TLDR: Dehydration can reduce our performance.
Bring your own bottles (BYOB) to training and monitor your fluid intake.
Hydration creed:
This is my bottle.
There are many like it, but this one is mine.
My bottle is my best friend. It is my life.
I must master it as I must master my life.
Without me, my bottle is useless.
Without my bottle, I am useless.
Below, I will explain the effects dehydration can have on our performance in simplified bullet points (the what) and then in detail from what evidence shows us (the how & why).
Why does hydration matter for performance? (simplified)
When we do physical work, we generate heat, our temperature increases and our body wants to maintain a certain temperature so we sweat in an effort to cool down.
Dehydration reduces the fluid volume of our blood, as a result our heart needs to beat faster to supply the same demand.
Studies show that dehydration may reduce performance through reduced work rate because of lower physical capacity and earlier onset of fatigue; reduced skill execution, poorer decision making and increased perceived exertion.
Dehydration can even become an injury risk factor.
When we experience dehydration, it happens everywhere, one important area is our brain; the fluid it’s suspended in, can be reduced and this can reduce the protection we have around our brain and cause it to travel further and faster within our skull if we get hit into the head/jolted.
Why does hydration matter for performance? (detailed)
When we exercise/train, to cope with the rise in temperature from physical work, our body can lose heat through many ways, one of the more effective methods our bodies have to cope with this rise in temperature is sweating. Sweat comes from the liquid portion of our blood (called plasma).
Cardiovascular system impact.
Therefore when we sweat, we are reducing our plasma volume, this means we can’t fill our heart with as much blood per pump (stroke volume) therefore our cardiac output (Stroke volume x Heart Rate) is reduced (Stohr et al, 2011) and to compensate for this while trying to maintain muscle blood flow our heart needs to beat faster (aka work harder than what was previously needed).
Performance impact.
Several studies have reported that sweat losses in excess of 5% of body weight can decrease the capacity for work by about 30% (Armstrong, Costill, and Fink 1985; Craig and Cummings 1966; Maughan 1991; Sawka and Pandolf 1990).
When dehydrated aerobic exercise tasks can be adversely affected, this negative effect is exacerbated at higher exercise intensities. (Sawka et al 2000).
As a result of hyperthermia premature fatigue during intense aerobic exercise has been noted (González et al, 1985 & Saltin et al 1964) this has also been shown to induce cardiovascular drift which is correlated with performance impairments such as declines in cycling peak power (Fritzsche et al 1985), anaerobic power and maximal aerobic capacity (Webster et al 1990).
Motor skills, inclusive of sports-specific movement patterns and cognitive performance decline following even a 2% BM loss via dehydration (Dougherty, Baker, Chow, & Kenney, 2006; Fogelholm, 1994).
Both Oopik et al (1996) & Green et al (2007) showed that 5% reduction in BM can increase probability of injury. Oopik et al showed that metabolism and muscle contraction patterns are negatively affected. Given the metabolic and mechanical complexities of multidirectional team sports, this increases athletes’ susceptibility to injuries.
The global effects of hydration & our brain.
As if that isn’t enough to convince you to try to manage the fluid losses around training; Dehydration is global within our bodies (i.e. the impacts aren’t regional to a specific area, when dehydrated it impacts everywhere) and our brain is suspended in cerebrospinal fluid (CSF).
One of the main functions of CSF is to protect our brain tissue from injury whenever our head is hit or jolted.
If the CSF fails to adequately protect the brain tissue upon impact, the consequences could result in haemorrhaging (in which the usual cause is the brain tissue coming into contact with the skull), brain damage and even death in severe cases (Streitburger et al 2012).
A reduction in protection of the brain tissue, higher velocities and further distance travelled result in increased risk of contusions upon impact.
The structural brain changes during dehydration have shown consistent findings which are well documented in the literature; cell shrinkage and osmolality changes throughout the brain and affects the entire ventricular system (Gullans et al, 1993).
Dickens et al (2005) showed that the volume of intra-cranial compartments is also affected by dehydration, causing an increased risk of brain damage from contusion and subdural haemorrhages.
After impact (strike) to the head, the brain will travel further within the cranium before it meets the skull due to subarachnoid space being enlarged compared to when normally hydrated.
It will also accelerate at higher velocities and this may increase likelihood of contusion injuries (Besenski et al, 2002).
Any questions? Reach out.