The Jungle Ultra

The Jungle Ultra

It is a self-supported 230 km race through the jungles of Manu National Park in Peru. There are 5 stages to this race which traverse jungle undergrowth, rivers and mountain valleys. The weather is unpredictable and it often rains with muddy terrains. Participants will require specialized gear, adequate nutrition and hydration. This unfavorable environmental conditions can add additional stress to participating individuals exercising in heat. Some physiological changes are increases in core body temperature and heart rate.

HOW TO PREPARE- EVERYONE IS DIFFERENT:

Acclimatization can help individuals battle the stress applied onto the body during the actual race event. This can be very taxing and demanding(Maughan and Shirreffs 2004). Adaptation occur at different rates for everyone, i.e. individual variability. It can take around 10-14 days for acclimatization to occur. Among the strategies for coping stresses during the ultra-race in the heat are: Acclimatization, Hydration, Heat experience, Clothing selection, Pre cooling.

Physiological changes occur during exercise in the heat. The optimal temperature for exercise based on research in the lab is around 10°C. It is important to note the that temperature in this event will range from 20-30°C with high humidity. Exercise performance tends to decline with increasing ambient temperature. With sweat loss, hypohydration and hyperthermia can exert negative effects on the cardiovascular and thermoregulatory system(Maughan and Shirreffs 2004).

REGULATING YOUR BODY TEMPERATURE:

Heat is loss from the body occurs via evaporation and convection. The main method of dissipating heat to the environment is via evaporation of sweat(Burke 2001). Sweat losses can be as high as 3L/hour in hot environment. Appropriate clothing such as short sleeve t shirt and mid-thigh shorts help reduce heat entrapment and allow air movement to help sweat evaporation(Gavin 2003). On the other hand, clothing also protects from radiation heat from the sun reducing thermal stress(Gavin 2003). White clothing is thought to reduce radiative heat gain. During exercise, plasma volume decreases and osmolality increases(Racinais, Alonso et al. 2015). This decreases the sweat rate for any given core body temperature and attenuates the body’s ability to lose heat(Racinais, Alonso et al. 2015). This leads to cardiovascular strain with dehydration reducing cardiac filling and affecting blood pressure regulation.

WHAT DO I EAT?

Exercising in hot temperature promote carbohydrate substrate utilization(Febbraio 2000). The body has a predilection for substrate utilization towards stored carbohydrate(CHO). Currently the literature suggests that exercise in heat promotes CHO catabolism. This leads to decrease in lipid and triglyceride utilization. (Febbraio 2000). CHO ingestion during exercise in ambient temperature reduces circulating stress hormones such as adrenaline. It is therefore possible that carbohydrate ingestion during and after exercise in the heat may negate this effect. In addition, there is a disruption of oxidative function of skeletal muscle glycogen stores due to mitochondrial dysfunction in heat stress(Febbraio 2000).

SHOULD I DRINK BEFORE THE RACE?

Some suggest that pre-exercise hyperhydration in hot environment helps to reduce the deleterious effects of dehydration.  This practice increases total body weight (TBW) and expands plasma volume with the goal of enhancing subsequent exercise. Nonetheless, sometimes this can be a disadvantage. Athletes might experience gastrointestinal distress, and frequent urination in early stages of the race(Burke 2001). A way to tackle this is to practice chronic acclimatization where fluid intake is increased in the weeks prior leading to the race.

Having a baseline measurement is good for hydration status. Measuring body mass during training preferably under similar conditions and time helps give a rough estimate of fluid losses. This can then be used by the athlete during the race to help with hydration.

Hyperhydration with large fluid tends to lead to diuresis(van Rosendal, Osborne et al. 2010). Glycerol use in bolus of water has shown to increase fluid retention, reduce sweat rate and thus improve thermoregulatory capacity(Febbraio 2000). Glycerol is a three carbon molecule and is released in the body via lipolysis(Burke 2001). When ingested, it is distributed amongst body fluid compartments and exerts osmotic pressure. Although the physiology is poorly understood, glycerol might play a role in increasing kidney’s medullary gradient which in turn promotes glomerular fluid resorption. Due to the dearth of studies on glycerol use in hyperhydration, there is no definite recommendation. One study on cyclist did show an advantage in terms of more work  being done as compared to the placebo group(Burke 2001). A study by Van Sorendal SP. et al. suggested the addition of glycerol of 1.2 g/kg of body weight(BW) fluid 30 mins prior to exercise and 1.0 g/kg BW post exercise for rehydration might restore plasma volume(van Rosendal, Osborne et al. 2010). The total volume of fluid used ranged from 20-29 mls/kg BW. There are some possible side effects from glycerol ingestion such as GI distress, nausea, and headaches due to increased intracranial pressure.  Although no strong convincing study has been carried out, it is plausible that adding glycerol to carbohydrate-electrolyte beverage is more beneficial than glycerol to water(van Rosendal, Osborne et al. 2010). Anyone with health issues or persistent glycerol use side effects should first seek medical clearance from their physician

FLUID INTAKE DURING EVENT- HOW MUCH?

• There is a misnomer that fluid requirement during exercise will decrease if an athlete is adjusted to heat. This is a false conception. Heat acclimatization will actually increase the demand of fluid rehydration because of earlier onset of sweat loss(Wendt, Van Loon et al. 2007).
• An athlete who has a normal TBW is said to be “euhydration”. Loss of fluid via the process of dehydration leads to “hypohydration” state and fluid overloading above TBW is “hyperhydration”. It is important to get the balance right for better exercise performance, aid recovery post exercise and also to prevent the detrimental effects of electrolyte imbalance(Burke 2001).
• Exercise-induced dehydration can result in increased core body temperature(Febbraio 2000). Fluid ingestion reduces core body temperature preventing hyperthermia and prevent carbohydrate depletion (reduces skeletal muscle glycogen use). Another benefit for fluid ingestion during exercise in the heat is to attenuate glycogen utilisation(Burke 2001). The average daily water turnover for sedentary individuals is 2-3 litres per day. Losses up to 10 litres can occur with exercise in the heat(Maughan and Shirreffs 2004).
• Thirst tends to be the main driver for fluid intake, although habit and social behavior play an important part as well. Taste is another important factor. Therefore, beverage palatability plays an important role when large amounts of fluid intake is required(Maughan and Shirreffs 2004).
• A loss of about 2% body mass can be tolerated without any physiological consequences. There are some suggestion 4% loss of body weight in order to maintain serum sodium levels(Glace, Murphy et al. 2002). Weight maintenance could mean retention of fluid in vascular space leading to hyponatremia(Glace, Murphy et al. 2002). Glace B. et al. in their study suggested an  ingestion of 1g/hour of sodium to prevent hyponatremia and its side effects such as altered mental status and cramps(Glace, Murphy et al. 2002). People who lose excessive salt in sweat, “heavy sweaters”, can deliberately increase salt intake by adding salt to their drinks prior to and following hot weather run e.g. 3 grams of salt can be added to 500 mL carbohydrate-electrolyte drink(Racinais, Alonso et al. 2015).  Water retention can be optimized by ingesting beverages containing more than 50 mmol/L of sodium in a volume more than 1.5 times than the amount in sweat loss(Wendt, Van Loon et al. 2007).
• Ideally, athletes are recommended to consume 200-300 mLs of fluids (preferably 4-6 % CHO concentrated sports drink) 20 minutes before the event and throughout the race. Stomach content <600 mLs to promote gastric emptying and at the same time not too much to cause gastric distress(Wendt, Van Loon et al. 2007).
• Certain food such as tomatoes contain large amount of water ~95% and therefore provide hydration.
• Monitoring urine parameters such as colour, volume, specific gravity and body weight is a good way of checking bodily fluid losses(Maughan and Shirreffs 2004). Drinks such as alcohol and caffeine should be avoided due to its diuretic effect leading to urinary fluid losses.

POST EXERCISE RECOVERY:

Post exercise rehydration is important. It should be high in CHO. A drink containing protein e.g. milk might better restore fluid balance rather than a standard electrolyte sports drink. Consider chocolate milk which has a carbohydrate to protein ratio of 4:1(Racinais, Alonso et al. 2015). Milk also contains potassium and sodium which aids with rehydration and muscle recovery(Watson, Love et al. 2008). A study by Watson P. et al. showed that skimmed milk was more effective at replacing sweat losses than carbohydrate-electrolyte drink(Watson, Love et al. 2008).

STRATEGIES FOR HYDRATION AND NUTRITION DURING THE RACE:  

Specific strategies can be put in place for athletes to increase fluid intake during sports in heat. Examples of which are recognizing specific opportunities for fluid intake during sport, provision of cool and palatable beverages, creative ideas to make fluid accessible, and using pre and post-exercise weighing to monitor fluid deficit. Fluid availability and event specificities plays an important role for rehydration during the event(Racinais, Alonso et al. 2015).

Thirst response lags 4-24 hours and voluntary rehydration where athletes being made aware of the importance of rehydration and fluid availability are crucial(Burke 2001). Avoid immediate ingestion of plain water following strenuous exercise in heat as this reduces plasma osmolality and sodium concentration, which stimulates urine production and delays rehydration process(Watson, Love et al. 2008).  Sodium can be ingested by having sodium containing food or salt added to food.

When exercising in heat, one should ingest carbohydrate/fluid/electrolyte drink regularly. There are fluid and salt losses with sweat. Both water and carbohydrate drink empties at similar rates from the stomach. Nevertheless, the carbohydrate drink should not be too concentrated. Keep the carbohydrate concentration  below 10%  to prevent changes in plasma volume and body core temperature(Febbraio 2000). From the plethora of studies, we can postulate that fluid losses in heat is approximately 1.6L per hour. The current recommendation for ideal fluid intake during exercise in heat is approximately 400 mL every 15 minutes of 2-8% carbohydrate drink(Maughan and Shirreffs 2004).  Commercially available sports drinks are designed to strike a balance between efficacy and palatability(Watson, Love et al. 2008).

Trong T.T. and colleagues in their study in 2015 demonstrated that ingestion of cold water/ice slurry with menthol improved exercise performance in hot and humid environment(Trong, Riera et al. 2015). Although this might have had psycho-physiological influences by stimulating the reward centre in the brain(Trong, Riera et al. 2015). It may be said that specific brain regions are triggered by sensing nice fresh cooling sensation in the throat therefore maintaining central drive and motivation for exercise(Trong, Riera et al. 2015). There is some suggestion of internal precooling with ice slurry with menthol in self-paced endurance exercise(Trong, Riera et al. 2015).

Due to preference of CHO oxidation during exercise in heat, athletes are recommended to take CHO 7-10g/kg of body mass to meet the demands of the body(Burke 2001). Muscle glycogen stores can be restored over 24-36 hours with high dose CHO ingestion. Glycogen loading 3 days prior to the event by having 8-10 g/kg of CHO may increase glycogen stores by 25-100%(Burke 2001). The ideal pre event intake should be CHO-rich snacks 2-4 hours prior to exercise(Burke 2001). The general rule of thumb is CHO intake should commence well in advance of fatigue and depletion of CHO stores. Adding protein to CHO in the recovery phase assists with glycogen restoration and muscle recovery. Some examples of fluid rich CHO are flavoured yoghurts, fruits, fruit smoothies, ice cream, sport meals, sport drinks and liquid meal supplements(Burke 2001).

In a nutshell, I hope this information helps participants prepare in advance for the event and help them achieve their goals during the ultra-race. All the best!