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Exercise physiology - wilderness events

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by

Mark Christensen

on 21 April 2015

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Transcript of Exercise physiology - wilderness events

Training Methods
Foot Care
Foot-related problems most common reason to seek medical care in wilderness endurance events (74%)
Most people get them, some don't
Prevention before blister begins - "hot spots"
159 prevention methods
Duct tape, paper tape, mole skin, petroleum jelly, antiperspirant
Exercise-Associated Hyponatremia
Exercise Physiology
The science of wilderness endurance events
Medical Support
for Wilderness Events

70,000 annual ultramarathoners = increased need for medical support
Logistics, communication, EMS/SAR protocols tailored to the specific event
Review course, environment, events
Goal -
Provide definitive treatment for minor illnesses and injuries
Initial stabilization & facilitate transfer
Develop medical support plan
Personnel
Equipment and supplies
Communication - GPS (Class I - III)
Send educational material directed at proper training techniques to the participants well in advance of the event
"IVF Rule" - Acceptance of medical care
Mark Christensen, D.O.
Wilderness Medicine Fellow
Stanford University School of Medicine

BASIC CONCEPTS
Maximum Oxygen Consumption
(VO Max)
Lactate Threshold
Efficiency of Movement
How efficient/powerful is your 'aerobic engine'?
Single best measure of cardiovascular fitness
Graded exercise treadmill test
Fick equation:
VO Max = CO X Extraction of oxygen
40 cc/kg/min (70-80 cc/kg/min)
Some animals up to 300 cc/kg/min
Trainability highly variable
Polygenic factors - family clusters
Point above which one's level of intensity cannot be sustained






Power (watts) or % of VO max
Rapid onset of fatigue when over 60-85% VO max
Important to know where athletes 'edge' is
Work Capacity at Altitude
Fraction of O2 in atmosphere is constant
At altitude barometric pressure drops so amount of O2 available (per volume/breath) decreases
Acclimatization - slow & fast adapters
Increased ventilation, improvement in gas exchange, erythropoesis, improved tissue oxidative capacity
“They repeatedly carried 25-kg loads to the lab- oratory hut at 5800 m, at the same speed as the Caucasians climbing without loads”
Hypoxic Training

Induce physiological adaptation to hypoxia to improve endurance performance
Retain benefits 10-18 days
When and how much?
"Live-high, Train-low"
Ultramarathons
1974 - Western states trail ride
23 hours 42 minutes
1977 - first official race
Ran with horses
13 pulled/quit
only one in 24 hours
Course record 14:46 (2012)
2704 entries for 400 spots
Grand slam,

Brian Morris 2006, 12min ahead of next runner, disqualified
Asymptomatic vs symptomatic
Incidence varies widely
Symptoms:
HA, dizziness, AMS, seizure, death
Mental status changes resulting from cerebral edema (EAHE)
Noncardiogenic pulmonary edema
Documented in hikers, trekkers, climbers
Misdiagnosed as AMS or dehydration?
Other Common Injuries
Dehydration
Trauma
Incidence low - morbidity/mortality high
Significant organization and financial commitment
EMS, SAR, Air med
Race-specific injuries
Cold injuries - Frostbite, hypothermia
Water related - Submersion injuries, envenomations, wild life
Endemic disease (leptospirosis during the Eco-Challenge-Sabah 2000 adventure race)
Heat dissipation, increased glycogen use, increased core temperature
Even mild dehydration has been shown to decrease VO max through reduced cardiac output up to 5%.
"Dehydration myth" collapse-heat exhaustion-dehydration = you need fluid
Adventure and Expedition-length Events
General Recommedations
Reduce over drinking
Fixed ranges vs "drink to thirst"
Space aid stations (<3km)
Sodium supplementation?
Excessive sodium supplementation not recommended
Replace sodium 1gm/hour
Body weight monitoring
Educate EMS and aid personnel
Symptoms of severe EAH
+ POCT Na
- POCT Na
Severe neuological deterioration
Unable to tolerate oral
Worsening condition despite oral
Mild Symptoms
Neurologically stable
Tolerating oral fluids
<130
>130
Alternate diagnoses
Bolus 100mL 3% Saline
Repeat every 10min X3
Limit free fluids
Salty snacks & fluids
Transport
Urination
Severe neuological deterioration
Unable to tolerate oral
Worsening condition despite oral
Mild Symptoms
Neurologically stable
Tolerating oral fluids
Bolus 100mL 3% Saline
Repeat every 10min X3
Limit free fluids
Salty snacks & fluids
Transport
Urination
If unable to differentiate from dehydration or heat illness - start with 1-2 L NS
Enhancing endurance
EPO (big boost to VO Max), transfusions (doping), anabolic steroids, DHEA
What methods are ethical?
1) enhances sport performance
2) poses a potential health risk to the athlete
3) violates the spirit of sport.
Lactate
Threshold
Efficiency
VO Max
Independent factors
age, sex, altitude, illness, genetics
VO max
Cardiac output improves
Increase in capillary and mitochondrial density
Lactate threshold
Increase in lactate oxidation and clearance
Oxidative stress (progressive muscle recruitment)
A lot of hours and miles?
Interval Training (IT) - stimulates physiologic changes
Target heart rate and heart rate zones?
"Functional exercise"
climb vs cycle, treadmill vs trail
Fuel + Oxygen = Energy Work
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2
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Functional Movement Screen
Optimizing biomechanics to turn energy into work
Genetic factors (habitus/coordination)
Stroke mechanics, rowing motion, running stride, cycling cadence, climber fatigue
Important for injury prevention



Modest measurable improvements can have significant overall effects
http://www.valencell.com/
http://www.topendsports.com/
http://www.adventurebeyond.co.uk/
Low-altitude vs High-altitude Natives
Enhancing?
http://www.dailymail.co.uk/
1. Krabak BJ, Waite B, Schiff MA. Study of injury and illness rates in multiday ultramarathon runners. Med Sci Sports Exerc. 2011;43:2314–2320.
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2. Vonhof J: Fixing your feet: Prevention and treatments for athletes. Berkeley, Calif.: Wilderness Press, 2004.
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1. Pinchan G, Gauttam RK, Tomar OS, Bajaj AC. Effects of primary
hypohydration on physical work capacity. Int J Biometeorol. 1988;32: 176–180.
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1. Krabak B.J., Waite B.W., and Lipman G.: Injury and illnesses prevention for ultra-marathoners. Curr Sports Med Rep 2013; 12: pp. 183-189
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