By Mike Craven:
Negligence, liability as it relates to exertional heat stroke. Courts apply a higher standard of care to coaches, athletic trainers and administrators which are all part of a team “vicarious liabilities”. The manner in which the defendants, negligence causes the death, need not be foreseeable to satisfy the causation of the element of negligence. Lawsuits implicating negligent conduct by coaches, staff, medical personnel and schools indicate a growing concern for reassessment of the standard of care that are owed to our athletes. “Lawsuits cause change not young men dying. Restricting water in practice today would be considered negligent. However, this was common place in football for many years. Exertional heat stroke (EHS) is an elevated core temperature above 104 degrees. EHS occurs when the body’s heat production exceeds heat loss and occurs during physical activity. EHS is caused by a confluence of risk factors. Dehydration which has been given the proper attention is just one of many risk factors. Others include barriers to evaporation, illness, history of heat illness, excessive or dark colored clothing, over motivation, supplements, medications and drugs, high body mass to surface area, low met scores VO2, and lack of acclimation to heat. A marine at Paris Island with a high body mass to surface area (fat or heavy muscle) with a low MET score (VO2) measurement of aerobic strength is eight times more likely to die of exertional heat stroke. So overweight players of low MET scores (VO2) being over motivated by what appears a lack of hustle versus what is a deficiency in aerobic strength that was neglected to be trained can elevate core temperatures to dangerous levels in the absence of significant dehydration in 20-30 minutes. When reviewing and investigating heat related deaths players are still dying where water was plentiful, there were rest breaks, coaches and athletic trainers were present, the players showed no visual signs of stress or were reached early when athletic trainers recognized them and all have passed physicals. We must reevaluate what is still not being done when our medical staff says “exertional heat stroke is 100% preventable.
A coach determines the intensity, duration and frequency of practice in a week. All exertion to physical activity produces heat. The amount of heat produced is directly proportional to the rate of energy expended, measured in MET score (VO2). This is a measured test like cholesterol, blood pressure, blood sugar or triglyceride health screening that cannot be faked. Players with low MET scores (VO2) are less tolerant to heat and humidity. Players with low MET scores (VO2) have the potential for more heat storage during exercise. As the MET score (VO2) of a player improves from proper aerobic strength training the ability to withstand heat stress improves independent of acclimatization and heat adapatation. The wider the window can become in aerobic strength by increasing your MET per minute the smaller inclement in rectal temperature with a given quantity of exercise. Thermoregulation is a complex interaction among the central nervous system, cardiovascular system and the skin to maintain a body core temperature of 37c. Heat generated by muscle contraction is transferred to blood flowing through the muscular vascular bed. The heated blood is returned to the heart and in turn to the brain centers that induce dilatation of skin vessels as well as secretion of sweat by the sweat glands. This has been called the “Benzinger Reflex”. A rise in intra-cranial temperature from temperature of blood produces an increase in skin blood flow also stimulating sweat gland activity. These two important body functions, increase skin blood flow and sweating with evaporation of sweat to the air pulls heat away from the body for heat loss. The cooler blood returns and the process starts, all over. When the environmental temperature is equal to or exceeds that of the body surface and the air is saturated with moisture “humidity” a progressive rise in body temperature is inevitable at a very rapid rate. When muscle generated heat and/or environmental heat gain accumulates faster than heat being dissipated football players die.
From the forgoing evidence it is clear players performing at high intensity for any duration of time in hot weather cause heat gain from muscle metabolism and environment. Their best defense is their capacity to increase and also to sustain cardiac performance (MET per minute-aerobic strength). Any stage of dehydration reduces cardio performance. One percent dehydration can cause the reduction of 10% in your MET per minute. A 285lb football player losing 3% of body mass is 8.5lbs. of water weight, a 150 lb football player losing 3%of body mass is 4.5 lbs. of water weight. For both athletes this causes a drop in blood volume that reduces cardiac output reducing the amount of circulating blood that causes heat from core to shell to be released inviting heat storage. Dehydration causes a reduction in your MET per minute. Elderly people with Congested Heart Failure have reduced cardiac output which equals a reduction in MET per minute so sitting in hot environments can bring on classic heat stroke sooner. Research from John Hopkins University compares sweating and skin blood flow during exercise with a MET per minute between 24 – 30 year olds which is the younger group and 58-74 which is the older group. Individuals greater than 60 years of age were more susceptible to increase core temperatures than younger people. However when you compare their MET per minute (VO2) the older men were of no greater risk if their MET per minute were equal to the younger men. This displays the importance to preventing a decline in your MET per minute. This prevents a decline in the body’s ability to release heat due to aging.
By doing the proper work a person can maintain or improve their aerobic strength. The body adapts to developing aerobic strength by a correct action by need. This is an example of “physiological” change. This is how the lungs learn to process more air, the blood increases red blood cell production to carry more oxygen. The blood increases its water content to improve circulation. The number of capillaries increases per muscle fiber for more blood supply routes. The heart increases their cardiac output by pumping more blood per beat. On the muscle level, what good would it do to improve delivery of oxygen but not the efficiency of the muscle to utilize it? Muscle efficiency describes the given amount of mechanical work that can be done before a high level of exhaustion and heat storage occurs. High intensity work or moderate work done for long periods of time exceeding an individuals heat tolerance is no different than work done in a state of dehydration. It “kills”. Player “A” with a MET score of 50ml/kg/min dehydrated 3% can reduce their MET per minute to 35ml/kg/min, player “A” has now a reduction in his window of aerobic strength from a dehydrated state. This causes his efficiency to drop due to the work demand (there will be more of a struggle to do the work that would be easy before). Player “B” has a MET score of 35ml/kg/min is not dehydrated but does not have the same exercise tolerance or heat tolerance as a player at 50ml/kg/min.
Whatever the amount of high intensity work performed, Lactic acid stacking drills, done at maximum effort Player B will reach a state of exhaustion sooner with a higher core temperature for work performed. If 50 young men were lifting on a bench press in their weight room and there are wide differences in their strength development (300 lbs vs. 95 lbs.). You cannot ignore this without serious consequence for liability. The weight on the bar is changed to meet the individual’s ability. The players don’t keep a fixed weight on the bar and assume that everyone can lift it. If 50 players all have difference MET per minute scores that show which players are superior to heat tolerance and which ones are not 67ml/kg/min vs. 23ml/kg/min you can’t force the players with lower scores over a short period of time to adapt to other’s high standards just like you can’t force the weaker to lift heavier weights. Number 1 reason of players dying of heat stroke is the intensity and duration of exercise in exceeding their heat tolerance not dehydration. However, “dehydration just lets it happen faster”. The coach must test to recognize this. Once tested there needs to be a period of time to address training for aerobic strength that is unique to the individuals VO2, RQ and heart rate. Training for this condition state comes from imposed demand and over compensating that leads to progressive overload.
Your player is different than in the 60’s, 70’s, 80’s or 90’s. As coach’s we have made them bigger, faster and stronger. The starting tackle at VA Tech was 6foot 2, 215 lbs. in 1955; today he is 6 foot 5, 320 lbs. The speed in which their muscles can contract in response to the force that they generate is to be amazed and admired. This is a reflection of exercise science on how the body adapts to absolute strength, speed strength, short term endurance and anaerobic strength training. The time spent developing these forms of strength we have neglected aerobic strength. This can be seen even in the way the game of football has changed, players playing just on special teams, offense or defense versus when the best athletes played both ways. For an athlete to play both ways offense and defense what form of strength is a necessity without him taking breaks on the field (aerobic strength). We have coach’s using players in a rotation between series because of this deficiency.
Physical characteristics such as total body mass, lean muscle mass, percentage of body fat, body surface area and surface area to mass ratio affect Thermoregulation. Linemen’s potential for greater heat storage includes a larger body mass, and lower body service area to mass ratio. So whether the lineman is fat or heavy muscle he is a walking heat bomb without a high level of aerobic strength. High body mass increases metabolic rate and therefore heat production. The lower body surface area to mass ratio in larger football players diminishes heat dissipation via dry avenues such as conduction, convection and radiation compared with smaller players. Research at the “Heat Institute” of West Chesler University showed that core temperatures was not correlated with either percent of dehydration or sweat rate in measuring football players in preseason, two a day practices. The purpose of this great field study was two fold. Number 1 to measure the rise in core temperature in football players during practice and compare the core temperatures of larger lineman to those of the backs and receivers. Number 2 to determine the highest core temperature reached if it was related either to the player’s level of dehydration or their sweat rate. A significant linear trend over time was found for core temperatures in both groups.
Measuring core temperatures every fifteen minutes the two highest incidences of core temperatures recorded in each subject were compared, core temperatures were higher in lineman than in backs. However as measured by change in mass during practice the linemen were less dehydrated. The change in core temperatures in the backs in response to bouts of exercise and rest were greater (their temperatures decreased sooner during rest). Core temperatures in athletes rise in periods of intense work and with proper rest periods implemented the temperatures are lowered. The more gradual heat storage in the linemen over the backs was concluded “a larger body mass and lower body surface area to mass ratio with lower aerobic strength” (MET per minute VO2). Even in cross country researchers have concluded that lighter runners have a distinct thermal regulating advantage over runners with greater mass who produce and store more heat at the same running speed.
Learning is of no value unless it leads to a correct action. Coaches are the leaders, it’s very important to be opened to learning but be able to communicate what is learned into a correct action. Coach Jason Meade, Lee Davis High School, Coach Latrell Scott, University of Richmond were the first High School and College coach’s to test their players MET scores to see which players were deficient versus superior. The MET score is an exact measurement that cannot be faked and is the direct link to the body’s ability to release heat from core to shell. If a coach today believes his athletic trainer handles all his heat related concerns he must ask if it is listed in their position stand as a reason for heat stroke; and when he finds out it is, why are we not testing for it? If we are not testing for it can I as a coach be more at risk for pushing players in any form of anaerobic work that causes the body to produce heat faster than can be dissipated. Testing brings measurement to exercise prescription for the time period to develop aerobic strength for physiological change. This is preparing to prevent which is being proactive versus having a tub of ice water ready when the young man drops from certain drills done above his exercise and heat tolerance. DON’T WAIT FOR LAWSUITS TO CAUSE CHANGE! Know what the standards of care are and act on them.
American College of Sports Medicine. Position Stand: Exertional Heat Illness during Training and Competition, 2007
Environmental Heat Illness by James P. Knochel, MD, Dallas
The National Athletics Trainers Association, Position Statement: Exertional Heat Illness, 2002.
Loyola of Los Angeles Entertainment Law Review (Volume 22:613).
The H.E.A.T. Institute of West Chesler University, West Chester, Pennsylvania: Core Temperature and Percentage of Dehydration in Professional Linemen and Backs during Preseason Practices
Human Stress Physiology Laboratory, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland: Sweating and skin blood flow during exercise: effects of age and maximal oxygen uptake.