Keeping Cool While Working Out

Workout clothing choice is important if you exercise in the heat

Choosing the right workout gear is important for healthy exercise. Clothing that traps heat may raise body temperature and even cause heat strokes.

Some sports clothing brands claim they can improve your performance by keeping you cool and dry. A new report looks at whether those claims are true.

Researchers used previous studies to see how natural materials like cotton and wool stacked up against synthetic ones like polyester. They paid special attention to body temperature and comfort to see what clothing is best for exercise.

They found that there is often no difference in comfort or coolness between cotton and synthetic fabrics, though synthetic fabrics are usually more expensive.

"Exercise in clothing that stays dry and allows for air flow."

Jon-Kyle Davis, PhD, and Phillip Bishop, EdD, conducted this review to see whether certain kinds of clothing are better for exercise than others.

Some sports clothing brands have said that their products keep exercisers dry, cool and comfortable in the heat. According to the companies, their sports clothing "wicks" sweat away through the material so that more air can flow through the garment.

Most of the fabrics are synthetic, or made from plastic, like polyester.

Keeping body temperature at a normal level is important for health, especially during exercise. Working out in the hot sun can cause heat stroke, a painful condition in which a person feels nauseous, confused and exhausted.

Exposure to extreme heat while exercising can even result in death.

The body naturally cools itself through sweat, but clothing can interfere with that process.

This report looked at previous studies to see how the construction of clothing and the type of fabric used affected "thermal balance," or how well the body cools itself during exercise. The authors also took the clothing wearer's comfort into account.

The information they gathered from previous studies compared polyester and cotton fabrics and different knit sizes.

They found that larger-knit fabrics generally left the wearer cooler, because air was able to circulate more easily through the garment.

Additionally, the report found that cotton can absorb more moisture than polyester, which is crucial in the cooling process. However, cotton also took longer to dry, and the absorbed sweat trapped heat.

Another study built off this finding and tried to identify a mix of fabrics that would be best at absorbing and wicking sweat. That study found that a 92 percent nylon and 8 percent spandex fabric blend worked well at promoting cooling.

Some studies that the researchers examined compared the wearer's comfort with different types of fabrics. In some of these studies, people reported chafing while wearing cotton because the fabric holds moisture for a longer time. However, comfort depends heavily on individual preference and the type and intensity of exercise.

Ultimately, the report found that there was no significant difference between cotton fabrics and synthetic fabrics on health, athletic performance or comfort.

Some studies found that synthetic fabrics kept skin temperature cooler. But core body temperature, which is more important for avoiding heat stroke, remained the same.

This report was published on April 26 in the journal Sports Medicine.

No funding sources were used to prepare the review. The authors did not disclose any direct conflicts of interest.

Review Date: 
August 4, 2013