The National Kidney Foundation reports that approximately 1 in 10 people will experience a kidney stone at some point during their lives. The prevalence of kidney stones is increasing in the United States for both adults and children. A kidney stone is a hard mass composed of mineral and acid salts that begin to crystallize because the urine becomes too concentrated (i.e., not enough liquid for the amount of waste present). The crystals begin to combine with other elements forming a mass. Some kidney stones are small enough to pass through the body without causing pain; however, if the stone is too large and does not move, a back-up of urine occurs and results in pain.

Risk Factors for Developing Kidney Stones

• dehydration/consuming too little water
• inactivity
• excessive exercise
• high salt or high sugar diet
• obesity
• diabetes mellitus
• hypertension
• infection
• family history
• urinary tract abnormalities
• gastric or intestinal bypass surgery

Symptoms of Kidney Stones

• severe pain in the back or side that may spread to the abdomen or groin area
• painful urination
• blood in the urine
• nausea
• vomiting
• fever and chills

The Role of Exercise in Kidney Stone Formation and Prevention

• Excessive exercise, such as marathon running, can increase the risk of kidney stone formation in susceptible individuals because it can lead to dehydration from fluid lost through sweat. This, in turn, increases the concentration of waste products in the urine and makes it more likely that crystals will form. To prevent dehydration, approximately 16 to 20 fluid ounces of liquid per pound of body weight lost through sweat should be consumed within two hours after completing exercise.
• Inactivity can increase the risk of kidney stone formation because of its role in the development of obesity, diabetes mellitus and hypertension. The National Kidney Foundation recommends that you have a goal of exercising for 30 to 60 minutes on most days of the week to lower your risk for these diseases.

Note: Before beginning an exercise program or increasing the intensity level of a current routine, a physician's approval should be obtained, especially for older adults and those at risk for or who currently have chronic health conditions.

References
National Kidney Foundation
Up-To-Date: Dietary Factors and Medical Problems that Increase the Risk of Kidney Stones
ACSM Position Stand: Exercise and Fluid Replacement

As the temperature drops and the warm days of summer become a distant memory, winter sport enthusiasts are gearing up for another season of outdoor exercise. If you are one to relish cold weather fitness activities, there are a few myths on which you need to put the "deep freeze" before you head outdoors.

Myth #1: Dehydration is not a concern when exercising in cold weather.

• Dehydration is as much of a concern during cold weather exercise as it is with warm weather exercise.
• Large amounts of water are lost through respiration during exercise in a cold environment. Your body needs to warm and humidify the cold, dry air that you inhale. Water is lost as you exhale the warmed and humidified air.
• If you wear heavy, impermeable clothing, large amounts of water can be lost through excessive sweating.
• Your thirst response is blunted in cold weather, making it less likely for you to feel the need to drink during and after the exercise - even when your body has lost significant amounts of water from the activity.
• There may be a tendency to purposely abstain from drinking fluids before heading outdoors in an attempt to avoid having to use the bathroom, and hence, needing to shed the many layers of clothing in order to do so. Therefore, your body is not adequately hydrated before you start the activity.

Solution: Drink plenty of fluids before, during, and after your exercise session. Drinking hot cocoa or spiced apple cider after you exercise is a good way to get both the fluid and carbohydrates that your body needs to replenish its stores.

Myth #2: I am not at risk for developing hyperthermia during cold weather exercise.

• A common mistake of winter sport enthusiasts is to dress too warmly and to wear heavy, impermeable clothing. Improper attire can trap the heat produced by your exercising body, putting you at risk for developing a heat illness.

Solution: Dress in layers so that you can add or remove articles of clothing as needed to maintain your core body temperature. The base layer (closest to your body) should be made of a material that wicks away moisture from your body, such as polypropylene. The mid-layer material should provide insulation, as well as wick away moisture. Fleece is a good option for this. The outer layer should be breathable, but waterproof to protect against the elements. An outer layer that has venting features, such as armpit zippers, is a good choice.

Myth #3: I do not need sunscreen during cold weather outdoor activities.

• Even during the cooler months of the year, you are at risk for developing a sunburn when exercising outdoors. This is especially true when the activities are performed in the snow, which reflects the sun back at you.

Solution: Wear a sunscreen that has an SPF of 15 or higher. The sunscreen should block both UVA and UVB rays. Protect your lips by using a lip balm that contains sunscreen.

Keep your cold weather exercise routine safe this season. Stay hydrated, dress in layers, and wear sunscreen.

Note: Before beginning an exercise program or increasing the intensity level of a current routine, a physician's approval should be obtained, especially for older adults and those at risk for or who currently have chronic health conditions.

Resources

"Exercise and cold weather: Stay motivated, fit and safe" by Mayo Clinic staff

ACSM Fit Society Page, Winter 2005, p. 5-6, "Winter and Nutrition: Fueling for Cold Weather Exercise," Clark, N.

     I have witnessed two individuals experience the early phases of exertional heat illness - a spectrum of conditions that, if left unchecked, can be potentially life-threatening.  Both episodes were in children.  Both occurred during summer camp, one a general day camp and the other a sport camp.  

     As you exercise, your body produces sweat in order to regulate body temperature.  As the sweat evaporates it cools your body.  Exercising during hot and humid weather inhibits the effectiveness of this process which can result in your body temperature reaching above normal levels.  When the heat stress exceeds your body's ability to dissipate the heat, and therefore maintain a normal core temperature, heat illness can result.  

     You are most susceptible to developing heat illness during the first few days of warm/hot weather when your body has not yet acclimated to the higher temperatures.  In addition to the excessive demands placed on your body's thermoregulatory system by the hot and humid environment, dehydration can compound the situation either directly or indirectly.  Heat illnesses can be minor and easily reversible, such as with muscle cramps, or they can be life threatening, such as with heat stroke.  

     Children are especially susceptible to developing heat illnesses because they have immature thermoregulatory systems.  It takes longer for children to start sweating compared to adults; and, the rate at which they produce sweat is not as fast.  Furthermore, children have a greater surface area to body mass ratio in comparison so when they are exposed to a hot environment, they gain heat more quickly.  Below is a list of heat related illnesses and their associated symptoms.

Heat Cramps:  These commonly occur following intense exercise of a prolonged duration.

• Painful involuntary muscle spasm/contraction
• Occur in muscles of the abdomen, legs, and arms
• Caused by dehydration and electrolyte imbalance
• Relieved by rest, prolonged stretching, and fluid and electrolyte replacement

Heat Exhaustion:  The most common form of heat illness.  It can occur during or after exercise.  It is characterized as the inability to continue physical activity.  Individuals experiencing heat exhaustion have core body temperatures that range from 97 degrees to 104 degrees Fahrenheit (36 degrees to 40 degrees Celsius).

• Pale, sweaty skin
• Dizziness
• Weakness
• Decreased muscle coordination
• Nausea
• Vomiting
• Diarrhea
• Headache
• Irritability
• Chills
• Treatment involves moving affected individual to a shaded or air conditioned area.  Feet should be elevated while in the supine (on the back) position.  Excess clothes should be removed and fluids given.  Medical attention should be sought if symptoms do not resolve.

Heat Stroke:  A medical emergency that can result in death.  It requires immediate treatment.  Associated with body core temperatures exceeding 104 degrees Fahrenheit (40 degress Celsius).

• Disoriented
• Irrational behavior
• Loss of muscle coordination and balance
• Fast breathing (hyperventilation)
• Rapid heart rate (tachycardia)
• Low blood pressure (hypotension)
• Vomiting
• Diarrhea
• Seizures
• Collapse/coma
• Treatment involves whole body cooling in the form of cold water and ice water immersion therapy.

Tips to Reduce your Child's Risk at Camp:

• Make sure your child is adequately hydrated before going to camp.  Serve a breakfast that includes a beverage and foods with a high water content such as fruit (watermelon, oranges, etc.).
• Send a water bottle/sports drink for consumption during the day.
• Pack an extra beverage and foods with a high water content for lunch.
• Have your child dress in loose-fitting, light-colored and light-weight (e.g. mesh) clothing.
• Talk to the camp counselor/coach to ensure adequate water and rest breaks will be taken throughout the day.
• Confirm that camp counselors/coaches are familiar with the signs and symptoms of heat illnesses and that they are prepared and equipped to take the necessary action if a situation arises.
• Inquire about the camp's protocol for high-risk days (Wet Bulb Globe Temperature greater than 82 degrees Fahrenheit [28 degrees Celsius]).  For example, will they decrease the intensity and/or length of events involving physical activity?  Will they move sessions to indoors where there is air conditioning?
• If possible, choose a sport camp that offers sessions in the early morning before temperatures get too high.

     Summer day and sport camps should be an enjoyable and rewarding experience for your child.  Increasing your awareness of the signs and symptoms of heat illnesses, as well as how to avoid these conditions from occurring, will help to prevent a negative experience for both you and your child this summer.  

Resources:

ACSM's Guidelines for Exercise Testing and Prescription, Eighth Edition.

ACSM's Resource Manual for Guidelines for Exercise Testing and Prescription, Sixth Edition.

ACSM's 2007 Position Stand: "Exertional Heat Illness during Training and Competition," Medicine & Science in Sports & Exercise.

     With the onset of warm weather comes the increased risk of exercise-related dehydration.  Sweating, a protective mechanism of your body, regulates your body temperature.  As your sweat evaporates, heat is dissipated.  This prevents your core body temperature from rising to dangerously high levels.  The rate at which your body sweats is dependent upon the intensity and duration of the exercise, environmental conditions, acclimatization, type and amount of clothing worn, individual biological differences, and your hydration status before exercise.

     Dehydration can result if fluid consumed does not match fluid lost from exercise.  When you are dehydrated your risk for heat-related illnesses increases and your exercise performance becomes impaired.  Physiologic function of the body starts to be compromised when 1%-2% of body weight is lost as a result of fluid loss.  Your risk for heat-related illnesses increases when 3% or more of your body weight is lost as a result of fluid loss.  If you are well-hydrated before exercise, it could take only one hour of exercise for this to occur, sooner if you are dehydrated from the start.

     An understanding of the signs and symptoms of dehydration is important in order for you to take appropriate action when they occur.

Signs and Symptoms of Dehydration

• Thirst
• Headache
• Nausea
• Vomiting
• Dizziness
• Cramps
• Weakness
• Chills

     You can reduce or prevent the likelihood of becoming dehydrated by following certain guidelines.  These include adhering to a fluid replacement schedule and incorporating steps to optimize your fluid replacement.

Fluid Replacement Schedule

Pre-Exercise

• Drink 17-20 fluid ounces of water or sports drink 2-3 hours before beginning exercise
• Ingest 7-10 fluid ounces of water or sports drink 10-20 minutes before exercise

During Exercise

• Ingest 7-10 fluid ounces every 10-20 minutes

Post-Exercise

• Drink approximately 16-20 fluid ounces of water or sports drink for every pound of weight lost from the activity within 2 hours after completing your exercise session

     If you find it difficult to adequately rehydrate, there are some tactics you can follow to optimize fluid replacement.

Steps to Optimize Fluid Replacement

• Carry water bottle with you while you exercise
• Choose a water bottle with measurement markings to keep track of the amount of liquid consumed
• Choose drinks that are palatable, such as flavored water or sports drink

Characteristics of Fluid to be Consumed

• Palatable
• Cool.  The ideal temperature range of the drink is 50-59 degrees Fahrenheit (10-15 degrees Celsius)
• Post-exercise drink should include a carbohydrate source, especially if your session lasts more that 45 minutes, to replenish glycogen (energy) stores 
  
• Contains electrolytes, such as sodium chloride (0.3 - 0.7 g/L), to offset loss from sweat and to reduce your risk for conditions associated with electrolyte imbalance (muscle cramps) - this is particularly important if exercise lasts longer than 4 hours and during the initial days of warm weather when your body hasn't yet been acclimated.

Drinks to Avoid

• Caffeinated and alcoholic beverages which can increase fluid loss through increased urine output
• Carbonated beverages which may lead to a "full" sensation causing you to decrease your fluid intake
• Drinks with carbohydrate concentrations that are greater than 8% are not recommended to drink during exercise because they interfere with stomach emptying and intestinal absorption
  

Resources

Journal of Athletic Training, 2000:35(2):212-224; "National Athletic Trainers' Association Position Statement: Fluid Replacement for Athletes," Casa D.J. et al.

Track Shack - Sports Nutrition Developed by the Gatorade Sports Science Institute www.trackshack.com