Environmental Factors and Other Issues with Exercise Flashcards
Core body temperature
Core body temperature ranges between 97°F and 100° F
Core body temperatures are generally lowest during sleep and highest during exercise or with exposure to hot environments
The ___ in the brain is the coordinating center for temperature regulation and acts much like an internal thermostat
preoptic/anterior hypothalamus (POAH)
preoptic/anterior hypothalamus (POAH)
initiates responses to reduce increases in core body temperature
When it perceives heat, it strives to increase heat loss through peripheral vasodilation of blood vessels, which redistributes blood carrying heat toward the periphery
When it perceives cold, it strives to decrease heat loss through peripheral vasoconstriction of blood vessels, which redistributes blood toward the core
Core temperature tolerance ranges.
limits of survival: 73.5-80.5 F
cold exposure: 80.5-97 F
normal range: 97-100 F
heat exposure: 100-105.8 F
heat stroke: 105.8-111 F
limits of survival: 111-115
Factors Affecting Heat Gain
Resting metabolism (RMR)
Muscle activity
Hormones and nervous activity
Thermic effect of food
Non-exercise thermogenesis (NEAT) anything not sleeping, sports or exercise related
Warm environments
The body’s thermoregulatory mechanisms that primarily protect against overheating at rest and during exercise:
conduction
evaporation
convection
radiation
All but evaporation are considered “dry Heat exchange”
resistance to dry heat exchange is called “insulation”
conduction
The exchange or transfer of heat from warmer objects to cooler objects via direct molecular contact
Its contribution to heat dissipation during land-based exercise is very small
Its contribution to heat removal when the body is immersed in water is significant
conduction depends on the following variables:
The thermal gradient (i.e., the temperature difference between the two surfaces)
The thermal properties of the two surfaces, objects, or mediums in contact
evaporation
transfer of heat when a liquid changes physical states by becoming gas, a process that requires energy to vaporize the liquid
ex) sweat evaporating off skin
As the vapor (gas) leaves the skin surface, so will the heat.
> Sweat must evaporate in order for heat to leave the body
The effectiveness of sweat evaporation from the skin depends on:
> Temperature gradient - when it is hot out, gradient is small so efficiency is reduced, and you need to sweat to thermoregulate
> Relative humidity of the surrounding air
> The amount of skin surface area exposed to the environment to facilitate sweat removal from the body
> Convective air currents that lift the vapor into the surrounding air
Not all sweat is lost to the environment
> Sweat that drips off the body does not contribute to cooling but does contribute to fluid losses and dehydration
high humidity =
air cannot readily accept more water vapor
convection
Its contribution to heat removal when the body is immersed in water is significant
Convection contributes more significantly to heat loss during land-based exercises performed on breezy or windy days
Heat removal dependent on the movement between the 2 surfaces and the thermal gradient:
Greater movement and larger thermal gradients exchange heat more rapidly
Ex: air current from a fan will remove more warm air from the skin surface
Treading water lightly facilitates rapid heat loss given the thermal properties of water, while active swimming generates adequate metabolic heat to offset this convective heat loss
radiation
involves the passage of electromagnetic heat waves moving along a temperature gradient from a warm or hot object into a cooler object
Ex. the sun’s rays warming the Earth at sunrise, or heat coming off tar streets in summer
The human body constantly radiates heat through skin into the surrounding cooler environment and any objects surrounding the body, while simultaneously ____
receiving heat from warmer objects surrounding it
Sweat and energy expenditure
A calorie: a unit of energy…
the energy needed to raise the temperature of 1 kilogram of water through 1 °C is equal to one thousand small calories and often used to measure the energy value of foods
For each liter of sweat lost, the body removes approximately 580 kcal (kilocalorie) (2,428 kJ) of heat
Excretion
involves the loss of heat via any materials excreted from the body
- gaseous (air exhalation)
- liquid (urine)
- solid (feces)
accounts for significant fluid removal from the body considering daily urine output, fluid volume contained in feces, and the estimated additional 300 mL of fluid lost through the mucous membranes of the respiratory passages
Women lose heat quicker than men in cold temperatures
Evaporation depends on the availability of fluid within the body, so ____
fluid lost to excretion may influence sweat rates
Factors That Influence Thermoregulation
Gender
Age
Body size and composition
Conditioning level
Hydration status
Clothing
Environmental factors
Gender =
> females less lean mass, less body water, have larger surface area/body mass ratios (more fat mass, less lean ms mass) favoring dry heat exchange vs sweating, and lose heat quicker than men in cold temps
> women have more % body fat, and can tolerate mild cold exposure better than men
Age =
> children sweat at lower rates because of smaller quantities of body water
Older adults are also more susceptible to the hot and cold stress =
> Dehydration (bc of a diminished sense of thirst)
> Loss of subcutaneous fat tissue to insulate
> Loss of muscle tissue to generate heat
> Potential cognitive losses associated with aging
> Changes within the skin layer
> Reduced thermoregulatory efficiency
> Medication usage that can affect hydration status
Body size and composition
> Muscle tissue capable of generating heat
> Both muscle mass and body fat offer insulation
> Larger surface areas dissipate heat quicker
> Less muscle generates less heat
Conditioning level
With increased fitness: Increased blood volume, improved circulation of blood to skin/periphery during exercise, increased sweat rates, reduced core temperature threshold to initiate sweating
Thermoregulation in Hot Environments
Warmer skin surface temperatures are detected by the peripheral receptors that stimulate both the POAH and cerebral cortex
Increases in blood temperature are identified by central receptors that activate sympathetic nervous system (SNS) responses from the POAH
The POAH stimulates an SNS response to the smooth muscles that encircle the surface arterioles to vasodilate and bring more blood (which is carrying heat) to the skin’s surface
The POAH stimulates an SNS response to initiate sweat production
During exercise in warmer environments, two competing cardiovascular demands exist:
Need for oxygen/nutrient delivery to the exercising muscles
Need for peripheral blood flow to the skin to remove heat
The increased demand for cardiac output is met by:
increasing heart rate and heart contractility to ensure appropriate circulation to these two regions
redistributing blood away from nonessential organs and systems
SNS initiates vasoconstriction in nonessential organs and vasodilation of vessels in the exercising muscles and near the skin surface
Eventually, the demands of exercise and thermoregulation will exceed the cardiovascular system’s ability to meet these demands- and blood delivery goes to exercising muscles……
The body becomes unable to regulate against a rising core temperature
When core temperatures rise to 104°F and 105.8°F (40°C and 41°C), it usually signals the brain to begin to cease exercise
Increases in core temperature elevate circulating levels of epinephrine, which enhances glycogen utilization, contributing to lactate build up, exhaustion and fatigue
Circulatory blood flow to muscle tissue takes precedence over temperature regulation
making the environment a key influence on the likelihood of developing heat-related illnesses
The body’s ability to remove heat is not influenced by air temperature alone
humidity, air currents, and thermal radiation all contribute to heat stress and heat removal from the body
Exertional Heat Stroke
can affect athletes during high-intensity/long-duration exercise and results in activity withdrawal/collapse during or following activity
exercise-associated muscle cramping, heat exhaustion, or Exertional Heatstroke (EHS)
Although some are more prone to heat illness, EHS can affect all athletes, even in relatively cool environments
The National Athletic Trainer’s Association (NATA) released a statement:
NATA diagnoses EHS as a core temp. greater than 104°F to 105°F accompanied by central nervous system dysfunction (e.g., disorientation, confusion, dizziness, loss of consciousness, collapse)
Treatment must reduce the core temperature to no less than 102°F as soon as possible to limit risk of morbidity and mortality
Treatment should advocate cold-water immersion
Adaptations to Heat Stress
The process of acclimation to hot environments normally occurs within 9 to 14 days, although well-conditioned individuals usually require less time to acclimate
To optimize one’s ability to acclimate to hot environments, individuals should reduce their normal training volume and intensity initially, training at intensities below 70% V̇O2max for durations lasting between 20 and 60 minutes
With appropriate exposure to hot environments, the cardiovascular system will undergo several important adaptations:
> A progressive expansion of blood volume, increasing over the first 10 days
> More effective cardiac output and blood distribution to the skin
> Improved cutaneous blood flow within the peripheral regions
With appropriate exposure to hot environments, the thermoregulatory system will undergo several important adaptations:
> Increased sweat rates to remove more heat
> Decreased sweat thresholds (i.e., the temperature at which sweating initiates)
> More effective distribution of sweat over the surface of the skin
> Decreased electrolyte concentrations in sweat, given improved efficiency in reabsorbing these electrolytes from sweat
Dehydration
The sensation of thirst in adults younger than 50 years is generally initiated at about 1% dehydration or loss of body weight
At 2% dehydration, performance is compromised
Performance diminishes and symptoms become more severe with increased levels of dehydration until around 8% loss of body weight when the risk for development of severe heat illnesses (exertional heat stroke) becomes significant
Hydration During Exercise
General guidelines:
Consume 7–10 ounces every 10 to 20 minutes
Ideal fluid temperatures exist between 50°F– 59°F
Sport drinks should not contain carbohydrate concentrations greater than 8%
Post-Exercise Rehydration
This includes consuming water to restore hydration, carbohydrates to replenish glycogen stores, and electrolytes to speed rehydration
12 hours to recover—usual meals, snacks, and plain water
General guidelines:
> Drink up to 1.5 L of fluid for each kilogram of body weight lost
Electrolyte imbalance
sodium concentration in serum (liquid part of blood without the clotting agents) is lower than normal (less than 135 milliEquivalents/L)
Hyponatremia
Can occur as a result of excess body water diluting serum sodium (i.e., over hydration), although the condition can be caused by excessive loss of sodium because of vomiting, diarrhea, or even sweating
result of a combination of losing excess sodium and overhydrating, and may sometimes occur during exercise when one rehydrates with water but fails to replace lost electrolytes
Fundamentals of Exercise Physiology and Nutrition
It’s important to consume the right foods and drinks in the right combinations and quantities
Strategic ingestion can positively impact performance:
Specific timing of nutrient and fluid intake
Composition of both nutrients and fluids
Quantities ingested
The Role of Macronutrients in Exercise Performance
Fat = Energy source during exercise at lower intensities
Carbohydrates = Quick energy source, especially when exercising at higher intensities
Protein = Helps build and repair muscle
An ideal eating plan will contain the right mix of foods and drinks to ensure adequate carbohydrates, protein, fat, and micronutrients to support the specific exercise demands on the body
Fat loading
Goal is to slow glycogen depletion
May be ill-advised for some athletes, as it may lead to general feelings of fullness, lethargy, and fatigue
Studies show no consistent benefits
Long-term exposure to high-fat and low carbohydrate diets may help the body adapt and increase fat utilization
Carbohydrates
benefit exercise as fuel for muscle activity
Availability is important for endurance performance, especially during high-intensity exercise or when individuals are glycogen depleted
Serious endurance athletes may need to practice carbohydrate loading
Protein
plays an important role in both endurance and muscle-strengthening exercise
Both modes of exercise stimulate muscle protein synthesis, which is further enhanced with consumption of protein around the time of exercise
helps to preserve lean muscle mass and assure that weight lost comes from fat rather than lean tissue
Sports nutrition strategies should address three exercise stages:
- Pre-exercise
- Exercise
- Post-exercise
Pre-Exercise Fueling
Typically describes the 4 hours before exercise
Carbohydrates
- Pre-exercise meal: aim to consume 2 to 4 g/kg of body weight (0.91–1.8 g/lb)
- Pre-exercise snack: aim to consume 1 to 1.5 g/kg of body weight. Carbohydrate loading for events lasting longer than 90 minutes may be beneficial
Protein
- (endurance athletes) Recommended intakes between 1.2 to 1.7 g/kg of body weight
Fueling During Exercise
0-60 minutes: replace water only, as electrolyte losses via sweat and muscle glycogen depletion are minimal, unless exercising in extreme environments or participating in vigorous exercise
60-90 minutes: replace water and electrolytes lost via sweat, giving consideration to carbohydrate refueling
90-120+ minutes: replace water and electrolytes lost via sweat, plus carbohydrates depleted from storage
Post-Exercise Refueling
The average client does not need any aggressive post-exercise replenishment
Clients following vigorous training regimens benefit from strategic refueling
Best post-workout meals include mostly carbohydrates accompanied by some protein
Consumption of protein immediately post-exercise helps in the repair and synthesis of muscle proteins
Refueling should begin within 30 minutes of a workout
High-carbohydrates meals within 2 hours
Athletes and Eating Disorders
A number of athletes take healthful habits to an extreme, and their behaviors become pathologic and detrimental to their overall health and well- being
Eating disorder—a severe alteration in eating patterns linked to psychological or emotional changes
Anorexia Nervosa
Formal Diagnosis:
Restriction of food leading to significant low body wt for age, sex, developmental trajectory and physical health
Intense fear of gaining weight or becoming fat, or persistent behavior that interferes with weight gain, even if already at low body wt
Disturbance in the way the body is perceived or experienced, body image, undue influence of body wt or shape on self evaluation, or lack of recognition of seriousness of the current low body wt
Anorexia Nervosa
Many causes:
Genetic predisposition
Personality traits of perfectionism and compulsiveness
Family history of depression and obesity
Peer, cultural, familial ideals of beauty
Issues of control
Bulimia Nervosa
Formal Diagnosis:
Recurrent episodes of uncontrolled binge eating
Recurrent inappropriate compensatory behavior
Self-induced vomiting, laxative misuse, diuretics, or enemas, fasting and/or excessive exercise
Binge eating and compensatory behavior >1/week for 3 months
More difficult to identify
> Often normal weight or sometimes overweight
Female athlete triad
(Relative Energy Deficiency Syndrome)
> Amenorrhea (at least 3 months without menstrual cycle)
Osteoporosis
Disordered eating
Female Athlete Triad (Relative Energy Deficiency Syndrome)
Caloric deficit and decreased energy availability = Body attempts to restore energy balance by using less energy for growth, reproduction, and various other important bodily functions
Somewhere around 25% of elite female athletes in endurance sports, ballet, and weight-class sports suffer from disordered eating and some variation of the female athlete triad
National Eating Disorders Association offers the following tips:
Take warning signs seriously
De-emphasize weight
Don’t assume that reducing body fat or weight will improve performance
Help other exercise professionals recognize the signs of eating disorders and be prepared to address them
Provide accurate information about weight, weight loss, body composition, nutrition, and sports performance
Have a broad network of referrals (such as physicians and registered dietitians) that may also be able to help educate your clients when appropriate
Preventing Eating Disorders in High-risk Populations:
Emphasize the health risks of low weight, especially for female athletes with menstrual irregularities (in which case, referral to a physician, preferably one who specializes in eating disorders, is warranted)
Avoid making any derogatory comments about weight or body composition
Do not curtail athletic performance and gym privileges to an athlete or client who is found to have eating problems unless medically necessary
Strive to promote a positive self-image and self-esteem in clients and athletes
- Hyponatremia is:
A. Higher than normal blood sodium concentration.
B. Lower than normal blood potassium concentration.
C. Lower than normal uric acid level.
D. Lower than normal blood sodium concentration.
D. Lower than normal blood sodium concentration.
- Your 18-year-old female client comes to you with a calcaneal stress fracture. She states that she started a running program to lose weight (although when you assess her BMI she underweight). She is concerned that she cannot run now and doesn’t want to gain weight. Your response to her is:
A. To have her reduce her caloric intake by 300calories a day in order to not gain any weight while she is recovering
B. To deemphasizeweight, while accurately going over her body composition andnutrition recommendations,particularly to help promote tissue healing
C. To provide her with other forms of cardiovascularexercise while she cannot runin order to continue losing weight
D. To curtail her exercise activity as you think she may be suffering from bulimia nervosa
B. To deemphasizeweight, while accurately going over her body composition andnutrition recommendations,particularly to help promote tissue healing
- Which of these options describes the transfer of heat via electromagnetic waves traveling from a higher temperature object to a lower temperature object along a temperature difference?
A. Conduction
B. Convection
C. Radiation
D. Absorption
C. Radiation
- Why are older adults more susceptible than younger adults to both hot and cold stresses?
A. They are more prone to dehydration due to a diminished sense of thirst.
B. They have a greater proportion of muscle tissue.
C. They have increased thermoregulatory efficiency.
D. They have increased subcutaneous fat.
A. They are more prone to dehydration due to a diminished sense of thirst.
- Which among the following is predominantly the most crucial element of a nutritional plan before exercising?
A. Protein
B. Amino acids and other fluids
C. Carbohydrates
D. Creatine
C. Carbohydrates
- Within how many minutes after completing exercise should adults consume a food rich in carbohydrates for the best recovery?
B. 30
- Which of the following is the transfer of heat when a liquid changes physical states by becoming a gas?
A. Conduction
B. Convection
C. Radiation
D. Evaporation
D. Evaporation
- On a hot and humid day, while your client engages in a moderate workout and experiences low sweating with fatigue, you conclude:
A. Her exercise intensity might be lower than claimed due to minimal sweating.
B. Insufficient pre-workout rest might be a contributing factor.
C. There’s a possibility of hyponatremia being a concern.
D. Her core temperature has increased, causing elevated levels ofcirculating epinephrine and enhanced glycogen utilization, contributing to lactate build up,exhaustion and fatigue
D. Her core temperature has increased, causing elevated levels ofcirculating epinephrine and enhanced glycogen utilization, contributing to lactate build up,exhaustion and fatigue
