Children do not respond to exercise – or heat – the same way adults do. In general, children have a shorter exercise tolerance time and lack the stamina and endurance for sustained physical activity that trained adults may have.
In addition, they adapt to changes in climate slower than adults and experience markedly faster increases in core temperature when dehydrated.
During exercise in hot climates, children have a harder time dissipating heat than adults do, perhaps due to their smaller body sizes, meaning less area to sweat in order to cool down.
This in no way means that children should be cloistered inside when a heat wave strikes. It does mean, however, that how they are fed and watered before, during and after activity becomes all the more important. Recommended amounts of water Because children grow rapidly, body weight instead of age is a more appropriate reference point for determining how much fluid they should consume.
The Holliday-Segar Method calculates fluid intake based on weight. For example, the method suggests a 55-pound child needs 53.33 ounces of fluid, an 85-pound child 63.33 ounces. If a child is exercising, then the recommended amount increases, especially in hot weather. Exercising in hot conditions increases the sweat rate and exacerbates the chance of dehydration. As little as a 2 percent decrease in body weight – 1-2 pounds in 55- to 85-pound children – can negatively impact sports performance and potentially cause heat-related illnesses such as heat stroke and heat exhaustion.
To ensure that children remain well hydrated during physical activity, incorporate hydration in the exercise regimen. Encourage children to consume fluids throughout the day, not just when exerting themselves.
Children planning to exercise later in the day should drink water with breakfast. In the two or three hours preceding exercise, prepare them with one to three glasses of water with a snack or meal. It is also important for children to drink fluids during activity. While many youth may insist that they’re not thirsty, parents and coaches should offer fluids before the first sensation of thirst kicks in.
Thirst is not a good indicator of hydration status, as the onset of thirst usually occurs after dehydration has already begun. For a growing child, three to four mouthfuls of water every 20 minutes is adequate.
Every 20 minutes may not be practical in all sports, so make water available whenever there’s a timeout. And continue to serve fluids after play stops. The truth about sports drinks Athletes of all ages are inundated with advertisements that promote sports drinks over regular water.
While sports drinks – and electrolyte replacements of all sorts – do serve a purpose, they are definitely not for everyday consumption. Sports drinks are generally recommended for activity lasting longer than 60 minutes. Such beverages are good options in extended cases, because they help replenish salts lost during sweating. Additionally, they provide a small amount of carbohydrates to help sustain energy levels during longer exercise bouts.
There are alternatives to sugar-laden sports drinks, including coconut water, which provides all the benefits of traditional sports drinks without the added sugars. A simple combination of apple juice, water and a pinch of sea salt can also replace electrolytes and energy lost during exercise.
For those averse to drinking water, other options can return fluid levels to normal, including those ubiquitous post-game snacks at children’s sporting events.
High-water-content fruits are an ideal alternative, especially citrus fruits and watermelon. Drinking milk after exercise will also help restore lost nutrients.
Warning: Sodas and caffeinated beverages actually increase an individual’s fluid requirements, so avoid them before, during and after physical activity, especially in the heat.
Tracey Downing is trainer and director and Matt Brockhaus is nutrition director at FIT, 600 Rancho Shopping Center, Los Altos.
For more information, call 947-9831 or visit www.focusedtrainers.com.