 percent on average–in both groups despite greater increases in carbohydrate-burning capacity in the carb group. So it appears that the benefits of training with carbs are counterbalanced by those of training without. One wonders if there might be an additive effect associated with mixing carb-fueled and non-carb-fueled workouts in training.

Endurance athletes commonly use sports drinks and carbohydrate gels interchangeably to get the carbohydrate they need to maximize performance in workouts and races. But are the two types of ergogenic aids equally effective? Researchers from the University of Birmingham sought to answer this question in a recent study. Eight trained cyclists were asked to ride stationary bikes at a fixed moderate intensity for three hours on three occasions. During one ride they consumed carbohydrate gels plus water at a rate sufficient to provide 1.8 grams of carbohydrate per minute. During a second ride they consumed a sports drink also at a rate sufficient to supply 1.8 g of carbs per minute. And during a third ride the subjects drank water at a rate that equaled the fluid intake during the other two rides. The researchers found that the carbs supplied by the gels and drink were oxidized at the same rate and with equal efficiency. Thus they concluded that the two types of ergogenic aids can be used interchangeably. The study was published in Medicine & Science in Sports & Exercise.

While hot weather conditions increase the likelihood of dehydration during exercise by increasing sweat rate, it is also possible to become dehydrated in cool conditions. Scientists from the Army Research Institute recently studied the relative effects of dehydration on aerobic exercise performance at a variety of environmental temperatures. Subjects performed 15-minute cycling time trials following 30-minute warm-ups at four different environmental temperatures: 10 degrees Celcius, 20 degrees, 30 degrees, and 40 degrees. Those exercising at each temperature level did so on two occasions: once when fully hydrated and once when 4 percent dehydrated. The rearchers found that dehydration reduced performance by 3 percent at 10 degrees, 5 percent at 20 degrees, 12 percent at 30 degrees, and 23 percent at 40 degrees. Of course heat itself reduces aerobic performance, but this study showed that, independent of this effect, heat also increases the performance cost of being dehydrated. The lesson is that the hotter the weather is, the more important it is to stay as well hydrated as possible.

Dehydration is well known to reduce endurance exercise performance. This effect is usually blamed on the loss of blood volume that attends dehydration, which increases cardiovascular stress. However, newer research suggests that the negative effect of dehydration on performance may be partly mediated by the brain. Most recently, a new study by researchers at King’s College London has shown that when subjects perform a cognitive task immediately following a dehydration-inducing workout, a higher level of brain resources are required than when the same task is performed in a fully hydrated state. This is essentially a sign of mental fatigue, and other research has shown that mental fatigue negatively affects endurance performance as much as muscle fatigue.

A new study in Medicine & Science in Sports & Exercise shows that when it comes to taking in water before running in the heat, temperature matters. On two occasions, 10 male volunteers ran to exhaustion at ventilatory threshold intensity on treadmills in a hot environment. Before one test, they were given cold water. Before another, they were given even colder ice surries. On average, the subjects were able to run a full 10 minutes longer (50 minutes versus 40 minutes) after consuming the ice slurry. Interestingly, while the ice slurry initially lowered core body temperature compared to cold water, core temperature was higher at the end of the test in the runners after they had consumed the ice slurry.

It is often assumed that lower body temperature is associated with higher performance, but as these results indicate, that’s not really true, as core temperature is affected by exercise intensity, and higher exercise intensity is associated with both greater performance and higher core body temperature. So performance is enhanced both by measures that reduce the body temperature associated with a given exercise intensity and also by measures that increase the maximum tolerable body temperature during exercise.

Researchers from the University of Edinburgh, Scotland, recently studied the effects of a sports drink on endurance running and sprinting in adolescent team sport athletes. Fifteen subjects between the ages of 12 and 14 years participated in the study. On two separate occasions, they completed workouts consisting of four 15-minute segments of shuttle sprinting followed by a submaximal interval run to exhaustion. On one occasion the kids were given a sports drink to consume before the workout and during breaks between segments of the workout. On the other they were given flavored water. The researchers found that the sports drink had no effect on performance in the shuttle sprint segment of the workout, but it increased time to exhaustion by a massive 24.4 percent in the interval run portion. The authors of the study, which was published in the European Journal of Applied Physiology, concluded, “These results demonstrate, for the first time, that ingestion of a carbohydrate-electrolyte solution significantly improves the intermittent, high-intensity endurance running capacity of adolescent team games players during an exercise protocol designed to simulate the physiological demands of team games.”

It used to be that sports drinks were just sports drinks. Now there are several subcategories of sports drinks: regular, low-calorie, recovery, extended endurance, etc. One of the newer sports drink subcategories is the pre-exercise category. According to a new study published in the Journal of the International Society of Sports Nutrition, “Pre-exercise sports drinks (PRX) are commonly used as ergogenic aids in athletic competitions requiring aerobic power. However, in most cases, claims regarding their effectiveness have not been substantiated.”

The authors of this study set out to test the effectiveness of a specific PRX formulation. Twenty-nine college women performed treadmill tests on two occasions, consuming the PRX before one test and a placebo (flavored water) before the other. VO2max and time to exhaustion were both greater in the PRX trial. So there you have it.