Heat Stress Danger: Red Flag, Stop Rowing

Preventing heat stress for rowers includes staying aware of conditions and communicating when to reduce or stop rowing practices or competitions. NK’s Kestrel Heat Stress Flag Kit is the perfect tool.

Hammering down a 1,000 m or 2,000 m racecourse, there are many things to pay attention to besides your bursting lungs and screaming legs. You must stay straight in your lane, know your progress down the course, and sense where your competitors are. You also need to watch for any signals from the Referee or Umpire following the racers down the course. The Umpire uses a white flag to direct a boat veering out of its lane and potentially interfering with another boat. The white flag is also used to stop any one crew to ensure the competitors' safety and prevent damage to boats and equipment. If the entire race must be stopped, the Umpire raises a red flag. That means everyone stops rowing.

Another important reason to raise the red flag is when rowers are at risk of heat stress. The risk of heat stress has amplified with record-shattering temperatures scorching much of North America and Europe. Athletes, coaches, tourists and those working outdoors have all been learning about the real dangers of being active outside in high heat and humidity. There are things that can be done to reduce the impact of heat, plus there are useful tools available.

Heat Stress for Rowers

The symptoms for heat-related illnesses are becoming familiar. But information on prevention, recognizing signs and addressing heat stroke or stress bears repeating, especially specific to rowing.

Dehydration can lead to heat exhaustion, characterized by some combination of cramps, fatigue, headache, light-headedness, nausea, dry mouth, and even vomiting. Sweating may continue, but skin can also be cool and pale. Heat stroke is the next stage and is very serious. Body temperature has risen to where body organs are impacted. The person might collapse or be very confused, even hallucinating. This is a medical emergency. Even with an ambulance on the way, the person must be cooled immediately. While dehydration is a frequent trigger, heat-related illnesses can occur in a well hydrated athlete who is exercising in extreme heat or humidity. Concern is greater for junior rowers and older masters rowers, but anyone can be impacted during training and racing, including Umpires in their blazers.

Raising the yellow flag at the US Rowing Youth Nationals in Sarasota, FL.

Prevention is Key

British Rowing distills prevention of heat stress for rowers into three key topics: stay hydrated; keep cool; and acclimate. Kestrel Instruments sources a more extensive list developed by the Korey Stringer Institute and useful for all sports.

An important way to prevent heat-related illnesses is to reduce or stop the activity. Rowing Australia clearly states in its Extreme Heat Recommendations that regatta organizers have a duty of care. The same could be said for coaches during training sessions. How does someone in a position of responsibility know when to limit or stop the rowing? It is especially challenging to make that call during a regatta, so good data and clear guidelines are necessary on when to raise the red flag and make everyone stop rowing. The same applies to rowing practices.

Measurement

Extreme heat alone can be dangerous. Even more significant is heat in combination with humidity, solar radiation and/or wind. There are three main measures: Heat Index, Humidex and WBGT or Wet Bulb Globe Temperature. They are not the same, but all three are useful.

Heat Index: The heat index, also known as the "apparent temperature" or "feels-like temperature," is a measure of how hot it feels to the human body when relative humidity is factored in with the actual air temperature.

It is often used to assess the perceived discomfort and health risks associated with high temperatures and humidity, especially during hot and humid weather conditions.

The heat index provides a more accurate representation of the heat's impact on the human body than the actual air temperature alone.

Humidex: Humidex, short for "humidity index," is a measurement used to express the combined effects of high temperature and high humidity on human comfort and health.

It quantifies the perceived level of discomfort caused by the heat and humidity by providing a single numerical value that represents the apparent temperature.

A higher humidex value indicates a greater level of discomfort and an increased risk of heat-related illnesses.

WBGT (Wet Bulb Globe Temperature): WBGT is a composite temperature measurement that takes into account multiple environmental factors to assess heat stress and its potential effects on the human body.

It incorporates readings from three different temperature sensors: the wet bulb temperature, the dry bulb temperature, and the globe temperature.

WBGT is particularly important in occupational settings, sports, and military operations, where it helps determine safe work and activity levels in hot and humid conditions.

The Kestrel 5400 Heat Stress Tracker

WBGT is considered the most accurate measurement for assessing heat stress risk because it takes into account not only the ambient temperature but also factors in humidity, wind speed, and radiant heat from the sun, providing a comprehensive and precise evaluation of the heat's impact on the human body in various environments.

The best measure of heat stress risk is the WBGT. It is the one typically used in athletics, military, and occupational health regulations. It takes into account air temperature, air movement, radiant heat and humidity. WBGT can be measured directly with instruments such as the Kestrel 5400 Heat Stress Tracker. Kestrel Instruments is a division of Nielsen-Kellerman, so you expect the same level of precision that you count on with your NK Sports instruments. The Heat Stress Tracker is used by the NFL, can be used as a handheld device, mounted on tripods as is done for the Boston Marathon, or connected to a wall-mounted tablet display which is particularly useful for workplace safety.

The Kestrel Heat Stress Flag Kit comes with color-coded flags to represent varying levels of heat safety.

Heat Index and Humidex are similar but still not the same. Both are measured in the shade, unlike WBGT, which is measured in the sun. Both factor in heat and the relative humidity. Both are often expressed as “feels like” measurement provided in weather forecasts. Which measure is used very much depends on where you live or where you go to row. For example, the United States uses Heat Index based on the Fahrenheit scale for temperature. The calculation includes other variables but a key one is the vapour pressure or dew point. In Canada the Humidex is calculated just on temperature in Celsius and dew point, but one which is lower than that used in the American heat index.

But the rowing association recommends using Heat Index as a measurement because it is easily accessible for event managers or others to monitor at regattas. Let’s talk more about that below.

Communication

Regardless of whether you measure the WBGT or think in terms of Heat Index or Humidex, interpretation of those measurements and what it means regarding heat stress for rowers is essential. And then you need to communicate what action is required.

Interpretation is subjective. Beyond age and level of activity, acclimation can be important. For example, a rower who trains regularly in Florida heat and humidity may be better able to exercise at higher WBGT than a rower from Maine. Each rowing organization can develop guidelines for athletes and coaches to follow. There are published examples which could be adopted. For example, the Princeton National Rowing Association has a clear hot weather policy indicating the Heat Index measurements at which both training and racing must be stopped for different age groups. The Heat Index table has been adapted specifically for rowing. Their policy also offers recommendations on preventative measures and responsibilities.

WBGT measurements also can be applied to rowing and decisions for rowing practices and regattas. The Kestrel Heat Stress Tracker comes preprogrammed with several athletics guidelines, such as for Vermont State High Schools which identifies level of risk associated with different WBGTs and what modifications are required for athletes. You can set your own WBGT thresholds in the Tracker along with alerts.

Indianapolis Rowing Centre, featured in a previous blog post Finding Her Voice through Coxing, has tailored colored rowing guidelines which match the flags in the kit. Red flag, stop rowing.

Source: Indianapolis Rowing Center