Physical Activity and Perspiration

Original Editor - Kapil Narale

Top Contributors - Kapil Narale, Rishika Babburu, Kim Jackson and Uchechukwu Chukwuemeka  

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Disorders of Sweat Gland Function

There are certain diseases or disorders that can alter the amount that a person sweats…

A chronic condition of Cystic Fibrosis would experience more sweating of Na+ and Cl- content due to a genetic deficiency or absence of functioning CFTR, which would lead to a lower reabsorption rates of Na+ and Cl- in the sweat ducts.

A chronic condition of Addison’s Disease would experience more sweating than normal of Na+ and Cl- due to an impaired adrenal cortex function, which would lead to a lower reabsorption rates of Na+ and Cl- in the sweat ducts.

A chronic condition of Diabetes Mellitus would cause decreased sweating with Type I and Type II diabetes mellitus. Possible mechanisms could be related to autonomic neuropathy and a decreased heat sensitivity, decreased maximal sweat rate, and/or a reduced number of active sweat glands. There is also an inhibited ability to control the heat, especially in higher temperatures and in less fit individuals.

A chronic condition of Multiple Sclerosis would cause decreased sweating due to lesions within the central nervous system, which would lead to a decreased sweat output per gland.

A chronic Spinal Cord Injury would cause decreased or absence of sweating in the on-sensory skin, which can be due to disruption in neural pathways involved in central and peripheral control of sweating. Contrarily, there is an increase in sweating in the sensory skin superior to the spinal lesion.                  

A chronic condition of severe Burns and Skin grafting would cause decreased or absence of sweating in the burned area, due to the removal of dermal and epidermal layers, including the sweat glands. Even as skin grafts heal, there is still a disruption in the ability to sweat.

An acute condition of sunburn would cause decreased sweating in artificially induced mildly sunburned skin

An acute condition of Miliaria rubra (heat rash or prickly heat) would cause decreased sweating due to pore occlusion via keratin plugs, which would cause mechanical blockage of sweat smoothy flowing onto the skin surface. This can be caused by increased humidity, which would cause excess sweat, on the skin surface for longer periods.

An episodic condition of Atopic dermatitis (eczema) would cause decreased sweating on the surface of the skin due to blockage of sweat pores by keratin plugs, sweat leaking into dermal tissue around the glands, and/or histamine-induced sweat prevention. Sweat glucose concentration can be higher than expected with acute atopic dermatitis.

A chronic condition of Anhidrotic ectodermal dysplasia would cause decreased or absence of sweating due to a small genetic disturbance, or eliminated sweat glands throughout the body.

A chronic or episodic condition of Primary hyperhidrosis will produce a greater amount of sweat, primarily affecting one or both axilla, palms, soles, and the head and face (craniofacial areas). This would be induced by neurogenic overactivity of sweat glands, which would otherwise be normal. This occurrence would be from genetic factors.

A chronic or episodic condition of Secondary hyperhidrosis will produce a greater amount of sweat on one or both sides, due to an underlying physiological condition (fever, pregnancy, menopause), pathology (malignancy, infection, cardiovascular disease, endocrine/metabolic, neurologic or psychiatric disorders), or medication.

A long-term tattoo usage can cause decreased sweating rate and higher sweat content of Na+ from  pharmacologically-induced local sweating compared to non-tattooed skin.

With acute or chronic use of medications, chemicals such as Antimuscarinic anticholinergic agents, carbonic anhydrase inhibitors, and tricyclic antidepressants can cause generalized hypohidrosis. As seen above hyperhidrosis is a factor in altered sweating and can be caused by cholinesterase inhibitors, SSRI, opioids, and TCA.  

Heat and sweating

Exercising in the heat doesn’t necessarily have the same effect on sweating as one may think. Excessive body heat is generally diminished from evaporation of sweat on the skin. With high humidity, water vapour pressure of air is high, thus sweating is not as effective in decreasing the body heat since evaporation cannot efficiently happen .  

In hot conditions it is seen that there is minimal conductive heat exchange between air and skin due to the small temperature difference between the environment and the skin (Olympic article).    

Wind speed is also an important factor. Wind can accelerate heat transfer form the skin, as the flowing air replaces the skin surface air which contains evaporating water, with more dry air, which enhances sweat evaporation (Olympic article).

Quick moving activities such as running or cycling will not have the same effect of high heat and humidity as slower moving activities such as beach volleyball or field events. It is noted that body heat release increases with wind speed, and an increase in ambient temperature reduces air density and air resistance (Olympic article).

The heat and light from the sun also need to be considered. Sunburns can aggravate thermal perceptions from exercise, which would limit thermoregulation from a sweat gland responsiveness (Olympic article)   

Dehydration and Sweating

Hydration is very important before during, and after exercise in the heat, for optimal activity performance. However, there cannot be a set amount of fluid intake or loss, as there is a variable fluid need between individuals. Fluid loss by sweating and hydration status can be assessed by analyzing pre- and post- exercise variations in body weight and urine color and volume.

The consumption of salt before, during, and after activity is important to maintain sodium balance in the body. Specifically in hot environments when sweating and loss of electrolytes is high, this would help to retain and distribute the ingested water throughout the body. (Olympics article).         

 

Heat acclimatization would happen with practicing of the activity int eh chosen/desired heat conditions. The acclimatization would be met with a decrease in sweat sodium concentration, an increase in sweat rate, decrease in core body temperature, and decreased heart rate with regular exercise in the heat. Work capacity will also be increased, with the reduction in the risk of exertional heat illnesses (Olympics article).

Ageing and Sweating

Older adults are seen to have a lower sweating response than younger adults. This would be a lower response per activated sweat gland from a particular pharmacological stimulus. It is seen that here is a decline in sweat response throughout adulthood, and there are regional differences within the body with the sweat gland function decline. However, this may be more likely due to a decrease in aerobic fitness and acclimation, as one ages. This may be due to the decrease in sensitivity of sweat gland to cholinergic stimulation.  

It's worth noting that UV and environmental exposures may play a role with sweat gland responsiveness as an individual ages. It’s interesting to note that there isn’t a big difference between sweating rates in older and younger adults with exercise in the heat, except for peak sweating rates in hot and dry climates.  

Thermal tolerance, between older and younger adults, is minimally affected when factors such as fitness level, body composition, and chronic disease, are not considered.

Gender/Sex and Sweating

It is interesting to note that Men have higher sweating rates than Women. They have a higher cholinergic response, and maximal sweating rates, than Women. However, when Men and Women with similar body mass, surface area, and metabolic heat production were compared, differences were only apparent in excess of usual environmental conditions, and metabolic heat production rate, which result in extreme evaporative needs for maintaining thermoregulation.

Sweat gland density is higher in Women than Men, which can be attributed to the lower body surface area n Women. Thus, the lower sweating rates from Women can be a result of lower output per sweat gland. In contrary, higher whole-body sweat rates in Men may be a result of higher body mass, and higher metabolic heat production from higher exercise intensities.

When considering differences between Men and Women, factors such as body size, surface area to mass ratio, heat acclimation status, aerobic capacity, exercise intensity, or environmental conditions all have a greater contribution than the differences of gender and sex in deciding the exercise-heat stress related autonomic responses. These factors can affect the evaporative rate needed for thermoregulation.

Menstrual cycle

Some other possible factors that can affect the stimulation of the autonomic response are maturation/development, altitude/hypoxia, circadian rhythm, and/or menstrual cycle. These alterations, though, in stimulation of regional sweating from an increased body core temperature are not directly related to whole-body sweating when it comes to exercise. In regards to the menstrual cycle, regional sweating during the luteal phase is decreased at a certain body temperature, since there is a greater threshold. Though there aren’t any major differences in whole-body sweating during the different menstrual cycle phases. However, for trained female athletes, exercising in the heat, the different phases of the menstrual cycle don’t have any effect on their physiology or performance.      

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