Welcome to the second sport science alert newsletter for 2015 from Topend Sports, the ultimate online sport and science resource. While currently living in hot and humid Indonesia, I have become acutely aware of the differences in weather around the world. Recently, I sat in the scorching sun watching my daughter's end of year school assembly while she was singing about a white Christmas! Then back at my desk under a fan reading about the issues of frozen footballs in the USA, at the same time as tennis players sweltering on centre court at the Australian Open.

The environment can have a significant impact on athletic performance, and at this time of year there are extremes at both ends of the spectrum, and as coaches, sport scientists and fitness trainers we need to be aware of the impact that it can have on athletes.

In the News

American Footballs: There was a big controversy this week in the US about under-inflated footballs. The NFL found that 11 of the Patriots' 12 game balls were inflated significantly below the NFL's requirements. The club is being accused of ball tampering, though a sports physicist has chimed into the discussion saying that temperature may have caused the deflation. Temperature can affect more than just the football pressure. Football players have a long history of competing in harsh winter weather, and such conditions can have a range of effects on the players, such as reducing core body temperature, reaction time and grip strength. These issues are discussed in our feature video below.

On Topend Sports

• The Australian Open Heat Policy: guidelines about under what conditions to stop matches.
• Winter Weather Workouts: considerations while exercising in cold weather.
• Altitude Nutrition: tips for athletes performing at altitude.

Measuring Heat: WBGT

The Wet Bulb Globe Temperature (WBGT) is a composite temperature used to estimate the effect of temperature, humidity, and solar radiation on humans. The WBGT is measured by a simple 3-temperature element device The natural wet-bulb temperature (Tw), which consists of a thermometer with its bulb covered with a wettened cotton wick The black globe temperature (Tg), which usually consists of black globe with a thermometer located at the center. The (shade) air temperature (Ta), which consists of a thermometer shielded from radiation Using the results from these three elements, you can determine WBGT using this formula: WBGT = (0.7 × Tw) + (0.2 × Tg) + (0.1 × Ta)

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