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Dehydration_Strength_Power_Endurance _A_Complete_Guide

The science of hydration has evolved considerably and quite dramatically in the last decade or so. When it comes to hydration, most people consider it an important aspect of exercise and performance, but just how important is this connection and what are the best practices when it comes to hydration and bodybuilding as well as other training types? To get the answers to these questions, it’s first important to know some quick facts about hydration.

HydrationHydration - Why is it Important?

Water makes up more than half your body weight. In fact, muscle tissue is made up of roughly 72% water. You are constantly losing water, when you sweat, when you urinate and even when you breathe. Without the replenishment of this lost water, you put yourself at risk of becoming dehydrated and potentially hypohydrated in the long run (a chronic total water deficit). Being dehydrated or hypohydrated causes a variety of negative symptoms to manifest including:

  • Fatigue
  • Sleepiness
  • Headaches
  • Confusion
  • Dizziness
  • Mood Swings



DehydrationDehydration - Who is at Risk?

Dehydration can affect anyone, but often occurs more often in athletes or trainers participating in high intensity or endurance exercises as well as older people. Older people have a decreased thirst signalling, so they are more prone to dehydration and hypohydration. Some other instances where you are at risk and might require more fluid include:

  • Vomiting and diarrhoea
  • Pregnant and breastfeeding
  • If you plan on being out for long periods in the sun and heat
  • Planning to lose weight
  • Fever
  • Other disease conditions

Dehydration - How Does it Happen?

Becoming dehydrated is as simple as losing more body water than you ingest causing a negative fluid balance. The reason why dehydration is so common in exercise and sports is due to the rises in heat that our body experiences. In order to dissipate this heat, sweating is one of our first lines of defence, the rate of which is influenced by a range of factors such as exercise intensity, training state, clothing, environmental conditions and how well you can acclimatize to different temperatures. The idea that dehydration affects performance though has come under quite intense scrutiny in the last few years. Simply put, there are almost as many studies arguing against negative impacts of dehydration on performance as there are for. In fact, some even suggest that the concept of dehydration has been blown such widely out of proportion due to commercial interests from sports drinks companies. But what does happen to your body when you become dehydrated? Let’s take a look at how dehydration might affect several performance factors.

EnduranceDehydration & Endurance

Most of the research on the effects of dehydration have been in reference to activities which are endurance based. This is because core temperature and sweating is generally higher in endurance events due to the sheer amount of time. Older, laboratory based studies have shown that a decrease in 2% of total body weight resulted in performance deficits and increased perceived exertion in longer endurance events in both cycling and running. Many recent studies though have shown the opposite in which endurance performance is not compromised with dehydration, even if core temperature rises. As such, it is still too hard to say conclusively just how much dehydration affects performance and at what percentage of body weight loss where deficits occur.

Dehydration & Strength

One of the key takeaway points of many studies looking at dehydration and its effects is that there is so much variability between people. How dehydration affects you is dependent on your dehydration tolerance and various hydration practice. Research points to a “critical point” of dehydration where it starts to affect performance, but this point is extremely individualised. Judelson et al (2007) examined over 70 publications and came to a conclusion that a 3-4% reduction in total body water results in a loss of approximately 2% of your strength. Losses to strength due to dehydration are greater in some exercises and training modes, such as with repeated bout exercises, higher metabolic demand activities and also situations where there is less opportunity to consume and replenish fluids.

StrengthDehydration & Power

While strength measures the amount of force you can generate, power is the amount of force over a period of time. Power is important in explosive activities, such as in jumping, swinging and kicking movements in sports as well as in weight training. The same review by Judelson at al (2007) found that a 3-4% reduction in total body water resulted in roughly a 3% drop in power. Other studies have shown that dehydration affects the power production of the lower body greater than the upper body and power deficits seem more pronounced in anaerobic activities (eg sprints, resistance training, etc). Although there are shown decreases in strength and power due to dehydration, does this actually affect overall performance?

Dehydration & Exercise Performance

Performance is an umbrella term that defines the level of achievement of a particular task. Whether it’s improving on a time trial, dribbling and shooting performance, number of forehand or backhand winners or cognitive performance improvements such as improved memory or decision making, performance is perhaps the single most important factor when considering the effects of dehydration. If you’re looking at resistance and weight training alone, strength, power and endurance outcomes tend to be the main indicators of performance. However, when it comes to sports and other skill based activities, it becomes a little more complicated. Studies are inconclusive with some indicating increased fatigue in basketball players and impaired dribbling in soccer players to no effect on shooting accuracy in basketball players and no detriments to boxing performance. When it comes to how dehydration affects performance, you need to look at three things:

1. Identify athletes and trainers who are most susceptible to performance detriments with increasing dehydration.

2. Identify skills and performance parameters that are more susceptible to effects of dehydration.

3. Identify at what stage of dehydration these detriments occur.

Dehydration & Cognitive Function

Perhaps the most pronounced effect of dehydration is on cognitive function. Many sports require a range of mental skills including vigilance, mental acuity, memory, decision making, and of course focus. Generally, it’s been shown that even a small 1-2% loss of body weight in water is shown to negatively affect cognition, however, studies have often been confounded with other factors that may occur such as fatigue and heat just to name a few. As such, it’s hard to say whether a reduction in cognitive function occurs first as a result of dehydration or whether it results from other symptoms associated with dehydration. Regardless, some of the more common changes that occur in terms of cognition with dehydration and hypohydration include:

  • Decrease in short term memory, reasoning, attention, vigilance and processing speed
  • Decreased motivation and vigor
  • Increased perception of effort
  • Altered mood states

Guidelines to Prevent Dehydration in Athletes, Bodybuilders & Trainers

The science of dehydration and hypohydration and its effect on training performance is still being elucidated. While old school paradigms of trying to avoid 2% body weight loss as it might affect training performance is slightly outdated, there is plenty of research to show that acute dehydration and chronic hypohydration can affect strength, power, endurance, cognition and performance, but perhaps at a higher level:

  • Cognitive Deficits and Perception of Fatigue occur earliest at 1% body weight water loss.
  • Sports specific tasks and skills will experience deficits at around 2% body weight water loss.
  • Strength, power and high intensity endurance will experience deficits later on at 3% body weight water loss and up.

As with the positive effects of training, the level of fluid loss and the effects of dehydration are extremely variable and individualised. It is affected by genetic factors, environment, training state, sporting demands. As such, it is important to follow these basic rules when trying to avoid becoming dehydrated.

  • Most people begin training at an already dehydrated state, so pay attention to before training hydration as well as during and post workout hydration.
  • Use thirst as an indicator for when to drink, especially if you’re a younger individual.
  • Urine colour is another excellent indicator. If it is clear, you are actually overhydrated. Rather, aim to have a pale or transparent yellow (straw to lemonade).
  • When it comes to the best fluid to support rehydration, simple water is a good control gold standard. For better results, full fat or skim milk, oral rehydration fluids and orange juice may be used. Contrary to popular belief, sports drinks such as Gatorade are on par with water when it comes to supporting rehydration after strenuous exercise.
  • Sports drinks such as Gatorade however do contain carbs and electrolytes, which can benefit performance.
1. Meyer, F et al, 2015. Fluid Balance, Hydration, and Athletic Performance. Edition. CRC Press.
2. Moyen NE, Ganio MS, Wiersma LD, Kavouras SA, Gray M, McDermott BP, Adams JD, Binns AP, Judelson DA, McKenzie AL, Johnson EC, Muñoz CX, Kunces LJ, Armstrong LE. ‘Hydration status affects mood state and pain sensation during ultra-endurance cycling.’ J Sports Sci. 2015;33(18):1962-9.
3. Cheung SS, McGarr GW, Mallette MM, Wallace PJ, Watson CL, Kim IM, Greenway MJ. ‘Separate and combined effects of dehydration and thirst sensation on exercise performance in the heat.’ Scand J Med Sci Sports. 2015 Jun;25 Suppl 1:104-11.
4. Wall BA, Watson G, Peiffer JJ, Abbiss CR, Siegel R, Laursen PB. ‘Current hydration guidelines are erroneous: dehydration does not impair exercise performance in the heat.’ Br J Sports Med. 2015 Aug;49(16):1077-83.
5. Maughan RJ, Watson P, Cordery PA, Walsh NP, Oliver SJ, Dolci A, Rodriguez-Sanchez N, Galloway SD. ‘A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index.’ Am J Clin Nutr. 2016 Mar;103(3):717-23.
 
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